Doxorubicin-Loaded Nanogel Assemblies with pH/Thermo-triggered Payload Release for Intracellular Drug Delivery

For improving intracellular doxorubicin (DOX) delivery, DOX‐encapsulated nanogel assemblies with pH/thermo‐responsive drug release are developed. DOX and a graft copolymer comprising acrylic acid (AAc) and 2‐methacryloyloxyethyl acrylate (MEA) units as the backbone and with poly( N ‐isopropylacrylamide) (PNIPAAm) and monomethoxy poly(ethylene glycol) as the grafts at pH 7.4 and 4 °C undergo electrostatically induced co‐association into copolymer/DOX nanocomplexes. After being crosslinked by polymerization of the MEA moieties, the complex nanoconstructs exhibit a unique nanogel‐like architecture. Taking advantage of the extensive electrostatic attraction of the DOX molecules with ionized AAc residues and π–π stacking among copolymer‐bound DOX molecules, the DOX‐loaded nanogels show a relatively high payload content. With the milieu pH being reduced from 7.4 to 4.7, the drug release is appreciably promoted due to the massive disruption of ionic AAc/DOX pairings. The thermo‐evolved phase transition of the PNIPAAm grafts further accelerates drug elution, particularly at pH 4.7. In vitro characterization indicates that the DOX‐embedded nanogels endocytosed by HeLa cells can progressively release DOX within acidic organelles. As a result, the viability of cancer cells treated with DOX‐loaded nanoparticles can be further reduced by prolonging incubation time. This work demonstrates the great potential of the DOX‐loaded nanogel assemblies for effective intracellular drug delivery. image