Design and Synthesis of Gatekeeper Coated Dendritic Silica/Titania Mesoporous Nanoparticles with Sustained and Controlled Drug Release Properties for Targeted Synergetic Chemo-Sonodynamic Therapy.

New dendritic silica/titania mesoporous nanoparticles (DSTNs) loaded with curcumin (CUR) were synthesized and coated with polyethylenimine-folic acid groups (PEI-FA) for an ultrasound (US)-triggered drug release and combined chemo-sonodynamic therapy. The PEI-FA groups play a gatekeeper role, strongly encapsulate the CUR molecules inside the nanocarrier, and prevent the unwanted premature release by blocking the mesoporous channels. The results showed that the specific cancer cell uptake is improved by FA groups on the surfaces of DSTNs via receptor-mediated endocytosis. The TiO2 layer as a sonosensitizer agent coated on the mesoporous silica nanoparticles generates reactive oxygen species. Following the US irradiation, the PEI molecules were cut off by free radicals, including OH· and O2-, on the exterior surface of DSTNs, and the CUR loaded in the nanocarrier was then released into the cancer cell cytosol. The release profiles of the CUR@PEI-FA-DSTN system showed that the amount of CUR released from DSTNs is controlled by tuning the US radiation time. The results of the MTT cytotoxicity tests of free CUR, free PEI-FA-DSTN nanocarrier, and CUR@PEI-FA-DSTNs against A549 (human lung carcinoma cell lines) and HeLa (human cervical carcinoma cell lines ( showed that the toxicity of CUR@PEI-FA-DSTNs is higher than those of CUR and PEI-FA-DSTNs alone. In addition, the specific targeting ability, the cellular uptake, and the anticancer activity of the synthesized compounds for targeted cancer treatment were investigated using different staining methods and fluorescence microscopy. The results revealed that the new system, CUR@PEI-FA-DSTNs, can be considered as a potent drug delivery system for increasing effectiveness of the anticancer activity of curcumin in the combined chemo-sonodynamic therapy.