Life science
Healthcare, Drug development, Diagnostics

Intracellular heat diffusion measured by newly developed
quantum nano sensors
Division of Protein Chemistry, Institute for Protein Research
Associate Professor Madoka Suzuki
Researchmap https://researchmap.jp/read0097299

Life science

Abstract
Biological thermogenesis is observed in mammals, birds, insects, and plants. Understanding the mechanism of thermogenesis
is one of the major targets in biology and physiology. However,there are very few knowledge about how the heat diffuses fromintracellular heat sources through the intracellular space. This isdue to the technical difficulties in measuring and manipulating
the temperature at the small scale such as a cell. Here, we newly
developed a method to determine the physical parameter for theheat diffusion (thermal conductivity) using a nanoparticle called aquantum nano sensor, and successfully applied the method to intracellular measurements.

▍ Background & Results
The quantum nano sensor is a diamond nanoparticle. Due to theimpurity in the lattice of carbon atoms, those nanodiamonds become fluorescent. From the temperature dependent fluorescencesignal, we can determine the temperature changes in the nanodiamond. Individual nanodiamonds were coated with a polymer that
releases heat upon light illumination. Thus, a heater-thermometer
nanohybrid was developed with which we can determine the thermal conductivity at the nanoscale.
We confirmed the accuracy of the new methodology using air,water and oil with known values of thermal conductivities, followedby the measurements in cells. It has been considered that the intracellular thermal conductivity is similar to that of water, and that thevalue is homogeneous within a cell. However, our measurementsrevealed that those considerations were wrong; the intracellularvalue is about one sixth of that of water, and the value deviates
around the mean significantly. Furthermore, according to the calculations using the measured values, there can be localized temperature rises that are high enough to accelerate enzymatic activities
and to thermally modulate biological molecules in a cell.

▍ Significance of the research and Future perspective
Accurate measurement of thermal properties is the importantfirst step towards the understanding of thermogenesis at the cellular scale. For example, the hot spot where the thermal conductivity
is lower can maintain higher temperature than other locations in acell. The high temperature can accelerate the enzymatic activities
around the heat source such as transcriptions and ATP synthesis.
It can also change the dynamics of lipid bilayers. If there are cellswith lower thermal conductivity, these cells can elevate the temperature higher than other cells. Our studies contribute the progressof basic biology and medical biology, but can also promote thedevelopment of anti-obesity treatments and novel methods of hyperthermia using artificial tiny heat sources.

P a t e n t Japanese Patent No.6919923，WO2017-073728
Sotoma, S. et al. In situ measurements of intracellular thermal conductivity using heater-thermometer hybrid diamond nanosensors. Science Advances.
2021; 7(3), eabd7888. doi: 10.1126/sciadv.abd7888
Suzuki, M; Plakhotnik, T. Opportunities for hybrid diamond nanosensors targeting photothermal applicatoins in biological systems. Applied Physics LetTr e a t i s eters. 2021; 119: 190502. doi: 10.1063/5.0063089
Plakhotnik, T; Suzuki, M. Backstage of rising body temperature: Advances in research on intracellular heat diffusion. Temperature. 2021; 8(4): 303-305.
doi: 10.1080/23328940.2021.1982363
https://resou.osaka-u.ac.jp/en/research/2021/20210116_1
UR
L https://www.scientificamerican.com/article/mysterious-heat-spikes-inside-cells-are-probed-with-tiny-diamonds/
https://physicsworld.com/a/nanodiamonds-measure-thermal-conductivity-in-living-cells/
K e y w o r d temperature, heat, fluorescent probe, fluorescence microscopy, imaging