Kalarical Janardhanan Sreeram

Stabilization of collagen with EDC/NHS in the presence of l-lysine: A comprehensive study

This paper reports the effect of L-lysine on the conformational, rheological, and thermal properties of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC) and N-hydroxysuccinimide (NHS) cross linked collagen and investigates the influence of l-lysine on the self assembly processes of collagen. In the absence of L-lysine, the rheological characterization of collagen cross linked with EDC/NHS showed an increase in shearing stress with shearing speed indicating that the collagen chains become rigid and the molecules are reluctant to flow. On the other hand, the increase in shearing stress with shearing speed is comparatively much less in the presence of L-lysine indicating a greater flexibility of the collagen molecules. The self assembly processes of collagen treated with EDC/NHS in the absence and presence of L-lysine were characterized using powder XRD, FT-IR, polarizing optical microscopy and kinetic studies. XRD studies show an increase in peak intensity and sharpness in the presence of L-lysine indicating the enhancement of crystallinity of collagen nano-fibrils. FT-IR results suggest that the incorporation of L-lysine in the EDC/NHS cross linking favors the molecular stability of collagen. From the present study, it is possible to conclude that the pre-treatment of collagen with L-lysine enhances EDC/NHS cross linking and can be used for biomaterial applications.

Enhancing collagen stability through nanostructures containing chromium(III) oxide

Stabilization of collagen for various applications employs chemicals such as aldehydes, metal ions, polyphenols, etc. Stability against enzymatic, thermal and mechanical degradation is required for a range of biomedical applications. The premise of this research is to explore the use of nanoparticles with suitable functionalization/encapsulation to crosslink with collagen, such that the three dimensional architecture had the desired stability. Collagen solution prepared as per standard protocols is treated with chromium(III) oxide nanoparticules encapsulated within a polymeric matrix (polystyrene-block-polyacrylic acid copolymer). Selectivity towards encapsulation was ensured by the reaction in dimethyl sulfoxide, where the PS groups popped out and encapsulated the Cr(2)O(3). Subsequently when immersed in aqueous solution, PAA units popped up to react with functional groups of collagen. The interaction with collagen was monitored through techniques such as CD, FTIR, viscosity measurements, stress analysis. CD studies and FTIR showed no degradation of collagen. Thermal stability was enhanced upon interaction of nanostructures with collagen. Self-assembly of collagen was delayed but not inhibited, indicating a compete binding of the metal oxide encapsulated polymer to collagen. Metal oxide nanoparticles encapsulated within a polymeric matrix could provide thermal and mechanical stability to collagen. The formed fibrils of collagen could serve as ideal material for various smart applications such as slow/sustained drug release. The study is also relevant to the leather industry in that the nanostructures can diffuse through the highly networked collagen fibre bundles in skin matrix easily, thus overcoming the rate limiting step of diffusion.

Effective synthesis route for red-brown pigments based on Ce – Pr – Fe – O and their potential application for near infrared reflective surface coating

AbstractNew cerium-based ceramic pigments, displaying Ce2Pr0.2FexO4.3+y stoichiometry, were obtained at low temperature using a sol–gel method. The powder precursor dissolved in 80% ethylene glycol was precipitated using ammonia and the obtained gel calcined at 800°C for 2 h to yield homogeneous and crystalline particles with a diameter of around 150 nm. The oxide was composed of cerium in its +4 oxidation state and Pr in its +3 oxidation state. The oxides with varying Fe content had an intense red-brown colour, with bandgap energy of around 2.2 eV at 0.1 mol% Fe doping. The near infra red reflectance from these pigments, a measure of their ability to reflect rather than absorb heat waves from sunlight was found to be 82.7%, even in the absence of a white reflective base. Such high near infra red reflectance from these pigments qualify them for being ideal cool pigments for surface coating applications.n Figureᅟ

Rare earth doped cobalt aluminate blue as an environmentally benign colorant

Increasing energy cost calls for exterior coatings with high near infra-red reflectance, so as to reduce heat absorption and in turn cost of air-conditioning. While modulations of substrate, use of white metal oxides as pigments or under-layers has been reported in past, reports on metal oxide or doped metal oxide pigments with high NIR reflectance is scarce. We report for the first time a blue colored cobalt aluminate type pigment prepared through doping of cerium, praseodymium or neodymium. CIELAB color measurements and calculation of ΔE indicated that the Nd doped sample had crystal size of (36±1) nm, bandgap value of (2.4±0.2) eV and color coordinates similar to that of cobalt aluminate. The molar ratio as estimated by EDX was found to be Al: Cu: Co: Ce: Nd: O=2: 0.06: 0.06: 0.012: 0.000 12: 6.18. The pigment was found to have potential applications as a cool blue colorant, owing to changes in optical properties arising out of crystal chemistry changes. Incorporation of rare earth metal ions was found to enhance the NIR reflectance by 10%, when compared to a conventional cobalt aluminate pigment. The oxide has been well characterized and its performance as a pigment evaluated. We have proposed that changes in crystal lattice when neodymium enters into Ce4+ sites enhance the NIR reflectance by about 9% as against the entry of praseodymium.

Hybrid composites: amalgamation of proteins with polymeric phenols as a multifunctional material for leather processing

In recent years, blending various protein wastes has resulted in the development of new hybrid composites, which display innovative functionalities with superior physico-chemical properties. One of the options explored in this work is the suitable modification of collagen hydrolysate (waste from the leather industry) along with degraded black liquor from the paper and pulp industry. In detail, the preparation of hybrid composites from collagen hydrolysates and degraded black liquor of different pH (14 and 7) was performed through a simple process. The characteristic features of the composites were thoroughly investigated by Fourier transform infrared spectroscopy (FTIR), dynamic light scattering (DLS) using a Malvern Zetasizer and scanning electron microscopy (SEM). The multifunctionality of the hybrid composites provided the opportunity to utilize this type of composite as a retanning agent in leather processing. The composites also exhibited enhanced functional properties as well as improved dyeing, thus making them a better retanning agent. The composite treated leather shows good softness, improved belly filling, and high strength with uniform dyeing. Hence, the potential use of multifunctional hybrid composites has gained more importance in economic processing.

Formation of necklace-shaped haematite nanoconstructs through polyethylene glycol sacrificial template technique

Haematite nanoparticles have been synthesised on polyethylene glycol (PEG) template, through a two-step method consisting of oriented attachment followed by growth. The process involves the binding of Fe2+ centres to PEG, followed by a high temperature calcination reaction. During the calcination process, the template is sacrificed and Fe2+ is converted to α-Fe2O3. Infrared spectroscopy and thermogravimetric analysis indicate that the template leaves behind a carbonaceous residue over the haematite surface, which prevents further aggregation of the nanoparticles even after the removal of the template. PEG helps in connecting the crystal flocs through a bridging mechanism. The residual magnetic moment, particle size, shape and ionic strength of the synthesised haematite nanoparticles promote the formation of necklace-shaped structures. Directional growth of haematite nanoparticles brought about by PEG results in an increase in coercivity and near-zero remnant magnetisation at zero field strength. The magnetisation curves do not attain saturation even at a field strength of 7 kOe, indicating a superparamagnetic behaviour. Such nanoparticles with a carbonaceous coat, a necklace structure and superparamagnetic behaviour can find extensive use in targeted drug delivery.