Study of the growth kinetics of biomimetically grown hydroxyapatite coatings in large gradient magnetic fields

Large gradient magnetic fields simultaneously provide both strong magnetic and simulated gravitational fields. Processes in such environments are subject to the influences of these two fields. Previous studies have shown that the deposition of hydroxyapatite (HAp) coatings induced by self-assembled monolayers (SAMs) is affected by large gradient magnetic fields. To further clarify the mechanism, we examined the effects of gravitational and magnetic fields on the deposition kinetics of the SAMs and the HAp coatings via surface analysis and molecular simulation. The chemical compositions of the SAMs and the HAp coatings in the fields were detected by X-ray photoelectron spectroscopy (XPS). The ability of the SAMs to induce the deposition of apatite was investigated via first principles calculations, which were performed to obtain information about the bonding interactions between the self-assembled functional groups and the -PO43− ions in simulated body fluid (SBF). The experimental results showed that the fields affected the compositions of the apatite layers. The first principles calculation results showed that the -PO4H2− functional group exhibited a stronger ability to induce apatite deposition than the -COOH functional group. This result suggested that hydrogen phosphate root groups are better nucleation sites than carboxyl root groups.