Photo-oxidation from mode-locked laser exposure to hTERT-RPE1 cells

Human retinal pigment epithelial (RPE) cells (hTERT-RPE1) were used to detect photo-oxidation products generated from chronic NIR (810 nm) laser exposure. Exposure of a discrete area within cell monolayers provided a means of distinguishing fluorescence above background levels. Oxidative stress was detected using the fluorescent dye H2DCF-DA and its analog CM-H2DCF-DA. Fluorescence was detected in cells exposed to mode-locked (76 MHz, ~160 femtoseconds) but not CW laser exposure. Detection of photo-oxidation from the mode-locked laser was dependent upon radiant exposure, but only if irradiance was greater than a threshold value. The CM-H2DCF-DA dye proved a more sensitive indicator of oxidation than H2DCF-DA, and the radiant exposure threshold for detection was dependent upon dye concentration. No oxidation was detected from CW exposures (using the most sensitive fluorescent dye conditions) when using 3 times the irradiance, and 10 times the radiant exposure needed to detect fluorescence from mode-locked exposure.

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