Collagen-based hydrogels are investigated extensively in tissue engineering for their tunable physiochemical properties, biocompatibility and biodegradability. However, the effect of the integrity of the collagen triple helical structure on biodegradability is yet to be studied. In this study, we monitored the degradation of intact collagen (C-coll) and hydrolyzed collagen (D-coll) hydrogels in collagenase Clostridium histolyticum to understand their degradation process. Our results show that when peptides are present on the surface of the fibrils of D-coll hydrogels, cleavage of amide bonds occur at a much higher rate. The fibrillar structure of D-coll hydrogel results in a more pronounced breakdown of the gel network and dissolution of collagen peptides. The results from this work will improve the understanding of enzymatic degradation and the resulting bioabsorption of collagen materials used in drug delivery systems and scaffolds.

We present a mechanism for the selectivity of covalent/electrostatic binding of the Cr(III) ion to collagen, mediated by the kosmotropicity of the anions. Although a change in the long-range ordered structure of collagen is observed after covalent binding (Cr(III)-OOC) in the presence of SO 4 2− at pH 4.5, the ν sym (COO −) band remains intense, suggesting a relatively lower propensity for the Cr(III) to bind covalently instead of electrostatically through Cr(H 2 O) 6 3+. Replacing SO 4 2− with Cl − reduces the kosmotropic effect which further favors the electrostatic binding of Cr(III) to collagen. Our findings allow a greater understanding of mechanism-specific metal binding in the collagen molecule. We also report for the first time, surfaceenhanced Raman spectroscopy to analyze binding mechanisms in collagen, suggesting a novel way to study chemical modifications in collagen-based biomaterials.

Nishanth Chemmangattuvalappil (2015): Luffa acutangula peel as an effective natural biosorbent for malachite green removal in aqueous media: equilibrium, kinetic and thermodynamic investigations, Desalination and Water Treatment, A B S T R A C TLuffa acutangula peel (LAP) was evaluated as an inexpensive natural biosorbent for the removal of malachite green (MG), a cationic dye, in batch mode. The effects of process parameters including initial pH, dosage, initial concentration, temperature and contact time on MG biosorption were assessed. Experimental data were analysed by the Langmuir, Freundlich, Temkin and Dubinin-Radushkevich models. The results showed that MG biosorption was well represented by the Langmuir model with a maximum sorption capacity of 69.64 mg/g. The pseudo-first-order and pseudo-second-order kinetic models were used to establish the biosorption kinetic. A good correlation of data with the pseudosecond-order model suggested the involvement of chemisorption in the process. Further kinetic analysis indicated intraparticle diffusion as one of the rate limiting steps. The biosorption process was endothermic (ΔH˚= 0.332-12.64 kJ/mol) and spontaneous (ΔG˚= −20.81 to −14.28 kJ/mol). Overall, the findings suggested that LAP can be an effective biosorbent for the removal of MG in aqueous solution.

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