Label-free mid-infrared photothermal microscopy revisits intracellular thermal dynamics: what do fluorescent nanothermometers measure?

Genki Ishigane; Hiroyuki Shimada; Keiichiro Toda; Kohki Okabe; Masaharu Takarada; Takuro Ideguchi; Venkata Ramaiah Badarla

arxiv: 2406.16265 · v4 · submitted 2024-06-24 · ⚛️ physics.bio-ph · physics.optics

Label-free mid-infrared photothermal microscopy revisits intracellular thermal dynamics: what do fluorescent nanothermometers measure?

Keiichiro Toda , Masaharu Takarada , Genki Ishigane , Hiroyuki Shimada , Venkata Ramaiah Badarla , Kohki Okabe , Takuro Ideguchi This is my paper

Pith reviewed 2026-05-24 00:32 UTC · model grok-4.3

classification ⚛️ physics.bio-ph physics.optics

keywords intracellular thermal dynamicsphotothermal microscopyfluorescent nanothermometrylocal thermal equilibriumthermal diffusivity10^5 gap issueheat conduction in cells

0 comments

The pith

Fluorescent nanothermometers detect a slow non-conductive signal rather than local thermal equilibrium temperature, resolving the 10^5 gap.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The paper uses label-free mid-infrared photothermal microscopy to measure true temperature changes in cells under local thermal equilibrium. It finds that heat spreads through cells almost as fast as in water, ruling out poor heat conduction as the reason for the large temperature variations seen with fluorescent probes. By comparing the two methods side by side, the fast temperature response matches between them, but fluorescent probes show an extra slow change that the label-free method does not. This indicates the fluorescent readings include a long-lived signal from other cellular processes, not just temperature. The result matters because it clarifies what these popular nanothermometers are actually reporting in single-cell studies.

Core claim

Label-free photothermal microscopy quantifies LTE temperature via refractive index changes and shows intracellular thermal diffusivity at 93-94% of water. Fluorescent nanothermometers match the fast response but add a slow variation absent in label-free data, so the 10^5 gap arises from comparing LTE temperature to this distinct non-conductive signal.

What carries the argument

Mid-infrared photothermal microscopy detecting refractive index variations to report local thermal equilibrium temperature changes, combined with transient thermal decay analysis for diffusivity.

If this is right

Intracellular heat conduction behaves like water, so large sustained temperature gradients are not possible under standard conduction.
The 10^5 gap cannot be explained by anomalous thermal properties inside cells.
Fluorescent nanothermometers report both rapid LTE temperature shifts and slower non-thermal intracellular processes.
Seconds-long heating experiments separate conductive thermal signals from longer-lived effects.

Where Pith is reading between the lines

These are editorial extensions of the paper, not claims the author makes directly.

Researchers using fluorescent nanothermometers for temperature claims may need to subtract or account for the slow non-conductive component.
The label-free method could serve as a reference to validate or reinterpret existing fluorescent thermometry data in cells.
Other slow cellular processes like pH changes or protein conformational shifts might be what the fluorescent probes are partly sensing.

Load-bearing premise

The photothermal signal accurately tracks LTE temperature without interference from other refractive index changes, and the fluorescent slow signal is entirely unrelated to conductive heat transfer.

What would settle it

Measuring intracellular thermal diffusivity much lower than 93% of water's value, or observing the same slow variation in the label-free photothermal signal under the same heating conditions, would falsify the explanation for the gap.

