Physicochemical and bone regeneration studies using scaffoldings of pure natural hydroxyapatite or associated with Nb2O5

Abstract Nowadays the increase in life expectancy of the population has made diseases related to bone structure a worldwide public health problem. In the field of bone regeneration, calcium phosphate-based ceramics hold the greatest promise of efficiency and hydroxyapatite presents itself as reference material because, in addition to presenting a chemical composition similar to the mineral composition of bone tissue, it is biocompatible, osteoconductive, and osteoinductive, and can be reinforced with other more resistant materials, such as titanium, aluminum, zirconia, and niobium. In this scenario, fish bones represent an abundant and low-cost natural source of hydroxyapatite that is promising for the production of more resistant devices for bone regeneration. The objective of this work was to evaluate the physicochemical properties of the natural HAp, extracted from bones of Nile tilapia (Oreochromis niloticus) and of the HAp-Nb-1080 composite. Besides, the bioperformance of scaffoldings of both materials was evaluated in terms of bone regeneration. The granulometric, XRD, ATR-FTIR, micro-Raman, micro-CT and, SEM analyzes were performed to HAp and HAp-Nb-1080 powders characterization. The bone regeneration was studied 15, 30, and 45 days after implantation of 8 mm scaffolds in critical-size defects in rat calvaria. The results showed that fishbone HAp presented the molar ratio (Ca/P) of 1.66. The average particle sizes of the HAp and HAp-Nb-1080 powders were in the order of 1150 and 750 nm, respectively. After sintering the composite, three new crystalline phases were formed: β-tricalcium phosphate Ca3(PO4)2 (34%), fersmite (CaNb2O6) (33.5%), and phosphorus niobium oxide (PNb9O25) (32.6%), confirmed by ATR-FTIR, and micro-Raman analyzes. The scaffolds porosities were 57% to HAp and 59% to HAp-Nb-1080 composite. SEM results showed the presence of opened macro and microporosity as well as porous interconnectivity. The histological study showed bone formation inside porous in all analyzed time interval after the implantation. In this study, we demonstrated that the HAp-Nb-1080 composite presented physicochemical characteristics that satisfy the requirements for a mechanically reinforced biomaterial for bone regeneration.