Upconversion nanoparticles coated organic photovoltaics for near infrared light controlled drug delivery systems

Highlights: • Upconversion nanoparticles coated organic photovoltaic cells are developed for implantable on-demand drug delivery systems. • The skin penetrating NIR light can trigger upconversion nanoparticles to emit visible light for organic photovoltaic cells. • The gold thin films sealing the drug reservoirs can be dissolved by NIR light irradiation for on-demand drug delivery. On-demand drug delivery systems (DDSs) have been widely investigated for spatiotemporally controlled therapy with greatly improved patient compliance. However, power systems to operate the DDSs are one of the serious unmet needs constraining their further applications. Here, we report implantable organic photovoltaic cells using upconversion nanoparticles (UCNPs) for on-demand controlled drug delivery. Although skin-penetrating near infrared (NIR) light cannot be used for flexible organic photovoltaic cells, UCNPs can convert NIR light to visible light for their operation after implantation to the body. The core-shell structured UCNPs coated on flexible organic photovoltaic cells generate current flow upon NIR irradiation for triggering on-demand drug delivery from microelectromechanical system (MEMS) drug reservoirs. Gold (Au) membrane sealing the reservoirs is dissolved to AuCl₄⁻ by the applied electrical current triggering the pulsatile drug release. The successful fabrication of NIR light triggered DDS by UCNPs coated organic photovoltaic cells is confirmed by transmission electron microscopy (TEM), scanning electron microscopy (SEM), atomic force microscopy (AFM), UV–vis spectroscopy, photoluminescence, current density–voltage characterization, and gold thin film dissolution tests. Furthermore, on-demand model drug release tests confirm the feasibility of the new paradigm light-triggered DDS and the relevant phototherapy.