Physicochemical aspects of structuring calcium phosphate on fibrillary collagen scaffolds

The structure and physicochemical properties of scaffolds obtained from acetate extracts of fibrillar collagen from the tendon membranes of Wistar rats have been the subject of study. The synthesis of a film-like scaffold at 37 °C and a volume scaffold at 6 °C was conducted. Scaffolds of both types are structured into glomerular and extraglomerular fractions. The volume ratios of fractions are determined by the influence of temperature on the kinking of collagen fibers. At 37 °С, kinking is suppressed, and a fraction with initially straightened fibers – the extracellular framework of a filmy scaffold – is formed. At 6 °С, kinking increases, and the growth of a fraction with initially twisted fibers – tangles of a volumetric scaffold – is accelerated. The typogenesis of hydroxyapatite is determined by the microstructure of the scaffolds and the direction of development of transpiring structures. Stoichiometric hydroxyapatite is synthesized in dominant water-evaporating fractions, while carbonate hydroxyapatite is synthesized in subdominant water-retaining fractions. The relationship between kinking and the strength of the peptide chains of fibrillar collagen is characterized by an inverse interdependence. Specifically, when kinking is weakened, the peptide chains are strengthened, and when kinking is strengthened, they are softened. Carbonate substitutions are sensitive to the temperature of scaffold synthesis. At 37 °C, CO₃^2– anions replace OH^–, and at 6 °C, PO₄³⁻ groups replace them. The comprehension of the mechanisms underlying the structuring of calcium phosphates on matrices of fibrillary collagen is essential for the design of collagen-apatite-based scaffolds with predefined functional properties.

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