Recent Advances in Poly(N-isopropylacrylamide) Hydrogels and Derivatives as Promising Materials for Biomedical and Engineering Emerging Applications

Temperature-sensitive (thermosensitive) hydrogels, which are part of the family of stimulus-sensitive hydrogels, consist of water-filled polymer networks that display a temperature-dependent degree of swelling. Thermosensitive hydrogels, which can undergo phase transition or swell/de-swell as temperature changes, have great potential in various technological and biomedical purposes for a number of reasons: their temperature response is reversible, hydrogels are stable and easy to prepare, they can be biocompatible and also be suitably combined with other organic and inorganic materials, resulting in new materials with outstanding properties. Among thermosensitive hydrogels poly(N-isopropylacrylamide) (PNIPAAm) is the most extensively studied because it brings together the best properties of these materials. Consequently, in the past few years, a wide number of applications and new chemical processes to prepare PNIPAAm and their derivatives are being proposed. The objective of this review is to summarize the fundamentals of thermosensitive hydrogels and recent advances in preparation and both technological and biomedical applications of thermosensitive hydrogel, with a special focus on PNIPAAm and their derivatives. Special attention has been given to the discussion of challenges and future research perspectives based on new horizons not yet considered.