Differences in production of melanin radicals by 694 nm ruby laser and UVA radiation.
Haywood RM, Linge C.
Lasers Surg Med. 2004;35(1):77-83.
RAFT Institute of Plastic Surgery, Mount Vernon Hospital, Northwood, Middlesex, HA6 2RN, United Kingdom. email@example.com
BACKGROUND AND OBJECTIVES: The 694 nm ruby laser is used clinically for hair removal and the mechanism is predominantly photo thermal via melanin targeting. We investigated 694 nm laser-irradiation of human hair, and laser-irradiation of synthetic dopa melanin to establish whether photolysis and oxygen radical production is also contributory, and which may have side effects. STUDY DESIGN/MATERIALS AND METHODS: Ultraviolet-A (UVA) irradiation of melanin was used as a positive control for radical production. Laser- and UVA-irradiated hair samples, and synthetic dopa melanin in media of different viscosity, were analyzed using electron spin resonance spectroscopy, and compared. The spin trap 5,5-dimethyl- 1-pyrroline N-oxide (DMPO) was used to probe laser-irradiated dopa melanin for superoxide radical production. RESULTS: Comparable to UVA, laser-irradiation of hair increased the signal-intensity of the intrinsic melanin radical. UVA-induced radicals decay rapidly; however, laser-induced radicals decayed slowly and did not fully revert to original levels after 24 hours. Laser-induced radicals were increasingly stable with viscosity of the medium. Superoxide radicals were detected using DMPO in UVA- but not laser-irradiated synthetic dopa-melanin at pH 4.5. CONCLUSIONS: Laser-irradiation of melanin does not result in oxygen radical formation; however, a paramagnetic species, long-lived in rigid media, is detected which is worth further investigation.
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