A biomimetic strategy for fabricating apatite hybrid materials and bioactive coatings

摘要

Biomimetic self-assembly is a facile and mild technique for generating apatite hybrid materials with controlled morphology and hierarchical structures.Template molecules, element substitutions and factors are considered to play key roles in the fabrication of biomimetic biomaterials for replacing bone or teeth. In this strategy, fibrous templates, such as collagen and silk fibroin, dominate the formation of calcium phosphate, which exists as hydroxyapatite (HAP) in bone and teeth. Some soluble acidic molecules such as citric acid are also important, although their roles are controversial. Mostly these acidic molecules are considered to retard the crystal formation. In addition, functional element substitutions in HAP attracted great interests because of their improved biological properties. The parameters of factors are not negligible, which make the synthesis versatile. Herein, silk fibroin is selected as the fibrous template and sodium alginate was the acid template. Zinc substituted hydroxyapatite (ZnHAP) was prepared by co-precipitation and the resulting products were characterized. The alginate ions interacted with silk fibroin, and they regulated the crystal morphology with the additional zinc ions. The transmission electron microscopic results revealed that small crystallites of several nanometers were assembled into large size sheets of 100 nm in width, which preferred to grow along (002) and (211) orientations. hybrid nanoparticles can be used as bricks for fabricating porous scaffolds for bone repairing. Furthermore, the biomimetic hybrid HAP and ZnHAP nanoparticles could be used to coat titanium by electrophoretic deposition with chitosan and multiwalled carbon nanotubes. Chitosan can help the formation of coatings, and carbon nanotubes can improve the hardness and strength. The composite coatings had homogeneous morphology and good apatite formation ability and the ZnHAP composite coating possessed class 5B adhesive strength using tape test. In addition, the ZnHAP composite coating had better corrosion resistance compared to the HAP composite coatings. In summary, the biomimetic strategy of bi-template and and zinc substitution provides a promising biomaterial for repairing hard tissues.