Single‐component cationic polyethylenimine thermogel for sustained and localized gene delivery to combat multi‐drug resistant cancer

Abstract Multi‐drug resistant cancer cells with over‐expression of Bcl2 anti‐apoptotic proteins can be effectively killed by transfecting them with Nur77 transcription factor (pNur77). Previous attempts are generally therapeutically unsatisfactory due to low sustained gene expression and are further disadvantaged by their multi‐component designs requiring complicated preparation. Herein, we designed a single cationic amphiphilic copolymer from branched poly(ethylenimine) (PEI‐25k), the gold standard non‐viral vector, that functions simultaneously as the non‐viral vector and hydrogel forming polymeric matrix. Our single‐component hydrogel gene delivery platform is highly facile to prepare as it only requires co‐dissolution of the copolymer with pNur77 to form a homogeneous sol. Due to the high cationic charge density of PEI‐25k, this PEI‐based copolymer effectively complexes a high payload of the plasmid. Subsequently, the copolymer's thermogelling ability enables it to spontaneously self‐assemble into a hydrogel depot by simply being warmed to physiological temperatures upon intra‐tumoral injection. Leveraging upon the high transfection efficiency of PEI‐25k, this PEI‐based thermogel achieved prolonged localized release of pNur77 with high transfection efficiency. This leads to successful tumor size reduction and suppressed tumor reoccurrence in mouse models with low systemic cytotoxicity. We believe this single‐component cationic thermogel non‐viral gene delivery platform is highly attractive for gene therapy.