Enhanced <i>In Vivo</i> Osseointegration with Allicin-Loaded Hydroxyapatite Coatings for Orthopedic and Dental Applications

This study investigates a strategy to improve the osteogenic capacity of Ti6Al4V implants by incorporating allicin onto hydroxyapatite-coated implant surfaces. Allicin, a bioactive compound derived from garlic, is recognized for its ability to modulate bone remodeling processes. Hydroxyapatite (HA) coatings were applied by using plasma spraying, and allicin was loaded and its release was characterized using UV-vis spectroscopy. <i>In vitro</i> studies were conducted on osteoblasts, osteoclasts, and coculture on HA-pressed disks, and their cytocompatibility, differentiation, and gene expression were evaluated through different assays. <i>In vivo</i> osseointegration was assessed using a rat distal femur model for 6 weeks. Allicin suppresses osteoclastic activity by 73% by day 21 while enhancing osteoblast proliferation and maturation. Coculture RT-qPCR reveals upregulation of osteogenic genes, osteocalcin (<i>BGLAP)</i>, runt-related transcription factor 2 <i>(RUNX2</i>), and alkaline phosphatase (<i>ALPL</i>─by 5.9-fold, 5.3-fold, and 4.7-fold, respectively, and downregulation of receptor activator of nuclear factor κB ligand <i>(RANKL)</i> to 0.16-fold by day 21. <i>In vivo</i> results show a ∼1.3-fold increase in new bone formation in HA-coated implants with allicin compared to those without allicin. These findings suggest that allicin-loaded HA-coatings can enhance implant osseointegration for orthopedic and dental applications.