Singlet oxygen-induced apoptosis of cancer cells using upconversion fluorescent nanoparticles as a carrier of photosensitizer

The photodynamic effect of upconversion nanoparticles loaded with a photosensitizer was studied on murine bladder cancer cells (MB49). Mesoporous silica was coated onto NaYF4 upconversion nanocrystals to form a core-shell structure and then loaded with the photosensitizer zinc (II)-phthalocyanine (ZnPc) into its porous silica. The nanoparticles displayed a uniform spherical shape with an average diameter of about 50 nm and showed good dispersibility in water. Intracellular uptake study in MB49 cells revealed a time- and concentration-dependent accumulation of these nanoparticles. Upon irradiation with 980 nm, their efficiency in activating the loaded ZnPc to generate singlet oxygen (1O2) molecules was confirmed in live cell. The cytotoxic effect of the released 1O2 from the nanoplatform was proven by cell viability assay, confocal microscopy, DNA agarose gel electrophoresis, cytochrome c releasing assay and prostate specific antigen-enzyme-linked immunosorbent assay (PSA-ELISA), all of which showed strong photodynamic effect of the nanoparticles on MB49 cells. This suggests the efficacy of NaYF4 upconversion nanoparticles as a carrier for photosensitizers and its use in photodynamic therapy of cancer and some other diseases.