Differences in production of melanin radicals by 694 nm ruby laser and UVA radiation.
OBJECTIVE
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.


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.
Haywood
Rachel M
RM
RAFT Institute of Plastic Surgery, Mount Vernon Hospital, Northwood, Middlesex, HA6 2RN, United Kingdom. haywoodr@raft.ac.uk
Linge
Claire
C
D005609:Free Radicals; D006197:Hair / Q000528:radiation effects*; D006801:Humans; D007834:Lasers; D008543:Melanins / Q000378:metabolism / Q000528:radiation effects*; D019097:Spin Trapping; D014466:Ultraviolet Rays
D005609:Free Radicals; D008543:Melanins