NaYF₄:Yb/Tm@SiO₂-Dox/Cur-CS/OSA nanoparticles with pH and photon responses

Stimulus-triggered drug delivery systems (DDSs) based on lanthanide-doped upconversion nanoparticles (UCNPs) have attracted significant attention for treating cancers due to their merits of high drug availability, precisely controlled drug release, and low side-effects. However, such DDSs usually exhibit a single stimulus-response, which may limit the efficiency of cancer treatment. To extend response types in a single DDS, we construct NaYF₄:Yb/Tm@SiO₂-doxorubicin (Dox)/curcumin (Cur)-chitosan (CS)/2-Octen-1-ylsuccinic anhydride (OSA) nanoparticles with core-shell structures. Our method is based on the exploration of the synergistic effect of UCNPs and multiple drugs. In particular, the NaYF₄:Yb/Tm is used to convert near-infrared light to visible light, activating Cur photosensitizers to produce singlet oxygen for photodynamic therapy, while CS/OSA responds to a low pH environment to release cancer drugs, including Dox and Cur for chemotherapy through breaking a free carboxyl group. The results show that the UCNPs with a 40 nm diameter, 23 nm thick mesoporous SiO₂, and 19/1 mol% Yb³⁺/Tm³⁺concentrations could continuously release Dox and Cur at a pH value of 6.5 within 6 h after the excitation of a 980 nm-wavelength CW laser. Our study provides a promising approach for developing efficient DDSs for cancer treatment.