Qualification: 
Ph.D
rajabiswas@aims.amrita.edu

Dr. Biswas joined Amrita in June 2009. He has completed his Ph D and post doctoral work in the field of Microbial Genetics and Infectious Diseases from the Department of Microbial Genetics, University of Tuebingen, Germany.

He is the recipient of Ramalingaswami fellowship, Rapid Grant for Young Scientists from Department of Biotechnology in 2009 and Fast track grant for young scientists from Department of science and technology in 2010. He has to his credit nearly 16 publications in reputed journals like Molecular Microbiology, Journal of Bacteriology, Infection & Immunity and Journal of Biological Chemistry.

Dr. Biswas's research is focused on understanding more about the mechanism of infectious diseases specifically in understanding the complex network of host - microbe interactions, pathogenic mechanisms to escape the surveillance of host immune system and mechanisms for drug resistance.

Publications

Publication Type: Journal Article

Year of Publication Publication Type Title

2017

Journal Article

A. Mohandas, Krishnan, A. G., Dr. Raja Biswas, Dr. Deepthy Menon, and Dr. Manitha B. Nair, “Antibacterial and cytocompatible nanotextured Ti surface incorporating silver via single step hydrothermal processing”, Materials Science and Engineering C, vol. 75, pp. 115-124, 2017.[Abstract]


Nanosurface modification of Titanium (Ti) implants and prosthesis is proved to enhance osseointegration at the tissue–implant interface. However, many of these products lack adequate antibacterial capability, which leads to implant loosening. As a curative strategy, in this study, nanotextured Ti substrates embedded with silver nanoparticles were developed through a single step hydrothermal processing in an alkaline medium containing silver nitrate at different concentrations (15, 30 and 75 μM). Scanning electron micrographs revealed a non-periodically oriented nanoleafy structure on Ti (TNL) decorated with Ag nanoparticles (nanoAg), which was verified by XPS, XRD and EDS analysis. This TNLAg substrate proved to be mechanically stable upon nanoindentation and nanoscratch tests. Silver ions at detectable levels were released for a period of 28 days only from substrates incorporating higher nanoAg content. The samples demonstrated antibacterial activity towards both Escherichia coli and Staphylococcus aureus, with a more favorable response to the former. Simultaneously, Ti substrates incorporating nanoAg at all concentrations supported the viability, proliferation and osteogenic differentiation of mesenchymal stem cells. Overall, nanoAg incorporation into surface modified Ti via a simple one-step thermochemical method is a favorable strategy for producing implants with dual characteristics of antibacterial activity and cell compatibility. © 2017 Elsevier B.V.

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2017

Journal Article

Rajitha Panonnummal, Dr. Raja Biswas, Dr. Sabitha M., and Dr. Jayakumar Rangasamy, “Methotrexate in the treatment of psoriasis and rheumatoid arthritis: Mechanistic insights, current issues and novel delivery approaches”, Curr Pharm Des, 2017.[Abstract]


Our review is focused on the use of methotrexate in drug therapy of two autoimmune diseases, psoriasis and rheumatoid arthritis (RA). The article describes the pathogenesis of psoriasis and RA, the role of methotrexate in the treatment of these diseases with more focused review on the mechanism behind the clinical benefits of methotrexate therapy. Methotrexate due to its cytotoxic, anti-inflammatory and immune modulatory activities provides clinical benefits in the therapy of the selected diseases. This review also gives a panorama of the problems associated with the use of methotrexate in the selected diseases and the guidelines provided by FDA for its safe use. The novel colloidal drug delivery systems of methotrexate, with particular emphasis on advantages offered by liposomal formulation, niosomal gel, hydrogel, albumin conjugates, nanoparticles and nano structured lipid carriers in psoriasis and RA are also reviewed. It seemed that the use of newer colloidal carriers with improved skin permeability by minimizing its systemic availability will be a useful strategy to reduce the toxic effects of the drug in psoriatic patients. In rheumatoid arthritis patients, the development of newer therapeutic strategies using appropriate targeting ligands that specifically deliver the drug to the inflamed joint space will help to overcome its toxic effects by minimizing the systemic exposure.

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2017

Journal Article

S. Vijayrajratnam, Pushkaran, A. Choorakott, Balakrishnan, A., Dr. Anil Kumar V., Dr. Raja Biswas, and Dr. Gopi Mohan C., “Understanding the molecular differential recognition of muramyl peptide ligands by LRR domains of human NOD receptors”, Biochem J, vol. 474, no. 16, pp. 2691-2711, 2017.[Abstract]


Human nucleotide-binding oligomerization domain proteins, hNOD1 and hNOD2, are host intracellular receptors with C-terminal leucine-rich repeat (LRR) domains, which recognize specific bacterial peptidoglycan (PG) fragments as their ligands. The specificity of this recognition is dependent on the third amino acid of the stem peptide of the PG ligand, which is usually meso-diaminopimelic acid (mesoDAP) or l-lysine (l-Lys). Since the LRR domains of hNOD receptors had been experimentally shown to confer the PG ligand-sensing specificity, we developed three-dimensional structures of hNOD1-LRR and the hNOD2-LRR to understand the mechanism of differential recognition of muramyl peptide ligands by hNOD receptors. The hNOD1-LRR and hNOD2-LRR receptor models exhibited right-handed curved solenoid shape. The hot-spot residues experimentally proved to be critical for ligand recognition were located in the concavity of the NOD-LRR and formed the recognition site. Our molecular docking analyses and molecular electrostatic potential mapping studies explain the activation of hNOD-LRRs, in response to effective molecular interactions of PG ligands at the recognition site; and conversely, the inability of certain PG ligands to activate hNOD-LRRs, by deviations from the recognition site. Based on molecular docking studies using PG ligands, we propose few residues - G825, D826 and N850 in hNOD1-LRR and L904, G905, W931, L932 and S933 in hNOD2-LRR, evolutionarily conserved across different host species, which may play a major role in ligand recognition. Thus, our integrated experimental and computational approach elucidates the molecular basis underlying the differential recognition of PG ligands by hNOD receptors.

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2016

Journal Article

V. Dhanalakshmi, Nimal, T. R., Dr. Sabitha M., Dr. Raja Biswas, and Dr. Jayakumar Rangasamy, “Skin and muscle permeating antibacterial nanoparticles for treating Staphylococcus aureus infected wounds”, Journal of Biomedical Materials Research - Part B Applied Biomaterials, 2016.[Abstract]


Majority of the chronic wounds are infected with bacteria like Staphylococcus aureus (S. aureus). The deep tissue infections are difficult to treat using topical antibiotics, due to their poor tissue penetration. In order to treat S. aureus deep tissue infections we have developed an antibiotic delivery system using chitosan nanoparticles (CNPs). To enhance their tissue penetration these CNPs were further coated using lecithin (CLNPs). Antibiotic tigecycline was loaded into chitosan nanoparticles (tCNPs) and then coated with lecithin to generate lecithin coated tigecycline loaded chitosan nanoparticles (tCLNPs). The prepared nanoparticles were characterized using DLS, SEM, TEM and FT-IR. The prepared CNPs, tCNPs, CLNPs and tCLNPs have the size range of 85±10, 90±18, 188±5 and 235±20 nm, respectively. The tCLNPs shows more sustained release pattern of tigecycline. The antibacterial activity of the developed nanoparticles was confirmed against laboratory and clinical strains of S. aureus using in vitro and ex vivo experiments. The ex vivo skin and muscle permeation study ensures the enhanced delivery of tigecycline to the deeper tissue. The prepared nanoparticles were hemo-compatible and cyto-compatible. Our study suggests that the prepared tCLNPs can be effectively used for the treatment of S. aureus infected wounds. © 2016 Wiley Periodicals, Inc.

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2016

Journal Article

Rajitha Panonnummal, Gopinath, D., Dr. Raja Biswas, Dr. Sabitha M., and Dr. Jayakumar Rangasamy, “Chitosan nanoparticles in drug therapy of infectious and inflammatory diseases”, Expert Opinion on Drug Delivery, vol. 13, no. 8, pp. 1177-1194, 2016.[Abstract]


Introduction: Chitosan, a polymer from the chitin family has diverse pharmaceutical and bio-medical utility because of its easy widespread availability, non-toxicity, biocompatibility, biodegradability, rich functionalities and high drug-loading capacity. Recent pharmaceutical research has examined the use of chitosan-based systems for drug delivery applications in various diseases. The availability of functional groups permits the conjugation of specific ligands and thus helps to target loaded drugs to the site of infection/inflammation. Slow biodegradation of chitosan permits controlled and sustained release of loaded moieties; reduces the dosing frequency and is useful for improving patient compliance in infectious drug therapy. The muco-adhesion offered by chitosan makes it an attractive candidate for anti-inflammatory drug delivery, where rapid clearance of the active moiety due to the increased tissue permeability is the major problem. The pH-dependent swelling and drug release properties of chitosan present a means of passive targeting of active drug moieties to inflammatory sites. Areas covered: Development of chitosan-based nanoparticulate systems for drug delivery applications is reviewed. The current state of chitosan-based nanosystems; with particular emphasis on drug therapy in inflammatory and infectious diseases is also covered. Expert opinion: The authors believe that chitosan-based nanosystems, due to the special and specific advantages, will have a promising role in the management of infectious and inflammatory diseases. © 2016 Informa UK Limited, trading as Taylor & Francis Group

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2016

Journal Article

S. Va Nair, Baranwal, Ga, Chatterjee, Ma, Sachu, Ac, Dr. Anil Kumar V., Bose, C., Dr. Asoke Banerji, and Dr. Raja Biswas, “Antimicrobial activity of plumbagin, a naturally occurring naphthoquinone from Plumbago rosea, against Staphylococcus aureus and Candida albicans”, International Journal of Medical Microbiology, vol. 306, pp. 237-248, 2016.[Abstract]


Candida albicans and Staphylococcus aureus are opportunistic pathogens. Despite causing a number of independent infections, both pathogens can co-infect to cause urinary tract infections, skin infections, biofilm associated infections, sepsis and pneumonia. Infections of these two pathogens especially their biofilm associated infections are often difficult to treat using currently available anti-bacterial and anti-fungal agents. In order to identify a common anti-microbial agent which could confer a broad range of protection against their infections, we screened several phytochemicals and identified plumbagin (5-hydroxy-2-methyl-1,4-naphthoquinone), a phytochemical from Plumbago species as a potent antimicrobial agent against S. aureus and C. albicans, with a minimum inhibitory concentration of 5 μg/ml. Antimicrobial activity of plumbagin was validated using an ex-vivo porcine skin model. For better understanding of the antimicrobial activity of plumbagin, a Drosophila melanogaster infection model was used, where D. melanogaster was infected using S. aureus and C. albicans, or with both organisms. The fly's survival rate was dramatically increased when infected flies were treated using plumbagin. Further, plumbagin was effective in preventing and dispersing catheter associated biofilms formed by these pathogens. The overall results of this work provides evidence that plumbagin, possesses an excellent antimicrobial activity which should be explored further for the treatment of S. aureus and C. albicans infections. © 2016 Elsevier GmbH.

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2016

Journal Article

J. Perayil, Menon, K. S., Dr. Raja Biswas, Fenol, A., and Vyloppillil, R., “Comparison of the efficacy of subgingival irrigation with 2% povidone-iodine and tetracycline HCl in subjects with chronic moderate periodontitis: A clinico microbiological study.”, Dent Res J (Isfahan), vol. 13, no. 2, pp. 98-109, 2016.[Abstract]


BACKGROUND: This study was performed to evaluate and compare the clinical and antimicrobial efficacy of subgingival irrigation with tetracycline and povidone-iodine as an adjunct to nonsurgical periodontal therapy.</p><p><b>MATERIALS AND METHODS: </b>Twenty subjects with chronic moderate periodontitis were recruited in this split-mouth study with probing pocket depth of >3 and ≤5 mm and clinical attachment loss of 3-4 mm in relation to 16, 36, and 46. In each subject, three selected periodontal pockets were assigned to receive one out of three irrigants (1) sterile water (control) in 16; (2) tetracycline at 10 mg/ml in 36; (3) 2% povidone-iodine in 46, and these sites were designated as Group A, Group B, and Group C, respectively. Plaque score, gingival score, pocket probing depth, and clinical attachment level were evaluated before treatment and at 1 and 3 months posttreatment. Multiplex polymerase chain reaction was used to detect Porphyromonas gingivalis and Tannerella forsythensis which have been implicated as the major risk factors for periodontal disease. Subgingival plaque collected before treatment and at 1 and 3 months posttreatment. Data were analysed using ANOVA and repeated measure ANOVA. Results were considered significant if P < 0.05.</p><p><b>RESULTS: </b>Clinical and microbiological parameters were reduced posttreatment, the reduction being significantly higher in Group B compared to Group C.</p><p><b>CONCLUSION: </b>It can be concluded that chemical and mechanical therapies were of slight benefit in the treatment of chronic moderate periodontitis, and there was an adjunctive effect of significance when scaling and root planing was combined with a single subgingival irrigation with tetracycline or povidone-iodine in lower concentration.

