In vitro and in vivo characterization of novel calcium phosphate and magnesium (CaP-Mg) bilayer coated titanium for implantation

Abstract

A novel bio-functional calcium phosphate and magnesium (CaP-Mg) bilayer coating on titanium (Ti) was fabricated and characterized in vitro and in vivo. The bilayer coating was fabricated by biomimetic method and physical vapor deposition (PVD). The intermediate calcium phosphate (CaP) layer was mainly composed of octacalcium phosphate (OCP) and hydroxyapatite (HA). Compared to the single magnesium (Mg) coating, Mg layer on bilayer coating was thicker, coarser and porous. Immersion test and electrochemical test showed that the intermediate CaP layer could not decrease the degradation rate，however, inhibit detachment of Mg. The Mg coating delaminated from the single Mg coated sample following immersion for 1 day, while no obvious evidence of detachment was observed for the bilayer even after immersion for 14 days. In vitro antibacterial assays proved that the CaP-Mg coating strongly reduced the viability of Staphylococcus aureus and performed an about 90% antibacterial efficacy after 3 h incubation due to high alkalinity produced by the degradation of Mg. The bare Ti bar and coated Ti bar implants were implanted into New Zealand white rabbit lower jaws for 4 and 12 weeks, respectively. Cone beam computed tomography (CBCT), and Masson and hematoxyline-eosin (HE) staining showed CaP-Mg coated Ti bar promoted superior osteointegration after 4 and 12 weeks implantations.