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Biomimetic nanofibrous scaffolds targeting multiple dysfunctional processes provide a multi-pronged strategy to restore functions and regenerate the damaged tissue. This study investigates a strategy of combining a regenerative component, Type I collagen Peptide (CP), along with a nitric oxide donor, S-Nitrosoglutathione (GSNO), in the form of nanofibrous scaffold to address the non-healing diabetic ulcer. Silk Fibroin-Polyvinyl alcohol (SF-PVA) nanofibrous scaffold is used as a carrier for delivering functional moieties. The developed nanofibrous electrospun mats (SF-PVA, CP-SF-PVA, and CP-GSNO-SF-PVA) showed continuous, bead-less and randomly oriented fibers with highly porous morphology. The in vitro biocompatibility was assessed by MTT assay, DAPI-Rhodamine 123 and FITC-Phalloidin imaging studies. CP-GSNO-SF-PVA nanofibrous scaffold showed a high degree of cell attachment, spreading of F-actin with viable cell morphology and appreciable inter-cellular connection. Thus the study showed that the proliferation of fibroblast cells are mainly facilitated by the presence of collagen peptide in the nanofibrous matrix. Griess assay demonstrated immediate release of NO for a day from the developed multifunctional scaffold. These results demonstrate the in vitro efficacy of CP-GSNO and indicate the opportunity of CP-GSNO-SF-PVA nanofibrous scaffold for the treatment of ischemic non-healing ulcers.

Accumulation of hair waste is a major burden to the leather industry, causing a negative impact on the industry's sustainable development. The industry is already bogged down by the usage of synthetic re-tanning agents that are not only extremely challenging for biodegradation but also release free-form of formaldehyde in the final leather stage. This research work focuses on developing a formaldehyde-free bio-based re-tanning agent from hair waste. In order to do so, hair waste is subjected to alkali hydrolysis and subsequently graft-copolymerized with methacrylic acid (MAA). These treatments were optimal using 20 % (w/w) sodium hydroxide and thermal activity at 90 °C. This resulted in effective hydrolysis of red sheep hair, which was the ideal candidate in this study. The hydrolysate was subjected to monomer in situ polymerization (using MAA) with potassium per sulfate/sodium meta-bisulphite redox system, leading to the development of keratin hydrolysate-g-methacrylic acid (KH-g-MA) copolymer (this was noted both at a laboratory level and pilot scale). The obtained KH-g-MA copolymer exhibited ideal characteristics such as increased protein content (78.3 ± 1.2), appropriate particle size (1516 nm), suitable pH (5) and required viscosity of 512 cP. The developed KH-g-MA copolymer was then applied as a re-tanning agent in the leather manufacturing process. Significant improvement in leather's mechanical strength characteristics was observed. In addition, the organoleptic properties of leather such as fullness, softness and grain tightness showed much improvement. Scanning electron microscopy (SEM) showed an enhanced surface smoothness and filling of the voids in experimental leather in comparison to the control leather. This recycle and reuse strategy of hair waste not only helps resolve issues with handling of hair solid waste but also results in producing an eco-friendly re-tanning agent in leather manufacturing, thereby paving the way for cyclic economic utilization and cleaner environment.

Here we report the preparation of biomimetic fibrin/chitosan/keratin hybrid scaffolds with a synergistic combination of ferulic acid loaded silica microspheres for antimicrobial wound dressing applications. The infrared and X-ray powder diffraction studies confirm the homogenous nature of the prepared hybrid scaffolds without any major interactions between the constituents. The developed hybrid scaffolds show good thermal, porosity, compression and water uptake properties. Scanning electron microscopic analysis shows that the as-synthesized ferulic acid loaded silica microspheres exhibit an average size of 35 ± 10 μm and also exposes the smooth surface with interconnected porosity in the prepared hybrid scaffolds. The incorporated ferulic acid loaded silica microspheres hybrid scaffolds show effective antimicrobial activity against the common wound pathogens. In vitro NIH3T3 fibroblast cell culture and drug release studies reveal that the prepared hybrid scaffolds have enhanced cell proliferation and adhesion with a prolonged drug release for about 72 h. In vitro wound healing and actin cytoskeleton analysis reveal that the incorporated ferulic acid loaded silica microspheres in fibrin/chitosan/keratin hybrid scaffolds facilitates cell growth and migration to damaged area through cell-cell interactions. These results suggest that the prepared hybrid scaffolds with ferulic acid loaded silica microspheres have great potential for soft tissue engineering applications particularly for the treatment of chronic and infected wounds.

