Dreams of mapping temperature differences within biological cells may soon come true, say researchers in Japan.

Seiichi Uchiyama and co-workers from the University of Tokyo, Japan, have developed thermometers consisting of mixtures of heat-responsive fluorescent polymers. These can be used to accurately map two- or three-dimensional temperature distributions in extremely small spaces, said Uchiyama. Prasanna de Silva, an expert in fluorescence sensors from Queen's University Belfast, Northern Ireland, rates this finding as 'important for thermal imaging research'.

The thermometers contain polymers which undergo temperature-induced structural changes, which alter the wavelength at which they fluoresce. The changes in fluorescence signal are so large that they can detect temperature differences as small as 0.2 °C. This is a better temperature resolution than previously reported using similar methods, says Uchiyama. This improvement was achieved by the addition of an ionic component to one of the polymers in the mixture to prevent aggregation. Aggregation made it difficult for structural changes to be reversed in previous thermometers of this type, said Uchiyama.

The ultimate goal of this research is to measure the temperature of specific organelle in biological cells, explained Uchiyama. De Silva said that further research will be needed to check that interactions between the polymers and the cell components do not disturb the thermal response.

Nina Athey-Pollard