Fabrication of novel kaolin-reinforced hydroxyapatite scaffolds with robust compressive strengths for bone regeneration

Abstract In this study, hydroxyapatite (HAp) microparticles obtained from animal bones were synthesized, and for the first time, HAp was reinforced with beneficiated kaolin using the sol-gel route to improve the mechano-biological properties of the bioceramic materials. The non-reinforced HAp as well as the reinforced samples (K-HAp) were sintered at 900, 1000 and 1100 °C to consolidate the mixture and detailed physico-chemical and mechanical characterizations was conducted. In-vitro experiments in phosphate buffer saline and simulated body fluid were used to confirm the degradability and compatibility of the HAp-derived bioceramic materials, respectively. XRD signatures showed that a dominant phase of hydroxyapatite was formed at all sintering temperatures (900, 1000, 1100 °C). The calcium to phosphate ratio (Ca/P) of the K-HAp-900 sample was approximately 1.67, which is the Ca/P ratio for stoichiometric hydroxyapatite prepared from synthetic sources. The active surface areas of the produced kaolin reinforced bioceramic materials: K-HAp 900–1100,were 0.9770, 0.2159 and 0.8659 m2/g, respectively, while the obtained micropore volumes were 0.000397, 0.001287, and 0.000334 cm3/g, respectively. At 900, 1000 and 1100 °C, compressive strengths (after applying the compaction pressure) with a value of 5.67, 6.33 and 7.66 MPa were obtained for the kaolin reinforced bioceramic materials, respectively. The mechanical measurement data further confirms that the reinforced bioceramic materials are suitable for human trabecular bone as the proposed scaffolds were endowed with an improved mechanical strength matching the bearable range of trabecular bone (2–12 MPa). In-vitro experiments showed the degradability and compatibility of the scaffolds. A relative neutral pH was maintained for sample K-HAp 900, and this sample also showed inhibitory potentials for bacterial strain (E. Coli).