Improvement in Water Stability and Other Related Functional Properties of Thin Cast Kafirin Protein Films

Abstract

Improvement in the water stability and other related functional properties of thin (<50 µm) kafirin protein films was investigated. Thin conventional kafirin films and kafirinmicroparticle films were prepared by casting in acetic acid solution. Thin kafirin films cast from microparticles were more stable in water than conventional cast kafirin films.Treatment of kafirinmicroparticles with heat and transglutaminase resulted in slightly thicker films with reduced tensile strength. In contrast,glutaraldehyde treatment resulted in up to 43% increase in film tensile strength. The films prepared from microparticles treated with glutaraldehyde were quite stable in ambient temperature water, despite the loss of plasticizer.This was probably due to the formation of covalent cross-linking between free amino groups of the kafirin polypeptides and carbonyl groups of the aldehyde. Thus, such thin glutaraldehyde-treated kafirinmicroparticle films appear to have good potential for use as biomaterials in aqueous applications.

Physicochemical Modification of Kafirin Microparticles and Their Ability To Bind Bone Morphogenetic Protein-2 (BMP-2), for Application as a Biomaterial

“…Kafirin was extracted from a mixture of grain of two similar white, tan-plant non-tannin sorghum cultivars PANNAR PEX 202 and 606, as described (17). The protein was defatted and freeze-dried.…”

“…Various methods of cross-linking kafirin microparticles have been investigated to improve the water resistance of bioplastic films made from them (17). Cross-linking has also been investigated to improve the tensile properties of cast kafirin films (18) and cast zein films (19).…”

Role of γ-Kafirin in the Formation and Organization of Kafirin Microstructures

“…Similar reduction resistant bands were observed with kafirin microparticle films. 47 It has been suggested that the presence of polymeric kafirin resistant to reduction could be due to some covalent crosslinks being inaccessible to the reducing agent.…”

Biocompatibility and biodegradation of protein microparticle and film scaffolds made from kafirin (sorghum prolamin protein) subcutaneously implanted in rodent models

“…The films have a much smaller total surface area than the vacuolated kafirin microparticles. There is evidence that kafirin microparticle films are more resistant to digestive_proteolytic enzymes (40.7% digested after 2 h) 16 than kafirin microparticles (86% digested after 2 h) 14 and so may be more inert when used as an implant in a small animal model. Kafirin microparticle films crosslinked with two commonly used cross-linking agents, either glutaraldehyde or sorghum polyphenols were included to investigate any potential adverse effects of kafirin micropa1ticle films when treated with these potentially toxic cross-linking agents.…”

“…13 Kafirin can be formed into highly vacuolated micropmticles, between approximaterly l-1 0 [!In diameter, 14 providing a large surface area for binding bioactive compounds such as polyphenolic nutraceuticals, 15 and bone morphogenetic proteins (BMP's). 16 Thin (<50 [!In), water stable kafirin bioplastic films can also be formed from these micropmticles. 16 Both structures may have potential for scaffold type applications, since kafirin is slowly biodegraded by mammalian digestive proteolytic enzymes, 12 is non-allergenic, 17 and there is good evidence that kafirin is nontoxic to celiac sufferers.…”