This paper presents a high-sensitivity luminescent nanoparticle thermosensor capable of real-time microthermography in a living organism. Microthermography, or microscopically visualizing the temperature distribution within living cells, tissues, and organisms, is a promising technology to explore various physiological activities at the microscale. Using a facile nanoprecipitation method, we fabricated a polymer-nanoparticle embedding EuDT, a thermosensitive high-luminescence-emitter dye molecule, and rhodamine 800, a luminescent molecule excitable with low energy light and less sensitive to temperature. The nanoparticle thermosensor was largely exempted from the background noise, which is the undesired luminescence from the target biological sample, enabling direct acquisition of luminescence intensities from the thermosensor within the specified area of 68 μm × 68 μm on the muscle tissue of a living insect, i.e., real-time microthermography, without the need of subtracting background noise. Thus, we successfully mapped out the temperature shift due to the animal's voluntary heat production. The nanoparticle thermosensor capable of in vivo temperature mapping must be a useful biological thermographic technology to explore microscopic heat productions in living organisms.
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