Development of biomaterials for tissue engineering applications is of great interest to meet the demand of different clinical requirements. The wound heal dressing biomaterials should necessarily contain well-defined therapeutic components and desirable physical, chemical and biological properties to support optimal delivery of therapeutics at the site of the wound. In this study, we developed collagen-silica wound heal scaffold incorporated with the extract of Cynodon dactylon, characterized and evaluated for its wound heal potential in vitro and in vivo against collagen (Col) and Collagen-silica (CS) scaffolds that served as controls. The prepared Collagen-Silica-Cynodon extract (CSCE) scaffold exhibits porous morphology with preferable biophysical, chemical, mechanical and mass transfer properties besides its controlled biodegradation at the wound site. Stability of CSCE was found to be better than that of native collagen due to intermolecular interactions between collagen and constituents of C. dactylon as confirmed by FTIR analysis. Notably, in vitro biocompatibility assay using DAPI and Rhodamine 123 staining demonstrated that the proliferation of NIH3T3 fibroblast cells was better for CSCE when compared to the Col and CS scaffolds. In vivo wound healing experiments with full-thickness excision wounds in wistar rat model demonstrated that the wounds treated with CSCE showed accelerated healing with enhanced collagen deposition when compared to wounds treated with Col and CS scaffolds, and these studies substantiated the efficacy of CSCE scaffold for treating wounds.

We report a novel method that exploits the differential solubility properties of native and denatured proteins to distinguish between them. We chose to study this using collagen because its unique native triple helical structure is critical for the desired properties of collagen-based biomaterials. We found that native and denatured collagen separate out from solution in alcohols(methanol, ethanol, n-propanol and isopropanol), but as different phases. Native collagen undergoes tight gel-like separation(macrophase) from the solution in alcohols(90%,v/v), whereas denatured collagen separates as particles(microphase), which turn milky-like turbid. It was found that the pH of the medium had to be alkaline for turbidity formation, which necessitated the use of buffered alcohols. In solutions having mixtures of native and denatured collagen, the method has sensitivity to visually confirm the presence of native collagen even as low as 10%. It was also confirmed that the formation of turbidity was a direct function of the concentration of denatured collagen. A thermal denaturation experiment, wherein stages of denaturation were studied both by the proposed method and circular dichroism, showed that information obtained from both methods of analysis was comparable. This highlights the potential of the proposed method to become an instant fool proof test for collagen.

Ulcerative colitis, particularly the chronic persistent form is characterized by the presence of active inflammation and extensive areas of ulceration in the colonic mucosa. The existing treatment protocol aims at only reducing intestinal inflammation, rather than targeting mucosal ulceration. In this study, type I collagen and its daughter peptides called collagen hydrolysate, highly popular reconstructive materials for tissue engineering applications, are hypothesized as healing matrices to target the recuperation of internal mucosal ulceration. The clinical assessments on day 10 of dextran sodium sulfate induced colitis in mice model revealed that both the collagen (1.56±0.29) and collagen hydrolysate treatments (1.33±0.33) showed a significant reduction in the rectal bleeding compared to the reference mesalamine treatment (2.50±0.33) and untreated negative control (2.40±0.40). VEGF, a potent angiogenic growth factor, over expressed during UC was down-regulated by collagen hydrolysate (1.06±0.25) and collagen (1.76±0.45) to a greater extent than by mesalamine (2.59±0.51) and untreated control (4.17±0.15). The down-regulation of proinflammatory cytokines such as TNF-α, IL-1β, and IL-6 also follows the same pattern. Histological observations were in accordance with the clinical indicators. Both collagen and collagen hydrolysate treatments showed significant reduction in mucosal damage score and facilitated faster regeneration of damaged mucosa.

