Multifunctional upconversion nanoparticles based on NaYGdF4 for laser induced heating, non-contact temperature sensing and controlled hyperthermia with use of pulsed periodic laser excitation

摘要

For clinical application in photothermal therapy the nanoparticles should be efficient light-to-heat converters and luminescent markers. In this work, we investigate upconversion nanoparticles with NaY_xGd_(1-x)F_4 (x=0-1) host lattice as self-monitored thermo-agents for bioimaging and local laser hyperthermia with real-time temperature control. The ability of non-contact temperature sensing using NaY_xGd_(1-x)F_4 on one hand and laser induced heating on the other hand was shown. It was found, that the heat conversion luminescence efficiency is strongly affected by the concentration ratio of Gd~(3+) to Y~(3+) ions in host lattice. The optimal composition among the studied is NaY_(0.4)Gd_(0.4)Yb_(0.17)Er_(0.03) with luminescence efficiency of 3.5% under 1 W/cm~2 pumping power. Higher Gd~(3+) concentrations lead to higher heating temperature, but also to the decrease of the luminescence intensity and the accuracy of the ratiometric temperature determination. It was also shown that the optimization of Yb~(3+) doping concentration is one of the possible ways for optimization of the conditions of laser induced photothermal effects. Experimental in vitro study of hyperthermia with use of upconversion nanoparticles on HeLa and C6 cell lines was performed. The investigated nanoparticles are capable of in vitro photothermal heating, luminescent localization and thermal sensing.