A research team has developed a method to measure the internal temperature of individual cells with a spatial resolution of tens of nanometres, far exceeding the precision of conventional cellular thermometers. The technique can record thermal variations of just a few thousandths of a degree between the cytoplasm and the nucleus, opening a window onto the bioenergetics of the living cell.

Until now, cellular thermometry has relied mainly on organic fluorescent probes or quantum dots, whose thermal sensitivity is limited by photodegradation, signal dispersion and the relatively large size of the particles. These limitations made it impossible to reliably distinguish subcellular thermal gradients, a frontier the new work crosses by combining next-generation nanosensors with high-resolution microscopy.

The method relies on nanosensors whose optical response — a spectral shift or a change in fluorescence intensity — varies in a reproducible and calibratable way with the local temperature. Once introduced into the cell, the researchers calibrate the signal against a thermostatic bath and reconstruct three-dimensional thermal maps, correcting for the effects of the cellular environment on emission.

The results show that cancer cells display a markedly different thermal profile from healthy cells, with internal differences of up to several thousandths of a degree between compartments. The measurement is consistently repeated across cells of the same type, suggesting that tumour metabolism leaves a characteristic thermal fingerprint.

The main implication is diagnostic: if a cell's thermal profile reflects its metabolic state, it could be used as an early marker of malignant transformation or as an indicator of drug response. The work also raises open questions about the physical origin of the observed gradients and their relationship to mitochondrial activity.

The authors plan to extend the technique to living tissues and combine it with multiparametric fluorescence imaging, with the goal of validating the findings in animal models before proposing clinical applications.