One-step preparation of reduction-responsive cross-linked gemcitabine prodrug micelles for intracellular drug delivery

A cross-linkable gemcitabine (GEM)-containing reduction-sensitive polymeric micelles based on the copolymer poly(PEG-co-CMA-co-GEM) was successfully fabricated. The copolymer which synthesized by one-step radical copolymerization of poly(ethylene glycol) methacrylate (PEGMA), 7-(2-Methylacryloylethoxy)-4-methylcoumarin (CMA), and 2-((2-hydroxyethyl)disulfanyl)ethyl acrylate (HSEA-GEM), endowed the micelles with "stealth" surface in circulation, photo cross-linkable property, and reduction-sensitivity. The designed micelles were fabricated by self-assembly of the copolymer in aqueous solution followed by UV-light induced cross linking of coumarin moieties to enhance stability, which would not disassemble even below critical micelle concentration (CMC) or in non-selective solvent (DMSO/H2O 1:1). In vitro drug release curve demonstrated that the intracellular-mimicking reductive microenvironment could accelerated the GEM release of the prodrug micelles. These micelles could be effectively internalized by BxPC-3 pancreatic cancer cells according to confocal laser scanning microscopy (CLSM) detection and flow cytometry analysis. Meanwhile, methyl thiazolyl tetrazolium (MrT) assay demonstrated that the cross-linked prodrug micelles could efficiently inhibit the proliferation of BxPC-3 cells.