Excess accumulation of collagen (fibrosis) is the hallmark of many fibrotic diseases such as keloids, hypertrophic scars, etc. The inhibition of collagen fibrillation during its accumulation is a therapeutic way to limit the fibrosis. Herein, the effect of Ferulic acid (FA), a natural phenolic acid compound, on collagen fibrillation is studied using biophysical methods. Optical density (OD) and microscopic analysis indicate that FA inhibits collagen self-association, and the inhibitory efficiency depends on the concentration and temperature. The absence of an increase in OD for matured collagen fibrillar solution upon addition of FA followed by collagen solution indicates that FA could also terminates the progression of preformed collagen fibrils. Spectroscopic measurements indicate that collagen retains its unique triple helical structure in the presence of FA. Saturation Transfer Difference NMR suggests that FAs are in proximity to collagen while fluorescence quenching upon addition of FA proposes that FA most likely binds to the telopeptide regions of collagen. Enzymatic studies suggest that FA protects collagen from enzymatic degradation. The current study demonstrates that FA is a potential inhibitor of collagen fibrillation and its propagation and thus it can be considered for therapeutic studies to make FA as a remedy for the plaques related to collagen deposition.

Excess accumulation of collagen (fibrosis) undergoes self-aggregation, which leads to fibrillar collagen, on the extracellular matrix is the hallmark of a number of diseases such as keloids, hypertrophic scars, and systemic scleroderma. Direct inhibition or disintegration of collagen fibrils by small molecules offer a therapeutic approach to prevent or treat the diseases related to fibrosis. Herein, the anti-fibrotic property of Glucono-δ-lactone (GdL), known as acidifier, on the fibrillation and its disintegration of collagen was investigated. As collagen fibrillation is pH dependent, the pH modulation property of GdL is attractive to inhibit self-association of collagen. Optical density and microscopic data indicate that GdL elicits concentration-dependent fibril inhibition and also disintegrates pre-formed collagen fibrils. The simultaneous pH analysis showed that the modulation(lowering) of pH by GdL is the primary cause for its anti-fibrotic activity. The intact triple helical structure of collagen upon treatment of GdL suggests that collagen fibril disintegration can be achieved without affecting the native structure of collagen which is essential for any anti-fibrotic agents. Saturation transfer difference (STD) NMR result reveals that GdL is in proximity to collagen. The present results thus suggest that GdL provides a lead to design novel anti-fibrotic agents for the pathologies related to collagen deposition.

A novel scaffold for effective wound healing treatment was developed utilizing natural product bearing collagen-based biocompatible electrospun nanofibers. Initially, ostholamide (OSA) was synthesized from osthole (a natural coumarin), characterized by 1H, 13C, DEPT-135 NMR, ESI-MS, and FT-IR spectroscopy analysis. OSA was incorporated into polyhydroxybutyrate (PHB) and gelatin (GEL), which serve as templates for electrospun nanofibers. The coating of OSA-PHB-GEL nanofibers with collagen resulted in PHB-GEL-OSA-COL nanofibrous scaffold which mimics extracellular matrix and serves as an effective biomaterial for tissue engineering applications, especially for wound healing. PHB-GEL-OSA-COL, along with PHB-GEL-OSA and collagen film (COLF), was characterized in vitro and in vivo to determine its efficacy. The developed PHB-GEL-OSA-COL nanofibers posed an impressive mechanical stability, an essential requirement for wound healing. The presence of OSA had contributed to antimicrobial efficacy. These scaffolds ...

Keratin has gained much attention in the recent past as a biomaterial for wound healing owing to its biocompatibility, biodegradability, intrinsic biological activity and presence of cellular binding motifs. In this paper, a novel biomimetic scaffold containing keratin, chitosan and gelatin was prepared by freeze drying method. The prepared keratin composite scaffold had good structural integrity. Fourier Transform Infrared (FTIR) spectroscopy showed the retention of the native structure of individual biopolymers (keratin, chitosan, and gelatin) used in the scaffold. Thermogravimetric Analysis (TGA) and Differential Scanning Calorimetry (DSC) results revealed a high thermal denaturation temperature of the scaffold (200-250°C). The keratin composite scaffold exhibited tensile strength (96 kPa), compression strength (8.5 kPa) and water uptake capacity (>1700%) comparable to that of a collagen scaffold, which was used as control. The morphology of the keratin composite scaffold observed using a Scanning Electron Microscope (SEM) exhibited good porosity and interconnectivity of pores. MTT assay using NIH 3T3 fibroblast cells demonstrated that the cell viability of the keratin composite scaffold was good. These observations suggest that the keratin-chitosan-gelatin composite scaffold is a promising alternative biomaterial for tissue engineering applications.

