Synthesis and characterization of P(NIPAAm-co-AAc) hydrogels with L-lysine-cross-linker

In order to improve the biocompatibility of the hydrogels, hydrogels composed of N-isopropylacrylamide (NIPAAm) and acrylic acid (A-Ac) were prepared by redox polymerization with L-lysine-cross-linker. L-lysine-cross-linker was synthesized by the acrylation of the amino groups of the L-lysine and characterized by H-1 NMR.With L-lysinc-cross-linker, loosely cross-linked poly(N-isopropylacrylamide-co-acrylic acid) [P(NIPAAm-co-AAc)] hydrogels were synthesized in phosphate-buffered saline (PBS, pH = 7.4 +/- 0.1) and their phase transition behaviour, low critical solution temperature (LCST), water content were investigated. The LCST Could be adjusted at 35-38 degrees C by changing the hydrogel's composition. The hydrogels contained more than 90 % water content at 37 degrees C in the ultra pure water and have a prospective swelling in the PBS (> 84.72 %), which was controlled by the molar ratio of NIPAAm/AAc, swelling media and cross-linking density. This L-lysine-cross-linked P(NIPAAm-co-AAc) hydrogels which can be tailored to create environmentally-responsive artificial extracellular materials will have a potential use in the future.