Risk estimation of skin damage due to ultrashort pulsed, focused near-infrared laser irradiation at 800 nm.
New imaging techniques using near-infrared (NIR) femtosecond lasers (fs-lasers) in multiphoton laser scanning microscopy (MPLSM) have great potential for in vivo applications, particularly in human skin. However, little is known about possible risks. In order to evaluate the risk, a "biological dosimeter" was used. We irradiated fresh human skin samples with both an fs-laser and a solar simulator UV source (SSU). DNA damage introduced in the epidermis was evaluated using fluorescent antibodies against cyclobutane-pyrimidin-dimers (CPDs) in combination with immunofluorescence image analysis. Four fs-irradiation regimes (at 800-nm wavelength) were evaluated differing in laser power and step width of horizontal scans. Fs-irradiation did not give CPDs at 15-mW or 30-mW irradiation power using 10 horizontal scans every 5 microns. CPDs could be seen at 60-mW laser power and 5-microm step size and at 35-mW using 1-micron step width. Quantitative comparison of SSU-induced CPDs showed that the 60-mW laser irradiation regime is comparable to UV-irradiation, giving 0.6 minimal erythemal dose (MED). The 1-micron irradiation regime was comparable to 0.45 MED. Under these experimental conditions, the risk of DNA damage due to fs-laser irradiation on skin is in the range of natural UV-exposure.
Fischer
Frank
F
Research Microscopy, Beiersdorf AG, Unnastrasse 48, D-20245 Hamburg, Germany. frank.fischer@beiersdorf.com
Volkmer
Beate
B
Puschmann
Stefan
S
Greinert
Ruediger
R
Breitbart
Wolfgang
W
Kiefer
Juergen
J
Wepf
Roger
R
D004247:DNA / Q000528:radiation effects*; D004249:DNA Damage; D004307:Dose-Response Relationship, Radiation; D006801:Humans; D066298:In Vitro Techniques; D007259:Infrared Rays / Q000009:adverse effects; D007834:Lasers / Q000009:adverse effects*; D011829:Radiation Dosage; D011855:Radiodermatitis / Q000209:etiology* / Q000235:genetics*; D018570:Risk Assessment / Q000379:methods*; D012307:Risk Factors
D004247:DNA