Collagen, the most abundant protein in mammals, is widely used for making biomaterials. Recently, organic solvents have been used to fabricate collagen-based biomaterials for biological applications. It is therefore necessary to understand the behavior of collagen in the presence of organic solvents at low (≤50%, v/v) and high (≥90%, v/v) concentrations. This study was conducted to examine how collagen reacts when exposed to low and high concentrations of ethanol, one of the solvents used to make collagen-based biomaterials. Solubility testing indicated that collagen remains in solution at low concentrations (≤50%, v/v) of ethanol but precipitates (gel-like) thereafter, irrespective of the method of addition of ethanol (single shot or gradual addition); this behavior is different from that observed recently with acetonitrile. Collagen retains its triple helix in the presence of ethanol but becomes thermodynamically unstable, with substantially reduced melting temperature, with increasing concentration of ethanol. It was also found that the CD ellipticity at 222 nm, characteristic of the triple-helical structure, does not correlate with the thermal stability of collagen. Time-dependent experiments reveal that the collagen triple helix is kinetically stable in the presence of 0-40% (v/v) ethanol at low temperature (5 °C) but highly unstable in the presence of ethanol at elevated temperature (~34 °C). These results indicate that when ethanol is used to process collagen-based biomaterials, such factors as temperature and duration should be done taking into account, to prevent extensive damage to the triple-helical structure of collagen.

Central Leather Research Institute (Council of Scientific and Industrial Research),Sardar Patel Road, Adyar, Chennai 600 020, IndiaReceived 11 January 2012; revised 30 August 2012; accepted 5 October 2012Published online in Wiley Online Library (wileyonlinelibrary.com). DOI: 10.1002/jbm.b.32856Abstract: A biodurable porous scaffold of collagen withgood biocompatibility and enhanced wound healing poten-tial is prepared through casting technique using tannic acid(TA) as crosslinker. The morphological analysis of the tannicacid cross-linked collagen scaffold (TCCs) distinctively showsscaly interlinks with large pores. The enzymatic stability ofthe scaffold is characterized in vitro to detail the role of TAin stabilization of collagen matrix against collagenolytic deg-radation. TCCs shows more stability (>54%) against collage-nase than that of the collagen scaffolds (Cs). The attenuatedtotal reflectance Fourier transform infrared analysis of theTCCs confirms the noncovalent interaction between collagenand TA. The biocompatibility of the scaffold (TCCs) in vitrohas been established using 3T3 fibroblasts. Therapeutic andwound healing potential of the TCCs has been studied invivo using excision wound model in rats. The results clearlyindicates that the TCCs has greater and significant effect inwound closure and increased the wound healing rate com-pared with native Cs. This biocompatible and biodurablescaffold may find broad applications in the tissue engineer-ing and drug delivery applications.

In the recent past, keratin has been fabricated into different forms of biomaterials like scaffold, gel, sponge, film etc. In lieu of the myriad advantages of the hydrogels for biomedical applications, a keratin-silica hydrogel was fabricated using tetraethyl orthosilicate (TEOS). Textural analysis shed light on the physical properties of the fabricated hydrogel, inturn enabling the optimization of the hydrogel. The optimized keratin-silica hydrogel was found to exhibit instant springiness, optimum hardness, with ease of spreadability. Moreover, the hydrogel showed excellent swelling with highly porous microarchitecture. MTT assay and DAPI staining revealed that keratin-silica hydrogel was biocompatible with fibroblast cells. Collectively, these properties make the fabricated keratin-silica hydrogel, a suitable dressing material for biomedical applications.