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2016

Journal Article

R. Vilangattu Kunjikuttan, Jayasree, A., Dr. Raja Biswas, and Dr. Jayakumar Rangasamy, “Recent developments in drug-eluting dressings for the treatment of chronic wounds.”, Expert Opin Drug Deliv, vol. 13, no. 12, pp. 1645-1647, 2016.

2016

Journal Article

R. Babu, Kumar, A., Karim, S., Warrier, S., Nair, S. G., Singh, S. K., and Dr. Raja Biswas, “Faecal carriage rate of extended-spectrum β-lactamase-producing Enterobacteriaceae in hospitalised patients and healthy asymptomatic individuals coming for health check-up.”, J Glob Antimicrob Resist, vol. 6, pp. 150-3, 2016.[Abstract]


The prevalence of extended-spectrum β-lactamase-producing Enterobacteriaceae (ESBL-PE) in hospitalised and community patients is of significant public health concern. The aim of this study was to estimate the faecal carriage rate of ESBL-PE in hospitalised patients and healthy asymptomatic individuals coming for health check-up. Non-repetitive, consecutive stool samples from 480 adults (260 healthy individuals and 220 hospitalised patients) aged ≥18 years from November 2011 to July 2013 were screened using MacConkey agar supplemented with ceftazidime. All screen-positive isolates were identified to species level and were tested for ESBL production. Representative ESBL-PE isolates were subjected to susceptibility testing and multiplex ESBL PCR. The faecal carriage rate of ESBL-PE was found to be 62.7% among hospitalised patients and 33.8% among healthy asymptomatic individuals. The most common ESBL-PE was Escherichia coli (70.3% and 78.4% in hospitalised patients and healthy individuals, respectively), followed by Klebsiella pneumoniae (26.8% and 17.0%). ESBL-PE showed the highest sensitivity to carbapenems (85% and 100%, respectively), followed by amikacin (67.2% and 98%), cefoperazone/sulbactam (27.8% and 88.2%) and piperacillin/tazobactam (18% and 74.5%). Ciprofloxacin exhibited a high level of resistance among both groups. Molecular analysis for ESBL genes showed a predominance of the CTX-M gene. In conclusion, the faecal carriage rate of ESBL-PE among hospitalised patients was almost double that of healthy individuals. Carriage of carbapenem-resistant isolates is emerging among hospitalised patients. The spread of these organisms in the community merits radical measures to improve sanitation and implement antibiotic stewardship.

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2016

Journal Article

T. R. Nimal, Baranwal, G., Bavya, M. C., Dr. Raja Biswas, and Jayakumar, R., “Anti-staphylococcal Activity of Injectable Nano Tigecycline/Chitosan-PRP Composite Hydrogel Using Drosophila melanogaster Model for Infectious Wounds”, ACS Applied Materials and Interfaces, vol. 8, pp. 22074-22083, 2016.[Abstract]


Compared to the current treatment modalities, the use of an injectable hydrogel system, loaded with antibiotic encapsulated nanoparticles for the purpose of treating Staphylococcus aureus (S. aureus) chronic wound infections have several advantages. These include adhesiveness to infection site, reduced frequency of dressings, sustained drug release, inhibition of bacterial growth, and increased healing. In the present work tigecycline nanoparticles were loaded into chitosan-platelet-rich plasma (PRP) hydrogel. The tigecycline nanoparticles (95 ± 13 nm) were synthesized through ionic cross-linking method using chitosan, tripolyphosphate, and tigecycline and characterized by dynamic light scattering (DLS), scanning electron microscope (SEM), and Fourier transform infrared spectroscopy (FT-IR). The synthesized nanoparticles and activated PRP powder were mixed with chitosan hydrogel to form a homogeneous gel. Rheology studies have confirmed the shear thinning property, thermal stability, and injectability of the prepared gel systems. The gel system was further assessed for its drug release property and found that it was released in a sustained manner. Hemolysis and blood-clotting assays demonstrated that the gel system was neither a hemolysin nor a hamper to the clotting cascade. Cell viability results showed that these nanoparticles were cyto-compatible. The bioactivity of PRP loaded chitosan gel toward fibroblast cell line was studied using cell proliferation and migration assay. In vitro antibacterial studies revealed that the gel system inhibited bacterial growth to a great extent. The antibacterial activity was further analyzed using ex vivo porcine skin assay. In vivo anti-Staphylococcal activity of the prepared hydrogels was studied using a Drosophila melanogaster infection model. The tigecycline and tigecycline nanoparticle incorporated chitosan gel showed a significant antibacterial activity against S. aureus. Thus, the gel system is an effective medium for antibiotic delivery and can be applied on the infection sites to effectively forestall various skin infections caused by S. aureus. © 2016 American Chemical Society. More »»

2016

Journal Article

S. Vijayrajratnam, Pushkaran, A. Choorakott, Balakrishnan, A., Dr. Anil Kumar V., Dr. Raja Biswas, and Dr. Gopi Mohan C., “Bacterial peptidoglycan with amidated meso-diaminopimelic acid evades NOD1 recognition: an insight into NOD1 structure-recognition.”, Biochem J, vol. 473, no. 24, pp. 4573-4592, 2016.[Abstract]


Nucleotide-binding oligomerization domain-containing protein 1 (NOD1) is an intracellular pattern recognition receptor that recognizes bacterial peptidoglycan (PG) containing meso-diaminopimelic acid (mesoDAP) and activates the innate immune system. Interestingly, a few pathogenic and commensal bacteria modify their PG stem peptide by amidation of mesoDAP (mesoDAPNH2). In the present study, NOD1 stimulation assays were performed using bacterial PG containing mesoDAP (PGDAP) and mesoDAPNH2 (PGDAPNH2) to understand the differences in their biomolecular recognition mechanism. PGDAP was effectively recognized, whereas PGDAPNH2 showed reduced recognition by the NOD1 receptor. Restimulation of the NOD1 receptor, which was initially stimulated with PGDAP using PGDAPNH2, did not show any further NOD1 activation levels than with PGDAP alone. But the NOD1 receptor initially stimulated with PGDAPNH2 responded effectively to restimulation with PGDAP The biomolecular structure-recognition relationship of the ligand-sensing leucine-rich repeat (LRR) domain of human NOD1 (NOD1-LRR) with PGDAP and PGDAPNH2 was studied by different computational techniques to further understand the molecular basis of our experimental observations. The d-Glu-mesoDAP motif of GMTPDAP, which is the minimum essential motif for NOD1 activation, was found involved in specific interactions at the recognition site, but the interactions of the corresponding d-Glu-mesoDAP motif of PGDAPNH2 occur away from the recognition site of the NOD1 receptor. Hot-spot residues identified for effective PG recognition by NOD1-LRR include W820, G821, D826 and N850, which are evolutionarily conserved across different host species. These integrated results thus successfully provided the atomic level and biochemical insights on how PGs containing mesoDAPNH2 evade NOD1-LRR receptor recognition.

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2015

Journal Article

N. Nair, Vinod, V., Suresh, M. K., Vijayrajratnam, S., Dr. Lalitha Biswas, Peethambaran, R., Vasudevan, A. K., and Dr. Raja Biswas, “Amidase, a cell wall hydrolase, elicits protective immunity against Staphylococcus aureus and S. epidermidis”, International Journal of Biological Macromolecules, vol. 77, pp. 314-321, 2015.[Abstract]


The morbidity and the mortality associated with Staphylococcus aureus and S. epidermidis infections have greatly increased due to the rapid emergence of highly virulent and antibiotic resistant strains. Development of a vaccine-based therapy is greatly desired. However, no staphylococcal vaccine is available till date. In this study, we have identified Major amidase (Atl-AM) as a prime candidate for future vaccine design against these pathogens. Atl-AM is a multi-functional non-covalently cell wall associated protein which is involved in staphylococcal cell separation after cell division, host extracellular matrix adhesion and biofilm formation. Atl-AM is present on the surface of diverse S. aureus and S. epidermidis strains. When used in combination with Freund's adjuvant, Atl-AM generated a mixed Th1 and Th2 mediated immune response which is skewed more toward Th1; and showed increased production of opsonophagocytic IgG2a and IgG2b antibodies. Significant protective immune response was observed when vaccinated mice were challenged with S. aureus or S. epidermidis. Vaccination prevented the systemic dissemination of both organisms. Our results demonstrate the remarkable efficacy of Atl-AM as a vaccine candidate against both of these pathogens. © 2015 Elsevier B.V.

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2015

Journal Article

A. G. Krishnan, Jayaram, L., Dr. Raja Biswas, and Dr. Manitha B. Nair, “Evaluation of antibacterial activity and cytocompatibility of ciprofloxacin loaded gelatin-hydroxyapatite scaffolds as a local drug delivery system for osteomyelitis treatment”, Tissue Engineering - Part A, vol. 21, pp. 1422-1431, 2015.[Abstract]


Surgical debridement of the dead bone and subsequent systemic antibiotic therapy is often ineffective in eliminating Staphylococcus aureus infections in osteomyelitic patients. The recurrence of S. aureus infection is mainly due to the intracellular growth of bacterial colonies within osteoblast cells that protect the organism from extracellular host defences and/or antibiotic therapy. In this study, porous gelatin-hydroxyapatite (HAP) scaffolds with various amounts of ciprofloxacin (1, 2, 5, and 10 wt%) were fabricated by freeze-drying technique and the release of the antibiotic was characterized, as was the efficacy of the released antibiotic against methicillin-sensitive and methicillin-resistant S. aureus. Furthermore, the impact of the released antibiotic on the viability and osteogenic differentiation of human adipose-derived mesenchymal stem cells (ADMSCs) cultured on the scaffolds were assessed. Finally, the efficacy of the released ciprofloxacin to enter the cells and abate intracellularly located S. aureus was evaluated. All the groups of CGHA scaffolds displayed sustained release of ciprofloxacin against S. aureus for 60 days above the minimum inhibitory concentration for the target species with zero-order kinetics and Korsmeyer-Peppas models. While comparing, the released antibiotic from CGHA5 scaffolds was found to be effective at reducing S. aureus through the study period, without detrimental effects on human ADMSC viability or osteogenic potential. When stem cells internalized with S. aureus were cultured onto the drug-loaded scaffolds, a significant reduction in the colony count of internalized bacteria was observed, resulting in the osteogenic differentiation capability of those cells. Our results clearly demonstrate that the ciprofloxacin incorporated gelatin-HAP scaffolds, which were cytocompatible and could target both intracellular and extracellular S. aureus, defining its potential to be used as local drug delivery system. © Copyright 2015, Mary Ann Liebert, Inc. 2015.

