Quantitative changes in collagen levels following 830‐nm diode laser welding

Background and Objective The actual mechanism by which laser irradiation welds tissue is presently unknown; however, collagen is a major constituent of tissue welded by laser irradiation. Study Design/Materials and Methods: Collagen was extracted from the abdominal aorta of Wistar rats by acetic acid extraction and repeated pepsin digestion after tissue welding (254 W/cm2) by using an 830-nm diode laser. The collagen levels were determined by using the Sircol Collagen Assay (Biocolor, Northern Ireland). Results Compared with untreated aorta, the collagen content of the treated vessel was obvious decreased (P < 0.001) immediately after laser irradiation. Levels then increased by day 3, with a peak at day 10 (P < 0.002). The collagen content returned to normal levels on day 30 and remained at this level throughout the rest of the experimental period. Conclusion These results suggest that a proportion of the collagen molecules in the vessel are denatured by the heat of the laser. Collagen synthesis is stimulated during the healing process after laser welding with the parameters used in the present study. Lasers Surg. Med. 22:207–211, 1998.