Abstract
Based on the thermal damage concept, our work proposes the concept and calculation method of collagen denaturation degree. By integrating experimental calculations with GROMACS molecular dynamics simulation and finite element COMSOL numerical simulation of skin optical properties, we investigate the mechanisms underlying collagen fiber thermal denaturation and photochemical changes induced by laser irradiation. When the energy is below 115.68 J/mm2, the dominant factor in skin wound repair is the thermal energy delivered by the laser. The collagen denaturation degree can be maintained around 0.0199 during an effective laser welding time of 300 s, resulting in a peak temperature of approximately 55℃ and noticeable wrinkling and scattering of monomeric helical protein chains within the fiber structure. This wrinkled structure indicates macroscopic recombination and recoupling of fractured collagen fibers on both sides of the skin wound. However, when the laser energy density further increases to 135.4 J/mm2, there is only a slight increase in collagen denaturation degree without significant alterations observed. For this phenomenon, Finite element simulations based on Helmholtz equation modules reveal that reflectivity towards laser photons decreases significantly across tissue blocks due to enhanced photonics effects. As energy reaches or exceeds 135.4 J/mm2 levels, photothermal effects assume a more prominent role but inevitably lead to higher peak temperatures (70.4℃). Therefore, precise reduction in laser welding time within 300 s can effectively control collagen denaturation within reversible and reasonable ranges.
Published Version
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