read the original abstract

Fluorescent nanothermometry has revealed pronounced intracellular temperature heterogeneity, establishing the field of single-cell thermal biology. However, these observations have sparked a controversy known as the "10^5 gap issue", because heat conduction calculations in aqueous environments predict that such large temperature distributions cannot be sustained within cells. Here, we address this issue using label-free mid-infrared photothermal microscopy. This technique quantifies heat-induced temperature changes under local thermal equilibrium (LTE), in accordance with the conventional thermodynamic and statistical-mechanical definition of temperature, by detecting refractive index variations. From transient thermal decay measurements, we determined that intracellular thermal diffusivity corresponds to 93-94% that of water. This result indicates that intracellular heat conduction is essentially water-like and rules out the hypothesis that anomalously slow intracellular heat conduction underlies the 10^5 gap discrepancy. We then directly compared fluorescent nanothermometry with our label-free thermometry. Under seconds-long heating, the label-free method exhibited a rapid temperature response consistent with water-like heat conduction. In contrast, fluorescent nanothermometers showed not only a similarly fast response but also an additional slow variation that was absent in the label-free readout. This slow component cannot be explained by temperature changes defined under LTE, but instead likely reflects slower intracellular processes not governed by conductive heat transfer. These results suggest that the "10^5 gap issue" stems from comparing two fundamentally distinct physical quantities: the LTE-defined temperature and a slowly-varying, long-lived non-conductive signal detected by fluorescent nanothermometers.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Desk Editor's Note private letter to a colleague

The paper's side-by-side comparison is the useful part, but the claim that photothermal microscopy cleanly isolates LTE temperature rests on an assumption that could use more checks.

read the letter

The main new result here is the direct experimental contrast: label-free mid-IR photothermal microscopy shows a fast temperature response under seconds-long heating that matches water-like conduction, while fluorescent nanothermometers add a slow extra component absent from the label-free trace. They also report intracellular thermal diffusivity at 93-94% of water from transient decay, which undercuts the idea that cells have anomalously poor heat conduction to explain the 10^5 gap. That comparison and the diffusivity number are the concrete advances worth noting. The work engages the controversy with independent readouts rather than just reinterpreting prior data. The soft spot is the assumption that the photothermal refractive-index signal reports only LTE temperature with no confounding non-thermal contributions from mid-IR absorption in proteins or lipids. The stress-test concern lands here; if those effects alter RI on similar timescales, both the fast-response match and the diffusivity extraction become less decisive. The abstract gives no detail on controls or error analysis for that separation, so the central distinction between LTE temperature and the slow fluorescent signal is plausible but not yet airtight. This is for labs working on intracellular thermometry or single-cell biophysics. It has enough new measurements and a clear framing of the gap to merit peer review, even if the interpretation of the photothermal channel needs tightening.

Referee Report

2 major / 2 minor

Summary. The manuscript claims that label-free mid-infrared photothermal microscopy measures intracellular temperature under local thermal equilibrium (LTE) via refractive index changes, yielding intracellular thermal diffusivity at 93-94% of water from transient decay data. This indicates water-like heat conduction and rules out slow conduction as the origin of the 10^5 gap. Direct comparison experiments show fluorescent nanothermometers exhibit both a fast response and an additional slow variation absent from the label-free readout, implying the gap arises from comparing LTE temperature to a distinct non-conductive signal.

Significance. If the central claims hold, the work resolves a prominent controversy in single-cell thermal biology by experimentally distinguishing LTE-defined temperature from other intracellular signals detected by fluorescent probes. A notable strength is the side-by-side comparison of two thermometry modalities under identical heating conditions, which supplies a concrete, falsifiable test of the non-conductive interpretation. This has direct implications for how temperature heterogeneity data are interpreted in the field.

major comments (2)

[Results, transient thermal decay measurements] Results, transient thermal decay measurements: the reported intracellular diffusivity of 93-94% of water is load-bearing for excluding slow conduction as the source of the 10^5 gap, yet the manuscript provides neither the explicit fitting model, number of independent cells, nor uncertainty estimates for this ratio, preventing assessment of whether the deviation from 100% is statistically meaningful.
[Section on photothermal signal interpretation] Section on photothermal signal interpretation: the claim that refractive-index variations report only LTE temperature (via dn/dT) with no non-thermal contributions is central to both the diffusivity value and the conclusion that fluorescent signals contain a distinct slow component. The manuscript does not address or control for possible mid-IR-induced conformational or solvation changes in proteins/lipids that could alter RI on microsecond-to-second timescales independently of temperature.

