Antibacterial polyelectrolyte coatings enable sustained release of rhBMP-2 from titanium alloy

The development of advanced technology to promote osteo-integration of metallic implants and to solve bacteria-associated infection is one of the urgent clinical requirements. A multilayer polyelectrolyte coating composed of phosphonate/quaternary amine block polymer (pDEMMP-co-pTMAEMA), polymethacrylic acid (PMAA) and polyethylenimine (PEI) was designed as the dual functional coating. Through a layer-by-layer technology, stable coatings were constructed on Ti alloy plate (TC4) substrates based on the strong covalent binding between phosphonate group and metallic substrate, and the electrostatic interaction between oppositely charged polymers. The polymeric coating enabled a high-efficiency sustained release of recombinant human bone morphogenetic protein 2 (rhBMP-2) from the TC4 substrates and promoted the trans-differentiation of C2C12 cells to osteoblast cells. Meanwhile, the polycationic component in the polyelectrolyte coating significantly improved the antibacterial properties of titanium alloy surface. The polyelectrolyte coating demonstrated here is a promising candidate to increase the osteo-integration and antibacterial property of metallic implants.