Ira Bhatnagar

Immense essence of excellence: marine microbial bioactive compounds.

Oceans have borne most of the biological activities on our planet. A number of biologically active compounds with varying degrees of action, such as anti-tumor, anti-cancer, anti-microtubule, anti-proliferative, cytotoxic, photo protective, as well as antibiotic and antifouling properties, have been isolated to date from marine sources. The marine environment also represents a largely unexplored source for isolation of new microbes (bacteria, fungi, actinomycetes, microalgae-cyanobacteria and diatoms) that are potent producers of bioactive secondary metabolites. Extensive research has been done to unveil the bioactive potential of marine microbes (free living and symbiotic) and the results are amazingly diverse and productive. Some of these bioactive secondary metabolites of microbial origin with strong antibacterial and antifungal activities are being intensely used as antibiotics and may be effective against infectious diseases such as HIV, conditions of multiple bacterial infections (penicillin, cephalosporines, streptomycin, and vancomycin) or neuropsychiatric sequelae. Research is also being conducted on the general aspects of biophysical and biochemical properties, chemical structures and biotechnological applications of the bioactive substances derived from marine microorganisms, and their potential use as cosmeceuticals and nutraceuticals. This review is an attempt to consolidate the latest studies and critical research in this field, and to showcase the immense competence of marine microbial flora as bioactive metabolite producers. In addition, the present review addresses some effective and novel approaches of procuring marine microbial compounds utilizing the latest screening strategies of drug discovery.

Alginate composites for bone tissue engineering: A review

Bone is a complex and hierarchical tissue consisting of nano hydroxyapatite and collagen as major portion. Several attempts have been made to prepare the artificial bone so as to replace the autograft and allograft treatment. Tissue engineering is a promising approach to solve the several issues and is also useful in the construction of artificial bone with materials including polymer, ceramics, metals, cells and growth factors. Composites consisting of polymer-ceramics, best mimic the natural functions of bone. Alginate, an anionic polymer owing enormous biomedical applications, is gaining importance particularly in bone tissue engineering due to its biocompatibility and gel forming properties. Several composites such as alginate-polymer (PLGA, PEG and chitosan), alginate-protein (collagen and gelatin), alginate-ceramic, alginate-bioglass, alginate-biosilica, alginate-bone morphogenetic protein-2 and RGD peptides composite have been investigated till date. These alginate composites show enhanced biochemical significance in terms of porosity, mechanical strength, cell adhesion, biocompatibility, cell proliferation, alkaline phosphatase increase, excellent mineralization and osteogenic differentiation. Hence, alginate based composite biomaterials will be promising for bone tissue regeneration. This review will provide a broad overview of alginate preparation and its applications towards bone tissue engineering.

Marine antitumor drugs: status, shortfalls and strategies.

Cancer is considered as one of the deadliest diseases in the medical field. Apart from the preventive therapies, it is important to find a curative measure which holds no loopholes and acts accurately and precisely to curb cancer. Over the past few decades, there have been advances in this field and there are many antitumor compounds available on the market, which are of natural as well as synthetic origin. Marine chemotherapy is well recognized nowadays and profound development has been achieved by researchers to deal with different molecular pathways of tumors. However, the marine environment has been less explored for the production of safe and novel antitumor compounds. The reason is a number of shortfalls in this field. Though ample reviews cover the importance and applications of various anticancerous compounds from marine natural products, in the present review, we have tried to bring the current status of antitumor research based on marine inhibitors of cancer signaling pathways. In addition, focus has been placed on the shortfalls and probable strategies in the arena of marine antitumor drug discovery.

Chitosan–amylopectin/hydroxyapatite and chitosan–chondroitin sulphate/hydroxyapatite composite scaffolds for bone tissue engineering

Over the past few decades, artificial graft materials for bone tissue engineering are gaining much importance. In this study, tri-component scaffolds of chitosan/natural hydroxyapatite with chondroitin sulfate (chitosan-CS/HAp) and amylopectin (chitosan-AP/HAp) have been developed for the first time via freeze-drying method and were characterized physicochemically for bone grafting substitutes. Chemical interactions and dispersion of HAp, CS and AP in the chitosan matrix have been evaluated by various analytical techniques. The porosity and water uptake/retention ability of these composite scaffolds decreased whereas thermal stability increased when compared to the chitosan scaffold. The pore size of the chitosan/HAp, chitosan-CS/HAp and chitosan-AP/HAp scaffolds varied from 60 to 180 μm, 60 to 400 μm and 80 to 500 μm, respectively. Cell proliferation, alkaline phosphatase activity and type-1 collagen production was evaluated in vitro using MG-63 cell line, which was observed to be higher in the composite scaffolds. Excellent interconnected porosity, controlled biodegradation and enhanced cell proliferation of the novel chitosan-CS/HAp and chitosan-AP/HAp scaffolds suggests that these scaffolds are promising biomaterials for bone tissue engineering.

Chitosan-Alginate Biocomposite Containing Fucoidan for Bone Tissue Engineering

Over the last few years, significant research has been conducted in the construction of artificial bone scaffolds. In the present study, different types of polymer scaffolds, such as chitosan-alginate (Chi-Alg) and chitosan-alginate with fucoidan (Chi-Alg-fucoidan), were developed by a freeze-drying method, and each was characterized as a bone graft substitute. The porosity, water uptake and retention ability of the prepared scaffolds showed similar efficacy. The pore size of the Chi-Alg and Chi-Alg-fucoidan scaffolds were measured from scanning electron microscopy and found to be 62–490 and 56–437 µm, respectively. In vitro studies using the MG-63 cell line revealed profound cytocompatibility, increased cell proliferation and enhanced alkaline phosphatase secretion in the Chi-Alg-fucoidan scaffold compared to the Chi-Alg scaffold. Further, protein adsorption and mineralization were about two times greater in the Chi-Alg-fucoidan scaffold than the Chi-Alg scaffold. Hence, we suggest that Chi-Alg-fucoidan will be a promising biomaterial for bone tissue regeneration.

