title: A cell-permeable fluorescent polymeric thermometer for intracellular temperature mapping in mammalian cell lines.
abstract: Changes in intracellular temperatures reflect the activity of the cell. Thus, the tool to measure intracellular temperatures could provide valuable information about cellular status. We previously reported a method to analyze the intracellular temperature distribution using a fluorescent polymeric thermometer (FPT) in combination with fluorescence lifetime imaging microscopy (FLIM). Intracellular delivery of the FPT used in the previous study required microinjection. We now report a novel FPT that is cell permeable and highly photostable, and we describe the application of this FPT to the imaging of intracellular temperature distributions in various types of mammalian cell lines. This cell-permeable FPT displayed a temperature resolution of 0.05°C to 0.54°C within the range from 28°C to 38°C in HeLa cell extracts. Using our optimized protocol, this cell-permeable FPT spontaneously diffused into HeLa cells within 10 min of incubation and exhibited minimal toxicity over several hours of observation. FLIM analysis confirmed a temperature difference between the nucleus and the cytoplasm and heat production near the mitochondria, which were also detected previously using the microinjected FPT. We also showed that this cell-permeable FPT protocol can be applied to other mammalian cell lines, COS7 and NIH/3T3 cells. Thus, this cell-permeable FPT represents a promising tool to study cellular states and functions with respect to temperature.
authors.affiliation: The Graduate School of Biological Sciences, Nara Institute of Science and Technology, Ikoma-shi, Nara, Japan.
authors.forename: Teruyuki
authors.initials: T
authors.lastname: Hayashi
authors.affiliation: The Graduate School of Biological Sciences, Nara Institute of Science and Technology, Ikoma-shi, Nara, Japan.
authors.forename: Nanaho
authors.initials: N
authors.lastname: Fukuda
authors.affiliation: Graduate School of Pharmaceutical Sciences, The University of Tokyo, Bunkyo-ku, Tokyo, Japan.
authors.forename: Seiichi
authors.initials: S
authors.lastname: Uchiyama
authors.affiliation: The Graduate School of Biological Sciences, Nara Institute of Science and Technology, Ikoma-shi, Nara, Japan.
authors.forename: Noriko
authors.initials: N
authors.lastname: Inada
mesh_terms: D002460:Cell Line; D004355:Drug Stability; D005456:Fluorescent Dyes / Q000737:chemistry / Q000378:metabolism*; D057809:HEK293 Cells; D006367:HeLa Cells; D006801:Humans; D042541:Intracellular Space / Q000378:metabolism*; D008856:Microscopy, Fluorescence; D010539:Permeability; D011108:Polymers / Q000737:chemistry / Q000378:metabolism*; D013696:Temperature
chemical_list: D005456:Fluorescent Dyes; D011108:Polymers