Enhancement of bone formation on LBL-coated Mg alloy depending on the different concentration of BMP-2

Abstract

To control the bio-absorption rate of Mg alloy and improve its biocompatibility, a BMP-2 of various concentrations (20, 50, and 100 ng/mL) was immobilized in the carrier layer formed by micro-arc oxidation + hydrothermal treatment on the surface of Mg alloy. Their morphological and chemical properties were evaluated by FE-SEM with EDS and XRD. The electrochemical corrosion behavior was examined, and the cytotoxicity was assessed by WST and ALP assay. After in vivo test during 2 and 4 weeks in the rat tibia, histological observation was performed. In the carrier layer, calcium phosphate ceramic and oxide layers (MgO and Mg(OH)₂) were formed. The layers enhanced the corrosion resistance. It was maintained even after loading the BMP-2. In the BMP-2-loaded group, the proliferation and differentiation of the osteoblast cells were promoted by the continuous release of the BMP-2. After implantation for 2 weeks, all BMP-2-loaded groups showed better biodegradation rate and osseointegration than the control group. After 4 weeks, the group with 50 ng/mL of BMP-2 exhibited the slowest biodegradation rate of all the BMP-2-loaded groups. This effected on the enhancement of new bone formation and the stable bone growth. Therefore, for the short term of implantation, this double coating method could be applied onto biodegradable Mg metal as an orthopedics and dental implant. For the long term of implantation over 4 weeks, to treat Mg implant with 50 ng/mL of BMP-2 was determined to be optimal.

Keywords: Bone morphogenic protein-2; Corrosion test; Cytotoxicity test; Hydrothermal treatment; In-vivo test; MAO coating.