Microstructured poly(N-isopropylacrylamide) hydrogels with fast temperature response for pulsatile drug delivery

Microstructured, temperature-sensitive poly(N-isopropylacrylamide) hydrogels were prepared with different proportions of poly(N-isopropylacrylamide) microparticles. The materials presented fast shrinkage at a temperature above their transition temperature (LCST = 32 °C), with highly reproducible swelling/shrinking cycles when temperature oscillates between below and above the LCST. They showed positive solute release control as a function of the temperature when small amount of microparticles were included in the hydrogels, making these hydrogels suitable for temperature controlled pulsatile drug release. The degree of crosslinking had a smaller impact than the percentage of microparticles in swelling and drug release in response to temperature. The inclusion of a small proportion of microparticles improved the mechanical propertied of the hydrogels. In addition, the polymerization steps are carried on in aqueous media, being a facile, scalable, and environmentally friendly technology.