Self-calibrated fluorescent thermometer nanoparticles enable in vivo micro thermography in milimeter scale living animals

We have developed a fluorescent nanoparticle thermometer capable of mapping out the temperature distributions in small animals with higher spatial resolution than conventional infrared thermography. To acquire the fluorescence intensity change solely owing to the temperature shift, we encapsulated both the thermo-sensitive dye and the thermo-insensitive (reference) dye into the nanoparticles. The nanoparticle thermometer exhibited a significantly high thermo-sensitivity of 3.6 %/°C, and could be orally dosed into fruit fly larvae so as to stably measure the temperature distributions in the animals. This thermal-microscopy system could provide a powerful experimental paradigm to illuminate physiological functions and activities in small living organisms.