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2015

Journal Article

A. Mohandas, Nimal, T. R., Das, V., Dr. Sahadev Shankarappa, Dr. Raja Biswas, and Dr. Jayakumar Rangasamy, “Drug loaded bi-layered sponge for wound management in hyperfibrinolytic conditions”, Journal of Materials Chemistry B, vol. 3, pp. 5795-5805, 2015.[Abstract]


Excessive bleeding due to premature clot lysis and secondary bacterial wound infection are two significant problems that contribute to increased morbidity in patients with hyperfibrinolytic conditions. In this study, we have developed a bi-layered sponge that promotes fibrin clot stability and prevents secondary bacterial wound infections. Using the technique of freeze-drying, a bi-layer matrix consisting of hyaluronic acid (HA) containing aminocaproic acid (amicar) and chitosan containing tetracycline loaded O-carboxymethyl chitosan nanoparticles (Tet-O-CMC NPs) were produced. We hypothesized that the top chitosan layer with Tet-O-CMC NPs will prevent wound infection and concomitantly act as a matrix for cellular migration and subsequent wound healing, while the amicar-containing layer would promote clot stability. Tet-O-CMC NPs and bi-layer sponges were characterized using Dynamic Light Scattering (DLS), Scanning Electron Microscopy (SEM) and Fourier Transform Infra Red (FT-IR) spectroscopy. Physiochemical characterization such as porosity, swelling and mechanical testing was performed. The drug release study shows that the bi-layered sponge demonstrates a robust burst release of amicar and a sustained release of tetracycline. The ex vivo muscle permeation study indicated that Tet-O-CMC NPs have enhanced tissue permeation compared to free Tet. In vitro antibacterial activity of the bi-layer sponge towards laboratory and clinical strains of Staphylococcus aureus and Escherichia coli was proved. The ex vivo bacterial sensitivity study using porcine muscles confirmed the antibacterial activity, while the cell viability study using human dermal fibroblast (HDF) cells revealed its biocompatible nature. The in vitro antifibrinolytic study shows that the bi-layered sponge with amicar showed significant protection against streptokinase induced clot lysis. These studies suggest that the prepared amicar and tetracycline loaded chitosan-HA bi-layered sponge can be used effectively to promote better wound healing by simultaneously preventing bacterial infection, and enhancing clot stability. This journal is © The Royal Society of Chemistry 2015.

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2015

Journal Article

V. Kiruthika, Maya, S., Suresh, M. K., V. Kumar, A., Jayakumar, R., and Dr. Raja Biswas, “Comparative Efficacy of cChloramphenicol Loaded Chondroitin Sulfate and Dextran Sulfate Nanoparticles to Treat Intracellular Salmonella Infections”, Colloids and Surfaces B: Biointerfaces, vol. 127, pp. 33-40, 2015.[Abstract]


Salmonella Paratyphi A is a food-borne Gram-negative pathogen and a major public health challenge in the developing world. Upon reaching the intestine, S. Paratyphi A penetrates the intestinal epithelial barrier; and infects phagocytes such as macrophages and dendritic cells. S. Paratyphi A surviving within macrophages is protected from the lethal action of antibiotics due to their poor penetration into the intracellular compartments. Hence we have developed chloramphenicol loaded chondroitin sulfate (CS-Cm Nps) and dextran sulfate (DS-Cm Nps) nanoparticles through ionotropic-gelation method for the intracellular delivery of chloramphenicol. The size of these nanoparticles ranged between 100 and 200. nm in diameter. The encapsulation efficiency of both the nanoparticles was found to be around 65%. Both the nanoparticles are found to be non-hemolytic and non-toxic to fibroblast and epithelial cells. The prepared nanoparticles exhibited sustained release of the drug of up to 40% at pH 5 and 20-25% at pH 7.0 after 168 h. The anti-microbial activities of both nanoparticles were tested under in vitro and ex vivo conditions. The delivery of DS-Cm Nps into the intracellular compartments of the macrophages was 4 fold more compared to the CS-Cm Nps which lead to the enhanced intracellular antimicrobial activity of Ds-Cm Nps. Enhanced anti-microbial activity of Ds-Cm Nps was further confirmed in an ex vivo chicken intestine infection model. Our results showed that Cm loaded DS Nps can be used to treat intracellular Salmonella infections. © 2015 Elsevier B.V.

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2015

Journal Article

K. T. Smitha, Nisha, N., Maya, S., Dr. Raja Biswas, and Dr. Jayakumar Rangasamy, “Delivery of rifampicin-chitin nanoparticles into the intracellular compartment of polymorphonuclear leukocytes”, International Journal of Biological Macromolecules, vol. 74, pp. 36 - 43, 2015.[Abstract]


Abstract Polymorphonuclear leukocytes (PMNs) provide the primary host defence against invading pathogens by producing reactive oxygen species (ROS) and microbicidal products. However, few pathogens can survive for a prolonged period of time within the PMNs. Additionally their intracellular lifestyle within the \{PMNs\} protect themselves from the additional lethal action of host immune systems such as antibodies and complements. Antibiotic delivery into the intracellular compartments of \{PMNs\} is a major challenge in the field of infectious diseases. In order to deliver antibiotics within the \{PMNs\} and for the better treatment of intracellular bacterial infections we synthesized rifampicin (RIF) loaded amorphous chitin nanoparticles (RIF-ACNPs) of 350 ± 50 nm in diameter. RIF-ACNPs nanoparticles are found to be non-hemolytic and non-toxic against a variety of host cells. The release of rifampicin from the prepared nanoparticles was ∼60% in 24 h, followed by a sustained pattern till 72 h. The RIF-ACNPs nanoparticles showed 5–6 fold enhanced delivery of \{RIF\} into the intracellular compartments of PMNs. The RIF-ACNPs showed anti-microbial activity against Escherichia coli, Staphylococcus aureus and a variety of other bacteria. In summary, our results suggest that RIF-ACNPs could be used to treat a variety of intracellular bacterial infections. More »»

2015

Journal Article

A. C. Pushkaran, Nataraj, N., Nair, N., Götz, F., Dr. Raja Biswas, and Dr. Gopi Mohan C., “Understanding the Structure–Function Relationship of Lysozyme Resistance in Staphylococcus aureus by Peptidoglycan O-Acetylation Using Molecular Docking, Dynamics, and Lysis Assay”, Journal of Chemical Information and Modeling, vol. 55, pp. 760-770, 2015.[Abstract]


Lysozyme is an important component of the host innate defense system. It cleaves the β-1,4 glycosidic bonds between N-acetylmuramic acid and N-acetylglucosamine of bacterial peptidoglycan and induce bacterial lysis. Staphylococcus aureus (S. aureus), an opportunistic commensal pathogen, is highly resistant to lysozyme, because of the O-acetylation of peptidoglycan by O-acetyl transferase (oatA). To understand the structure–function relationship of lysozyme resistance in S. aureus by peptidoglycan O-acetylation, we adapted an integrated approach to (i) understand the effect of lysozyme on the growth of S. aureus parental and the oatA mutant strain, (ii) study the lysozyme induced lysis of exponentially grown and stationary phase of both the S. aureus parental and oatA mutant strain, (iii) investigate the dynamic interaction mechanism between normal (de-O-acetylated) and O-acetylated peptidoglycan substrate in complex with lysozyme using molecular docking and molecular dynamics simulations, and (iv) quantify lysozyme resistance of S. aureus parental and the oatA mutant in different human biological fluids. The results indicated for the first time that the active site cleft of lysozyme binding with O-acetylated peptidoglycan in S. aureus was sterically hindered and the structural stability was higher for the lysozyme in complex with normal peptidoglycan. This could have conferred reduced survival of the S. aureus oatA mutant in different human biological fluids. Consistent with this computational analysis, the experimental data confirmed decrease in the growth, lysozyme induced lysis, and lysozyme resistance, due to peptidoglycan O-acetylation in S. aureus.

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2014

Journal Article

B. M. Alphonsa, Kumar, P. T. Sudheesh, Praveen, G., Dr. Raja Biswas, Chennazhi, K. P., and Dr. Jayakumar Rangasamy, “Antimicrobial drugs encapsulated in fibrin nanoparticles for treating microbial infested wounds”, Pharmaceutical Research, vol. 31, pp. 1338-1351, 2014.[Abstract]


Purpose: In vitro evaluation of antibacterial and antifungal drugs encapsulated fibrin nanoparticles to prove their potential prospect of using these nanocomponent for effective treatment of microbial infested wounds. Methods: Surfactant-free oil-in-water emulsification-diffusion method was adopted to encapsulate 1 mg/ml each of antimicrobial drugs (Ciprofloxacin and Fluconazole) in 4 ml of aqueous fibrinogen suspension and subsequent thrombin mediated cross linking to synthesize drug loaded fibrin nanoparticles. Results: Ciprofloxacin loaded fibrin nanoparticles (CFNPs) showed size range of 253∈±∈6 nm whereas that of Fluconazole loaded fibrin nanoparticles (FFNPs) was 260∈±∈10 nm. Physico chemical characterizations revealed the firm integration of antimicrobial drugs within fibrin nanoparticles. Drug release studies performed at physiological pH 7.4 showed a release of 16% ciprofloxacin and 8% of fluconazole while as the release of ciprofloxacin at alkaline pH 8.5, was 48% and that of fluconazole was 37%. The antimicrobial activity evaluations of both drug loaded systems independently showed good antibacterial activity against Escherichia coli (E.coli), Staphylococcus aureus (S. aureus) and antifungal activity against Candida albicans (C. albicans). The in vitro toxicity of the prepared drug loaded nanoparticles were further analyzed using Human dermal fibroblast cells (HDF) and showed adequate cell viability. Conclusion: The efficacies of both CFNPs and FFNPs for sustained delivery of encapsulated anti microbial drugs were evaluated in vitro suggesting its potential use for treating microbial infested wounds (diabetic foot ulcer). © 2013 Springer Science+Business Media New York.

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2014

Journal Article

T. Ra Arunraj, Rejinold, N. Sa, Mangalathillam, Sb, Saroj, Sb, Dr. Raja Biswas, Jayakumar, Ra, and Dr. Sabitha M., “Synthesis, characterization and biological activities of curcumin nanospheres”, Journal of Biomedical Nanotechnology, vol. 10, pp. 238-250, 2014.[Abstract]


Curcumin is one of the most versatile compounds obtained from Curcuma longa. The major obstacle in the therapeutic use of curcumin is its aqueous solubility. To enhance its aqueous solubility and biological activities, we prepared curcumin nanospheres (CNSs) by wet milling-solvent evaporation technique without any surfactants. In this study, we have focused on the synthesis, characterization and biological effects of CNSs. DLS and SEM analyses showed 50-80 nm spherical shaped CNSs with a zeta potential of -31.65 mV. FTIR revealed that there were no structural changes to CNSs. Antibacterial and antifungal studies proved that CNSs were much more effective than curcumin against Escherichia coli, Staphylococcus aureus and Candida albicans. Antioxidant activity of CNSs showed promising result for therapeutic applications. The in vitro anti-inflammatory studies proved that CNSs possessed enhanced anti-inflammatory effect against protein denaturation. Cytotoxicity and uptake of CNSs showed more toxicity on cancer cells (T47D, MG63, A375) sparing normal HDF and IEC cell lines. Skin permeation studies showed CNSs retained at different layers of pig skin. These results give clear evidence for their use against microbial and fungal skin infections as well as cancer treatment. Copyright © 2014 American Scientific Publishers All rights reserved.

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2014

Journal Article

S. N. Reddy, Sowmya, S., Bumgardner, J. D., Chennazhi, K. P., Dr. Raja Biswas, and Jayakumar, R., “Tetracycline nanoparticles loaded calcium sulfate composite beads for periodontal management”, Biochimica et Biophysica Acta - General Subjects, vol. 1840, pp. 2080-2090, 2014.[Abstract]


Background

The objective of this study was to fabricate, characterize and evaluate in vitro, an injectable calcium sulfate bone cement beads loaded with an antibiotic nanoformulation, capable of delivering antibiotic locally for the treatment of periodontal disease.

Methods

Tetracycline nanoparticles (Tet NPs) were prepared using an ionic gelation method and characterized using DLS, SEM, and FTIR to determine size, morphology, stability and chemical interaction of the drug with the polymer. Further, calcium sulfate (CaSO4) control and CaSO4-Tet NP composite beads were prepared and characterized using SEM, FTIR and XRD. The drug release pattern, material properties and antibacterial activity were evaluated. In addition, protein adsorption, cytocompatibility and alkaline phosphatase activity of the CaSO4-Tet NP composite beads in comparison to the CaSO4control were analyzed.

