Photo- and thermo-responsive multicompartment hydrogels for synergistic delivery of gemcitabine and doxorubicin

Abstract

Hydrogels have found promising applications in drug delivery due to their biocompatibility, high drug loading capability, and tunable release profiles. However, hydrogel-based carriers are primarily employed for delivering hydrophilic payloads while hydrophobic drugs cannot be efficiently delivered due to the lack of hydrophobic domains within conventional hydrogel matrices. Herein, we report that thermo- and photo-responsive hydrogels could be constructed from amphiphilic triblock copolymers, poly(N-isopropylacrylamide)-b-poly(4-acryloylmorpholine)-b-poly(2-((((2-nitrobenzyl)oxy)carbonyl) amino)ethyl methacrylate) (PNIPAM-b-PNAM-b-PNBOC), and the resulting hydrogels could be further engineered a new carrier for both hydrophilic gemcitabine (GCT) and hydrophobic doxorubicin (DOX). PNIPAM-b-PNAM-b-PNBOC triblock copolymers were first self-assembled into micelles with hydrophobic photosensitive PNBOC cores, hydrophilic PNAM inner shells, and thermoresponsive PNIPAM coronas below the lower critical solution temperature (LCST), while hydrogels of physically cross-linked micellar nanoparticles were achieved at elevated polymer concentrations and high temperatures above the critical gelation temperature (CGT). Rheological experiments revealed that the CGT was highly dependent on polymer compositions and concentrations, that is, a longer hydrophobic PNBOC block or a higher polymer concentration led to a decreased CGT. However, the CGT prior to UV irradiation (CGT₀) could be drastically elevated after UV irradiation (CGT_UV) as a result of UV irradiation-induced concurrently cross-linking and hydrophobic-to-hydrophilic transition within PNBOC cores. As such, gel-to-sol transition could be accomplished by either temperature decrease or exposure to UV irradiation at a fixed temperature lower than the CGT_UV. Note that both GCT and DOX could be simultaneously encapsulated into the hydrogels due to the coexistence of extramicellar aqueous phase and hydrophobic micellar cores. Intriguingly, the subsequent co-release of GCT and DOX could be regulated by taking advantage of either temperature or UV irradiation-mediated gel-to-sol transitions.

Keywords: Drug delivery; Hydrogels; Photoresponsive; Sol-gel transition; Thermoresponsive.