Enhanced in vitro biocompatibility and osteogenesis of titanium substrates immobilized with dopamine-assisted superparamagnetic Fe ₃ O ₄ nanoparticles for hBMSCs

Titanium (Ti) is an ideal bone substitute due to its superior bio-compatibility and remarkable corrosion resistance. However, in order to improve the osteoconduction and osteoinduction capacities in clinical applications, different kinds of surface modifications are typically applied to Ti alloys. In this study, we fabricated a tightly attached polydopamine-assisted Fe 3 O 4 nanoparticle coating on Ti with magnetic properties, aiming to improve the osteogenesis of the Ti substrates. The PDA-assisted Fe 3 O 4 nanoparticle coatings were characterized by scanning electron microscopy, energy dispersive spectroscopy, atomic force microscopy and water contact angle measurements. The cell attachment and proliferation rate of the human bone mesenchymal stem cells (hBMSCs) on the Ti surface significantly improved with the Fe 3 O 4 /PDA coating when compared with the pure Ti without a coating. Furthermore, the results of in vitro alkaline phosphatase (ALP) activity at 7 and 14 days and alizarin red S staining at 14 days showed that the Fe 3 O 4 /PDA coating on Ti promoted the osteogenic differentiation of hBMSCs. Moreover, hBMSCs co-cultured with the Fe 3 O 4 /PDA-coated Ti for approximately 14 days also exhibited a significantly higher mRNA expression level of ALP, osteocalcin and runt-related transcription factor-2 (RUNX2). Our in vitro results revealed that the present PDA-assisted Fe 3 O 4 nanoparticle surface coating is an innovative method for Ti surface modification and shows great potential for clinical applications.