Scandium oxide-polypropylene imine dendrimer nanocomposite as a promising antimicrobial coating for orthopedic implants

Polypropylene imine (PPI) dendrimer has antimicrobial efficiency, bioactivity, and enhanced biocompatibility. Scandium dioxide (Sc₂O₃) has cell viability, cell growth, cell proliferation, and biostability. Sc₂O₃-PPI dendrimer nanocomposite-coated Ti substrate was studied for its bioactivity by immersing in Kokubo’s simulated body fluid for 21 days at 36.5^oC (pH: 7.4). The physio-chemical and electrochemical characterization revealed a high level of crystallinity and exhibited superior adhesion and biostability to the Ti substrate. Vickers microhardness test under various loads (50 gm) confirmed the mechanical stability of the coatings. SEM-EDS studies demonstrated that the formation of a homogenous apatite layer on the surface of the coatings was produced by the interaction of the Sc₂O₃-PPI dendrimer nanocomposite coating and simulated body fluid. In vitro antibacterial and in vitro cytotoxicity tests were used to evaluate the antibacterial properties and toxic effects of the Sc₂O₃-PPI dendrimer nanocomposite coatings. The coating excellently inhibited bacterial activity, and the highest zone of inhibition was obtained for S. aureus (gram-positive bacteria) and P. aeruginosa (gram-negative bacteria). Moreover, employing the theoretical studies of a small model system, stability of Sc₂O₃-PPI dendrimer composite is also explained by the existence of a hydrogen bond as well as Sc and O interaction. Preferential doping of PPI dendrimer into Sc₂O₃ proved high bioactivity, effective antibacterial properties, great mechanical stability of the coating, and no evidence of cytotoxic effect, suggesting that the Sc₂O₃-PPI dendrimer nanocomposite coating is expected to be a promising bioactive long-term orthopedic implant.