The long-term goal is early diagnosis of malignant melanoma. It is proposed to test a possibility that malignant transformation modifies physical characteristics of melanin. Physical characteristics will be monitored by fluorescence. It is proposed to compare fluorescence of melanin from normal cells with fluorescence of melanin from a series of melanoma cell lines with varying degrees of aggressiveness. Fluorescence will be collected from a small number of molecules by a modified confocal microscope. Fluorescence of a few molecules should be an accurate indicator of early events of malignant transformation, because it it is not averaged over the entire population of melanins in a melanocyte. Confocal microscope is the instrument of choice when attempting to measure fluorescence of a small number of molecules. However, a commercial instrument is unable to detect less than about 1000 molecules. To decrease this number, the sensitivity is increased by replacing vacuum tubes with semiconductor detectors and by processing signal digitally. Preliminary results show that this modification improves sensitivity by two orders of magnitude. Fluorescence of melanin is induced by the absorption of infrared light. Three parameters of fluorescence - its intensity, lifetime and spectrum -- are measured simultaneously. The method is important because it can be extended to measurements on skin samples in situ. The modifications are relatively simple, inexpensive and not tied to a specific brand of instrument. It is expected that the method will find application in a small diagnostic laboratory.