Results

Tet NPs showed a size range of 130 ± 20 nm and the entrapment efficiency calculated was 89%. The composite beads showed sustained drug release pattern. Further the drug release data was fitted into various kinetic models wherein the Higuchi model showed higher correlation value (R2 = 0.9279) as compared to other kinetic models. The composite beads showed antibacterial activity against Staphylococcus aureus and Escherichia coli. The presence of Tet NPs in the composite bead didn't alter its cytocompatibility. In addition, the composite beads enhanced the ALP activity of hPDL cells.

Conclusions

The antibacterial and cytocompatible CaSO4-Tet NP composite beads could be beneficial in periodontal management to reduce the bacterial load at the infection site.

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2014

Journal Article

N. Nataraj, Anjusree, G. S., Madhavan, A. A., Priyanka, P., Sankar, D., Nisha, N., Lakshmi, S. V., Jayakumar, R., Balakrishnan, A., and Dr. Raja Biswas, “Synthesis and anti-staphylococcal activity of TiO2 nanoparticles and nanowires in ex vivo porcine skin model”, Journal of Biomedical Nanotechnology, vol. 10, pp. 864-870, 2014.

2014

Journal Article

S. N Rejinold, Dr. Raja Biswas, Chellan, G., and Jayakumar, R., “Multifaceted chitin/poly (lactic-co-glycolic) acid composite nanogels”, International journal of biological macromolecules, vol. 67, pp. 279–288, 2014.[Abstract]


Cyto-compatible, 80 nm sized chitin/PLGA composite nanogels (chit/PLGA-comp NGs) were prepared by regeneration method and characterized. The multifaceted chit/PLGA-comp NGs were surface modified with Au, Fe3O4, CdTe/ZnTe-QDs and umbelliferone, respectively. 185 nm sized Au-chit/PLGA-comp NGs, 170 nm sized QD-chit/PLGA-comp-NGs and 160 nm sized Fe3O4-chit/PLGA-comp-NGs showed RF heating. The QD-chit/PLGA-comp-NGs and 180 nm sized umb-chit/PLGA-comp-NGs were well uptaken by Escherichia coli, Staphylococcus aureus and Candida albicans. The chit/PLGA-comp NGs could be useful for microbial monitoring and RF application for cancer therapy. The preliminary data showed that multifaceted chit/PLGA-comp-NGs could be useful for hyperthermia for cancer treatment and microbial labelling and imaging. More »»

2014

Journal Article

K. T. Smitha, Sreelakshmi, M., Nisha, N., Jayakumar, R., and Dr. Raja Biswas, “Amidase encapsulated O-carboxymethyl chitosan nanoparticles for vaccine delivery”, International Journal of Biological Macromolecules, vol. 63, pp. 154-157, 2014.[Abstract]


This work reports the development of amidase encapsulated O-carboxymethyl chitosan nanoparticles (Ami-O-CMC NPs) of 300 ± 50 nm size by ionic cross-linking method. The prepared Ami-O-CMC NPs had an encapsulation efficiency of 55.39%. Haemolysis assay and cytotoxicity studies proved the hemocompatibility and cytocompatibility of the prepared NPs. The sustained release of Ami from the NPs is expected to prolong its immunogenicity and in turn lead to development of better protective immunity against Staphylococcus aureus infections. More »»

2014

Journal Article

A. Kumar, Sreehari, S., Velayudhan, K., Biswas, L., Babu, R., Ahmed, S., Sharma, N., Kurupath, V. P., Jojo, A., Dinesh, K. R., and Dr. Raja Biswas, “Autochthonous Blastomycosis of the Adrenal: First Case Report from Asia”, The American journal of tropical medicine and hygiene, vol. 90, pp. 735–739, 2014.[Abstract]


Systemic endemic mycoses, such as blastomycosis, are rare in Asia and have been reported as health risks among travelers who visit or reside in an endemic area. Adrenal involvement is rarely seen in blastomycosis and has never been reported from Asia. We report the first case of blastomycosis with bilateral involvement of the adrenals in a diabetic patient residing in the state of Arunachal Pradesh, India. More »»

2014

Journal Article

N. Nair, Dr. Raja Biswas, Götz, F., and Biswas, L., “Impact of Staphylococcus aureus on pathogenesis in polymicrobial infections”, Infection and immunity, vol. 82, pp. 2162–2169, 2014.[Abstract]


Polymicrobial infections involving Staphylococcus aureus exhibit enhanced disease severity and morbidity. We reviewed the nature of polymicrobial interactions between S. aureus and other bacterial, fungal, and viral cocolonizers. Microbes that were frequently recovered from the infection site with S. aureus are Haemophilus influenzae, Enterococcus faecalis, Pseudomonas aeruginosa, Streptococcus pneumoniae, Corynebacterium sp., Lactobacillus sp., Candida albicans, and influenza virus. Detailed analyses of several in vitro and in vivo observations demonstrate that S. aureus exhibits cooperative relations with C. albicans, E. faecalis, H. influenzae, and influenza virus and competitive relations with P. aeruginosa, Streptococcus pneumoniae, Lactobacillus sp., and Corynebacterium sp. Interactions of both types influence changes in S. aureus that alter its characteristics in terms of colony formation, protein expression, pathogenicity, and antibiotic susceptibility. More »»

2014

Journal Article

V. Sukhithasri, Vinod, V., Varma, S., and Dr. Raja Biswas, “Mycobacterium tuberculosis treatment modalities and recent insights”, Current drug delivery, vol. 11, pp. 744–752, 2014.[Abstract]


Antimicrobial therapy of infections caused by M. tuberculosis is a challenge due to poor response to therapy and recurrent infections. Under in vitro conditions, antibiotics effectively kill M. tuberculosis within the first two weeks. However, an extended treatment time of 6-9 months is required to eradicate M. tuberculosis infection, mainly due to the intracellular survival of this pathogen and poor penetration of the antibiotics into the intracellular compartment of the host cells. Recent advances in the field of drug delivery have led to the use of different antibiotic incorporated nano- and micro- formulations such as liposomes, polymeric particles, mesoporous silica particles and particulate suspensions for targeted drug delivery applications into the intracellular compartment of the macrophages. The drug incorporated nano- and micro-particles are prone to be easily internalized, which leads to preferential delivery of the drugs into the tissues and organs of interest. Other advantages of these nano- and micro-particles over the free drugs are their comparatively higher stability and bioavailability. This review highlights the current strategies and challenges in treatment, the different antibiotics available, their modes of action, generation and mechanism of drug resistance and recent advances in the intracellular drug delivery using nanoparticles for the treatment of tuberculosis. More »»

2014

Journal Article

N. Nair, Dr. Raja Biswas, Götz, F., and Biswas, L., “Staphylococcus aureus in polymicrobial infections: impact on pathogenesis”, Infection and Immunity, p. IAI–00059, 2014.[Abstract]


Polymicrobial infections involving S. aureus exhibit enhanced disease severity and morbidity. We reviewed the nature of polymicrobial interactions between S. aureus and other bacterial, fungal and viral co-colonizers. Microbes that were frequently recovered from the infection site with S. aureus are Haemophilus influenzae, Enterococcus faecalis, P. aeruginosa, S. pneumoniae, Corynebacterium sp, Lactobacillus sp, Candida albicans and influenza virus. Detailed analysis of several in vitro and in vivo observations demonstrate that S. aureus exhibits cooperative relations with C. albicans, E. faecalis, H. influenzae and influenza virus and competitive relations with P. aeruginosa, Streptococcus pneumoniae, Lactobacillus sp, and Corynebacterium sp. Both of these interactions influence changes in S. aureus that alter its characteristics in terms of colony formation, protein expressions, pathogenicity and antibiotic susceptibility. More »»

2013

Journal Article

B. M. Alphonsa, Kumar, P. T. Sudheesh, Praveen, G., Dr. Raja Biswas, Chennazhi, K. P., and Dr. Jayakumar Rangasamy, “Antimicrobial Drugs Encapsulated in Fibrin Nanoparticles for Treating Microbial Infested Wounds”, Pharmaceutical Research, pp. 1-14, 2013.[Abstract]


Purpose: In vitro evaluation of antibacterial and antifungal drugs encapsulated fibrin nanoparticles to prove their potential prospect of using these nanocomponent for effective treatment of microbial infested wounds. Methods: Surfactant-free oil-in-water emulsification-diffusion method was adopted to encapsulate 1 mg/ml each of antimicrobial drugs (Ciprofloxacin and Fluconazole) in 4 ml of aqueous fibrinogen suspension and subsequent thrombin mediated cross linking to synthesize drug loaded fibrin nanoparticles. Results: Ciprofloxacin loaded fibrin nanoparticles (CFNPs) showed size range of 253 ± 6 nm whereas that of Fluconazole loaded fibrin nanoparticles (FFNPs) was 260 ± 10 nm. Physico chemical characterizations revealed the firm integration of antimicrobial drugs within fibrin nanoparticles. Drug release studies performed at physiological pH 7.4 showed a release of 16% ciprofloxacin and 8% of fluconazole while as the release of ciprofloxacin at alkaline pH 8.5, was 48% and that of fluconazole was 37%. The antimicrobial activity evaluations of both drug loaded systems independently showed good antibacterial activity against Escherichia coli (E.coli), Staphylococcus aureus (S. aureus) and antifungal activity against Candida albicans (C. albicans). The in vitro toxicity of the prepared drug loaded nanoparticles were further analyzed using Human dermal fibroblast cells (HDF) and showed adequate cell viability. Conclusion: The efficacies of both CFNPs and FFNPs for sustained delivery of encapsulated anti microbial drugs were evaluated in vitro suggesting its potential use for treating microbial infested wounds (diabetic foot ulcer). © 2013 Springer Science+Business Media New York.

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2013

Journal Article

B. S. Anisha, Dr. Raja Biswas, Chennazhi, K. P., and Dr. Jayakumar Rangasamy, “Chitosan-hyaluronic acid/nano silver composite sponges for drug resistant bacteria infected diabetic wounds”, International Journal of Biological Macromolecules, vol. 62, pp. 310-320, 2013.[Abstract]


The aim of this work was to develop an antimicrobial sponge composed of chitosan, hyaluronic acid (HA) and nano silver (nAg) as a wound dressing for diabetic foot ulcers (DFU) infected with drug resistant bacteria. nAg (5-20. nm) was prepared and characterized. The nanocomposite sponges were prepared by homogenous mixing of chitosan, HA and nAg followed by freeze drying to obtain a flexible and porous structure. The prepared sponges were characterized using SEM and FT-IR. The porosity, swelling, biodegradation and haemostatic potential of the sponges were also studied. Antibacterial activity of the prepared sponges was analysed using Escherichia coli, Staphylococcus aureus, methicillin-resistant Staphylococcus aureus (MRSA), Pseudomonas aeruginosa and Klebsiella pneumonia. Chitosan-HA/nAg composite sponges showed potent antimicrobial property against the tested organisms. Sponges containing higher nAg (0.005%, 0.01% and 0.02%) concentrations showed antibacterial activity against MRSA. Cytotoxicity and cell attachment studies were done using human dermal fibroblast cells. The nanocomposite sponges showed a nAg concentration dependent toxicity towards fibroblast cells. Our results suggest that this nanocomposite sponges could be used as a potential material for wound dressing for DFU infected with antibiotic resistant bacteria if the optimal concentration of nAg exhibiting antibacterial action with least toxicity towards mammalian cells is identified. © 2013 Elsevier B.V.

