SYNTHESIS AND RELEASE PROFILE ANALYSIS OF THERMO-SENSITIVE ALBUMIN HYDROGELS

Novel thermo-responsive hydrophilic microspheres were prepared by free radical polymerization ofmethacrylate bovine serum albumin and N-Isopropylacrylamide, as cross-linker and functional monomer, respectively.The incorporation of monomers in the network was confirmed by infrared spectroscopy, while the network density and shape of hydrogels strictly depend on concentration of monomers in the polymerization feed. The thermal analyses showed negative thermo-responsive behavior with pronounced water affinity of microspheres at temperaturelower than lower critical solution temperature (LCST). Thein vitro release studies of drug-loaded thermo-sensitivehydrogels were performed. Experimental data showed, forthe copolymers with functional monomer/cross-linker ratio≤1, a predominant drug release in the collapsed state, whilethe copolymers with functional monomer/cross-linker ratio>1 showed prominent drug release in the swollen state. Below the hydrogel LCST, drug release through the swollenpolymeric networks was observed, while a squeezing-out effect at temperature above the LCST was predominant.