pH and Temperature Sensitive Block Copolymer Hydrogels Based on Poly(ethylene glycol) and Sulfamethazine

摘要

A novel pH and temperature sensitive block copolymer was prepared by adding a pH sensitive moiety to a temperature sensitive block copolymer. An oligomer incorporating pH-sensitive moieties and containing an s-triazine ring was synthesized from sulfamethazine (SM) by radical polymerization. Novel pH- and temperature-sensitive biodegradable penta block copolymers were synthesized from the sulfamethazine oligomer (OSM) incorporating pH-sensitive moieties and a temperature sensitive degradable triblock copolymer hydrogel style ABA based on PEG. The sol-gel phase transition behavior of these block copolymers was investigated both in solution and injection into PBS buffer at pH 7.4 and 37°C. Aqueous solutions of these block copolymers showed sol-gel transition behavior upon both temperature and pH changes under physiological conditions (37°C, pH 7.4). When the block copolymer solution is in the sol state at 10°C and pH 8.0, both temperature and pH changes are needed for gelation to occur. The sol-gel transition properties of these block copolymers are influenced by the hydrophobic/hydrophilic balance of the copolymers, block length, hydrophobicity, stereoregularity of the hydrophobic components within the block copolymer, and the ionization of the pH functional groups in the copolymer, which depends on the environmental pH. The degradation time of these polymers could be controlled by changing the hydrophobic block of the temperature sensitive degradable triblock copolymer hydrogel. These materials could be employed as injectable carriers for hydrophobic drugs and proteins, etc. Gelation inside the needle can be prevented by increasing the temperature during the injection of the hydrogel, because it does not change into the gel form solely upon increasing the temperature. This material could even be used for a long guide catheter into the body.