Design, characterization, and biocompatibility of chitosan-nano-hydroxyapatite/tricalcium phosphate sponges

Chitosan-based sponges, incorporating tricalcium phosphate and hydroxyapatite, are extracellular components that represent a novel and impactful advancement in bone regeneration. Their bioactive composition, porous structure, and controlled release capacity are designed to stimulate osteogenesis effectively and could enhance the interrelations of cells in tissues and organs. The objective is to manufacture and characterize chitosan (CHT)-based sponges with different concentrations of nano-hydroxyapatite (nHAP) and tricalcium phosphate (TCP), as well as evaluate their biocompatibility. Composite sponges were manufactured in different concentrations: CHT (S1), 50:30:20 (S2), 60:20:20 (S3), and 70:20:10 (S4) and characterized by FTIR-ATR, TGA, and swelling. For biocompatibility, a cell proliferation assay, hemocompatibility, alizarin red, and its bactericidal effect were performed. Main groups of CHT are detected, and the presence of phosphate groups characteristic of TCP and nHAP was confirmed by FTIR. The nHAP/TCP content was validated using the Thermo Gravimetric Analysis (TGA), and the swelling tests were carried out with simulated body fluid (SBF), which proved stable for S2 and S3. About the biocompatibility tests of the cell proliferation assay, The TCP and nHAP present in the sponges caused a significant increase in cell proliferation (up 50-80 %). In contrast, in the control sample (S1), cell proliferation decreased without becoming cytotoxic (down 25 %). The hemolysis degree was less than 2 % at the times evaluated. Using alizarin red (ARS), it was shown that the different sponges were able to increase calcium deposits by approximately 10-45 % Through the antibiogram, it is assumed that the zone of inhibition occurs about the amount of CHT present in each sponge. Incorporating nHAP/TCP into CHT sponges favors the physical and thermal stability of the material. The sponges were demonstrated to have biocompatible and osteoinductive properties.