A Facile Approach to Upconversion Crystalline CaF₂:Yb³⁺,Tm³⁺@mSiO₂ Nanospheres for Tumor Therapy

A new facile approach, namely chemical-assisted sol-gel growth (CASGG), was successfully developed to induce the formation of fine CaF₂:Yb³⁺, Tm³⁺ nanocrytals within the pore channels of mesoporous silica (mSiO₂) nanoparticles. A series of upconversion photoluminescent crystalline CaF₂:Yb³⁺,Tm³⁺@mSiO₂ nanospheres with controlled diameters from ^~65 nm to ^~290 nm were fabricated. All nanospheres presented sound cyto-compatibility and unique ratiometric spectral monitoring functionalities for drug release kinetics. The nanospheres with smallest dimension (UCNP-2.5, ^~65nm) induced the most sustained DOX release kinetics. More importantly, the in-vitro study demonstrated that the DOX loaded UCNP-2.5 nanopheres presented the strongest anti-cancer efficacy to MCF-7 human breast cancer cells due to its stronger penetration ability to cell nuclei due to the size effect.