Bioactivity and Biocompatibility of a Polydopamine-Bridged, BMP-2-Functionalized Multilayer Coating on Stainless Steel for Bone Implant Applications

Implant failure due to poor osteogenesis and bacterial infection remains a major concern, emphasizing the importance of enhancing both the osteogenic and antibacterial activities of implants. This study focuses on using polydopamine (PDA)-bridged bone morphogenetic protein-2 (BMP2) and grafting it onto benzophenone (BP)-photoinitiated 2-methacryloyloxyethyl phosphorylcholine (MPC)-coated stainless steel (SS) to form a functionalized SS substrate (SS-BP-MPC-PDA-BMP2). The PDA bridge layer induced a greater BMP2 immobilization level (6-fold improvement), mitigated burst release, and sustained a controlled release rate (0.44 ng/cm²/day) over a ten-day period. Surface wettability (at a water contact angle of 33°) and smoothness (at a root mean square of 24 nm) were achieved in the BMP2-coated sample, with a higher antibacterial fouling efficacy (41%) against <i>Staphylococcus aureus</i>-(<i>S. aureus</i>) than the pristine SS and MPC-functionalized substrate (13-34%). Finally, this PDA-BMP2-modified SS prevented biofilm formation onto the surface and demonstrated the highest preosteoblast cell (MC3T3-E1 cell) metabolic activity (100-110% of the control value), with excellent proliferation behavior among the tested samples. The developed protocol is promising for implant material modification, particularly for orthopedic and dental applications.