Stimuli-responsive functionalized mesoporous silica nanoparticles for drug release in response to various biological stimuli

A silica-based mesoporous nanosphere (MSN) controlled-release drug delivery system has been synthesized and characterized. The system uses l-cysteine derivatized gold nanoparticles (AuNPs), bound to the MSNs using Cu²⁺ as a bridging ion. The AuNPs serve as removable caps that hinder the release of drug molecules inside the amino functionalized MSN mesoporous framework. The modified MSNs themselves exhibit negligible cytotoxicity to living cells, as revealed using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. The drug delivery system requires one of two biological stimuli to trigger drug release. These stimuli are either: low pH (pH < 5); or elevated levels of adenosine triphosphate (ATP) (concentration > 4 mM). The feasibility of biologically controlled release was demonstrated through the stimuli-induced removal of the AuNP caps over the MSN releasing the anticancer drug doxorubicin. We envisage that this MSN system could play a significant role in developing new generations of controlled-release delivery vehicles.