Optical temperature measurement in biological systems

Temperature is an important biomarker that regulates many processes in the body, from the cellular level upward. Changes in temperature affect metabolism, gene expression, and cell death mechanisms. This makes local temperature control a valuable tool not only for understanding cellular processes, but also for monitoring disease progression and evaluating therapy effectiveness.

A major challenge of conventional thermometry is that needles and thermocouples are too large to measure temperature within cells, and therefore, at nanoscale, optical thermometry methods are often used. They rely on detecting temperature-dependent optical signals from luminescent nanoparticles. Under laser illumination, these nanoparticles emit light, and the radiation properties — intensity, spectral peak position, and fluorescence lifetime — change with temperature. By interpreting these signals, we can “see” the temperature inside a cell in real time. However, the use of many luminescent nanothermometers is limited by light scattering in biological tissues, dependence of the signal on nanoparticle concentration, and complex equipment.

Our research group is addressing these challenges by developing methods for precise, non-invasive temperature monitoring during photothermal therapy and photoinduced intracellular delivery. We employ materials such as silicon, silicon–gold, and silicon–germanium nanoparticles, germanium oxide nanoparticles, nanodiamonds with nitrogen-vacancy (NV) centers, and rare-earth metals.

Our goal is to make laser-based therapies safe, controllable, and predictable.