Hydroxyapatite coating on magnesium with MgF2 interlayer for enhanced corrosion resistance and biocompatibility

Abstract

Hydroxyapatite (HA) was coated onto pure magnesium (Mg) with an MgF(2) interlayer in order to reduce the surface corrosion rate and enhance the biocompatibility. Both MgF(2) and HA were successfully coated in sequence with good adhesion properties using the fluoride conversion coating and aerosol deposition techniques, respectively. In a simulated body fluid (SBF), the double layer coating remarkably enhanced the corrosion resistance of the coated Mg specimen. The in vitro cellular responses of the MC3T3-E1 pre-osteoblasts were examined using a cell proliferation assay and an alkaline phosphatase (ALP) assay, and these results demonstrated that the double coating layer also enhanced cell proliferation and differentiation levels. In the in vivo study, the HA/MgF(2) coated Mg corroded less than the bare Mg and had a higher bone-to-implant contact (BIC) ratio in the cortical bone area of the rabbit femora 4 weeks after implantation. These in vitro and in vivo results suggested that the HA coated Mg with the MgF(2) interlayer could be used as a potential candidate for biodegradable implant materials.

Mg and Mg alloys: How comparable are in vitro and in vivo corrosion rates? A review

“…Table 4 also demonstrates the effect of calculating the corrosion rate by mass-loss measurements without removing the corrosion products [86] that can lead to a negative rate. The comparability of in vitro corrosion was difficult because the rates were provided in different units, as parts per million (ppm) of Mg ion released to the corrosion solution [85,87], mg/cm 2 day [18,73,88,89], and percentage of weight or volume loss [21,84,[90][91][92] among others. In this study, the corrosion rates were then all converted to mm/year, as this unit is the most frequently used unit observed in the literature.…”

Calcium orthophosphate deposits: Preparation, properties and biomedical applications

“…In order to produce thicker deposits, a multilayer deposition could be performed [565]. An AD technique was used to deposit HA onto the surface of Ti [15,596,570], Ti alloys [571], Mg previously covered by either MgF 2 [80] or poly(ε-caprolactone) (PCL) [572], as well as onto various polymers [573,574]. Namely, to perform AD, HA powder was sprayed onto Mg samples in a deposition chamber using oxygen carrier gas at a flow rate of 5 × 10 -4 m 3 /s under a pressure of 9.2 Torr.…”

“…Namely, to perform AD, HA powder was sprayed onto Mg samples in a deposition chamber using oxygen carrier gas at a flow rate of 5 × 10 -4 m 3 /s under a pressure of 9.2 Torr. According to SEM observations, when HA was deposited onto Mg with the PCL interlayer, it was partially embedded into this interlayer, forming composite-like structures [572]; however, when HA was deposited onto Mg with the MgF 2 interlayer, no composite-like structures were observed [80]. In addition, the HA deposits on Mg with the PCL interlayer were found to have better stability during deformation if compared to those on Mg without the interlayer [572].…”

Surface modification of magnesium and its biodegradable alloys by calcium orthophosphate coatings to improve corrosion resistance and biocompatibility

“…This procedure can be performed in acetone Cui et al, 2013;Hiromoto et al, 2008;Hiromoto, Tomozawa, & Maruyama, 2013;Hiromoto & Yamamoto, 2009;Jo et al, 2011;Jo, Li, Kim, Kim, & Koh, 2013;Kannan, 2013;Noorakma, Zuhailawati, Aishvarya, & Dhindaw, 2013;Ohtsu, Hiromoto, Yamane, Satoh, & Tomozawa, 2013; Hu et al, 2010;Gray-Munro & Strong, 2009), and/or autoclaving . The preparation normally consists of cleaning and/or degreasing to remove any sort of surface contamination arising from manufacturing.…”