Experimental study of the effect of temperature on collagen conformational changes in skin tissue welded by femtosecond laser

In this study, in vitro skin tissues were welded using various laser settings at four temperature ranges, 30–40 °C, 40–60 °C, 60–80 °C, and > 80 °C., Raman spectra between 500 and 2000 cm−1 were examined in order to examine the relationship between the changes of collagen and the mechanical properties of skin tissue bonding and the degree of thermal damage of tissue. How collagen in skin tissues changed into disordered and less stable structures due to the thermal damage, and how the structure of protein and amino acid-related bands changed with increasing temperature were analyzed. Analysis of the deconvolution of the amide I band (1580–1720 cm−1) and the secondary structure of collagen showed that the secondary structure of collagen changed from α-like helix-dominated to β-aggregate-dominated structures due to the thermal damage. As the temperature increased, the number of protein molecule chain dissociation and reconnection within the skin tissue increased, which contributed to the improvement of the tensile strength of the skin after welding. However, when the temperature was too high, the collagen structure presented an extremely unstable state, and the degree of protein denaturation increased, causing serious thermal damage. When the skin tissue was welded using the femtosecond laser process parameters of laser power of 18 W, scanning speed of 50 mm/s, and scanning 50 times, the tensile strength of the in vitro skin tissue incision was greater and the degree of protein denaturation was less. The degree of thermal damage characterized by the degree of protein denaturation was consistent with that characterized by the microstructure texture characteristics parameters of the skin tissue.