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2013

Journal Article

A. N. Kumar, N. Rejinold, S., Anjali, P., Balakrishnan, A., Dr. Raja Biswas, and Dr. Jayakumar Rangasamy, “Preparation of chitin nanogels containing nickel nanoparticles”, Carbohydrate Polymers, vol. 97, pp. 469-474, 2013.[Abstract]


In this work, we developed 120-150 nm sized nickel nanoparticles loaded chitin nanogels (Ni-Chitin NGs) by regeneration chemistry approach to investigate and determine its cytocompatibility and antibacterial activity against Staphylococcus aureus. The nickel nanoparticles were prepared by hydrothermal method. The prepared Ni-Chitin NGs were well characterized by SEM, FTIR, TG/DTA/DTG and XRD and the in vitro cytocompatibility was tested on A549 and L929 cells which showed that they are completely non-toxic. Ni-Chitin NGs showed better toxicity to the bacterial strains when compared to previous study with other nanoparticles using serial dilution method. The rhodamine labeled-Ni-Chitin NGs showed cellular localization on both L929 and A549 cells without perturbing their cellular constituents. These studies showed that the Ni-Chitin NGs could be used for various applications in biomedical filed. © 2013 Elsevier Ltd. All rights reserved. More »»

2013

Journal Article

Va Sukhithasri, Nisha, Na, Dr. Lalitha Biswas, Kumar, VbAnil, and Dr. Raja Biswas, “Innate immune recognition of microbial cell wall components and microbial strategies to evade such recognitions”, Microbiological Research, vol. 168, pp. 396-406, 2013.[Abstract]


The innate immune system constitutes the first line of defence against invading microbes. The basis of this defence resides in the recognition of defined structural motifs of the microbes called "Microbial associated molecular patterns" that are absent in the host. Cell wall, the outer layer of both bacterial and fungal cells, a unique structure that is absent in the host and is recognized by the germ line encoded host receptors. Nucleotide oligomerization domain proteins, peptidoglycan recognition proteins and C-type lectins are host receptors that are involved in the recognition of bacterial cell wall (usually called peptidoglycan), whereas fungal cell wall components (N- and O-linked mannans, β-glucans etc.) are recognized by host receptors like C-type lectins (Dectin-1, Dectin-2, mannose receptor, DC-SIGN), Toll like receptors-2 and -4 (TLR-2 and TLR-4). These recognitions lead to activation of a variety of host signaling cascades and ultimate production of anti-microbial compounds including phospholipase A2, antimicrobial peptides, lysozyme, reactive oxygen and nitrogen species. These molecules act in cohort against the invading microbes to eradicate infections. Additionally pathogen recognition leads to the production of cytokines, which further activate the adaptive immune system. Both pathogenic and commensal bacteria and fungus use numerous strategies to subvert the host defence. These strategies include bacterial peptidoglycan glycan backbone modifications by O-acetylation, N-deacetylation, N-glycolylation and stem peptide modifications by amidation of meso-Diaminopimelic acid; fungal cell wall modifications by shielding the β-glucan layer with mannoproteins and α-1,3 glucan. This review focuses on the recent advances in understanding the role of bacterial and fungal cell wall in their innate immune recognition and evasion strategies. © 2013 Elsevier GmbH.

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2013

Journal Article

S. Sivasundar, Oommen, A. T., Prakash, O., Baskaran, S., Dr. Raja Biswas, Nair, S., Mohan, C. G., and Biswas, L., “Molecular defect of 'Prothrombin Amrita': Substitution of arginine by glutamine (Arg553 to Gln) near the Na+ binding loop of prothrombin”, Blood Cells, Molecules, and Diseases, vol. 50, pp. 182-183, 2013.[Abstract]


Prothrombin, the precursor to thrombin, is a serine protease that plays a key role in hemostasis and thrombosis. Several studies have reported mutations resulting from the deletion, substitution, or insertion of a single nucleotide in the prothrombin gene that lead to hypoprothrombinemia, dysprothrombinemia, or thrombosis [1]. One of the most common genetic variations predisposing to deep venous thrombosis is a polymorphism in the factor V gene (Arg506Gln) resulting in the factor V Leiden mutation. Transition of guanine to adenine at nucleotide position 20210 in the 3′ untranslated region of the prothrombin gene is the second most common genetic risk factor for venous thrombosis, which we diagnose in approximately 50 patients annually in Amrita hospital. Several other mutations in the prothrombin gene that are associated with the thrombosis have been reported. The eponym of some of the prothrombin point mutations identified globally are — Padua (Arg271 to His), Corpus Christi (Arg382 to Cys), Obhiro (Arg271 to Cys), Barcelona (Arg273 to Cys), San Antonio (Arg320 to His), Himi (Met337 to Thr and Arg388 to His), Denver (Arg457 to Gln), Dhahran (Arg271 to His), Clamart (Arg320 to Ile), Segovia (Gly319 to Arg), Vellore 1 (Ala362 to Thr), Perijaá (Gly548 to Ala), Himi (Arg388 to His and Met337 to Thr), Habana, Poissy, Houston, Salakta, Thrombin Greenvillae (Arg517 to Gln), etc.

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2013

Journal Article

P. TaSudheesh Kumar, Lakshmanan, V. - Ka, Raj, Ma, Dr. Raja Biswas, Hiroshi, Tb, Nair, S. Va, and Jayakumar, Ra, “Evaluation of wound healing potential of β-chitin hydrogel/nano zinc oxide composite bandage”, Pharmaceutical Research, vol. 30, pp. 523-537, 2013.[Abstract]


Purpose: β-chitin hydrogel/nZnO composite bandage was fabricated and evaluated in detail as an alternative to existing bandages. Methods: β-chitin hydrogel was synthesized by dissolving β-chitin powder in Methanol/CaCl2 solvent, followed by the addition of distilled water. ZnO nanoparticles were added to the β-chitin hydrogel and stirred for homogenized distribution. The resultant slurry was frozen at 0 C for 12 h. The frozen samples were lyophilized for 24 h to obtain porous composite bandages. Results: The bandages showed controlled swelling and degradation. The composite bandages showed blood clotting ability as well as platelet activation, which was higher when compared to the control. The antibacterial activity of the bandages were proven against Staphylococcus aureus (S. aureus) and Escherichia coli (E.coli). Cytocompatibility of the composite bandages were assessed using human dermal fibroblast cells (HDF) and these cells on the composite bandages were viable similar to the Kaltostat control bandages and bare β-chitin hydrogel based bandages. The viability was reduced to 50-60% in bandages with higher concentration of zinc oxide nanoparticles (nZnO) and showed 80-90% viability with lower concentration of nZnO. In vivo evaluation in Sprague Dawley rats (S.D. rats) showed faster healing and higher collagen deposition ability of composite bandages when compared to the control. Conclusions: The prepared bandages can be used on various types of infected wounds with large volume of exudates. © 2012 Springer Science+Business Media New York.

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2013

Journal Article

Na Mohammed, Rejinold, NaSanoj, Mangalathillam, Sb, Dr. Raja Biswas, Nair, S. Va, Jayakumar, Ra, and Dr. Sabitha M., “Fluconazole loaded chitin nanogels as a topical ocular drug delivery agent for corneal fungal infections”, Journal of Biomedical Nanotechnology, vol. 9, pp. 1521-1531, 2013.[Abstract]


Poor bioavailability of antifungal drugs due to the various protective mechanisms of the eye is a serious concern for the treatment of corneal fungal infections in today's world. The use of nanosystems that can improve the bioavailability of these antifungal drugs is relatively a new idea being conceived and here we have synthesized fluconazole loaded chitin nanogels (Flu-CNGs) which can be used for the treatment of corneal fungal infections. These nanogels were characterized using DLS, Zeta potential, SEM, FTIR and TG/DTA. The prepared Flu-CNGs have controlled release pattern which is ideal for the continuous availability of fluconazole over a longer period of time for an effective fungal treatment. Flu- CNGs are haemocompatible, cytocompatible and also showed very good cell uptake in human dermal fibroblast cells and penetration to the deeper sections of the porcine cornea with no signs of destruction or inflammation to corneal cells as shown in ex vivo permeation studies. Copyright © 2013 American Scientific Publishers All rights reserved.

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2013

Journal Article

V. Aa Kumar, Steffy, Ka, Chatterjee, Mb, Sugumar, Mc, Dinesh, K. Ra, Manoharan, Ac, Karim, Sa, and Dr. Raja Biswas, “Detection of oxacillin-susceptible mecA-positive Staphylococcus aureus isolates by use of chromogenic medium MRSA ID”, Journal of Clinical Microbiology, vol. 51, pp. 318-319, 2013.[Abstract]


Reports of oxacillin-susceptible mecA-positive Staphylococcus aureus strains are on the rise. Because of their susceptibility to oxacillin and cefoxitin, it is very difficult to detect them by using routine phenotypic methods. We describe two such isolates that were detected by chromogenic medium and confirmed by characterization of the mecA gene element. Copyright © 2013, American Society for Microbiology. All Rights Reserved.

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2013

Journal Article

V. Anil Kumar, Nair, N., Thachathodiyl, R., Nandakumar, A., Dinesh, K. R., Thatcher, E., Karim, S., and Dr. Raja Biswas, “Molecular characterization of methicillin-resistant staphylococcus aureus causing fatal purulent pericarditis”, Journal of laboratory physicians, vol. 5, p. 136, 2013.[Abstract]


Though pericardial disease is common in patients with renal disease, purulent pericarditis is very rare. We report a fatal case of purulent pericarditis and sepsis due to methicillin-resistant Staphylococcus aureus in a 78-year-old male with systemic hypertension and renal disease along with the molecular characterization of its resistant mechanism. More »»

2012

Journal Article

P. T. S. Kumar, Lakshmanan, V. - K., Dr. Raja Biswas, Nair, S. V., and Dr. Jayakumar Rangasamy, “Synthesis and biological evaluation of chitin hydrogel/nano ZnO composite bandage as antibacterial wound dressing”, Journal of Biomedical Nanotechnology, vol. 8, pp. 891-900, 2012.[Abstract]


We developed chitin hydrogel/nano ZnO composite bandages using chitin hydrogel and ZnO nanoparticles (nZnO). The homogenized mixture of chitin hydrogel and nZnO was freeze-dried to obtain micro-porous composite bandages. The prepared nanocomposite bandages were characterized using FT-IR, XRD and SEM. In addition, blood clotting, antibacterial, swelling, cytocompatibility and cell attachment capability of the prepared nanocomposite bandages were evaluated. The nanocomposite bandages showed enhanced swelling, blood clotting and antibacterial activity. The incorporation of nZnO helped to attain antibacterial activity. Cytocompatibility studies were carried out using human dermal fibroblast (HDF) cells proved the non-toxic nature of the composite bandages. HDF cell attachment and infiltration analysis showed that the cells were attached and penetrated into the interior (250μm) of the nanocomposite bandages. These studies revealed that, this nanocomposite can be used for burn, diabetic and chronic wound defects. Copyright © 2012 American Scientific Publishers All rights reserved.

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2012

Journal Article

S. Maya, Indulekha, S., Sukhithasri, V., Smitha, K. T., Nair, S. V., Dr. Jayakumar Rangasamy, and Dr. Raja Biswas, “Efficacy of tetracycline encapsulated O-carboxymethyl chitosan nanoparticles against intracellular infections of Staphylococcus aureus”, International Journal of Biological Macromolecules, vol. 51, pp. 392-399, 2012.[Abstract]


Intracellular bacterial infections are recurrent, persistent and are difficult to treat because of poor penetration and limited availability of antibiotics within macrophages and epithelial cells. We developed biocompatible, 200. nm sized tetracycline encapsulated O-carboxymethyl chitosan nanoparticles (Tet-O-CMC Nps) via ionic gelation for its sustained delivery of Tet into cells. S. aureus binds and aggregates with Tet-O-CMC Nps increasing drug concentrations at the infection site. Tet-O-CMC Nps were sixfold more effective in killing intracellular S. aureus compared to Tet alone in HEK-293 and differentiated THP1 macrophage cells proving it to be an efficient nanomedicine to treat intracellular S. aureus infections. © 2012 Elsevier B.V.

