Preparation And Characterization Of Biodegradable PH-and Temperature-sensitive Hydrogels And Microgels

With the rapid development of modern medicine, the kinds of protein drugs which can be applied to medicine are increasing. These protein drugs have excellent pharmacological effects and little side effects, but they are easy to be degraded by the digestive enzymes and their pharmacological effects thus are reduced. Drug controlled release system is an effective way to solve above-mentioned problems due to its advantages of target and sustained release in the body, and so drugs can be selectively concentrated on the target site. Therefore, the biodegradable polymer as drug controlled carriers play an important role on realizing the functionalities of protein drugs.From applications'point of view, single smart polymer material can not meet the requirements of the development; the research on the polymer materials with biocompatibility and multiple smart responsibility, especially the smart hydrogels which respond simultaneously to two or more environmental stimulus, have become the research hotspot.In this study, Oligo (caprolactone)-Pluronic-oligo (caprolactone) (PFCL) block copolymer was synthesized by ring-opening copolymerization, and macromonomer with acryloyl group was prepared through the reaction of PFCL with acryloyl chloride. The hydrogel was obtained by radical copolymerization of the macromonomer/methacrylic acid aqueous solution initiated by redox initiator. The synthesized Oligo (caprolactone)-Pluronic-oligo (caprolactone) (PFCL) block copolymer and diacrylated macromer were characterized further by FTIR. The hydrogels based on the above diacrylated macromer and MAA has been investigated systematically such as swelling kinetics , temperature sensitivity,pH sensitivity and biodegradability.The results confirmed that the swelling ratio of series hydrogels of PFCLX-D-MAA-y increased significantly at the iniate stage and reached the swelling balance within 12 h. Hydrogels displayed favorable temperature response and its equilibrium swelling ratio (ESR) decreased not only with the increasing temperature but with the increasing MAA content. In addition,ε-caprolactone content played slight effect on the temperature-sensitivity. The hydrogels exhibited pH-sensitivity at both 4oC and 37oC. An evident swelling transition is observed in pH〉6, Additionally, with the increase of MAA content, the ESR value decreased before the swelling transition by contrast to the increase of ESR at high pH.The microgels was obtained by inverse suspension polymerization, in which the macromonomer/methacrylic acid aqueous solution initiated by redox initiator. The effects of various factors, such as the accelerator concentration, the dispersant, stirrer rate and ratio of oil phase to water phase, on the formation of microgels and diameter of the microgels were examined. The experimental results showed that microgel successfully prepared by using inverse suspension polymerization, the optimum conditionswere obtained as following: 1.0μL/mL of accelerator concentration, 500rpm of stirring rate, 7% (the weight percent of dispersion medium) of dispersant, 10/1 (w/w) of oil phase/water phase ratio. The microgel exhibited pH and temperature sensitivity.