Silk fibroin (SF)-based materials are exposed to both natural and artificial ultraviolet (UV) light during preparation or administration. However, the effects of UV irradiation on SF films prepared under different conditions have not yet been described in detail. In this study, four SF films with different molecular weight (MW) distribution were fabricated using SF solutions, which were prepared by dissolving degummed SF for 0.5–24 h. We observed UV (365 nm) irradiation on SF films induced the increase of yellowness and absorbance at 310 nm of SF films, indicating the formation of new photo-products and di-tyrosine bonds by photo-oxidation. Due to di-tyrosine cross-links between SF chains, UV-irradiated SF films were not fully dissociated in urea solution. In addition to formation of new products, UV reduced the crystallinity of SF films by breaking hydrogen bonds of β-sheet conformation. Unlike the UV-induced decomposition of physical interactions, UV did not affect the covalent bonds (i.e., peptide bonds). Through these experiments, we could expect that SF with higher MW was more susceptible and SF with lower MW was more resistant to UV-induced photo-oxidation and photo-degradation. These results provide useful information about UV-induced aging of SF-based materials under natural sunlight and UV irradiating conditions.

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紫外线对不同条件下制备的丝素蛋白膜的影响

在制备或给药过程中，基于丝素蛋白（SF）的材料会暴露于自然和人工紫外线（UV）。然而，尚未详细描述UV辐射对在不同条件下制备的SF膜的影响。在这项研究中，使用SF溶液制备了四种具有不同分子量（MW）分布的SF膜，这些溶液是通过将脱胶的SF溶解0.5-24 h而制备的。我们观察到SF膜上的紫外线（365 nm）辐射导致SF膜在310 nm处发黄和吸光度增加，表明通过光氧化形成了新的光产物和二酪氨酸键。由于SF链之间的二酪氨酸交联，紫外线辐射的SF膜在尿素溶液中不能完全解离。除了形成新产品之外，紫外线通过破坏β-折叠构象的氢键降低了SF膜的结晶度。与紫外线诱导的物理相互作用分解不同，紫外线不影响共价键（即肽键）。通过这些实验，我们可以预期MW较高的SF对UV敏感，而MW较低的SF对UV诱导的光氧化和光降解具有更强的抵抗力。这些结果提供了有关在自然阳光和紫外线照射条件下紫外线诱发的SF基材料老化的有用信息。我们可以预期，MW较高的SF对UV敏感，而MW较低的SF对UV诱导的光氧化和光降解更具抵抗力。这些结果提供了有关在自然阳光和紫外线照射条件下紫外线诱发的SF基材料老化的有用信息。我们可以预期，MW较高的SF对UV敏感，而MW较低的SF对UV诱导的光氧化和光降解更具抵抗力。这些结果提供了有关在自然阳光和紫外线照射条件下紫外线诱发的SF基材料老化的有用信息。