Temperature Sensing Using Fluorescent Nanothermometers

TLDR

Measuring temperature in single living cells is challenging. The study introduces a novel nanothermometer that accurately measures temperatures in solutions and living cells. The device relies on temperature‑dependent green fluorescence of NaYF₄:Er³⁺,Yb³⁺ nanoparticles, with intensity ratios of Er³⁺ bands changing with temperature, and was calibrated using a pump‑probe heating experiment on a colloidal solution. The nanothermometers successfully tracked HeLa cell temperatures from 25 °C to 45 °C, the point of thermally induced death.

Abstract

Acquiring the temperature of a single living cell is not a trivial task. In this paper, we devise a novel nanothermometer, capable of accurately determining the temperature of solutions as well as biological systems such as HeLa cancer cells. The nanothermometer is based on the temperature-sensitive fluorescence of NaYF(4):Er(3+),Yb(3+) nanoparticles, where the intensity ratio of the green fluorescence bands of the Er(3+) dopant ions ((2)H(11/2) --> (4)I(15/2) and (4)S(3/2) --> (4)I(15/2)) changes with temperature. The nanothermometers were first used to obtain thermal profiles created when heating a colloidal solution of NaYF(4):Er(3+),Yb(3+) nanoparticles in water using a pump-probe experiment. Following incubation of the nanoparticles with HeLa cervical cancer cells and their subsequent uptake, the fluorescent nanothermometers measured the internal temperature of the living cell from 25 degrees C to its thermally induced death at 45 degrees C.