Effect of Hydroxyapatite Coating Surface Morphology on Adsorption Behavior of Differently Charged Proteins

The morphology of bone repair materials, such as particle size and roughness of the materials surface, can affect the adsorption of protein molecules. The effects of surface morphology on the absorption of proteins with different charges were studied. Submicron and nano hydroxyapatite (HA) powders prepared by the chemical precipitation method were coated on the surface of a gold sheet by electrophoretic deposition. Various hydroxyapatite coating morphologies were obtained by controlling the powder particle size and the deposition time. The coating surface morphology was analyzed by Atomic Force Microscopy (AFM), and the adsorption behavior of differently charged proteins on the surface was dynamically monitored by Quartz Crystal Microbalance with Dissipation (QCM-D). The adsorption dependence of two proteins with different charges upon hydroxyapatite coating surface morphology was investigated. Results show that coating surfaces with smaller deposited particle sizes are favorable for the adsorption of negatively-charged bovine albumin, while with larger deposited particles facilitate the adsorption of positively-charged lysozyme. This may be because that the negatively-charged hydroxyapatite coating exhibits stronger electrostatic effect as the increase in the coating particle size, which facilitates the adsorption of positively-charged proteins and hinders the adsorption of negatively-charged proteins. Increasing coating surface roughness facilitates protein adsorption, though the particle size exhibits a dominant influence. These results are significant for selective adsorption of proteins on material surfaces.