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Protein adsorption is essential for determining material biocompatibility and promoting adherent cell growth. In this study, we focused on the a-plane structure of hydroxyapatite (HAp). This a-plane structure closely resembles the crystal plane where apatite is exposed in long bones. We conducted protein adsorption experiments using HAp ceramics with a preferred orientation to a-planes (aHAp), employing bovine serum albumin (BSA), lysozyme, and fetal bovine serum (FBS) as protein models to mimic the in vivo environment. Higher zeta potential and contact angle values were found in aHAp than in HAp ceramics fabricated from commercial HAp powder (iHAp). Bradford-quantified protein adsorption revealed BSA adsorption of 212 ng·mm−2 in aHAp and 28.4 ng mm−2 in iHAp. Furthermore, the Bradford-quantified protein adsorption values for FBS were 2.07 μg mm−2 in aHAp and 1.28 µg mm−2 in iHAp. Two-dimensional electrophoresis (2D-PAGE) showed a higher number of protein-derived major spots in aHAp (37 spots) than in iHAp (12 spots). Mass spectrometry analysis of the resulting 2D-PAGE gels revealed proteins adsorbed on aHAp, including secreted frizzled-related protein 3 and vitamin K epoxide reductase complex 1, which are involved in cellular bone differentiation. Overall, these proteins are expected to promote bone differentiation, representing a characteristic property of aHAp.

We investigated the interface phenomena between the electrode by a low fire-through electrode paste and the silicon substrate in a crystalline silicon solar cell. Oblique polishing was used to evaluate the chemical bonding states in the depth direction. From the evaluation by X-ray photoelectron spectroscopy (XPS) and the hard X-ray photoelectron spectroscopy (HAXPES), we found changes in the chemical bonding states of Ag 3d, Si 2p, O 1s, and N 1s at the electrode–silicon interface. In addition, it was possible to confirm the reduction of Ag induced by the heat treatment at the interface. Thus, it became possible to evaluate the chemical bonding states at the interface between the electrode and the silicon substrate by adapting oblique polishing and XPS measurement. [ABSTRACT FROM AUTHOR]