Inhibitory effect of green tea polyphenols viz., catechin and epigallocatechin gallate (EGCG) on the action of collagenase against collagen has been probed in this study. Catechin and EGCG treated collagen exhibited 56 and 95% resistance, respectively, against collagenolytic hydrolysis by collagenase. Whereas direct interaction of catechin and EGCG with collagenase exhibited 70 and 88% inhibition, respectively, to collagenolytic activity of collagenase against collagen and the inhibition was found to be concentration dependent. The kinetics of inhibition of collagenase by catechin and EGCG has been deduced from the extent of hydrolysis of (2-furanacryloyl-L-leucyl-glycyl-L-prolyl-L-alanine), FALGPA. Both catechin and EGCG exhibited competitive mode of inhibition against collagenase. The change in the secondary structure of collagenase on treatment with catechin and EGCG has been monitored using circular dichroism spectropolarimeter. CD spectral studies showed significant changes in the secondary structure of collagenase on treatment with higher concentration of catechin and EGCG. Higher inhibition of EGCG compared to catechin has been attributed to the ability of EGCG to exhibit better hydrogen bonding and hydrophobic interaction with collagenase.

Collagen, a unique connective tissue protein finds extensive application as biocompatible biomaterial in wound healing, as drug carriers, cosmetics, etc. A work has been undertaken to study the stabilization of type I collagen using the plant polyphenol catechin. Catechin treated collagen fibres showed a shrinkage temperature around 70 degrees C implying that catechin is able to impart thermal stability to collagen. Catechin treated collagen fibres has been found to be stable even after treatment with high concentration of the secondary structural destabilizer, urea. Circular dichroism studies revealed that there is no major alteration in the structure of collagen on treatment with catechin. The study has demonstrated the involvement of hydrogen bonding and hydrophobic interactions as the major forces involved in the stabilization of collagen by the plant polyphenol, catechin.

Arthritic diseases, such as osteoarthritis and rheumatoid arthritis, inflict an enormous health care burden on society. Osteoarthritis, a degenerative joint disease with high prevalence among older people, and rheumatoid arthritis, an autoimmune inflammatory disease, both lead to irreversible structural and functional damage to articular cartilage. The aim of this study was to investigate the effect of polyphenols such as catechin, quercetin, epigallocatechin gallate, and tannic acid, on crosslinking type II collagen and the roles of these agents in managing in vivo articular cartilage degradation. The thermal, enzymatic, and physical stability of bovine articular cartilage explants following polyphenolic treatment were assessed for efficiency. Epigallocatechin gallate and tannic acid-treated explants showed >12 °C increase over native cartilage in thermal stability, thereby confirming cartilage crosslinking. Polyphenol-treated cartilage also showed a significant reduction in the percentage of collagen degradation and the release of glycosaminoglycans against collagenase digestion, indicating the increase physical integrity and resistance of polyphenol crosslinked cartilage to enzymatic digestion. To examine the in vivo cartilage protective effects, polyphenols were injected intra-articularly before (prophylactic) and after (therapeutic) the induction of collagen-induced arthritis in rats. The hind paw volume and histomorphological scoring was done for cartilage damage. The intra-articular injection of epigallocatechin gallate and tannic acid did not significantly influence the time of onset or the intensity of joint inflammation. However, histomorphological scoring of the articular cartilage showed a significant reduction in cartilage degradation in prophylactic- and therapeutic-groups, indicating that intra-articular injections of polyphenols bind to articular cartilage and making it resistant to degradation despite ongoing inflammation. These studies establish the value of intra-articular injections of polyphenol in stabilization of cartilage collagen against degradation and indicate the unique beneficial role of injectable polyphenols in protecting the cartilage in arthritic conditions.

Capsaicin is a versatile plant product which has been ascribed several health benefits and anti-inflammatory and analgesic properties. We have investigated the effect of capsaicin on the molecular stability, self-assembly, and fibril stability of type-I collagen. It was found that capsaicin suppresses collagen fibril formation, increases the stability of collagen fibers in tendons, and has no effect on the molecular stability of collagen. Turbidity assay data show that capsaicin does not promote disassembly of collagen fibrils. However, capsaicin moderately protects collagen fibrils from enzymatic degradation. Computational studies revealed the functions of the aromatic group and amide region of capsaicin in the collagen–capsaicin interaction. The results may have significant implications for capsaicin-based therapeutics that target excess collagen accumulation-linked pathology, for example thrombosis, fibrosis, and sclerosis.

