A novel stimuli-responsive hydrogel for K+-induced controlled-release

A novel family of stimuli-responsive smart hydrogel is developed in this study for K+-induced self-regulated controlled-release, which is featured with isothermally K+-induced pulse-release mode at a certain temperature due to the isothermally K+-induced shrinking behavior of the hydrogel by recognizing the increase of K+ concentration in the environment. The proposed poly(N-isopropylacrylamide-co-benzo-15-crown-5-acrylamide) hydrogel is composed of crown ether 15-crown-5 as ion-signal sensing receptor and poly(N-isopropylacrylamide) as actuator. The selective formation of stable 2:1 “host-guest” complexation between the crown ether 15-crown-5 and potassium ion drives the polymeric network of the hydrogel to shrink; as a result, the hydrogel exhibits especial and selective response to potassium ions. A K+-recognition pulse-release performance of loaded drug from the fabricated hydrogel is achieved by using the K+-induced isothermal shrinkage property of the hydrogel. The proposed hydrogel provides a new mode of K+-recognition volume change for stimuli-responsive smart actuators, which is highly attractive for targeting drug delivery systems, biomedical devices, and sensors and so on.