Mesoporous-silica-coated upconversion nanoparticles loaded with vitamin B12 for near-infrared-light mediated photodynamic therapy

Abstract Near-infrared (NIR)-to-visible upconversion nanotechnology has potential to be used for photodynamic therapy (PDT) because the use of NIR-irradiation provides deep tissue penetration and avoids photodamge to nomal cells, thus overcoming a major hurdle in the treatment of deep-seated tumors. In this study, a novel nano-platform of mesoporous-silica-coated NaYF4:Yb/Er upconverting nanoparticles with a large surface area of 770 m2/g and an average pore size of 2 nm, was fabricated and used for NIR-mediated PDT. Vitamin B12 (VB12), a nontoxic, easy-to-obtain and biocompatible photosensitizer, was incorporated into the mesoporous silica and used as PDT drug. There is a good overlap (545 nm) between the fluorescence emission of NaYF4:Yb/Er nanoparticles and the UV–visible absorption of VB12. Under NIR-irradiation, the visible fluorescent emission from the upconverting nanoparticles will be absorbed by the VB12 coated on their surfaces. Then, the VB12 molecules under excited-state interact with surrounding ground-state molecular oxygen, generating reactive oxygen species, leading to oxidative damage of cancer cells.