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M. L. Denton, G. D. Noojin, L. E. Estlack, R. J. Thomas; Temperature Threshold for Photothermal Damage in Cultured RPE Cells Using Real-Time Thermography. Invest. Ophthalmol. Vis. Sci. 2008;49(13):478. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
Establish thresholds for laser irradiance and cellular temperature at which cultured RPE cells are irreversibly damaged, and to relate the effects of varying intracellular pigmentation on laser absorption.
Pigmented hTERT-RPE1 cells were used to determine an ED50 irradiance threshold for damage (fluorescence staining with calcein AM and ethidium homodimer1) by a photothermal laser exposure (1 mm, 0.1 s, 514 nm, flat-top profile). Binary (yes/no) damage endpoints, based on a fluorescent dye assay (calcein-AM and ethidium homodimer1) one hr post-exposure, were used as input to the Probit computer program. In addition to threshold irradiances, real-time thermography (FLIR IR camera, 800 fps) and visible movies of laser exposures were acquired. Correlations between dead cells (measured after exposure) and cellular temperature during laser exposure were made for various levels of pigmentation.
Threshold irradiances for photothermal damage from the 1 mm beam were proportional to the degree of intracellular pigmentation (melanin granules), although the slight cell-to-cell differences within a culture were not significant. Temperature threshold for damage in our cultures appeared to be more deterministic rather than probabilistic. Levels of intracellular pigmentation did not significantly alter the temperature at which the RPE cells were damaged. The thermography data were used to test and refine our existing predictive thermal models of laser-tissue interaction.
Our real-time thermography method will be used in the development of non-isothermal rate-process models for cellular damage.
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