Production and characterization of a boron-doped composite biomaterial for bone reconstruction

Critical-sized maxillofacial bone defects remain a significant clinical challenge due to the limitations of current grafting materials, including infection risk, donor site morbidity, and insufficient osteoinductive capacity. This study developed a novel boron-doped polyhydroxybutyrate-tricalcium phosphate (PHB-TCP) composite sponge scaffold and evaluated its potential as a safe and effective biomaterial for bone reconstruction. PHB was produced via bacterial fermentation and characterized by ¹H-NMR. Porous PHB-TCP scaffolds with (PHBs-B) and without boron (PHBs) were fabricated by freeze-drying, using sodium metaborate at a pre-determined non-cytotoxic concentration (125 µg/mL). Scaffolds were characterized for their physicochemical properties (micro-CT, SEM, ATR-FTIR, mechanical testing), cytocompatibility with MC3T3-E1 pre-osteoblasts, antibiofilm activity against oral pathogens, and in vivo biocompatibility according to ISO 10,993 standards. PHBs-B exhibited a highly porous honeycomb-like architecture (~ 88% porosity). Boron incorporation slightly enhanced the compressive properties and promoted MC3T3-E1 cell adhesion. The scaffolds demonstrated sustained boron release (~ 80% over seven months) and selective antibiofilm activity, particularly against Aggregatibacter actinomycetemcomitans (~ 43% inhibition). Critically, comprehensive in vivo biocompatibility testing confirmed the absence of skin sensitization, intracutaneous irritation, acute or subacute systemic toxicity, and genotoxicity. These findings demonstrate that the PHBs-B combines favorable physicochemical properties, controlled boron release, and selective antibiofilm activity with excellent in vitro cytocompatibility and in vivo biocompatibility. The comprehensive safety profile established in accordance with ISO 10,993 positions PHBs-B as a promising and safe biomaterial candidate for maxillofacial bone reconstruction.