minor comments (2)

[Abstract] Abstract: the diffusivity is stated only as the range '93-94%' without reference to the underlying data or fitting; adding a parenthetical note on the measurement protocol would improve precision.
[Comparison experiment description] Comparison experiment description: the duration and spatial profile of the 'seconds-long heating' are not quantified, which affects reproducibility of the fast-versus-slow response distinction.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for their constructive and insightful comments, which help clarify key aspects of our work. We provide point-by-point responses to the major comments below.

read point-by-point responses

Referee: [Results, transient thermal decay measurements] Results, transient thermal decay measurements: the reported intracellular diffusivity of 93-94% of water is load-bearing for excluding slow conduction as the source of the 10^5 gap, yet the manuscript provides neither the explicit fitting model, number of independent cells, nor uncertainty estimates for this ratio, preventing assessment of whether the deviation from 100% is statistically meaningful.

Authors: We agree that these details are necessary to evaluate the robustness and statistical significance of the reported diffusivity ratio. In the revised manuscript, we will add the explicit functional form of the fitting model used for the transient decay analysis, report the number of independent cells (or replicates) from which the 93-94% value was derived, and include uncertainty estimates (e.g., standard error or 95% confidence intervals). These additions will allow readers to determine whether the small deviation from water's diffusivity is statistically meaningful. revision: yes
Referee: [Section on photothermal signal interpretation] Section on photothermal signal interpretation: the claim that refractive-index variations report only LTE temperature (via dn/dT) with no non-thermal contributions is central to both the diffusivity value and the conclusion that fluorescent signals contain a distinct slow component. The manuscript does not address or control for possible mid-IR-induced conformational or solvation changes in proteins/lipids that could alter RI on microsecond-to-second timescales independently of temperature.

Authors: We acknowledge this as a legitimate point that merits explicit discussion. While the photothermal signal is interpreted via the established dn/dT mechanism under LTE, we will revise the relevant section to address potential mid-IR-induced non-thermal effects (e.g., conformational or solvation changes). Our response will note that (i) the observed decay timescales align quantitatively with thermal diffusion rather than slower biomolecular relaxation processes, (ii) the label-free readout lacks the slow component seen in fluorescent probes under identical conditions, and (iii) the technique's prior validation in biological samples supports a predominantly thermal origin. We will expand the text accordingly but maintain that the data do not indicate significant non-thermal contributions on the relevant timescales. revision: partial

Circularity Check

0 steps flagged

No circularity; results from independent experimental readouts

full rationale

The derivation chain consists of direct measurements: photothermal RI signals calibrated to LTE temperature via standard thermo-optic response, transient decay times fitted to extract diffusivity (yielding the empirical 93-94% water value), and side-by-side comparison of time responses between two distinct instruments. None of these steps reduce a claimed prediction to a fitted input by the paper's own equations, invoke self-citations as load-bearing uniqueness theorems, or smuggle ansatzes; the central distinction between LTE temperature and slow non-conductive signals follows from the observed difference in the two independent readouts rather than from definitional equivalence.

Axiom & Free-Parameter Ledger

1 free parameters · 1 axioms · 0 invented entities

Limited to abstract content; main fitted element is the diffusivity ratio, with the core assumption being direct mapping of photothermal signal to LTE temperature.

free parameters (1)

intracellular thermal diffusivity ratio = 93-94% of water
Determined from transient thermal decay measurements to be 93-94% of water.

axioms (1)

domain assumption Refractive index variations detected by mid-infrared photothermal microscopy correspond directly to temperature changes under local thermal equilibrium
Basis for label-free thermometry as stated in the abstract.

pith-pipeline@v0.9.0 · 5840 in / 1369 out tokens · 31150 ms · 2026-05-24T00:32:18.122611+00:00 · methodology

discussion (0)

Lean theorems connected to this paper

Citations machine-checked in the Pith Canon. Every link opens the source theorem in the public Lean library.

