Label‐Free Imaging of Intracellular Temperature by Using the O−H Stretching Raman Band of Water

• Published in: Angewandte Chemie International Edition 2020-05, Vol.59 (20), p.7755-7760
• Main Authors: Sugimura, Toshiki, Kajimoto, Shinji, Nakabayashi, Takakazu
• Format: Article
• Language: English
• Subjects: analytical methods; biophysics; Calibration; Carbonyl compounds; Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone - chemistry; Carbonyls; Cyanides; Cytoplasm; Extracellular Space - chemistry; HeLa Cells; Humans; Hydrogen - chemistry; Intracellular; Intracellular Space - chemistry; Molecular Imaging; Oxygen - chemistry; Raman spectra; Raman spectroscopy; Spectrum Analysis, Raman; Stretching; Temperature; thermochemistry; Water - chemistry
• ISSN: 1433-7851; 1521-3773
• DOI: 10.1002/anie.201915846

We propose a label‐free method for measuring intracellular temperature using a Raman image of a cell in the O−H stretching band. Raman spectra of cultured cells and the medium were first measured at various temperatures using a Raman microscope and the intensity ratio of the two regions of the O−H stretching band was calculated. The intensity ratio varies linearly with temperature in both the medium and cells, and the resulting calibration lines allow simultaneous visualization of both intracellular and extracellular temperatures in a label‐free manner. We applied this method to the measurement of temperature changes after the introduction of FCCP (carbonyl cyanide‐p‐trifluoromethoxyphenylhydrazone) in living cells. We observed a temperature rise in the cytoplasm and succeeded in obtaining an image of the change in intracellular temperature after the FCCP treatment. A label‐free method for imaging intracellular and extracellular temperatures using the O−H stretching Raman band of water is proposed. The method is based on changes in the O−H band shape with temperature. The shown image of the temperature changes after adding a mitochondrial uncoupling agent to a cell was obtained in a label‐free manner.