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• PDA/PLL hybrid coatings were developed to functionalize hydroxyapatite scaffolds. • The hybrid coatings realize tunable and sustained release of BMP2. • The hybrid coatings promote BMSC adhesion and differentiation. • The coating-functionalized scaffolds possess excellent osteoinductive properties. The scaffold for bone tissue engineering should possess proper porosity, adequate mechanical properties, cell affinity for cell attachment, and the capability to bind bioactive agents to induce cell differentiation. In this study, we successfully prepared a porous hydroxyapatite (HA) scaffold that is functionalized by poly(L-lysine)/polydopamine (PLL/PDA) hybrid coating. The PLL/PDA coating takes advantages of the high protein and cell affinity of PDA, as well as the biodegradability of PLL. Therefore, the coating can anchor bone morphogenic protein-2 (BMP2) to the HA scaffold via catechol chemistry under a mild condition so as to protect the bioactivity of BMP2. Meanwhile, the coating can also release BMP2 in a tunable and sustainable manner as the PLL degrades in the physiological environment. The BMP2-entrapped PLL/PDA coating on the HA scaffold can more efficiently promote osteogenic differentiation of bone marrow stromal cells (BMSCs) in vitro and induce ectopic bone formation to a much greater level in vivo compared with a bare HA scaffold that delivers BMP2 in a burst manner. All of these results suggest that the PDA-mediated catechol modification of the HA scaffold can be an effective strategy to develop sustainable protein delivery system, and that the PLL/PDA-coated HA scaffold could be a promising candidate for bone tissue engineering applications. [ABSTRACT FROM AUTHOR]

• Combination of experimental study and DFT calculation found that F− ions stabilized the Sr-doped HA crystals. • Sr/F-codoped HA showed excellent antibacterial activities against Streptococcus mutans. • An appropriate level of Sr doping caused the optimal osteogenic properties for the Sr/F-codoped HA. Multiple ions codoping may effectively modulate physicochemical and biological properties of hydroxyapatite (HA) for diverse biomedical applications. This study synthesized strontium (Sr)-, fluorine (F)- doped, and Sr/F-codoped HA nanoparticles by a hydrothermal method, and investigated the effect of ion doping on characteristics of HA, including crystallinity, crystal size, lattice parameters, and substitution sites by experiments and simulation with density functional theory (DFT) methods. It was found that, Sr doping increased the lattice parameters of HA whereas F doping decreased these parameters. Additionally, F doping enhanced the structural stability of the Sr-doped HA. F doping created excellent antibacterial properties to effectively inhibit growth of Streptococcus mutans. An appropriate Sr doping level endowed HA with optimum osteogenic ability to promote osteoblastic differentiation of bone marrow stem cells. These suggest that, Sr/F codoping is an effective approach to synthesizing HA-based materials with both antibacterial and osteogenic properties. More broadly, HA nanomaterials with specific characteristics may be designed for meeting diverse requirements from biomedical applications. [ABSTRACT FROM AUTHOR]