IndisputableMonolith/Cost/FunctionalEquation.lean washburn_uniqueness_aczel unclear

?

unclear
Relation between the paper passage and the cited Recognition theorem.

From transient thermal decay measurements, we determined that intracellular thermal diffusivity corresponds to 93-94% that of water... the label-free method exhibited a rapid temperature response consistent with water-like heat conduction. In contrast, fluorescent nanothermometers showed... an additional slow variation
IndisputableMonolith/Foundation/RealityFromDistinction.lean reality_from_one_distinction unclear

?

unclear
Relation between the paper passage and the cited Recognition theorem.

heat conduction calculation... 10-5 K within a cell... thermal diffusion in a cell, which is assumed to have thermal properties similar to those of an aqueous environment

What do these tags mean?

matches: The paper's claim is directly supported by a theorem in the formal canon.
supports: The theorem supports part of the paper's argument, but the paper may add assumptions or extra steps.
extends: The paper goes beyond the formal theorem; the theorem is a base layer rather than the whole result.
uses: The paper appears to rely on the theorem as machinery.
contradicts: The paper's claim conflicts with a theorem or certificate in the canon.
unclear: Pith found a possible connection, but the passage is too broad, indirect, or ambiguous to say the theorem truly supports the claim.

Reference graph

Works this paper leans on

46 extracted references · 46 canonical work pages

[1]

Okabe, K. et al. Intracellular temperature mapping with a fluorescent polymeric thermometer and fluorescence lifetime imaging microscopy. Nat. Commun. 3, 705 (2012)

work page 2012
[2]

Dominique, C. et al. Mitochondria are physiologically maintained at close to 50 ℃. PLoS Biol. 16, 201–210 (2018)

work page 2018
[3]

Qiao, J. et al. Ratiometric Fluorescent Polymeric Thermometer for Thermogenesis Investigation in Living Cells. Anal. Chem. 87, 10535–10541 (2015)

work page 2015
[4]

Kiyonaka, S. et al. Genetically encoded fluorescent thermosensors visualize subcellular thermoregulation in living cells. Nat. Methods 10, 1232–1238 (2013)

work page 2013
[5]

Tanimoto, R. et al. Detection of Temperature Difference in Neuronal Cells. Sci. Rep. 6, 22071 (2016)

work page 2016
[6]

Zhou, J. et al. Advances and challenges for fluorescence nanothermometry. Nat. Methods 17, 967–980 (2020)

work page 2020
[7]

Kucsko, G. et al. Nanometre-scale thermometry in a living cell. Nature 500, 54–58 (2013)

work page 2013
[8]

Kamei, Y. et al. Infrared laser–mediated gene induction in targeted single cells in vivo. Nat. Methods 6, 79–81 (2009)

work page 2009
[9]

Huang, H. et al. Remote control of ion channels and neurons through magnetic-field heating of nanoparticles. Nat. Nanotechnol. 5, 602–606 (2010)

work page 2010
[10]

Baffou, G. et al. A critique of methods for temperature imaging in single cells. Nat. Methods 11, 899–901 (2014)

work page 2014
[11]

Hong, S. et al. Sub-nanowatt microfluidic single-cell calorimetry. Nat. Commun. 11, 1–9 (2020)

work page 2020
[12]

Kyoo Park, B. et al. Thermal conductivity of single biological cells and relation with cell viability. Appl. Phys. Lett. 102, 203702 (2013)

work page 2013
[13]

Suzuki, M. et al. The 105 gap issue between calculation and measurement in single-cell thermometry. Nat. Methods 12, 802–803 (2015)

work page 2015
[14]

Sotoma, S. et al. In situ measurements of intracellular thermal conductivity using heater -thermometer hybrid diamond nanosensors. Sci. Adv. 7: eabd7888 (2021)

work page 2021
[15]

Lu, K. et al. Intracellular Heat Transfer and Thermal Property Revealed by Kilohertz Temperature Imaging with a Genetically Encoded Nanothermometer. Nano Lett. 22, 5698–5707 (2022)

work page 2022
[16]

