Proteomics of serum proteins adsorbed onto hydroxyapatite single-crystal particles with an anisotropic structure

Abstract

Hydroxyapatite (HAp) has a high adsorption affinity for proteins. Here, the adsorption specificity of proteins from fetal bovine serum (FBS) onto three types of HAp particles with different crystal planes was examined via proteomics using liquid chromatography-tandem mass spectrometry (LC-MS/MS). Fiber-like (f-HAp) and plate-like (p-HAp) HAp single-crystal particles were used as models for a-plane- and c-plane-oriented HAps, respectively, together with randomly oriented HAp particles (HAp-100), as a control. The amount of protein adsorption was as follows: f-HAp > p-HAp > HAp-100. The number of protein-derived spots was as follows: f-HAp > HAp-100 > p-HAp. LC-MS/MS analysis detected the most abundant proteins in the f-HAp sample, followed by p-HAp and HAp-100 before the removal of abundant proteins; after their removal, the highest number of detected proteins was recorded in the p-HAp sample, followed by f-HAp and HAp-100. Approximately 60 % of the proteins adsorbed onto the three HAp particles were extracellular matrix (ECM) proteins, which were identified via gene ontology (GO) analysis as proteins related to blood coagulation, binding, and cellular/metabolic processes. Mimecan, a protein involved in bone formation/differentiation, was among the proteins adsorbed on f-HAp. These results highlight the potential of this technology to control the orientation plane of HAp for highly specific protein adsorption.