TYPE I COLLAGEN: FROM MOLECULAR BIOLOGY AND EXTRACTION TO BIOMEDICAL APPLICATIONS—A COMPREHENSIVE REVIEW

Collagen Type I (Col-I) is the most abundant structural protein of the vertebrate extracellular matrix, providing the principal mechanical scaffold of skin, bone, tendon, and corneal tissue. This review synthesizes current literature on the biology, extraction, and biomedical application of Col-I, with particular emphasis on chicken skin as a source yielding both Type I and Type III collagen. The genetic and molecular basis of Col-I is discussed, including the COL1A1/COL1A2 gene loci, the Sp1-binding polymorphism governing transcriptional regulation, and the homotrimeric and heterotrimeric isoforms implicated in wound repair and fibrotic pathology. Comparative sourcing across bovine, porcine, marine, and avian tissues is examined alongside the structural organization of Col-I, encompassing its telopeptide and central triple-helical domains, and its defining physicochemical characteristics, namely molecular weight, denaturation temperature, amino acid composition, solubility, and mechanical strength. Extraction methodologies are critically reviewed, spanning conventional acid, alkaline, enzymatic, and salt-based solubilization alongside emerging ultrasound- and microwave-assisted techniques, with subsequent downstream purification achieved through salting-out, low-temperature centrifugation, and dialysis. Analytical approaches for structural and purity confirmation, including electrophoresis, chromatography, spectroscopy, differential scanning calorimetry, energy-dispersive X-ray analysis, and X-ray diffraction, are further evaluated. By integrating source characterization, extraction technology, and translational application, this review offers a consolidated reference to guide future optimization of Col-I production for regenerative medicine and pharmaceutical development.