Submitted to: Biomacromolecules
Publication Type: Peer reviewed journal
Publication Acceptance Date: 1/29/2003
Publication Date: 8/1/2003
Citation: PAYNE, G.F., CHEN, T., EMBREE, H.D., BROWN, E.M., TAYLOR, M.M. ENZYME-CATALYZED GEL-FORMATION OF GELATIN AND CHITOSAN. POTENTIAL FOR IN SITU APPLICATIONS. BIOMACROMOLECULES. 2003. V. 24. P. 2831-2841. Interpretive Summary: There is currently much interest in the development of products from renewable resources, such as plant and animal by-products, for use in the production of goods that have traditionally been petroleum based. Both gelatin, a protein byproduct of the meat and leather industries, and chitosan, a carbohydrate from crab shells, are large molecules with industrially useful qualities. Historically these materials individually have been chemically modified for industrial use in adhesives and thermally stable gels. In this work, gelatin and chitosan were blended and treated with crosslinking enzymes under mild conditions to form gels that have unique characteristics and are completely biobased. A major advantage of these composites is that the byproduct blend can be placed where needed and then gelled without the use of toxic chemicals.
Technical Abstract: We compared the ability of two enzymes to catalyze the formation of gels from solutions of gelatin and chitosan. A microbial transglutaminase, currently under investigation for food applications, was observed to catalyze the formation of strong and permanent gels from gelatin solutions. Chitosan was not necessary for transglutaminase-catalyzed gel formation, although gel formation was faster, and the resulting gels were stronger if reactions were performed in the presence of this polysaccharide. Consistent with transglutaminase's ability to crosslink proteins, we observed that the transglutaminase-catalyzed gelatin-chitosan gels lost the ability to undergo the reversible sol-gel transition characteristic of gelatin. Mushroom tyrosinase was observed to catalyze gel formation for gelatin-chitosan blends, but no gels were observed in the absence of chitosan. Tyrosinase-catalyzed gelatin-chitosan gels were observed to be considerably weaker than transglutaminase-catalyzed gels. Tyrosinase-catalyzed gels were strengthened by cooling below gelatin's gel-point suggesting that gelatin's ability to undergo its characteristic coil-to-helix transition is unaffected by tyrosinase-catalyzed reactions. Further, tyrosinase-catalyzed gelatin-chitosan gels were transient as their strength (i.e. elastic modulus) peaked at about 5 hours after which the gels were observed to break over the course of two days. The strength of both gels could be adjusted by altering the gelatin and chitosan compositions. Potential applications of these gels for in situ applications in tissue engineering and burn dressings are considered.