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2012

Journal Article

Dr. Raja Biswas, Martinez, R. E., Göhring, N., Schlag, M., Josten, M., Xia, G., Hegler, F., Gekeler, C., Gleske, A. - K., Götz, F., and , “Proton-binding capacity of Staphylococcus aureus wall teichoic acid and its role in controlling autolysin activity”, PloS one, vol. 7, p. e41415, 2012.[Abstract]


Wall teichoic acid (WTA) or related polyanionic cell wall glycopolymers are produced by most Gram-positive bacterial species and have been implicated in various cellular functions. WTA and the proton gradient across bacterial membranes are known to control the activity of autolysins but the molecular details of these interactions are poorly understood. We demonstrate that WTA contributes substantially to the proton-binding capacity of Staphylococcus aureus cell walls and controls autolysis largely via the major autolysin AtlA whose activity is known to decline at acidic pH values. Compounds that increase or decrease the activity of the respiratory chain, a main source of protons in the cell wall, modulated autolysis rates in WTA-producing cells but did not affect the augmented autolytic activity observed in a WTA-deficient mutant. We propose that WTA represents a cation-exchanger like mesh in the Gram-positive cell envelopes that is required for creating a locally acidified milieu to govern the pH-dependent activity of autolysins. More »»

2010

Journal Article

P. Varma, Dinesh, K. R., Menon, K. K., and Dr. Raja Biswas, “Lactobacillus Fermentum Isolated from Human Colonic Mucosal Biopsy Inhibits the Growth and Adhesion of Enteric and Foodborne Pathogens”, Journal of Food Science, vol. 75, pp. M546-M551, 2010.[Abstract]


Abstract: A number of Lactobacillus species are used as probiotic strains in order to benefit health. We have isolated L. fermentum from human colonic mucosal biopsy samples that possess antimicrobial activities against entroinvasive and foodborne pathogens such as Escherichia coli, Salmonella paratyphi A, Shigella sonnei, Staphylococcus aureus, Enterococcus faecalis, Proteus mirabilis, Pseudomonas aeruginosa, and Vibrio sp. In addition to lactic acid, L. fermentum secretes antimicrobial proteinacious compound(s) that was found to be active even at neutral pH (pH 7.0). The compound was sensitive to heat treatment and trypsin digestion. Lactobacillus fermentum inhibited the adhesion of enteropathogens to intestinal epithelial cells in vitro. Isolated cell surface associated proteins (SAPs) from L. fermentum were sufficient for the adhesion exclusions of enteropathogenic E. coli. Our results indicate that L. fermentum produces antimicrobial compounds and SAPs to inhibit the growth and adhesion of enteropathogens, respectively. © 2010 Institute of Food Technologists®.

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2010

Journal Article

M. Schlag, Dr. Raja Biswas, Krismer, B., Kohler, T., Zoll, S., Yu, W., Schwarz, H., Peschel, A., and Götz, F., “Role of staphylococcal wall teichoic acid in targeting the major autolysin Atl”, Molecular Microbiology, vol. 75, pp. 864–873, 2010.[Abstract]


Staphylococcal cell separation depends largely on the bifunctional autolysin Atl that is processed to amidase-R1,2 and R3-glucosaminidase. These murein hydrolases are targeted via repeat domains (R) to the septal region of the cell surface, thereby allowing localized peptidoglycan hydrolysis and separation of the dividing cells. Here we show that targeting of the amidase repeats is based on an exclusion strategy mediated by wall teichoic acid (WTA). In Staphylococcus aureus wild-type, externally applied repeats (R1,2) or endogenously expressed amidase were localized exclusively at the cross-wall region, while in ΔtagO mutant that lacks WTA binding was evenly distributed on the cell surface, which explains the increased fragility and autolysis susceptibility of the mutant. WTA prevented binding of Atl to the old cell wall but not to the cross-wall region suggesting a lower WTA content. In binding studies with ConcanavalinA-fluorescein (ConA-FITC) conjugate that binds preferentially to teichoic acids, ConA-FITC was bound throughout the cell surface with the exception of the cross wall. ConA binding suggest that either content or polymerization of WTA gradually increases with distance from the cross-wall. By preventing binding of Atl, WTA directs Atl to the cross-wall to perform the last step of cell division, namely separation of the daughter cells. More »»

2010

Journal Article

O. Nasir, Artunc, F., Wang, K., Rexhepaj, R., Foeller, M., Ebrahim, A., Kempe, D. S., Dr. Raja Biswas, Bhandaru, M., Walter, M., and , “Downregulation of mouse intestinal Na+-coupled glucose transporter SGLT1 by Gum Arabic (Acacia senegal)”, Cellular Physiology and Biochemistry, vol. 25, pp. 203–210, 2010.[Abstract]


Intestinal Na+-coupled glucose transporter SGLT1 determines the rate of glucose transport, which in turn influences glucose-induced insulin release and development of obesity. The present study explored effects of Gum Arabic (GA), a dietary polysaccharide from dried exudates of Acacia Senegal, on intestinal glucose transport and body weight in wild-type C57Bl/6 mice. Treatment with GA (100 g/l) in drinking water for four weeks did not affect intestinal SGLT1 transcript levels but decreased SGLT1 protein abundance in jejunal brush border membrane vesicles. Glucose-induced jejunal short-circuit currents revealed that GA treatment decreased electrogenic glucose transport. Drinking a 20% glucose solution for four weeks significantly increased body weight and fasting plasma glucose concentrations, effects significantly blunted by simultaneous treatment with GA. GA further significantly blunted the increase in body weight, fasting plasma glucose and fasting insulin concentrations during high fat diet. In conclusion, the present observations disclose a completely novel effect of gum arabic, i.e. its ability to decrease intestinal SGLT1 expression and activity and thus to counteract glucose-induced obesity. More »»

2010

Journal Article

Dr. Raja Biswas, “Author Index”, Molecular Microbiology, vol. 75, pp. 1592–1596, 2010.

2009

Journal Article

L. Biswas, Dr. Raja Biswas, Schlag, M., Bertram, R., and Götz, F., “Small-colony variant selection as a survival strategy for Staphylococcus aureus in the presence of Pseudomonas aeruginosa”, Applied and environmental microbiology, vol. 75, pp. 6910–6912, 2009.[Abstract]


Previously it has been demonstrated that Staphylococcus aureus is sensitive toward Pseudomonas-secreted exotoxins, which preferentially target the electron transport chain in staphylococci. Here it is shown that a subpopulation of S. aureus survives these respiratory toxins of Pseudomonas aeruginosa by selection of the small-colony variant (SCV) phenotype. Purified pyocyanin alone causes the same effect. A hemB mutant of S. aureus survives cocultivation with P. aeruginosa without a decrease in CFU. More »»

2009

Journal Article

L. Biswas, Dr. Raja Biswas, Nerz, C., Ohlsen, K., Schlag, M., Schäfer, T., Lamkemeyer, T., Ziebandt, A. - K., Hantke, K., Rosenstein, R., and , “Role of the twin-arginine translocation pathway in Staphylococcus”, Journal of bacteriology, vol. 191, pp. 5921–5929, 2009.[Abstract]


In Staphylococcus, the twin-arginine translocation (Tat) pathway is present only in some species and is composed of TatA and TatC. The tatAC operon is associated with the fepABC operon, which encodes homologs to an iron-binding lipoprotein, an iron-dependent peroxidase (FepB), and a high-affinity iron permease. The FepB protein has a typical twin-arginine (RR) signal peptide. The tat and fep operons constitute an entity that is not present in all staphylococcal species. Our analysis was focused on Staphylococcus aureus and S. carnosus strains. Tat deletion mutants (ΔtatAC) were unable to export active FepB, indicating that this enzyme is a Tat substrate. When the RR signal sequence from FepB was fused to prolipase and protein A, their export became Tat dependent. Since no other protein with a Tat signal could be detected, the fepABC-tatAC genes comprise not only a genetic but also a functional unit. We demonstrated that FepABC drives iron import, and in a mouse kidney abscess model, the bacterial loads of ΔtatAC and Δtat-fep mutants were decreased. For the first time, we show that the Tat pathway in S. aureus is functional and serves to translocate the iron-dependent peroxidase FepB. More »»

2009

Journal Article

I. Bourgeois, Camiade, E., Dr. Raja Biswas, Courtin, P., Gibert, L., Götz, F., Chapot-Chartier, M. - P., Pons, J. - L., and Pestel-Caron, M., “Characterization of AtlL, a bifunctional autolysin of Staphylococcus lugdunensis with N-acetylglucosaminidase and N-acetylmuramoyl-l-alanine amidase activities”, FEMS Microbiology Letters, vol. 290, pp. 105–113, 2009.[Abstract]


The nucleotide sequence of atlL, a gene encoding a putative Staphylococcus lugdunensis peptidoglycan hydrolase, was determined using degenerate consensus PCR and genome walking. This 3837-bp gene encodes a protein, AtlL, that appears as a putative bifunctional autolysin with a 29-amino acid putative signal peptide and two enzymatic putative centres (N-acetylmuramoyl-l-alanine amidase and N-acetylglucosaminidase) interconnected with three imperfect repeated sequences displaying glycine–tryptophan motifs. In order to determine whether both lytic domains were functional, and verify their exact enzymatic activities, gene fragments harbouring both putative domains, AM (N-acetylmuramoyl-l-alanine amidase enzymatic centre plus two repeated sequences) and GL (N-acetylglucosaminidase enzymatic centre plus one repeated sequence), were isolated, subcloned, and expressed in Escherichia coli. Purified recombinant AM and GL protein truncations exhibited cell wall lytic activity in zymograms performed with cell walls of Micrococcus lysodeikticus, Bacillus subtilis, and S. lugdunensis. AtlL is expressed during the whole growth, with an overexpression in the early-exponential stage. Liquid chromatography-mass spectrometry analysis of muropeptides generated by digestion of B. subtilis cell walls demonstrated the hydrolytic bond specificities and confirmed both of the acetyl domains’ activities as predicted by sequence homology data. AtlL is the first autolysin described in S. lugdunensis, with a bifunctional enzymatic activity involved in peptidoglycan hydrolysis. More »»

2009

Journal Article

A. Rotte, Bhandaru, M., Föller, M., Dr. Raja Biswas, Mack, A. F., Friedrich, B., Rexhepaj, R., Nasir, O., Ackermann, T. F., Boini, K. M., and , “APC sensitive gastric acid secretion”, Cellular Physiology and Biochemistry, vol. 23, pp. 133–142, 2009.[Abstract]


Adenomatous polyposis coli (APC) is a tumor suppressor gene inactivated in familial adenomatous polyposis and sporadic colorectal cancer. Mice carrying a loss-of-function mutation in the apc gene (apcMin/+) spontaneously develop gastrointestinal tumors. APC fosters degradation of β-catenin, which in turn upregulates the serum- and glucocorticoid-inducible kinase SGK1. SGK1 stimulates KCNQ1, which is required for luminal K+ recycling and thus for gastric acid secretion. BCECF-fluorescence was utilized to determine gastric acid secretion in isolated gastric glands from apcMin/+mice and their wild type littermates (apc+/+). Western blotting was employed to analyse β-catenin and SGK1 expression and immunohistochemistry to determine KCNQ1 protein abundance. β-catenin and SGK1 expression were enhanced in apcMin/+mice. Cytosolic pH was similar in apcMin/+ mice and apc+/+ mice. Na+-independent pH recovery following an ammonium pulse (ΔpH/min), which reflects H+/K+ ATPase activity, was, however, significantly faster in apcMin/+ mice than in apc+/+mice. In both genotypes ΔpH/min was abolished in the presence of H+/K+ ATPase inhibitor omeprazole (100 μM). Treatment of apcMin/+ and apc+/+mice with 5 μM forskolin 15 minutes prior to the experiment or increase in local K+-concentrations to 35 mM (replacing Na+/NMDG) significantly increased ΔpH/min and abrogated the differences between genotypes. The increase of ΔpH/min in apcMin/+mice required SGK1, as it was abolished by additional knockout of SGK1 (apcMin/+/sgk1-/-). In conclusion, basal gastric acid secretion is significantly enhanced in apcMin/+mice, pointing to a role of APC in the regulation of gastric acid secretion. The effect of APC requires H+/K+ATPase activity and is at least partially due to SGK1-dependent upregulation of KCNQ1. More »»

2009

Journal Article

M. Föller, Dr. Raja Biswas, Mahmud, H., Akel, A., Shumilina, E., Wieder, T., Goetz, F., and Lang, F., “Effect of peptidoglycans on erythrocyte survival”, International Journal of Medical Microbiology, vol. 299, pp. 75 - 85, 2009.[Abstract]


Peptidoglycans (PGNs) from bacterial cell walls belong to ‘pathogen-associated molecular patterns’ (PAMP), which modify the course of an infection with bacterial pathogens. Bacterial infections may lead to anaemia, which at least partially could result from accelerated erythrocyte death. The present study explored the effect of \{PGNs\} on eryptosis, a stress-induced suicidal death of erythrocytes, characterized by cell shrinkage and cell membrane scrambling with phosphatidylserine exposure at the erythrocyte surface. Eryptotic cells are phagocytosed and thus rapidly cleared from circulating blood. Eryptosis is triggered by an increase in the cytosolic Ca2+ concentration and by formation of ceramide. Erythrocyte Ca2+ activity was estimated from Fluo3 fluorescence, ceramide formation by fluorescent antibodies, phosphatidylserine exposure from annexin V-binding, and erythrocyte volume from forward scatter in fluorescence activated cell sorting (FACS) analysis. Exposure of erythrocytes to \{PGNs\} increased cytosolic Ca2+ concentration, increased ceramide formation, enhanced the percentage of annexin V-binding erythrocytes, decreased erythrocyte forward scatter, and lowered the intracellular \{ATP\} concentration. The effect of peptidoglycans was significantly blunted in the absence of extracellular Ca2+. The clearance of erythrocytes exposed to \{PGNs\} was significantly enhanced in vivo. In conclusion, peptidoglycans induce eryptosis at least partially through an increase in the cytosolic Ca2+ concentration, an effect presumably contributing to the development of anaemia during bacterial infections.