Figueroa, B. et al. Real-Time Microscale Temperature Imaging by Stimulated Raman Scattering. J. Phys. Chem. Lett. 11, 7083–7089 (2020)

work page 2020
[17]

Inomata, N. et al. Measurement of cellular thermal properties and their temperature dependence based on frequency spectra via an on-chip-integrated microthermistor. Lab Chip 23, 2411-2420 (2023)

work page 2023
[18]

Song, P. et al. Heat transfer and thermoregulation within single cells revealed by transient plasmonic imaging. Chem 7, 1569–1587 (2021)

work page 2021
[19]

Tamamitsu, M. et al. Label-free biochemical quantitative phase imaging with mid -infrared photothermal effect. Optica 7, 359 (2020)

work page 2020
[20]

Park, Y. K. et al. Quantitative phase imaging in biomedicine. Nat. Photonics 12, 578–589 (2018)

work page 2018
[21]

Toda, K. et al. Ludwig-Soret microscopy with vibrational photothermal effect. arXiv:2502.04578

work page arXiv
[22]

Arrio-Dupont, M. et al. Translational diffusion of globular proteins in the cytoplasm of cultured muscle cells. Biophys. J. 78, 901–907 (2000)

work page 2000
[23]

García-Pérez, A. I. et al. Molecular crowding and viscosity as determinants of translational diffusion of metabolites in subcellular organelles. Arch. Biochem. Biophys. 362, 329–338 (1999)

work page 1999
[24]

Balderas-López, J. A. et al. Thermal-wave resonator cavity design and measurements of the thermal diffusivity of liquids. Rev. Sci. Instrum. 71, 2933–2937 (2000)

work page 2000
[25]

Pertoft, H. et al. Isopycnic Separation of Cells and Cell Organelles by Centrifugation in Modified Colloidal Silica Gradients. Methods of Cell Separation 25-65 (1977)

work page 1977
[26]

Giering, K. et al. Determination of the specific heat capacity of healthy and tumorous human tissue. Thermochim. Acta 251, 199–205 (1995)

work page 1995
[27]

Shrestha, R. et al. Thermal conductivity of a Jurkat cell measured by a transient laser point heating method. Int. J. Heat Mass Transf. 160, 120161 (2020)

work page 2020
[28]

Yu, X. et al. Heat flow in proteins: Computation of thermal transport coefficients. J. Chem. Phys. 122, 054902 (2005)

work page 2005
[29]

ElAfandy, R. T. et al. Nanomembrane-Based, Thermal-Transport Biosensor for Living Cells. Small 13, 7 (2017)

work page 2017
[30]

Takarada, M. et al. High-speed Intracellular Temperature Mapping Reveals the Existence of Non -Conductive Dissipation of Energy by Heating. https://doi.org/10.1101/2024.08.29.610413 (https://www.biorxiv.org/content/10.1101/2024.08.29.610413v1)

work page doi:10.1101/2024.08.29.610413 2024
[31]

Uchiyama, S. et al. A cationic fluorescent polymeric thermometer for the ratiometric sensing of intracellular temperature. Analyst 140, 4498–4506 (2015)

work page 2015
[32]

Umeda, K. et al. Activity-dependent glassy cell mechanics II: Nonthermal fluctuations under metabolic activity. arXiv: 2302.13323 (2023)

work page arXiv 2023
[33]

Intracellular thermometry uncovers spontaneous thermogenesis and associated thermal signaling

Okabe, K et al. Intracellular thermometry uncovers spontaneous thermogenesis and associated thermal signaling. Commun. Biol. 4, 1–7 (2021)

work page 2021
[34]

Chuma, S. et al. Implication of thermal signaling in neuronal differentiation revealed by manipulation and measurement of intracellular temperature. Nat. Commun. 15, 4–8 (2024)

work page 2024
[35]

Ishigane, G. et al. Label-free mid-infrared photothermal live-cell imaging beyond video rate. Light Sci. Appl. 12, 48 (2023)

work page 2023
[36]