Collagen is one of the most widely used biomaterial for various biomedical applications. In this Research Article, we present a novel approach of using collagen hydrolysate, smaller fragments of collagen, as an alternative to traditionally used collagen scaffold. Collagen hydrolysate composite scaffold (CHCS) was fabricated with sol-gel transition procedure using tetraethoxysilane as the silica precursor. CHCS exhibits porous morphology with pore sizes varying between 380 and 780 μm. Incorporation of silica conferred CHCS with controlled biodegradation and better water uptake capacity. Notably, 3T3 fibroblast proliferation was seen to be significantly better under CHCS treatment when compared to treatment with collagen scaffold. Additionally, CHCS showed excellent antimicrobial activity against the wound pathogens Staphylococcus aureus, Bacillus subtilis, and Escherichia coli due to the inherited antimicrobial activity of collagen hydrolysate. In vivo wound healing experiments with full thickness excision wounds in rat model demonstrated that wounds treated with CHCS showed accelerated healing when compared to wounds treated with collagen scaffold. These findings indicate that the CHCS scaffold from collagen fragments would be an effective and affordable alternative to the traditionally used collagen structural biomaterials.

Development of a bio-composite using synergistic combination is a promising strategy to address various pathological manifestations of acute and chronic wounds. In the present work, we have combined three materials viz., mupirocin as an antimicrobial drug, sol-gel processed silica microsphere as drug carrier for sustained delivery of drug and collagen, an established wound healer as scaffold. The mupirocin-loaded silica microspheres (Mu-SM) and Mu-SM loaded collagen scaffold were characterized for surface morphology, entrapment efficiency and distribution homogeneity, in vitro drug release, water uptake capacity, cell proliferation and antibacterial activity. In vivo wound healing efficacy of the bio-composite was experimented using full thickness excision wound model in Wistar albino rats. The Mu-SM incorporated collagen scaffold showed good in vitro characteristics in terms of better water uptake, sustained drug availability and antimicrobial activity. The wound closure analysis revealed that the complete epithelialisation was observed at 14.2 ± 0.44 days for Mu-SM loaded collagen, whereas this was 17.4 ± 0.44 days and 20.6 ± 0.54 days for collagen and control groups, respectively. Consequently, the synergistic strategy of combining mupirocin-loaded silica microspheres and collagen as a Mu-SM loaded collagen dressing material would be an ideal biomaterial for the treatment of surface wounds, burns and foot ulcers.

We recently experimented with collagen coating on the surface of quercetin loaded polycaprolactone microspheres by simple adsorption technique to mimic extra cellular matrix and reduce immune or inflammatory responses at the site of implants. The collagen immobilization on polymeric scaffold surfaces through various surface modification techniques was the current scenario to improve bio-integration of the polymers with the in vivo system. Nevertheless, it requires other chemicals or processing methods to modify the surface of polymers to immobilize the collagen covalently. Here protein adsorption principle is used for the coating of collagen onto the surface of solid microspheres and characterized. Optical, ATR-FTIR, SEM analysis confirm collagen coating. The reduction in burst release of the quercetin from the PCL microspheres further confirms its presence and role in the controlled release. The results indicate that the adsorption technique can be the simple strategy to coat collagen on the surface of polyester implants to develop stealth implant in shorter time with low cost technology.