More »»

2009

Journal Article

L. Biswas, Dr. Raja Biswas, Schlag, M., Bertram, R., and Götz, F., “Staphylococcus aureus survival strategy to resist Pseudomonas aeruginosa is SCV selection”, Applied and Environmental Microbiology, 2009.[Abstract]


Previously it has been demonstrated that Staphylococcus aureus is sensitive towards Pseudomonas secreted exotoxins, which preferentially target the electron transport chain in staphylococci. Here it is shown that a subpopulation of S. aureus survives these respiratory toxins of P. aeruginosa by selection of small colony variant (SCV) phenotype. Purified pyocyanin alone causes the same effect. A hemB mutant of S. aureus survives co-cultivation with P. aeruginosa without decrease in CFU More »»

2008

Journal Article

Dr. Raja Biswas, Ghosh, P., Banerjee, N., Das, J. K., Sau, T., Banerjee, A., Roy, S., Ganguly, S., Chatterjee, M., Mukherjee, A., and , “Analysis of T-cell proliferation and cytokine secretion in the individuals exposed to arsenic”, Human & experimental toxicology, vol. 27, pp. 381–386, 2008.[Abstract]


Over six million people in nine districts of West Bengal, India are exposed to very high levels of arsenic primarily through their drinking water. More than 300,000 people showed arsenic-induced skin lesions in these districts. This is regarded as the greatest arsenic calamity in the world. Chronic arsenicosis causes varied dermatological signs ranging from pigmentation changes, hyperkeratosis to non-melanocytic cancer of skin, and also malignancies in different internal organs. Higher incidences of opportunistic infections are found in the arsenic-exposed individuals, indicating that their immune systems may be impaired somehow. We have thus investigated the effect of arsenic on T-cell proliferation and cytokine secretion in 20 individuals with arsenic-induced skin lesions and compared the results with 18 arsenic-unexposed individuals. A marked dose-dependent suppression of Concanavalin A (Con A) induced T-cell proliferation was observed in the arsenic-exposed individuals compared with the unexposed (P < 0.001) individuals. This correlated with a significant decrease in the levels of secreted cytokines by the T cells (TNF-alpha, IFN-gamma, IL2, IL10, IL5, and IL4) in the exposed individuals (P < 0.001). Thus it can be inferred that arsenic exposure can cause immunosuppression in humans.

More »»

2008

Journal Article

K. Wang, Mahmud, H., Föller, M., Dr. Raja Biswas, Lang, K. S., Bohn, E., Goetz, F., and Lang, F., “Lipopeptides in the triggering of erythrocyte cell membrane scrambling”, Cellular Physiology and Biochemistry, vol. 22, pp. 381–386, 2008.[Abstract]


Sepsis is paralleled by anemia, an effect partially resulting from eryptosis, the suicidal death of erythrocytes. Eryptosis is characterized by cell membrane scrambling with phosphatidylserine exposure at the erythrocyte surface. Pathogen-induced eryptosis may partially result from interaction of bacterial cell wall components such as lipoproteins with the erythrocyte cell membrane. The present study explored, whether the synthetic lipopeptide Pam3CSK4 mimicking the acylated amino terminus of bacterial lipoproteins triggers eryptosis. According to annexin-V-binding in FACS analysis, Pam3CSK4 (1 μg/ml) stimulated phosphatidylserine exposure, an effect significantly blunted in the nominal absence of Ca2+. According to Fluo3 fluorescence, Pam3CSK4 increased cytosolic Ca2+ activity and moderately stimulated erythrocytic ceramide formation, both major triggers of eryptosis. In conclusion, bacterial lipoproteins participate in the stimulation of erythrocyte cell membrane scrambling by bacterial cell wall components. Thus, lipoprotein-dependent suicidal erythrocyte death may contribute to the pleotropic effects of sepsis. More »»

2008

Journal Article

A. Hussain, Wyatt, A. W., Wang, K., Bhandaru, M., Dr. Raja Biswas, Avram, D., Föller, M., Rexhepaj, R., Friedrich, B., Ullrich, S., and , “SGK1-dependent upregulation of connective tissue growth factor by angiotensin II”, Kidney and Blood Pressure Research, vol. 31, pp. 80–86, 2008.[Abstract]


Angiotensin II has previously been shown to trigger fibrosis, an effect involving connective tissue growth factor (CTGF). The signaling pathways linking angiotensin II to CTGF formation are, however, incompletely understood. A gene highly expressed in fibrosing tissue is the serum- and glucocorticoid-inducible kinase SGK1. The present study explored whether SGK1 is transcriptionally regulated by angiotensin II and participates in the angiotensin II-dependent regulation of CTGF expression. To this end, experiments have been performed in human kidney fibroblasts and mouse lung fibroblasts from gene-targeted mice lacking SGK1 (sgk1–/–) and their wild-type littermates (sgk1+/+). In human renal fibroblasts, SGK1 and CTGF protein expression were enhanced by angiotensin II (10 nM) within 4 h. In sgk1+/+ mouse fibroblasts, SGK1 transcript levels were significantly increased after 4 h of angiotensin II treatment. Angiotensin II stimulated both transcript and protein abundance of CTGF in fibroblasts from sgk1+/+ mice, effects significantly blunted in fibroblasts of sgk1–/– mice. In conclusion, angiotensin II stimulates the expression of SGK1, which is in turn required for the stimulating effect of angiotensin II on the expression of CTGF. Thus, SGK1 presumably contributes to the profibrotic effect of angiotensin II. More »»

2008

Journal Article

S. G. Abdel Hamid, Abdulle, A. M., Abouchacra, S., Abraham, G., Agyemang, C., Ajdačić, M., Aleksandrowicz, E., Arena, A., Arendshorst, W. J., Avram, D., and Dr. Raja Biswas, “Cseh, J. 47 Csiky, B. 47 Davidovitz, A. 210 Djukanović, L. 307 Donato, V. 330”, Kidney Blood Press Res, vol. 31, p. 441, 2008.

2007

Journal Article

D. S. Kempe, Akel, A., Lang, P. A., Hermle, T., Dr. Raja Biswas, Muresanu, J., Friedrich, B., Dreischer, P., Wolz, C., Schumacher, U., Peschel, A., Götz, F., Döring, G., Wieder, T., Gulbins, E., and Lang, F., “Suicidal erythrocyte death in sepsis”, Journal of Molecular Medicine, vol. 85, pp. 273–281, 2007.[Abstract]


Sequelae of sepsis include anemia which presumably results from accelerated clearance of erythrocytes from circulating blood. The underlying mechanisms, however, remained hitherto elusive. Most recent studies disclosed that increased cytosolic Ca2+ activity and ceramide both trigger suicidal erythrocyte death (i.e., eryptosis), which is characterized by lipid scrambling of the cell membrane leading to phosphatidylserine exposure at the erythrocyte surface. Phosphatidylserine exposing erythrocytes may adhere to vascular walls or may be engulfed by macrophages equipped with phosphatidylserine receptors. To explore whether sepsis leads to eryptosis, erythrocytes from healthy volunteers were exposed to plasma of patients suffering from sepsis, or to supernatants from sepsis producing pathogens. Then, phosphatidylserine exposure (annexin V binding), cell volume (forward scatter), cytosolic Ca2+ activity (Fluo3 fluorescence), and ceramide formation (anti-ceramide antibody) were determined by flow cytometry. Challenge of erythrocytes with plasma from the patients but not with plasma from healthy individuals triggered annexin V binding. The effect of patient plasma on erythrocyte annexin V binding was paralleled by formation of ceramide and a significant increase of cytosolic Ca2+ activity. Exposure of erythrocytes to supernatant of pathogens similarly induced eryptosis, an effect correlating with sphingomyelinase activity. The present observations disclose a novel pathophysiological mechanism leading to anemia and derangement of microcirculation during sepsis. Exposure to plasma from septic patients triggers phosphatidylserine exposure leading to adherence to the vascular wall and clearance from circulating blood. More »»

2007

Journal Article

A. A. Gust, Dr. Raja Biswas, Lenz, H. D., Rauhut, T., Ranf, S., Kemmerling, B., Götz, F., Glawischnig, E., Lee, J., Felix, G., and , “Bacteria-derived peptidoglycans constitute pathogen-associated molecular patterns triggering innate immunity in Arabidopsis”, Journal of Biological Chemistry, vol. 282, pp. 32338–32348, 2007.[Abstract]


Pathogen-associated molecular pattern (PAMP)-triggered immunity constitutes the primary plant immune response that has evolved to recognize invariant structures of microbial surfaces. Here we show that Gram-positive bacteria-derived peptidoglycan (PGN) constitutes a novel PAMP of immune responses in Arabidopsis thaliana. Treatment with PGN from Staphylococcus aureus results in the activation of plant responses, such as medium alkalinization, elevation of cytoplasmic calcium concentrations, nitric oxide, and camalexin production and the post-translational induction of MAPK activities. Microarray analysis performed with RNA prepared from PGN-treated Arabidopsis leaves revealed enhanced transcript levels for 236 genes, many of which are also altered upon administration of flagellin. Comparison of cellular responses after treatment with bacteria-derived PGN and structurally related fungal chitin indicated that both PAMPs are perceived via different perception systems. PGN-mediated immune stimulation in Arabidopsis is based upon recognition of the PGN sugar backbone, while muramyl dipeptide, which is inactive in this plant, triggers immunity-associated responses in animals. PGN adds to the list of PAMPs that induce innate immune programs in both plants and animals. However, we propose that PGN perception systems arose independently in both lineages and are the result of convergent evolution. More »»

2007

Journal Article

A. Bera, Dr. Raja Biswas, Herbert, S., Kulauzovic, E., Weidenmaier, C., Peschel, A., and Götz, F., “Influence of wall teichoic acid on lysozyme resistance in Staphylococcus aureus”, Journal of bacteriology, vol. 189, pp. 280–283, 2007.[Abstract]


Staphylococcus aureus peptidoglycan (PG) is completely resistant to the hydrolytic activity of lysozyme. Here we show that modifications in PG by O acetylation, wall teichoic acid, and a high degree of cross-linking contribute to this resistance. More »»

2007

Journal Article

I. Fedtke, Mader, D., Kohler, T., Moll, H., Nicholson, G., Dr. Raja Biswas, Henseler, K., Götz, F., Zähringer, U., and Peschel, A., “A Staphylococcus aureus ypfP mutant with strongly reduced lipoteichoic acid (LTA) content: LTA governs bacterial surface properties and autolysin activity”, Molecular Microbiology, vol. 65, pp. 1078–1091, 2007.[Abstract]


