UV-light cross-linked and pH de-cross-linked coumarin-decorated cationic copolymer grafted mesoporous silica nanoparticles for drug and gene co-delivery in vitro.

The chemotherapy combined with gene therapy has emerged as a promising strategy for cancer therapy because of enhanced anticancer efficacy. To this end, we constructed a novel UV-light cross-linked and pH de-cross-linked coumarin-decorated cationic copolymer functionalized mesoporous silica nanoparticles (MSN) for co-delivery of chemotherapeutic agent 5-FU and tumor suppresser p53 gene. The multifunctional MSN were modified with poly(glycidyl methacrylate)-b-poly(2-(dimethylamino)ethyl methacrylate) (PGMA-b-PDMAEMA) via two sequential surface-initiated atom transfer radical polymerization (ATRP), followed by ring-opening of epoxy groups with ethanediamine and covalent conjugation with coumarin moieties via acid-liable cis-aconityl bonds. The in vitro drug release results indicated that the premature release was negligible at physiological pH when coumarin moieties on the MSN-g-PCAAMC-b-PDMAEMA surface underwent UV-light induced photo-dimerization (cross-linking), while the release of embedded drugs was accelerated under acidic conditions, which was attributed to the hydrolytic cleavage of cis-aconityl bonds (de-crosslinking). In addition to small-molecule drug, the established MSN-g-PCAAMC-b-PDMAEMA also could carry p53 gene in outer cationic copolymers, and the formed complex exhibited good gene transfection activity. Interestingly, coumarin moieties themselves could emit blue fluorescence, which was used to track the cellular uptake of the nanocarriers without the need of additional fluorescence probes. Importantly, the cytotoxicity and cell apoptosis assays confirmed that co-delivery of 5-FU and p53 gene by the cross-linked MSN-g-PCAAMC-b-PDMAEMA@5-FU/p53 induced enhanced chemotherapeutic efficacy as compared to 5-FU delivery alone. In conclusion, these results suggested that the constructed stimuli-responsive co-delivery system may hold the promise for cancer therapeutic application.
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