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 mSiO 2 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.