Mild Focused Ultrasound-Induced Microscopic Heating\nof Nanoparticles Observed by Lanthanide Luminescence for Precise Sonothermal\nCancer Therapy

Focused\nultrasound (FUS) is a recognized tool that can be used\nclinically for the thermal ablation of tumors. However, excessive\nheat can cause side effects on the ultrasound transmission path and\nnormal tissues around the tumor. To address the issue, this work detected\nfor the first time the effect of microscopic heating of nanoparticles\nunder the action of FUS through the luminescence intensity ratio (LIR)\nand luminescence lifetime of temperature-responsive lanthanide-doped\nnanoparticles. When FUS is applied to the tissue embedded with nanoparticles,\nthe increase in the microscopic temperature of the nanoparticles synchronously\nmonitored by LIR is more obvious than the increase in the macroscopic\ntemperature. Based on this phenomenon, the intensity of focused ultrasound\ncan be finely regulated to avoid overheating while ensuring a therapeutic\neffect. This work achieves the measurement of the microscopic heating\nof nanoparticles under FUS, which is of great significance for the\ndevelopment of sonothermal cancer therapy.