In recent years, researchers have found that individual cells can exhibit temperature variations of several degrees Celsius due to heat generation, a phenomenon that has attracted considerable interest in biology and medicine. Conventionally, heat inside cells was thought to spread almost instantaneously through thermal conduction, producing temperature increases of only about 0.00001℃. The striking discrepancy between this prediction and experimentally measured temperature changes has remained a longstanding puzzle.
A research team led by Project Associate Professor Kohki Okabe of the Graduate School of Pharmaceutical Sciences at the University of Tokyo developed a new method that combines a fluorescent polymer thermometer for local temperature measurements with infrared laser-based heating. The technique enables researchers to track temperature distributions within living cells with exceptionally high spatiotemporal resolution, achieving a temporal resolution of 9 milliseconds and a spatial resolution of 280 nanometers. Using this approach, the team analyzed temperature changes after transiently heating cells and found that intracellular heat dissipates far more slowly than predicted by conventional heat conduction models. Rather than diffusing away within microseconds, as theory suggests, localized temperature increases persisted for several seconds. Further experiments revealed that the cell nucleus and biomolecules contribute to this remarkably slow temperature recovery. The team also found that heat transfer inside cells lacks the diffusive nature that is a fundamental characteristic of conventional heat conduction, instead remaining localized and dissipating gradually over time.
These findings challenge the conventional view that heat rapidly diffuses and dissipates within cells, suggesting the existence of a previously unrecognized mode of heat transfer mediated by biomolecules. This discovery could advance the development of technologies for manipulating cellular functions in biology and medicine, while also providing new insights into the remarkable energy efficiency of living organisms and the mechanisms underlying disease.
(Article: Masanori Nakajo)
