Charge-Driven Engineering of Titanium Implants with Chitosan and Poly- l -Lysine for Dual Antiadhesive and Anticorrosive Functionality

Peri-implant infections remain a major cause of implant failure, motivating the development of multifunctional titanium surfaces capable of preventing bacterial colonization while preserving implant performance. Herein, a chitosan/poly-l-lysine (CH-PLL) bilayer coating was engineered on hydroxyl-rich titanium surfaces generated by hydrothermal treatment (HT) or plasma electrolytic oxidation (PEO). We hypothesized that the CH-PLL bilayer would establish a stable cationic interface capable of impairing early bacterial adhesion and modulating polymicrobial biofilm development, whereas the PEO substrate would provide superior mechanical and electrochemical stability. Surface characterization confirmed successful bilayer formation and showed that PLL functionalization increased positive surface charge and hydrophilicity while improving tribological and electrochemical performance, with the PEO@CH-PLL coating exhibiting a friction coefficient of ∼0.01 and significantly enhanced corrosion resistance (P < 0.05). Accordingly, PLL-coated surfaces reduced bacterial adhesion by 3.9 and 3.1 log CFU for Staphylococcus aureus and Escherichia coli, respectively. Against a saliva-derived polymicrobial biofilm, the coating reduced the total bacterial burden by ∼1.8 log while suppressing disease-related peri-implant pathogens. Importantly, these antibacterial effects were accompanied by preserved protein adsorption and enhanced preosteoblastic activity after 7 days. Collectively, these findings demonstrate that combining a stable cationic CH-PLL interface with a PEO-generated oxide layer provides a multifunctional titanium surface integrating biofilm control with improved mechanical, electrochemical, and biological performance.