Design and characterization of anionic hydrogels confined in Daisogel silica composites microspheres and their application in sustained release of proteins

This paper presents the synthesis and characterization of some composite sorbents prepared by the impregnation and cross-linking copolymerization of acrylamide in the pores of two grades of Daisogel silica, followed by post-hydrolysis of amide groups with generation of COO- functional groups. Polymer content of the composites was determined from the thermally decomposed amount of organic part by thermogravimetric analysis. Fourier transform infrared spectroscopy was used to show the structure of polymers confined in the silica pores and potentiometric titration to determine the point of zero charge (pzc). The silica supported functional polymers were tested in the loading/release of lysozyme (LYS) as macromolecular drug. H type sorption isotherms of LYS onto the novel composites were found which support a very high affinity of the anionically charged composite for the positively charged protein. Release mechanism of LYS as a function of the environment was a Fickian diffusion irrespective of the medium and the morphology of Daisogel. This study demonstrates, for the first time, the feasibility of the anionically modified poly( acrylamide) hydrogel confined in the silica pores as very promising sustained release system. (C) 2015 Elsevier B.V. All rights reserved.