Natarajan Duraipandy

Plumbagin caged silver nanoparticle stabilized collagen scaffold for wound dressing

The present work describes the development of a novel wound dressing material based on nano-biotechnological intervention by caging plumbagin on silver nanoparticle (PCSN) as a multi-site cross-linking agent of collagen scaffolds with potent anti-microbial and wound healing activity. Cross-linking of collagen with PCSN enhanced the physical, thermal, and mechanical properties along with the kinetics of micro structural fibril assembly of the collagen molecule. FTIR and CD analysis revealed that cross-linking of collagen using PCSN did not induce any structural changes in the collagen molecule. Further, cross-linking of collagen with PCSN resulted in uniform alignment of collagen fibrils to form orderly aligned porous structured scaffolds with potent anti-bacterial activity that in turn enhanced its ability to promote cell proliferation and wound healing. The cross-linking ability, and biochemical and therapeutic properties of plumbagin caged silver nanoparticles were attributed to the cumulative effect of plumbagin and silver nanoparticles because individual molecules had minimal effect on these parameters.

Fabrication of Hybrid Collagen Aerogels Reinforced with Wheat Grass Bioactives as Instructive Scaffolds for Collagen Turnover and Angiogenesis for Wound Healing Applications

The present study illustrates the progress of the wheat grass bioactive-reinforced collagen-based aerogel system as an instructive scaffold for collagen turnover and angiogenesis for wound healing applications. The reinforcement of wheat grass bioactives in collagen resulted in the design and development of aerogels with enhanced physicochemical and biomechanical properties due to the intermolecular interaction between the active growth factors of wheat grass and collagen fibril. Differential scanning calorimetry analysis revealed an enhanced denaturation temperature when compared to those of native collagen aerogels. Fourier transform infrared spectroscopy analysis confirmed that the reinforcement of bioactives in the wheat grass did not affect the structural integrity of the collagen molecule. Additionally, the reinforced biomaterial with a systematic absorptive morphology resulted in a three-dimensional (3D) sponge-like aerogel exhibiting a potent highly oriented 3D structural assembly that showed increased water retention ability and substance permeability that would enable the passage of nutrients and gaseous components for cellular growth. Furthermore, the cumulative effect of the growth factors in wheat grass and the collagen molecule augments the angiogenic ability and collagen production of the aerogel by restoration of the damaged tissue thereby making it a potential 3D wound dressing scaffold. The results were confirmed by in vivo wound healing assays. This study shows the possibility for progress of a biocompatible, biodegradable, and nonadhesive nutraceutical-reinforced collagen aerogel as an instructive scaffold with good antimicrobial properties for collagen turnover and angiogenic response for wound healing applications.

Fabrication of Nontoxic Reduced Graphene Oxide Protein Nanoframework as Sustained Antimicrobial Coating for Biomedical Application

Bacterial colonization on medical devices is a major concern in the healthcare industry. In the present study, we report synthesis of environmental sustainable reduced graphene oxide (rGO) on the large scale through biosynthetic route and its potential application for antibacterial coating on medical devices. HRTEM image depicts formation of graphene nanosheet, while DLS and ζ potential studies reveal that in aqueous medium the average hydrodynamic size and surface charge of rGO are 4410 ± 116 nm and -25.2 ± 3.2 mV, respectively. The Raman, FTIR, and XPS data suggest in situ conjugation of protein with rGO. The as-synthesized rGO protein nanoframework exhibits dose-dependent antibacterial activity and potential of killing of 94% of Escherichia coli when treated with 80 μg/mL of rGO for 4 h. The hemolytic and cytotoxicity studies demonstrate that rGO protein nanoframework is highly biocompatible at the same concentration showing significant antimicrobial properties. The rGO coated on the glass surface obtained through covalent bonding exhibits potent antibacterial activity. Antibacterial mechanism further demonstrates that rGO-protein nanoframework in dispersed state (rGO solution) exerts bactericidal effect through physical disruption accompanied by ROS-mediated biochemical responses. The rGO subsequently entering into the cytoplasm through the damaged membrane causes metabolic imbalance in the cells. In sharp contrast, physical damage of the cell membrane is the dominant antibacterial mechanism of rGO in the immobilized state (rGO coated glass). The obtained results help indepth understanding of the antibacterial mechanism of the biosynthesized rGO and a novel way to develop nontoxic antibacterial coating on medical devices to prevent bacterial infection.

A new platinum(II) complex for bioimaging applications

Two platinum(II) complexes containing imidazolyl terpyridine (1) and benzimidazolyl terpyridine (2) were synthesized and characterized by ESI-MS, 1H NMR, UV-Visible and fluorescence spectroscopy. Pt(II) complex 1 emits weakly in an aqueous solution but not complex 2. On addition of DNA, a 21-fold increase in the emission intensity of complex 1 was observed. Both complexes did not exhibit any change in emission maxima with serum albumin. No uptake of the complexes by live cells was observed. In dead cells, complex 1 stains the nuclear DNA specifically without addition of any external fluorophore. The apoptotic pathway of the cells induced by plumbagin was monitored using complex 1. Application of complex 1 as a DNA staining dye was tested in agarose gel electrophoresis. Taken together, the results from this study presents a new platinum(II) complex as a DNA staining agent, an alternative to highly mutagenic ethidium bromide in gel electrophoresis as well as in dead cells at a non-toxic concentration.

