Degradation of phospholipid polymer hydrogel by hydrogen peroxide aiming at insulin release device

The purpose of this study is to ascertain the applicable possibility of H2O2 degradable hydrogel for fabrication of insulin release system synchronized with the change in the glucose concentration in the medium. The hydrogel was prepared by using 2-methacryloyloxyethyl phosphorylcholine (MPC) and crosslinker. The favorable characteristic of the hydrogel was H2O2 concentration responsive degradation. The H2O2 was utilized and produced by enzymatic reaction between glucose oxidase and glucose. Poly(MPC) (PMPC) was easily degraded in H2O2 aqueous solution, and the PMPC hydrogel was also degraded in H2O2 aqueous solution. The degradation mechanism was considered to be main chain scission of PMPC. The degradation profile was evaluated by using weight swelling ratio and volume swelling ratio. The weight swelling ratio of PMPC hydrogel firstly increased due to the reduction of crosslink density, then the ratio decreased to zero (complete degradation). The degradation profile was proportional to the H2O2 concentration. Furthermore, volume swelling ratio also increased, and complex elastic modulus decreased with degradation in H2O2 aqueous solution. These results indicated that the hydrogel was degraded by hydroxy and/or hydroperoxy radicals which was produced by H2O2, the crosslink density and mechanical property decreased. The release profile from the hydrogel was estimated by using lipid microsphere (LM) as an insulin model. The LM was released with the degradation of PMPC hydrogel. Taking these results into account, the PMPC hydrogel was available for H2O2 degradable hydrogel for synchronization with glucose concentration by using enzymatic reaction.