γ-Polyglutamic acid mediated crosslinking PNIPAAm-based thermo/pH-responsive hydrogels for controlled drug release

The most important drawbacks of the thermo sensitive hydrogels based on N-isopropylacrylamide (NIPAAm) are the lack of other responsive groups and these hydrogels are not biodegradable; moreover, chemical cross-linking agents were commonly used in hydrogels formation process. In order to overcome these inconvenience, poly (NIPAAm-co- poly (γ-glutamic acid) - Allyl glycidyl ether) (poly (NIPAAm-co-γ-PGA-AGE)) hydrogels were obtained by cross-linking polymerization of the corresponding monomers. Poly (γ-glutamic acid) (γ-PGA) of biocompatible and biodegradable was functionalized with an appropriate amount of vinyl groups, thus acting both as a co-monomer and as a bio-degradable cross-linker. The morphology, thermal-behavior, swelling/deswelling kinetics, pH sensitivity and biodegradability of poly (NIPAAm-co-γ-PGA-AGE) hydrogels were studied. The results indicated that the hydrogels not only had good thermal response sensitivities, but also behaved with pH response sensitivities and showed degradation behavior. The hydrogels were loaded with the model drug naproxen and the release studies were performed under simulated physiological conditions. The results showed that drug was efficiently loaded and released in a controlled manner from these hydrogels. In addition, the more amount of γ-PGA-AGE added to the poly (NIPAAm-co-γ-PGA-AGE) hydrogels, the better cytocompatibility of the hydrogels. These hydrogels have more attractive application prospects in the biomedical field.