Free electron laser infrared wavelength specificity for cutaneous contraction.

BACKGROUND AND
OBJECTIVE: Short pulsed and scanned CO(2) lasers that target water molecules are currently used for cutaneous resurfacing. These CO(2) resurfacing lasers produce acute cutaneous contraction, which can be quantitated as a measure of the laser's effect. We postulated that targeting the vibrational and rotational modes of proteins with specific infrared laser wavelengths might be more effective at inducing cutaneous contraction than the CO(2) resurfacing lasers. STUDY DESIGN/
MATERIALS AND METHODS: The Vanderbilt University Free Electron Laser (FEL) was used at wavelengths between 6.0-8.6 microm. The cutaneous contraction and histologic thermal damage observed was compared to that seen with a scanned CO(2) resurfacing laser.
RESULTS: Peaks of cutaneous contraction at 7.2-7.4 and 7.6-7.7 microm were found, which were three-fold more efficient at producing cutaneous contraction than the 10.6 microm CO(2) laser. The 7.2 microm wavelength is associated with the CH bend of C-CH(3), 7.4 microm to the CH bend of O=C-CH(3), 7.6 microm to the C-C-C stretch, and 7.7 microm to the amide III (C-N-H) absorption band for proteins. Using light microscopy, an approximately 40 microm denaturation zone of dermal collagen was found at all FEL wavelengths tested, regardless of the effectiveness of cutaneous contraction.
CONCLUSION: The mechanism of action of these infrared wavelengths on cutaneous contraction is unknown, but appears to be independent of the amount of collagen denatured as observed by light microscopy. Infrared lasers such as the FEL that target vibrational and rotational modes of proteins therefore hold promise for cutaneous application at selected wavelengths. Copyright 1999 Wiley-Liss, Inc.