Modulation of phase transition of poly(N‐isopropylacrylamide)‐based microgels for pulsatile drug release

Abstract

AbstractThis work aims to synthesize poly(N‐isopropylacrylamide)‐based microgels with sharp phase transition by introducing a specific secondary structure to achieve pulsatile drug release near body temperature. To achieve this, N‐isopropylacrylamide (NiPAM) based microgels were synthesized by surfactant free‐radical polymerization of NiPAM in the presence of polyalanine terminated α‐methallyl poly(ethylene glycol) ether (HPEG‐Alax) as a macro‐comonomer and N,N′‐methylene bisacrylamide (MBA) as a chemical crosslinker. A series of microgels were characterized by TEM, DLS, UV–Vis, 1H NMR, and other analytical methods. The introduction of hydrophilic HPEG allows the volume phase transition temperature (VPTT) to move towards the body temperature, and α‐helix structure confers a high deswelling ratio and response sensitivity to the microgel, overcoming the disadvantage of a broadened phase transition caused by hydrophilic monomers. The presence of HPEG‐Alax significantly improves the stability of the microgel in the electrolyte solution at high temperatures. The drug release of the microgels was investigated with the model drugs, hydrophilic DOX and hydrophobic curcumin, showing that the microgels can release hydrophilic drugs in a pulsatile mechanism.