Mussel-inspired bioactive ceramics with improved bioactivity, cell proliferation, differentiation and bone-related gene expression of MC3T3 cells

Mussels possess the ability to attach to virtually any type of inorganic and organic surfaces due to the existence of phenylalamine and lysine amino acids. Inspired by the property of mussels, polydopamine has been used for modifying bioinert materials, such as metals, semiconductors and plastics to improve their surface hydrophilicity. However, there are no reports about the effect of a polydopamine modification on apatite mineralization and the biological response of bioactive ceramics (not bioinert materials) for bone regeneration applications. Akermanite bioceramics (AKT, Ca₂MgSi₂O₇) are a typical bioactive material with osteostimulation properties for bone tissue regeneration. The aim of this study is to systematically investigate the effect of a polydopamine modification on the physicochemical and biological properties of AKT bioceramics, including attachment, proliferation, ALP activity and bone-related gene expression of tissue cells. The results show that a self-assembled polydopamine layer on the surface of AKT bioceramics was formed by incubating AKT bioceramics in a dopamine/Tris-HCl solution. Polydopamine-modified AKT (PDB-AKT) bioceramics showed significantly improved surface roughness, hydrophilicity and apatite-mineralization ability compared to AKT bioceramics. In addition, the polydopamine modification distinctively enhanced the attachment, proliferation, alkaline phosphate activity and bone-related gene expression of MC3T3 cells on AKT bioceramics. The possible reason for the improved cytocompatibility may be related to the improved surface roughness and apatite mineralization as well as the ionic environment at an early stage of cell culture. Our results suggest that the polydopamine modification is a viable method to further improve the apatite mineralization and biological response of bioactive ceramics for better bone regeneration applications, indicating that the polydopamine modification is a universal method to enhance the bioactivity for both bioinert and bioactive materials.