Degradation and In Vivo Response of Hydroxyapatite-Coated Mg Alloy

Abstract

Nowadays there is a need for new generation of biodegradable implants, which should be able to stimulate the healing responses of injured tissues at the molecular level. Magnesium alloys attract great attention as perspective bone implants due to their biocompatibility, physical properties and ability to degrade completely under physiological conditions. The main purpose of this research was assessment of in vitro corrosion and surface morphology after short term in vivo implantation of Mg based implant covered by hydroxyapatite (HA). Mg alloys with the addition of Zr (0.65%), Al (1.85%) and Nd (1.25%) were used. In our work, we propose dipping method for hydroxyapatite coatings formation which has been shown to reduce the corrosion rate of magnesium implants in vivo. Simulated body fluid (SBF; pH 7.4) with ion concentrations approximately equal to those of human blood plasma resembling physiological conditions and citrate buffer with pH 5—simulating inflammation were selected as modelling environments for in vitro degradation test. The rod samples were implanted into the tibia bone of rats and after 1 day and 5 days of implantation were taken out to observe cells adhesion on surface samples. SEM was used to assess surface morphology after in vitro and in vivo tests. SBF solution causes some cracks on the surface of HA coatings, while citrate solution at pH 2 caused complete dissolving of the coating. The HA coating favoured cell adhesion and rapid fibrous tissue formation.

A Facile Synthesis Process and Evaluations of α-Calcium Sulfate Hemihydrate for Bone Substitute

“…The ratio of total surface area to Tris–SBF-27 solution volume was 10 mm 2 mL −1 at pH 7.4 and 37 °C for each disk-shaped sample. The solution was refreshed every 24 h to ensure constant initial chemical composition [ 27 ]. The pH value of the solution was measured daily for a group of samples without refreshing.…”

Comparative Study of the Structure, Properties, and Corrosion Behavior of Sr-Containing Biocoatings on Mg0.8Ca

“…The reaction products formed and precipitated on the surface of the samples. The degradation mechanism of magnesium in aqueous solution can be presented as the following reactions [22]:…”

“…The rate of coatings dissolution and their biological properties depend on the substances that the coatings are consisted of. The most common biocoatings are based on the calcium orthophosphates such as hydroxyapatite (HA) [22,25,27,40] and tricalcium phosphate (TCP) [34] or include their combinations. Hydroxyapatite has the lowest dissolution rate in body fluids.…”

Effect of Surface Pre-Treatments on the Formation and Degradation Behaviour of a Calcium Phosphate Coating on Pure Magnesium

“…The top CaPh coatings offer the resistance of the initial immersion period [47]. However, as mentioned above, the corrosion resistance of a single CaPh coating is inadequate for long-term immersion in SBF due to the loose structure and the dissolution of CaPh compounds.…”