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 the effectiveness of therapy.

A major challenge of conventional thermometry is that needles and thermocouples are simply too large to measure temperature at the cellular scale. This is why optical thermometry methods are often used at the nanoscale. They rely on detecting temperature-dependent optical signals from luminescent nanoparticles. When illuminated with a laser, these nanoparticles emit light, and the characteristics of this emission — such as intensity, spectral peak position, and fluorescence lifetime — change with temperature. By interpreting these signals, we can effectively “see” the temperature inside a cell in real time.

However, the use of many luminescent nanothermometers is limited by light scattering in biological tissues, the dependence of the signal on nanoparticle concentration, and the complexity of the required 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 work with a range of materials, including silicon, silicon–gold, and silicon–germanium nanoparticles, germanium oxide nanoparticles, nitrogen-vacancy (NV) center nanodiamonds, and rare-earth-based materials.

Our goal is to make laser-based therapies safer, more controllable, and more predictable by enabling precise real-time monitoring of temperature at the cellular level.