title: A nanoparticle-based ratiometric and self-calibrated fluorescent thermometer for single living cells.
abstract: The homeostasis of body temperature and energy balance is one of the major principles in biology. Nanoscale thermometry of aqueous solutions is a challenging but crucial technique to understand the molecular basis of this essential process. Here, we developed a ratiometric nanothermometer (RNT) for intracellular temperature measurement in real time. Both the thermosensitive fluorophore, β-diketonate chelate europium(III) thenoyltrifluoroacetonate, and the thermoinsensitive fluorophore, rhodamine 101, which was used as a self-reference, are embedded in a polymeric particle that protects the fluorophores from intracellular conditions. The ratiometric measurement of single RNT spots is independent of the displacement of the RNT along the z-axis. The temperature is therefore determined at the location of each RNT under an optical microscope regardless of the dynamic movement of living cells. As a demonstration of the spot-by-spot intracellular thermometry, we successfully followed the temperature change in individual RNT spots in a single cell together with the Ca(2+) burst induced by the Ca(2+) ionophore ionomycin. The temperature increases differently among different spots, implying heterogeneous heat production in the cell. We then show that, in some spots, the temperature gradually decreases, while in others it remains high. The average temperature elevation within a cell is positively correlated to the increase in Ca(2+), suggesting that the activity and/or number of heat sources are dependent on the Ca(2+) concentration.
authors.affiliation: Department of Life Science & Medical Bioscience, Graduate School of Advanced Science & Engineering, Waseda University , 2-2 TWIns, Wakamatsu-cho, Shinjuku-ku, Tokyo, 162-8480 Japan.
authors.forename: Yoshiaki
authors.initials: Y
authors.lastname: Takei
authors.forename: Satoshi
authors.initials: S
authors.lastname: Arai
authors.forename: Atsushi
authors.initials: A
authors.lastname: Murata
authors.forename: Masao
authors.initials: M
authors.lastname: Takabayashi
authors.forename: Kotaro
authors.initials: K
authors.lastname: Oyama
authors.forename: Shin'ichi
authors.initials: S
authors.lastname: Ishiwata
authors.forename: Shinji
authors.initials: S
authors.lastname: Takeoka
authors.forename: Madoka
authors.initials: M
authors.lastname: Suzuki
mesh_terms: D002138:Calibration; D005456:Fluorescent Dyes / Q000737:chemistry; D053758:Nanoparticles; D011874:Radiometry; D013050:Spectrometry, Fluorescence
chemical_list: D005456:Fluorescent Dyes