title: Thermal monitoring: Raman spectrometer system for remote measurement of cellular temperature on a microscopic scale.
abstract: A simple setup is demonstrated for remote temperature monitoring of water, water-based media, and cells on a microscopic scale. The technique relies on recording changes in the shape of a stretching band of the hydroxyl group in liquid water at 3,100-3,700 cm(-1). Rather than direct measurements in the near-infrared (IR), a simple Raman spectrometer setup is realized. The measured Raman shifts are observed at near optical wavelengths using an inverted microscope with standard objectives in contrast to costly near-IR elements. This allows for simultaneous visible inspection through the same optical path. An inexpensive 671-nm diode pump laser (< 100 mW), standard dichroic and lowpass filters, and a commercial 600-1,000 nm spectrometer complete the instrument. Temperature changes of 1 degrees C are readily distinguished over a range consistent with cellular processes (25-45 degrees C) using integration times below 10 s. Greatly improved sensitivity was obtained by an automated two-peak fitting procedure. When combined with an optical camera, the instrument can be used to monitor changes in cell behavior as a function of temperature without the need for invasive probing. The instrument is very simple to realize, inexpensive compared with traditional Raman spectrometers and IR microscopes, and applicable to a wide range of problems in microthermometry of biological systems. In a first application of its kind, the instrument was used to successfully determine the temperature rise of a cluster of H1299 derived human lung cells adhered to polystyrene and immersed in phosphate-buffered saline (PBS) under exposure of RF millimeter wave radiation (60 GHz, 1.3, 2.6, and 5.2 mW/mm2).
authors.affiliation: Neural Engineering Program of the Huntington Medical Research Institutes.
authors.forename: Victor
authors.initials: V
authors.lastname: Pikov
authors.forename: Peter H
authors.initials: PH
authors.lastname: Siegel
mesh_terms: D002468:Cell Physiological Phenomena; D004867:Equipment Design; D019544:Equipment Failure Analysis; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012815:Signal Processing, Computer-Assisted / Q000295:instrumentation*; D013059:Spectrum Analysis, Raman / Q000295:instrumentation* / Q000379:methods*; D013696:Temperature; D013817:Thermography / Q000295:instrumentation* / Q000379:methods*