Thermo-responsive polyplex micelles with PEG shells and PNIPAM layer to protect DNA cores for systemic gene therapy

Simultaneous achievement of prolonged retention in blood circulation and efficient gene transfection activity in target tissues has always been a major challenge hindering in vivo applications of nonviral gene vectors via systemic administration. The engineered strategies for efficient systemic gene delivery are under wide investigation. These approaches include the thermo-responsive formation of a hydrophobic intermediate layer on PEG-shielded polyplex micelles. Herein, we constructed novel rod-shaped ternary polyplex micelles (TPMs) via complexation between the mixed block copolymers of poly(ethylene glycol)-b- poly{ N ′-[N - (2-aminoethyl)-2-aminoethyl]aspartamide} (PEG-b-PAsp(DET)) and poly(N - isopropylacrylamide)-b- PAsp(DET) (PNIPAM-b-PAsp(DET)) and plasmid DNA (pDNA) at room temperature (RT), exhibiting distinct temperature-responsive formation of a hydrophobic intermediate layer between PEG shells and pDNA cores through facile temperature increase from RT to body temperature (~37 °C).