Controlling absorbency in gelatin networks: Preparation and characterization of alkylated, crosslinked gelatin

Gelatin is a highly abundant and relatively inexpensive protein which is used in a variety of gel applications including photography, drug delivery, microencapsulation, and food preparation. Control of network formation in gelatin may therefore provide methods of preparing protein gels tailored for specific applications. In this study, circular dichroism(CD), Raman, and nuclear magnetic resonance (NMR) spectroscopies were used to characterize ordering processes which occur in gelatin and their relationship to absorbency. Ordering of the unmodified protein, studied as a function of concentration, temperature, and time after initial preparation, correlates inversely with absorbency. Chemical modification was used to control the absorbency and solubility of the protein gels. Alkylation of gelatin using glycidyltrimethylammonium chloride causes substantial increases in water absorbency with degrees of substitution as low as 0.5%. Increases in saline swelling were observed only after additional modification of the alkylated gelatin with a nonionic polyoxyalkyleneamine crosslinking agent (Jeffamine(R)). Limiting the initial degree of substitution prior to crosslinking (to just below 1%) plays a key role in optimizing the absorbency and minimizing the dissolution of the gel in saline. The methods and principles used to manipulate the absorbency of gelatin may also find use for other natural protein systems. (C) 1998 John Wiley & Sons, Inc.