Venyaminov, S. Y. et al. Water (H2O and D2O) Molar Absorptivity in the 1000–4000 cm−1 Range and Quantitative Infrared Spectroscopy of Aqueous Solutions. Anal. Biochem. 248, 234–245 (1997)

work page 1997
[37]

Jewel, J. M. Thermooptic Coefficients of some Standard Reference Material Glasses. J.Am. Ceram. Soc. 74, 1689– 1691 (1991)

work page 1991
[38]

Ramires, M. L. V. et al. Standard Reference Data for the Thermal Conductivity of Water. J. Phys. Chem. Ref. Data 24, 1377–1381 (1995)

work page 1995
[39]

Calibration curve of 𝛿𝑛𝜌 on ∆T

Lotfi, M. et al. Experimental Measurements on the Thermal Conductivity of Glycerol -Based Nanofluids with Different Thermal Contrasts. J. Nanomater. 3190877 (2021). Methods MIP-ODT system. A detailed schematic of the MIP-ODT system is represented in Fig. S1 of Supplementary Note 1. A homemade Ti- Sapphire laser at a repetition rate of 1 kHz serves 10-ns v...

work page 2021
[40]

Zhao, H. et al. On the distribution of protein refractive index increments. Biophys. J. 100, 2309–2317 (2011)

work page 2011
[41]

Oh, S. et al. Protein and lipid mass concentration measurement in tissues by stimulated Raman scattering microscopy. Proc. Natl. Acad. Sci. U. S. A. 119, 1–11 (2022)

work page 2022
[42]

Bashkatov, A. et al. Water refractive index in dependence on temperature and wavelength: a simple approximation. in SPIE 5068, Saratov Fall Meeting 2002 393–395 (2003)

work page 2002
[43]

Uchiyama, S. et al. A cationic fluorescent polymetric thermometer for the ratiometric sensing of intracellular temperature. Analyst 140, 4498-4506 (2015)

work page 2015
[44]

Toda, K. et al. Label-free intracellular thermophoretic imaging. Manuscript in preparation

work page
[45]

Andika, M. et al. Excitation temporal pulse shape and beam size on pulsed photothermal lens of single particle JOSA B 27, 796-805 (2010)

work page 2010
[46]

Popescu, G. et al. Optical imaging of cell mass and growth dynamics. Am. J. Physiol. - Cell Physiol. 295, 538–544 (2008)

work page 2008

[1] [1]

Okabe, K. et al. Intracellular temperature mapping with a fluorescent polymeric thermometer and fluorescence lifetime imaging microscopy. Nat. Commun. 3, 705 (2012)

work page 2012

[2] [2]

Dominique, C. et al. Mitochondria are physiologically maintained at close to 50 ℃. PLoS Biol. 16, 201–210 (2018)

work page 2018

[3] [3]

Qiao, J. et al. Ratiometric Fluorescent Polymeric Thermometer for Thermogenesis Investigation in Living Cells. Anal. Chem. 87, 10535–10541 (2015)

work page 2015

[4] [4]

Kiyonaka, S. et al. Genetically encoded fluorescent thermosensors visualize subcellular thermoregulation in living cells. Nat. Methods 10, 1232–1238 (2013)

work page 2013

[5] [5]

Tanimoto, R. et al. Detection of Temperature Difference in Neuronal Cells. Sci. Rep. 6, 22071 (2016)

work page 2016

[6] [6]

Zhou, J. et al. Advances and challenges for fluorescence nanothermometry. Nat. Methods 17, 967–980 (2020)

work page 2020

[7] [7]

Kucsko, G. et al. Nanometre-scale thermometry in a living cell. Nature 500, 54–58 (2013)

work page 2013

[8] [8]

Kamei, Y. et al. Infrared laser–mediated gene induction in targeted single cells in vivo. Nat. Methods 6, 79–81 (2009)

work page 2009

[9] [9]

