Chemical reactions occurring in biological processes are either endergonic or exergonic, which exchange heat between the system and surrounding. Detecting thermogenic responses with high sensitivity is of fundamental importance to characterize and diagnose the biological systems. In regenerative medicine, the culture temperature and the thermogenic properties of stem-cells significantly affect the subsequent growth of regenerative cells and tissues, thereby preventing efficient growth of regenerative organs from stem cells. However, such thermogenic analyses at single cellular level have been elusive until now.
Here we demonstrate microscope-based thermometry of adipose-tissue derived stem cells (ASCs ) taken from mice by using quantum sensors based on the electron spin resonance of color defect centers in fluorescent nanodiamonds (FNDs) . ASCs are successfully labeled with FNDs while keeping the original ability for the proliferation and differentiation to osteocytes and adipocytes. The FND-labeled ASCs are measured to detect the intracellular temperature change. The FNDs act as nanoparticle thermometers in ASCs with the temperature dependence of - 63 kHz/oC with temperature accuracy of ± 0.9 oC and precision of ± 0.5 oC . The present demonstration makes a new direction of the quantum sensor applications toward stem-cell research and regenerative medicine.
 Yukawa et al., Adv. Drug Deliv. Rev. 95 , 2 (2015).
 Fujiwara et al., Nanotech. 27, 455202 (2016): arXiv:1803.06179. (2018).
 Manuscript in preparation.