UV-induced optical modifications of collagen biomembrane scaffolds under solar and artificial irradiation

Collagen-based biomaterials are widely used as scaffolds in regenerative medicine, yet their physicochemical stability under environmental stress remains incompletely understood. Ultraviolet (UV) radiation is a principal extrinsic factor capable of inducing photochemical and structural changes in collagen matrices. In this study, acid-soluble Ordered Collagen Biomembranes (OCB) and Non-Ordered Collagen Biomembranes (NOCB) were used as comparative models to investigate UV-induced optical and structural collagen changes under natural outdoor solar exposure and controlled indoor UV irradiation. Spectroscopy (UV-VIS and FTIR), UV dosimetry, differential scanning calorimetry (DSC) and scanning electron microscopy (SEM) were employed for characterization. Both solar and artificial UV exposure produced progressive modifications in the absorption spectra, particularly within the 250-290 nm region associated with aromatic amino acid residues, with the magnitude of these changes depending on both the cumulative UV dose and the spectral distribution of the irradiation source. FTIR analysis revealed the emergence of a non-amide carbonyl band at 1727 cm^-1 following solar exposure, consistent with photooxidative modification of amino acid side chains alongside preservation of the polypeptide backbone. DSC measurements showed that UV irradiation altered the thermal stability of both biomembrane types, with solar-exposed OCB displaying the most pronounced broadening of the endothermic denaturation transition. These findings demonstrate that collagen organization significantly influences resistance to UV-induced degradation and highlight the importance of structural organization in determining the environmental durability of collagen-based scaffolds relevant to regenerative medicine applications.