Opto-magnetic nanoparticles with upconverting properties for optical imaging and photothermal therapies

Multifunctional opto-magnetic nanoparticles (NPs) with upconverting properties were designed for cancer detection and treatment. The upconversion was achieved from NaYF4 doped by 20 %Yb and 2 % Er nanoparticles (UCNPs). The UCNPs were coated by a thin SiO2 shell and decorated with 6 nm magnetic Fe3O4 that resulted in the formation of NaYF4:Yb,Er@SiO2@Fe3O4 multifunctional nanoplatform. The connection between UCNPs and Fe3O4 NPs was proved by SEM, TEM, SQUID, absorption, and luminescence techniques. The specific absorption rate (SAR) values for prepared colloids were calculated for colloidal suspension of heterostructures after 808 and 880 nm laser irradiation as a function of lasers power. The highest conversion effectiveness was obtained for an 880 nm light source with 1600 mW (SAR = 87 W/g). The low MDA-MB-231 cells cytotoxicity of NaYF4:Yb,Er@SiO2@Fe3O4 NPs was observed (up to 500 µg/ml). At the same time, a strong upconverting signal after 980 nm of excitation was observed from the sites of the cells without autofluorescence from its components. This phenomenon with relatively good SAR parameters suggested that multifunctional nanoconstructs for simultaneous cancer detection (imaging) and photothermal therapy have been successfully obtained.