Luminescent mesoporous nanoreservoirs for the effective loading and intracellular delivery of therapeutic drugs

Development of biocompatible and multifunctional nanocarriers is important for the therapeutic efficacy of drug molecules in the treatment of disease and tissue repair. A novel nanocarrier of luminescent hollowed mesoporous silica (L-hMS) was explored for the loading and controlled delivery of drugs. For the synthesis of L-hMS, self-activated luminescence hydroxyapatite (LHA) was used as a template. Different thicknesses (∼7-62 nm) of mesoporous silica shell were obtained by varying the volume of silica precursor and the subsequent removal of the LHA core, which resulted in hollow-cored (size of ∼40 nm × 10 nm) mesoporous silica nanoreservoirs, L-hMS. While the silica shell provided a highly mesoporous structure, enabling an effective loading of drug molecules, the luminescent property of LHA was also well preserved in both the silica-shelled and the hollow-cored nanocarriers. Doxorubicin (DOX), used as a model drug, was shown to be effectively loaded onto the mesopore structure and within the hollow space of the nanoreservoir. The DOX release was fairly pH-dependent, occurring more rapidly at pH 5.3 than at pH 7.4, and a long-term sustainable delivery over the test period of 2 weeks was observed. The nanoreservoir exhibited favorable cell compatibility with low cytotoxicity and excellent cell uptake efficiency (over 90%). Treatment of HeLa cells with DOX-loaded L-hMS elicited a sufficient degree of biological efficacy of DOX, as confirmed in the DOX-induced apoptotic behaviors, including stimulation in caspase-3 expression, and was even more effective than the direct DOX treatment. Overall, the newly developed L-hMS nanoreservoirs may be potentially useful as a multifunctional (luminescent, mesoporous and biocompatible) carrier system to effectively load and sustainably deliver small molecules, including anticancer drugs.