Facile Preparation of Pyrenemethyl Ester-Based Nanovalve on Mesoporous Silica Coated Upconversion Nanoparticle for NIR Light-Triggered Drug Release with Potential Monitoring Capability

A novel light-responsive nanovalve is facilely prepared on mesoporous silica (mSiO2) coated upconversion nanoparticles (UCNP) through modification of photo-cleavagable pyrenemethyl ester (Py) molecules on its surface. These Py molecules can associate with β-cyclodextrin (β-CD) molecules as gatekeepers to block the mSiO2 pore channels and entrap the loaded drugs. Upon NIR light irradiation, NIR light is upconverted to ultraviolet (UV) and visible (Vis) light by UCNP, and the modified Py molecules are cleaved by the upconverted UV light leading to the detachment of β-CD gatekeepers to trigger drug release. For the fabrication of a monitoring system, β-CD is covalently conjugated with the fluorescein isothiocyanate (FITC) as drug release indicator (FITC-β-CD). The luminescence resonance energy transfer (LRET) from UCNP to Py/FITC-β-CD before drug release results in the quenching of Vis emission of UCNP while the detachment of Py/FITC-β-CD nanovalves after drug release diminishes the LRET between UCNP and FITC-β-CD which recovers the luminescence of UCNP, the change in luminescence provides a potential capability for one to quantitatively monitor the drug release process. in vitro study shows a remarkable killing ability on HeLa cancer cell of this system.