Mussel-inspired nanostructured coatings assembled using polydopamine nanoparticles and hydroxyapatite nanorods for biomedical applications

Producing hierarchical nanostructured coatings with a biomimetic composition is an effective surface modification strategy to improve the bioactivity of biomaterials. In this study, mussel-inspired polydopamine nanoparticles (PDA-NPs) and hydroxyapatite (HA) nanorods were used to modify Ti surfaces. Firstly, the PDA-NPs were prepared via oxidative self-polymerization of dopamine. Secondly, the HA nanorods were decorated with a PDA nanolayer in order to improve the adhesion of the HA nanorods. Thirdly, the PDA-NPs and PDA-decorated HA nanorods were alternately assembled to form a porous and hierarchical micro/nanostructured {PDA/HA} composite coating on the Ti surfaces. Finally, Bone ​morphogenetic protein-2 (BMP-2) was immobilized on the {PDA/HA} composite coating using the functional groups of PDA. The BMP-2-loaded {PDA/HA} composite coating exhibited excellent biocompatibility and promoted the adhesion, proliferation, and differentiation of bone marrow stromal cells. The animal implantation tests indicated that the BMP-2-loaded {PDA/HA} composite coating promoted the formation of new bone tissue.