Cytocompatibility and osteogenic response of 1- and 2-dimensional (D) nanostructured hydroxyapatite: Influence of surface chemistry, ion release and hydrophilicity

Abstract

In living bone, hydroxyapatite (HA) exists in the form of nanoplates (NPLs), which contributes exceptional osteogenic performance to bone. However, there is a scarcity of research on the cytocompatibility and osteogenic potential of artificial HA nanoplates as compared to the other shapes of nanostructured hydroxyapatite (nHA). Therefore, this study investigates the cytocompatibility and osteogenic activity of HA NPLs along with other nHA morphologies; HA nanorods (NRs) and thin nanoplates (TNPLs). The shapes of nHA were controlled using polyvinyl alcohol as a surface-capping molecule under hydrothermal condition. Moreover, the influence of morphology of nHA on their surface charge, oxygen vacancy, and wettability was analyzed using zeta potential measurement, X-ray photoelectron spectroscopy (XPS), and contact angle measurement, respectively. The zeta potential value, oxygen vacancy, and hydrophilicity have been found to be the highest on HA TNPLs. However, these features are moderate in HA NPLs and lowest in NRs. Hemolysis results demonstrated that HA NRs, NPLs and TNPLs are non-toxic to red blood cells at various nHA concentrations (0.2, 2 and 20 mg/ml), indicating good hemocompatibility. In addition, HA NPLs significantly accelerates the cell adhesion, proliferation and differentiation as compared to HA NRs and TNPLs. However, HA TNLPs showed the lower cytocompatibility and osteogenic response. The synergistic influence of surface chemistry, hydrophilicity, and ion release on such biological response of different morphological nHA was explored. It was revealed that negatively-charged and good hydrophilic surface, as well as comparatively low release of Ca2+ are mainly attributed to promote the cellular response of HA NPLs. © 2024 Elsevier B.V.