Kinetics of BSA release from poly(N-isopropylacrylamide) hydrogels

The thermo-sensitive poly(N-isopropylacrylamide) (poly(NIPAAm)) hydrogel is synthesized by free radical polymerization. As a model solute in the study of drug loading and release kinetics with hydrogels, the bovine serum albumin (BSA) protein was used to measure the volume changes and the release kinetics by thermal deswelling. Experiments are performed at different temperatures around the low critical solution temperature (LCST). The effect of the release temperature upon polymer characteristics and release properties was investigated. The BSA release coupled with shrinking of the hydrogel particles was modelled with a bi-dimensional diffusion model with moving boundary conditions. The influence of the variable diffusion coefficient is observed and leaded to better description of the kinetic curve in the case of important deformation around the LCST. A good correlation between experimental and calculated data was obtained.