In vivo study of chitosan-natural nano hydroxyapatite scaffolds for bone tissue regeneration

Significant development has been achieved with bioceramics and biopolymer scaffolds in the construction of artificial bone. In the present study, we have developed and compared chitosan-micro hydroxyapatite (chitosan-mHA) and chitosan-nano hydroxyapatite (chitosan-nHA) scaffolds as bone graft substitutes. The biocompatibility and cell proliferation of the prepared scaffolds were checked with preosteoblast (MC3T3-E1) cells. Total Volume (TV), bone volume (BV), bone surface (BS), trabecular thickness (Tb.Th), trabecular number (Tb.N) and trabecular separation (Tb.Sp) were found to be higher in chitosan-nHA than chitosan-mHA scaffold. Hence, we suggest that chitosan-nHA scaffold could be a promising biomaterial for bone tissue engineering.

Antimicrobial Activity of Chitosan-Carbon Nanotube Hydrogels

In the present study, we have prepared chitosan-carbon nanotube (Chitosan-CNT) hydrogels by the freeze-lyophilization method and examined their antimicrobial activity. Different concentrations of CNT were used in the preparation of Chitosan-CNT hydrogels. These differently concentrated CNT hydrogels were chemically characterized using Fourier Transform-Infrared Spectroscopy, Scanning Electron Microscopy and Optical microscopy. The porosity of the hydrogels were found to be >94%. Dispersion of chitosan was observed in the CNT matrix by normal photography and optical microscopy. The addition of CNT in the composite scaffold significantly reduced the water uptake ability. In order to evaluate antimicrobial activity, the serial dilution method was used towards Staphylococcus aureus, Escherichia coli and Candida tropicalis. The composite Chitosan-CNT hydrogel showed greater antimicrobial activity with increasing CNT concentration, suggesting that Chitosan-CNT hydrogel scaffold will be a promising biomaterial in biomedical applications.

Chitosan as biomaterial in drug delivery and tissue engineering

Chitin is one of the most abundant polysaccharide found on earth. The deacetylated form of chitin viz. chitosan has been reported for its various important pharmacological properties and its role in tissue engineering and regenerative medicine is also well documented. Chitosan based bone graft substitutes are biocompatible, biodegradable, osteoconductive, osteoinductive and structurally similar to bone, with excellent mechanical strength and cost effectiveness. Chitosan based hydrogels and wound healing bandages have also found a great market in the field of medicine. More recently, chitosan has gained popularity for its use as a matrix molecule for drug delivery and also finds an upcoming utility in the area of dentistry. The present article has tried to review the latest research on chitosan based tissue engineering constructs, drug delivery vehicles as well as dental care products. An attempt has also been made to discuss the various modifications of chitosan that enhance its use for a given set of applications which would pave a way for future applied research in the field of biomedical innovation and regenerative medicine.

Pharmacologically prospective antibiotic agents and their sources: a marine microbial perspective.

Marine microbes have been a storehouse of bioactive metabolites with tremendous potential as drug candidates. Marine microorganism derived secondary metabolites (chemical compounds/peptides) are considered to be a burning area of research since recent past. Many of such compounds have been proven to be anti-bacterial, anti-fungal, anti-algal, anti-HIV, anti-helminthic, anti-protozoan, anti-tumor and anti-allergic agents. Marine bacteria and fungi have been reported to be the producers of such compounds owing to their defense mechanisms and metabolic by products. Although the number of natural products isolated from these classes of marine microbial flora is large, a limited number of such compounds reach the clinical trial and even less number of them get approved as a drug. Here we discuss the recent studies on the isolation, characterization and the pharmacological significances of anti-bacterial, anti-fungal and anti-infective agents of marine microbial origin. Further, the clinical status of such compounds has also been discussed in comparison with those derived from their terrestrial counterparts.

Chitosan: An undisputed bio-fabrication material for tissue engineering and bio-sensing applications

Biopolymers have been serving the mankind in various ways since long. Over the last few years, these polymers have found great demand in various domains which includes bio medicine, tissue engineering, bio sensor fabrications etc. because of their excellent bio compatibility. In this context, chitosan has found global attention due to its environmentally benign nature, biocompatibility, biodegradability, and ease of availability. In last one decade or so, extensive research in active biomaterials, like chitosan has led to the development of novel delivery systems for drugs, genes, and biomolecules; and regenerative medicine. Additionally, chitosan has also witnessed its usage in functionalization of biocompatible materials, nanoparticle (NP) synthesis, and immobilization of various bio-recognition elements (BREs) to form active bio-surfaces with great ease. Keeping these aspects in mind, we have written a comprehensive review which aims to acquaint its readers with the exceptional properties of chitosan and its usage in the domain of biomedicine, tissue engineering, and biosensor fabrication. Herein, we have briefly explained various aspects of direct utilization of chitosan and then presented vivid strategies towards formulation of chitosan based nanocomposites for biomedicine, tissue engineering, and biosensing applications.