Fluorescent carbon dot-gated multifunctional mesoporous silica nanocarriers for redox/enzyme dual-responsive targeted and controlled drug delivery and real-time bioimaging

A distinctive and personalized nanocarrier is described here for controlled and targeted antitumor drug delivery and real-time bioimaging by combining a redox/enzyme dual-responsive disulfide-conjugated carbon dot with mesoporous silica nanoparticles (MSN-SS-CDHA). The carbon dot with controlling and targeting abilities was prepared through a polymerizing reaction by applying citric acid and HA as starting materials (named CDHA). The as-prepared MSN-SS-CDHA exhibited not only superior photostability and excellent biocompatibility, but also the ability to target A549 cells with overexpression of CD44 receptors. Upon loading the antitumor drug, doxorubicin (DOX), into the mesoporous channels of MSN nanoparticles, CDHA with a diameter size of 3 nm completely blocked the pore entrance of DOX-encapsulated MSN nanoparticles with a pore size of about 3 nm, thus preventing the premature leakage of DOX and increasing the antitumor activity until being triggered by specific stimuli in the tumor environment. The results of the cell imaging and cytotoxicity studies demonstrated that the redox/enzyme dual-responsive DOX-encapsulated MSN-SS-CDHA nanoparticles can selectively deliver and control the release of DOX into tumor cells. Ex vivo fluorescence images showed a much stronger fluorescence of MSN-SS-CDHA-DOX in the tumor site than in normal tissues, greatly facilitating the accumulation of DOX in the target tissue. However, its counterpart, MSN-SH-DOX exhibited no or much lower tumor cytotoxicity and drug accumulation in tumor tissue. In addition, MSN-SS-CD was also used as a control to investigate the ability of MSN-SS-CDHA to target A549 cells. The results obtained indicated that MSN-SS-CDHA possessed a higher cellular uptake through the CD44 receptor-mediated endocytosis compared with MSN-SS-CD in the A549 cells. Such specific redox/enzyme dual-responsive targeted nanocarriers are a useful strategy achieving selective controlled and targeted delivery of therapeutic reagents with realtime bioimaging, and may also facilitate the development of drug delivery systems for a number of clinical applications. (C) 2017 Elsevier B.V. All rights reserved.