Huang, H. et al. Remote control of ion channels and neurons through magnetic-field heating of nanoparticles. Nat. Nanotechnol. 5, 602–606 (2010)

work page 2010

[10] [10]

Baffou, G. et al. A critique of methods for temperature imaging in single cells. Nat. Methods 11, 899–901 (2014)

work page 2014

[11] [11]

Hong, S. et al. Sub-nanowatt microfluidic single-cell calorimetry. Nat. Commun. 11, 1–9 (2020)

work page 2020

[12] [12]

Kyoo Park, B. et al. Thermal conductivity of single biological cells and relation with cell viability. Appl. Phys. Lett. 102, 203702 (2013)

work page 2013

[13] [13]

Suzuki, M. et al. The 105 gap issue between calculation and measurement in single-cell thermometry. Nat. Methods 12, 802–803 (2015)

work page 2015

[14] [14]

Sotoma, S. et al. In situ measurements of intracellular thermal conductivity using heater -thermometer hybrid diamond nanosensors. Sci. Adv. 7: eabd7888 (2021)

work page 2021

[15] [15]

Lu, K. et al. Intracellular Heat Transfer and Thermal Property Revealed by Kilohertz Temperature Imaging with a Genetically Encoded Nanothermometer. Nano Lett. 22, 5698–5707 (2022)

work page 2022

[16] [16]

Figueroa, B. et al. Real-Time Microscale Temperature Imaging by Stimulated Raman Scattering. J. Phys. Chem. Lett. 11, 7083–7089 (2020)

work page 2020

[17] [17]

Inomata, N. et al. Measurement of cellular thermal properties and their temperature dependence based on frequency spectra via an on-chip-integrated microthermistor. Lab Chip 23, 2411-2420 (2023)

work page 2023

[18] [18]

Song, P. et al. Heat transfer and thermoregulation within single cells revealed by transient plasmonic imaging. Chem 7, 1569–1587 (2021)

work page 2021

[19] [19]

Tamamitsu, M. et al. Label-free biochemical quantitative phase imaging with mid -infrared photothermal effect. Optica 7, 359 (2020)

work page 2020

[20] [20]

Park, Y. K. et al. Quantitative phase imaging in biomedicine. Nat. Photonics 12, 578–589 (2018)

work page 2018

[21] [21]

Toda, K. et al. Ludwig-Soret microscopy with vibrational photothermal effect. arXiv:2502.04578

work page arXiv

[22] [22]

Arrio-Dupont, M. et al. Translational diffusion of globular proteins in the cytoplasm of cultured muscle cells. Biophys. J. 78, 901–907 (2000)

work page 2000

[23] [23]

García-Pérez, A. I. et al. Molecular crowding and viscosity as determinants of translational diffusion of metabolites in subcellular organelles. Arch. Biochem. Biophys. 362, 329–338 (1999)

work page 1999

[24] [24]

Balderas-López, J. A. et al. Thermal-wave resonator cavity design and measurements of the thermal diffusivity of liquids. Rev. Sci. Instrum. 71, 2933–2937 (2000)

work page 2000

[25] [25]

Pertoft, H. et al. Isopycnic Separation of Cells and Cell Organelles by Centrifugation in Modified Colloidal Silica Gradients. Methods of Cell Separation 25-65 (1977)

work page 1977

[26] [26]

Giering, K. et al. Determination of the specific heat capacity of healthy and tumorous human tissue. Thermochim. Acta 251, 199–205 (1995)

work page 1995

[27] [27]

Shrestha, R. et al. Thermal conductivity of a Jurkat cell measured by a transient laser point heating method. Int. J. Heat Mass Transf. 160, 120161 (2020)

work page 2020

[28] [28]

Yu, X. et al. Heat flow in proteins: Computation of thermal transport coefficients. J. Chem. Phys. 122, 054902 (2005)

work page 2005

[29] [29]

ElAfandy, R. T. et al. Nanomembrane-Based, Thermal-Transport Biosensor for Living Cells. Small 13, 7 (2017)

work page 2017

[30] [30]