Many Gram-positive bacteria produce lipoteichoic acid (LTA) polymers whose physiological roles have remained a matter of debate because of the lack of LTA-deficient mutants. The ypfP gene responsible for biosynthesis of a glycolipid found in LTA was deleted in Staphylococcus aureus SA113, causing 87% reduction of the LTA content. Mass spectrometry and nuclear magnetic resonance spectroscopy revealed that the mutant LTA contained a diacylglycerol anchor instead of the glycolipid, whereas the remaining part was similar to the wild-type polymer except that it was shorter. The LTA mutant strain revealed no major changes in patterns of cell wall proteins or autolytic enzymes compared with the parental strain indicating that LTA may be less important in S. aureus protein attachment than previously thought. However, the autolytic activity of the mutant was strongly reduced demonstrating a role of LTA in controlling autolysin activity. Moreover, the hydrophobicity of the LTA mutant was altered and its ability to form biofilms on plastic was completely abrogated indicating a profound impact of LTA on physicochemical properties of bacterial surfaces. We propose to consider LTA and its biosynthetic enzymes as targets for new antibiofilm strategies. More »»

2006

Journal Article

Dr. Raja Biswas, Voggu, L., Simon, U. Karsten, Hentschel, P., Thumm, G., and Götz, F., “Activity of the major staphylococcal autolysin Atl”, FEMS Microbiology Letters, vol. 259, pp. 260–268, 2006.[Abstract]


The major autolysin of Staphylococcus aureus (AtlA) and of Staphylococcus epidermidis (AtlE) are well-studied enzymes. Here we created an atlA deletion mutant in S. aureus that formed large cell clusters and was biofilm-negative. In electron micrographs, the mutant cells were distinguished by rough outer cell surface. The mutant could be complemented using the atlE gene from S. epidermidis. To study the role of the repetitive sequences of atlE, we expressed in Escherichia coli the amidase domain encoded by the gene, carrying no repeat regions (amiE) or two repeat regions (amiE-R1,2), or the three repeat regions alone (R1,2,3) as N-terminal His-tag fusion proteins. Only slight differences in the cell wall lytic activity between AmiE and AmiE-R1,2 were observed. The repetitive sequences exhibit a good binding affinity to isolated peptidoglycan and might contribute to the targeting of the amidase to the substrate. AmiE and AmiE-R1,2 have a broad substrate specificity as shown by similar activities with peptidoglycan lacking wall teichoic acid, O-acetylation, or both. As the amidase activity of AtlA and AtlE has not been proved biochemically, we used purified AmiE-R1,2 to determine the exact peptidoglycan cleavage site. We provide the first evidence that the amidase indeed cleaves the amide bond between N-acetyl muramic acid and l-alanine. More »»

2006

Journal Article

A. Bera, Dr. Raja Biswas, Herbert, S., and Götz, F., “The presence of peptidoglycan O-acetyltransferase in various staphylococcal species correlates with lysozyme resistance and pathogenicity”, Infection and immunity, vol. 74, pp. 4598–4604, 2006.[Abstract]


Human-pathogenic bacteria that are able to cause persistent infections must have developed mechanisms to resist the immune defense system. Lysozyme, a cell wall-lytic enzyme, is one of the first defense compounds induced in serum and tissues after the onset of infection. Recently, we showed that Staphylococcus aureus is resistant to lysozyme by O acetylating its peptidoglycan (PG) by O-acetyltransferase (OatA). We asked the question of which staphylococcal species PG is O acetylated. We applied various methods, such as genome analysis, PCR, Southern blotting, lysozyme sensitivity assay, and verification of O acetylation of PG by high-performance liquid chromatography (HPLC) analysis. PCR analysis using S. aureus-derived oatA primers and Southern blotting did not yield reliable results with other staphylococcal species. Therefore, we used the HPLC-based assay to directly detect PG O acetylation. Our studies revealed that the muramic acid was O acetylated only in pathogenic, lysozyme-resistant staphylococci (e.g., S. aureus, S. epidermidis, S. lugdunensis, and others). All nonpathogenic species were lysozyme sensitive. They can be divided into sensitive species (e.g., S. carnosus, S. gallinarum, and S. xylosus) and hypersensitive species (e.g., S. equorum, S. lentus, and S. arlettae). In all lysozyme-sensitive species, the analyzed PG was de-O-acetylated. When we transformed the oatA gene from lysozyme-resistant S. aureus into S. carnosus, the corresponding transformants also became lysozyme resistant. More »»

2006

Journal Article

L. Voggu, Schlag, S., Dr. Raja Biswas, Rosenstein, R., Rausch, C., and Götz, F., “Microevolution of cytochrome bd oxidase in staphylococci and its implication in resistance to respiratory toxins released by Pseudomonas”, Journal of bacteriology, vol. 188, pp. 8079–8086, 2006.[Abstract]


Pseudomonas aeruginosa and Staphylococcus aureus are opportunistic pathogens and frequently coinfect the lungs of cystic fibrosis patients. P. aeruginosa secretes an arsenal of small respiratory inhibitors, like pyocyanin, hydrogen cyanide, or quinoline N-oxides, that may act against the commensal flora as well as host cells. Here, we show that with respect to their susceptibility to these respiratory inhibitors, staphylococcal species can be divided into two groups: the sensitive group, comprised of pathogenic species such as S. aureus and S. epidermidis, and the resistant group, represented by nonpathogenic species such as S. carnosus, S. piscifermentans, and S. gallinarum. The resistance in the latter group of species was due to cydAB genes that encode a pyocyanin- and cyanide-insensitive cytochrome bd quinol oxidase. By exchanging cydB in S. aureus with the S. carnosus-specific cydB, we could demonstrate that CydB determines resistance. The resistant or sensitive phenotype was based on structural alterations in CydB, which is part of CydAB, the cytochrome bd quinol oxidase. CydB represents a prime example of both microevolution and the asymmetric pattern of evolutionary change. More »»

1990

Journal Article

S. Mahanti, Bhatta, A. K., Dr. Raja Biswas, Bhatia, J., and Singh, S. N., “Development of a meta-stable semi-synthetic lubricant for cold rolling of steel”, Journal of Synthetic Lubrication, vol. 6, pp. 285–298, 1990.[Abstract]


A semi-synthetic meta-stable oil system for cold rolling of steel was developed as a substitute for a mineral oil based ‘stable emulsion’-type soluble oil. The developed oil system, comprising a ‘coating oil’ for post-pickling application and a ‘rolling oil’ for the rolling operation, was tested in the laboratory and subsequently subjected to extensive field trials in an integrated steel plant. Use of the developed oil system resulted in 25–50 per cent lower roll loads and 30–50 per cent reduction of inter-stand tensions compared with the mineral oil-based ‘stable emulsion’. It was also possible to increase the ‘strip reduction ratio’ and input coil width with the use of the newly-developed oil. Overall performance of the new semi-synthetic oil was found to be far superior to that of the mineral oil based ‘stable emulsion’. More »»

Publication Type: Conference Paper

Year of Publication Publication Type Title

2008

Conference Paper

Dr. Raja Biswas, Paul, K., Mukherjee, A. K., Bhattacherjee, I., and Mondal, S., “A comparative assessment of efficacy and safety of oral antidiabetic drug combinations, metformin plus pioglitazone versus metformin plus glimepiride in type-2 diabetes mellitus”, in INDIAN JOURNAL OF PHARMACOLOGY, 2008.

2007

Conference Paper

J. Buschmann, Dr. Raja Biswas, Nega, M., Volz, T., Biedermann, T., and Goetz, F., “Signalling activity of staphylococcal cell wall components”, in INTERNATIONAL JOURNAL OF MEDICAL MICROBIOLOGY, 2007.

2007

Conference Paper

M. Schlag, Dr. Raja Biswas, Zoll, S., and Goetz, F., “Characterisation of cell wall hydrolases in Staphylococcus sp.”, in INTERNATIONAL JOURNAL OF MEDICAL MICROBIOLOGY, 2007.

2006

Conference Paper

D. Schultz, Fedtke, I., Henseler, K., Dr. Raja Biswas, Gotz, F., Nicholson, G., and Peschel, A., “Lipoteichoic acid governs surface properties and autolysin activity in Staphylococcus aureus”, in INTERNATIONAL JOURNAL OF MEDICAL MICROBIOLOGY, 2006.

Publication Type: Thesis

Year of Publication Publication Type Title

2006

Thesis

Dr. Raja Biswas and , “Characterization of Staphylococcus aureus peptidoglycan hydrolases and isolation of defined peptidoglycan structures”, Universität Tübingen, 2006.[Abstract]


Peptidoglycan (PG) hydrolases or autolysins are a group of enzymes which catalyze the degradation of bacterial cell wall at specific sites. Staphylococcus aureus produces two major PG hydrolases: major autolysin (Atl) and Aaa, a autolysin/ adhesin protein. The major autolysins of Staphylococcus aureus (AtlA) and of Staphylococcus epidermidis (AtlE) are well-studied enzymes. But little is known about the Aaa protein. To analyse the possible role of these PG hydrolases we constructed the atlA and aaa deletion mutants in S. aureus. SA?atlA formed large cell clusters and was biofilm-negative owing to a deficiency in adherence to the indwelling device surface. In electron micrographs, the mutant cells were distinguished by a rough outer cell surface. A high proportion of abnormally formed multicells that were septated but not separated from each other were observed, which suggested hampered cell separation. Both atlA and atlE complemented the mutant. The atl gene product is a bifunctional protein that has an N-terminal N-acetyl L-alanine amidase (Ami) domain, three internal repeat domains (R1, 2, 3) and a C- terminal endo-ß-N-acetylglucosaminidase (GL) domain which undergo proteolytic processing to generate the two extracellular lytic enzymes (62 kDa Ami-R1, 2 and 51 kDa R3-GL) found in the culture broth of S. aureus. In the mature protein repeats R1 and R2 are located at the C-terminal portion of the amidase (Ami-R1, 2) and repeat R3 is located at N-terminal portion of the glucosaminidase (R3-GL). To study the role of the repetitive sequences of atlE, we expressed in Escherichia coli the amidase domain encoded by the gene, carrying no repeat regions (amiE) or two repeat regions (amiE-R1, 2), or the three repeat regions alone (R1, 2, 3) as N-terminal His-tag fusion proteins. Only slight differences in the cell wall lytic activity between AmiE and AmiE-R1, 2 were observed. The repetitive sequences have a good binding affinity to isolated peptidoglycan and might contribute to the targeting of the amidase to the substrate. AmiE and AmiE-R1, 2 have a broad substrate specificity as shown by similar activities with peptidoglycan (PG) lacking wall teichoic acid, O-acetylation, or both. Since the amidase activity of AtlA and AtlE has not been proved biochemically, we used purified AmiE-R to determine the exact PG cleavage site. We provide the first evidence that the amidase indeed cleaves the amide bond between N-acetyl muramic acid and L-alanine. SA?aaa mutant did not differ from the wild type in its colony morphology, growth rate, cell cluster and biofilm formation, suggesting that Aaa does not play a vital role in cell separation or, more probably, that the function of Aaa in cell separation may have been taken over by the major autolysin Atl, which seemed to be more strongly expressed in the aaa mutant than in the wild type. Autolysin/adhesin protein Aaa is a 35 kDa protein containing two direct LysM (lysine motif) repeats at the N-terminal and catalytic domain in the C-terminus. The C-terminal catalytic domain of Aaa is homologous to the CHAP (cysteine, histidine-dependent amidohydrolases/ peptidases) domain. This domain is often found in PG hydrolysing enzymes. This work also established a purification method for isolation of soluble defined staphylococcal peptidoglycan fragments (PGs). Compared to earlier methods, which were based on using insoluble purified peptidoglycan, we standardize the purification method soluble PGs using HPLC. Commercially available mutanolysin and lysostaphin can be used to cleave PG structures. Apart from these two lytic enzymes, we biochemically characterized the amidase, which provides an alternative tool for PG analysis. Mutanolysin, lysostaphin and amidase can be used individually or together to isolate muropeptides, stem peptides or sugar residues for studying host cell signaling activities. More »»

2006

Thesis

Dr. Raja Biswas, “Characterization of Staphylococcus Aureus Peptidogylcan [peptidoglycan] Hydrolases and Isolation of Defined Peptidoglycan Structures”, 2006.

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