Snapshot of Phase Transition in Thermoresponsive Hydrogel PNIPAM: Role in Drug Delivery and Tissue Engineering

Abstract

Hydrogels are physically and chemically cross-linked, 3D, porous, hydrated molecular structures that mimic the native tissue microenvironment. Hydrogels fabricated with environmentally sensitive polymers can possess additional properties such as thermoresponsiveness. This property originates from its phase transition from gel to solution and vice versa with temperature variation. Phase transition mechanisms also depend on the interaction between the polymers and surrounding environment. Their thermoresponsiveness makes hydrogels attractive for drug delivery, gene therapy, cell culture, and tissue engineering approaches. The resemblance to living tissue of such thermoresponsive hydrogels produced by crosslinking of natural polymers opens up many biomedical application opportunities for human use. The most intensively studied natural thermoresponsive polymer is poly(N-isopropyl-acrylamide) (PNIPAM). This review focuses on the phase transition mechanism in thermoresponsive PNIPAM, the factors affecting the behavior of the gel, its specific properties, and, in particular, the role of PNIPAM's phase transition in drug delivery, cell culture, and tissue engineering.