Anti-inflammatory and osteoconductive multi-functional nanoparticles for the regeneration of an inflamed alveolar bone defect

Abstract

Infected alveolar bone defects pose challenging clinical issues due to disrupted intrinsic healing mechanisms. Thus, the employment of advanced biomaterials enabling the modulation of several aspects of bone regeneration is necessary. This study investigated the effect of multi-functional nanoparticles on anti-inflammatory/osteoconductive characteristics and bone repair in the context of inflamed bone abnormalities. Tannic-acid mineral nanoparticles (TMPs) were prepared by the supramolecular assembly of tannic acid with bioactive calcium and phosphate ions, which were subsequently incorporated into collagen plugs via molecular interactions. Under physiological conditions, in vitro analysis confirmed that tannic acid was dissociated and released, which significantly reduced the expression of pro-inflammatory genes in lipopolysaccharide (LPS)-activated RAW264.7 cells. Meanwhile, the bioactive ions of Ca²⁺ and PO₄³⁻ synergistically increased the gene and protein expressions of osteogenic markers of bone marrow-derived stem cells. For in vivo studies, combined endodontic-periodontal lesions were induced in beagle dogs where the plugs were readily implanted. After 2 months of the implantation, analysis of micro-computed tomography and histomorphometry revealed that groups of dogs implanted with the plug incorporating TMPs exhibited a significant decrease in bone surface density as well as structural model index, and significant increase in the mineralized bone content, respectively, with positive OPN expression being observed in reversal lines. Notably, the profound improvement in bone regeneration relied on the concentration of TMPs in the implants, underscoring the promise of multi-functional nanoparticles for treating infected alveolar bones.