Composite Beads of Alginate and Biological Hydroxyapatite from Poultry and Mariculture for Hard Tissue Repair

Synthesizing materials that stimulate the natural growth of living tissues and restore damaged parts of the body is one of the most challenging problems in regenerative medicine. Despite being the most commonly used biomaterial, synthetic hydroxyapatite is a calcium phosphate with a relatively low rate of bioresorption related to new tissue growth. For specific applications, the speed of resorption is essential, and synergy between polymer and hydroxyapatite composite materials from natural sources can be developed. Therefore, this study attempts to synthesize hydroxyapatite from poultry and mariculture by-products and produce spheres with alginate for use as biomaterials for tissue repair. Shells different shellfish and eggs were used as sources of CaCO3 and added to a phosphoric acid solution as precursors in wet synthesis. The powders were dried, thermally treated and characterized. Structural analysis revealed hydroxyapatite in nanometric crystallites (61–72 nm) with high crystallinity (86–89%). The calcium phosphate obtained from Mozambique shellfish acquired the best characteristics. Beads with various sizes and porosities were produced through changes in the process parameters, including the type and size of the dripper, speed of agitation of the solution, and type of drying. The results show that the type of dripper strongly influences the size of the beads and that the rotation speed influences the sphericity. The styling directly influenced the fluid absorption, demonstrating that the spheres dried by lyophilization can absorb up to 223% of their weight. In comparison, samples dried in a desiccator could absorb only 112% of their weight in body fluids. The porosity of the optimized beads was up to 90%, which is similar to that of human bone, and they did not show cytotoxicity. Therefore, the beads composed of alginate and hydroxyapatite produced here have the potential for application in tissue repair.