Calcium phosphate formation in gelatin matrix using free ion precursors of Ca²⁺ and phosphate ions

Objectives: Hydroxyapatite (HAp)/gelatin (GEL) nanocomposite has been developed as a bone substitute. The nanocomposite formation in the GEL matrix is greatly affected by the reaction between Ca²⁺ and phosphate ions. The mineralization of GEL macromolecules was investigated through a co-precipitation of calcium phosphates (Ca-P) by using free ions of Ca²⁺ and phosphate ions, Pi. The purpose of this study was to prepare a dense HAp/GEL nanocomposite through a free ion production process. Methods: Free ionic calcium, Ca²⁺, was produced through electrodialysis process using a cation membrane (CMV). Triprotic acid ions were diffused through an anion membrane (AMV) from an aqueous solution of H₃PO₄. The HAp/GEL nanocomposite was prepared by the co-precipitation process. As a reference material for comparison, Ca(OH)₂ and H₃PO₄ were used for the preparation of a HAp/GEL nanocomposite. Results: The dense compact body of dried Ca-P/GEL nanocomposite was obtained through the fine chemical reaction of Ca²⁺ and Pi. The free calcium ion Ca²⁺, diffused from the CMV of the cation reactor greatly affected the formation of Ca-P phase. Phosphate ion species diffused through the AMV in the anion reactor definitely influenced the reaction with Ca²⁺. For the formation of the Ca-P phase in the GEL matrix, the organic-inorganic interaction was analyzed using FT-IR. The crystal growth of HAp in the GEL matrix increased with the increase of GEL from XRD, FT-IR and TEM. Significance: The mineralization reaction in GEL macromolecules was critically influenced by the free ions of Ca²⁺ and inorganic phosphate ions, Pi. The interaction between Ca²⁺ and Pi in the GEL matrix was very fine compared to the HAp/GEL nanocomposite prepared from Ca(OH)₂ and H₃PO₄ with the GEL. The dense compact body of HAp/GEL nanocomposite was obtained for an artificial bone application.