Nano-caged shikimate as a multi-site cross-linker of collagen for biomedical applications

The present study evaluated the application of a nano-biotechnological intervention of nutraceutical shikimate for the development of a potential multi-site cross-linker with enhanced cross linking, anti-microbial and cell proliferative activities. The cross-linking and therapeutic properties of the nutraceutical shikimate were simultaneously utilized by caging them onto silver nanoparticles. The caging of shikimate on silver nanoparticles resulted in the cumulative expression of the physico-chemical properties of both silver nanoparticles and shikimate. We observed that in shikimic acid caged silver nanoparticle (SCS nanoparticle) cross-linked collagen, the viscosity and self-assembly process of collagen, along with its mechanical and thermal properties, were significantly improved when compared with native collagen. The three dimensional conformation of collagen was also retained after cross-linking with SCS nanoparticles. Cell viability with SCS nanoparticle cross-linked collagen was found to be enhanced, in comparison to collagen films cross-linked with shikimic acid and native collagen. SCS nanoparticle-stabilized collagen possessed both cell proliferative and anti-microbial properties, which would make SCS nanoparticles a superior cross-linker of collagen. The results suggested a new strategy for cross-linking collagen and provide scope for alternative biocompatible interventions in the development of biomaterials.

Curcumin cross-linked collagen aerogels with controlled anti-proteolytic and pro-angiogenic efficacy

This paper elucidates the development of a curcumin cross-linked collagen aerogel system with controlled anti-proteolytic activity and pro-angiogenic efficacy. The results of this study showed that in situ cross-linking of curcumin with collagen leads to the development of aerogels with enhanced physical and mechanical properties. The integrity of collagen after cross-linking with curcumin was studied via FTIR spectroscopy. The results confirmed that the cross-linking with curcumin did not induce any structural changes in the collagen. The curcumin cross-linked collagen aerogels exhibited potent anti-proteolytic and anti-microbial activity. Scanning electron and atomic force microscopic analysis of curcumin cross-linked collagen aerogels showed a 3D microstructure that enhanced the adhesion and proliferation of cells. The highly organized geometry of collagen-curcumin aerogels enhanced the permeability and water-retaining ability required for the diffusion of nutrients that aid cellular growth. The pro-angiogenic properties of collagen-curcumin aerogels were ascribed to the cumulative effect of the nutraceutical and the collagen molecule, which augmented the restoration of damaged tissue. Further, these aerogels exhibited controlled anti-proteolytic activity, which makes them suitable 3D scaffolds for biomedical applications. This study provides scope for the development of biocompatible and bioresorbable collagen aerogel systems that use a nutraceutical as a cross-linker for biomedical applications.

Role of nanoparticle size in self-assemble processes of collagen for tissue engineering application

Nanoparticle mediated extracellular matrix may offer new and improved biomaterial to wound healing and tissue engineering applications. However, influence of nanoparticle size in extracellular matrix is still unclear. In this work, we synthesized different size of silver nanoparticles (AgNPs) comprising of 10nm, 35nm and 55nm using nutraceuticals (pectin) as reducing as well as stabilization agents through microwave irradiation method. Synthesized Ag-pectin nanoparticles were assimilated in the self-assemble process of collagen leading to fabricated collagen-Ag-pectin nanoparticle based scaffolds. Physico-chemical properties and biocompatibility of scaffolds were analyzed through FT-IR, SEM, DSC, mechanical strength analyzer, antibacterial activity and MTT assay. Our results suggested that 10nm sized Ag-pectin nanoparticles significantly increased the denaturation temperature (57.83°C) and mechanical strength (0.045MPa) in comparison with native collagen (50.29°C and 0.011MPa). The in vitro biocompatibility assay reveals that, collagen-Ag-pectin nanoparticle based scaffold provided higher antibacterial activity against to Gram positive and Gram negative as well as enhanced cell viability toward keratinocytes. This work opens up a possibility of employing the pectin caged silver nanoparticles to develop collagen-based nanoconstructs for biomedical applications.

Anti-oxidant enriched hybrid nanofibers: Effect on mechanical stability and biocompatibility

Despite being a favorable candidate in wound dressing, collagen based biomaterials possess inferior mechanical properties which limit their usage. Collagen based hybrid nanofibers with other polymers can enhance their mechanical strength as well as their biological properties. Herein, we report collagen-silk fibroin hybrid nanofibers incorporated with fenugreek, an antioxidant, as a bioactive wound dressing material. The nanofiber mats were characterized using various experimental techniques. From the results, it was found that an increase in silk fibroin content in nanofibers improves the fiber diameter and tensile strength. The nanofibers also showed good antioxidant properties estimated using 1,1-diphenyl-2-picrylhydrazyl (DPPH) scavenging assay. Presence of collagen in the nanofibers enhanced the biocompatibility of the nanofibers. Fenugreek released from the matrix enhanced the migration of fibroblasts in vitro. In vivo studies showed that collagen-silk fibroin-fenugreek nanofibers enhanced the wound closure via minimal inflammation and early epithelialization than the untreated and silk fibroin-fenugreek nanofibers treated wounds. Our study suggests that the fenugreek incorporated collagen-silk fibroin nanofibers is a potential candidate for wound dressings in clinical applications.