Fibrils of Type I collagen in the skin are exposed to ultraviolet (UV) light and there have been claims that collagen photo-degradation leads to wrinkles and may contribute to skin cancers. To understand the effects of UV radiation on collagen, Type I collagen solutions were exposed to the UV-C wavelength of 254 nm for defined lengths of time at 4°C. Circular dichroism (CD) experiments show that irradiation of collagen leads to high loss of triple helical content with a new lower thermal stability peak and SDS-gel electrophoresis indicates breakdown of collagen chains. To better define the effects of UV radiation on the collagen triple-helix, the studies were extended to peptides which model the collagen sequence and conformation. CD studies showed irradiation for days led to lower magnitudes of the triple-helix maximum at 225 nm and lower thermal stabilities for two peptides containing multiple Gly-Pro-Hyp triplets. In contrast, the highest radiation exposure led to little change in the Tm values of (Gly-Pro-Pro)10 and (Ala-Hyp-Gly)10, although (Gly-Pro-Pro)10 did show a significant decrease in triple helix intensity. Mass spectroscopy indicated preferential cleavage sites within the peptides, and identification of some of the most susceptible sites of cleavage. The effect of radiation on these well defined peptides gives insight into the sequence and conformational specificity of photo-degradation of collagen. © 2011 Wiley Periodicals, Inc. Biopolymers 97:189–198, 2012.

Stabilization of type I rat tail tendon (RTT) collagen by various aldehydes, viz. formaldehyde, gluteraldehyde, glyoxal and crotanaldehyde was studied to understand the effect of each on the thermal, enzymatic and conformational stability of collagen. The aldehydes have been found to increase the heat stability of rat tail tendon collagen fibres from 62 to 77-86 degrees C. The increase in thermal stability was found to be in a species dependent manner. The variation in the thermal stability of collagen brought about by aldehydes was in the order of formaldehyde > gluteraldehyde > glyoxal > crotanaldehdye. The aldehydes also impart a high degree of stability to collagen against the activity of the degrading enzyme, collagenase. The order of enzymatic stability brought about by aldehydes follows the same trend as the thermal stability brought about by them. This shows that the number of cross-links formed influence both the thermal and enzymatic stability in the similar manner. The effect of various aldehydes on the secondary structure of collagen was studied using circular dichroism and it was found that the aldehydes lead to changes in the amplitude of the circular dichroic (CD) spectrum but did not alter the triple helical conformation of collagen. The secondary structure of collagen is not significantly altered on interaction with different aldehydes.

The presence of chromium in the effluent is a major concern for the tanning industry. Currently, chemical precipitation methods are practiced for the removal of chromium from the effluent, but that leads to the formation of chrome-bearing solid wastes. The other membrane separation and ion exchange methods available are unfeasible due to their cost. In this study, the removal of chromium from tannery effluent has been carried out using abundantly available brown seaweed Sargassum wightii. Simulated chrome tanning solution was used for the standardization of experimental trials. Various factors influencing the uptake of chromium, viz., quantity of seaweed, concentrations of chromium, pH of the chrome-bearing wastewater, and duration of treatment, have been studied. Chemical modification of the seaweed through pretreatment with sulfuric acid, magnesium chloride, and calcium chloride showed improved uptake of chromium. Langmuir and Freundlich isotherms have been fitted for various quantities of seaweed. The dynamic method of treatment of protonated seaweed with simulated chrome tanning solution at a pH of 3.5-3.8 for a duration of 6 h gave the maximum uptake of about 83%. A similar uptake has been established for commercial chrome tanning wastewater containing the same concentration of chromium. The Sargassum species exhibited a maximum uptake of 35 mg of chromium per gram of seaweed. Fourier transform infrared spectroscopy, energy-dispersive X-ray analysis, and flame photometry studies have been carried out to understand the mechanistic pathway for the removal of chromium. The potential reuse of chromium-containing seaweed for the preparation of basic chromium sulfate (tanning agent) has been demonstrated.

Collagen, a unique connective tissue protein finds extensive application as biocompatible biomaterial in wound healing, as drug carriers, cosmetics, etc. A study has been undertaken to stabilise Type-I collagen of rat-tail tendon using plant polyphenol (Acacia Mollissima) in the presence of an acrylic polymer. It has been found that collagen fibres pre-treated with acrylic polymer followed by the treatment with Acacia Mollissima exhibited an increase in hydrothermal stability by 25°C. Infrared spectroscopic studies display the changes in the spectral characteristics of native and treated collagen films. Transmission electron microscopic and circular dichroic studies provide an insight into the understanding of the improved stabilisation of collagen, due to treatment with acrylic polymer and plant polyphenols. The study is expected to enhance the biomaterial applications of collagen tissues.