Takarada, M. et al. High-speed Intracellular Temperature Mapping Reveals the Existence of Non -Conductive Dissipation of Energy by Heating. https://doi.org/10.1101/2024.08.29.610413 (https://www.biorxiv.org/content/10.1101/2024.08.29.610413v1)

work page doi:10.1101/2024.08.29.610413 2024

[31] [31]

Uchiyama, S. et al. A cationic fluorescent polymeric thermometer for the ratiometric sensing of intracellular temperature. Analyst 140, 4498–4506 (2015)

work page 2015

[32] [32]

Umeda, K. et al. Activity-dependent glassy cell mechanics II: Nonthermal fluctuations under metabolic activity. arXiv: 2302.13323 (2023)

work page arXiv 2023

[33] [33]

Intracellular thermometry uncovers spontaneous thermogenesis and associated thermal signaling

Okabe, K et al. Intracellular thermometry uncovers spontaneous thermogenesis and associated thermal signaling. Commun. Biol. 4, 1–7 (2021)

work page 2021

[34] [34]

Chuma, S. et al. Implication of thermal signaling in neuronal differentiation revealed by manipulation and measurement of intracellular temperature. Nat. Commun. 15, 4–8 (2024)

work page 2024

[35] [35]

Ishigane, G. et al. Label-free mid-infrared photothermal live-cell imaging beyond video rate. Light Sci. Appl. 12, 48 (2023)

work page 2023

[36] [36]

Venyaminov, S. Y. et al. Water (H2O and D2O) Molar Absorptivity in the 1000–4000 cm−1 Range and Quantitative Infrared Spectroscopy of Aqueous Solutions. Anal. Biochem. 248, 234–245 (1997)

work page 1997

[37] [37]

Jewel, J. M. Thermooptic Coefficients of some Standard Reference Material Glasses. J.Am. Ceram. Soc. 74, 1689– 1691 (1991)

work page 1991

[38] [38]

Ramires, M. L. V. et al. Standard Reference Data for the Thermal Conductivity of Water. J. Phys. Chem. Ref. Data 24, 1377–1381 (1995)

work page 1995

[39] [39]

Calibration curve of 𝛿𝑛𝜌 on ∆T

Lotfi, M. et al. Experimental Measurements on the Thermal Conductivity of Glycerol -Based Nanofluids with Different Thermal Contrasts. J. Nanomater. 3190877 (2021). Methods MIP-ODT system. A detailed schematic of the MIP-ODT system is represented in Fig. S1 of Supplementary Note 1. A homemade Ti- Sapphire laser at a repetition rate of 1 kHz serves 10-ns v...

work page 2021

[40] [40]

Zhao, H. et al. On the distribution of protein refractive index increments. Biophys. J. 100, 2309–2317 (2011)

work page 2011

[41] [41]

Oh, S. et al. Protein and lipid mass concentration measurement in tissues by stimulated Raman scattering microscopy. Proc. Natl. Acad. Sci. U. S. A. 119, 1–11 (2022)

work page 2022

[42] [42]

Bashkatov, A. et al. Water refractive index in dependence on temperature and wavelength: a simple approximation. in SPIE 5068, Saratov Fall Meeting 2002 393–395 (2003)

work page 2002

[43] [43]

Uchiyama, S. et al. A cationic fluorescent polymetric thermometer for the ratiometric sensing of intracellular temperature. Analyst 140, 4498-4506 (2015)

work page 2015

[44] [44]

Toda, K. et al. Label-free intracellular thermophoretic imaging. Manuscript in preparation

work page

[45] [45]

Andika, M. et al. Excitation temporal pulse shape and beam size on pulsed photothermal lens of single particle JOSA B 27, 796-805 (2010)

work page 2010

[46] [46]

Popescu, G. et al. Optical imaging of cell mass and growth dynamics. Am. J. Physiol. - Cell Physiol. 295, 538–544 (2008)

work page 2008