Hierarchical HA-PL/TA composite coating on titanium alloy with antibacterial activity and improved osteoblast adhesion and proliferation

Titanium alloy implants face persistent risks of bacterial infection and insufficient early osseointegration. In this work, a hierarchical micro/nano-structured hydroxyapatite (HA)-ε-polylysine (PL)-tannic acid (TA) composite coating was fabricated on sandblasted titanium alloy via a controlled drop-casting strategy. Surface roughness increased with deposition cycles and was tuned from 1.91 to 5.01 μm after eight cycles. The HA-PL/TA 8 coating exhibited excellent antibacterial activity (> 99.99%) against both Staphylococcus aureus and Escherichia coli , mainly attributed to the intrinsic antibacterial properties of PL and TA. The coating maintained structural integrity and antibacterial performance after 7-day PBS immersion. Meanwhile, the bioactivity of HA and hierarchical structure promoted MC3T3-E1 osteoblast adhesion and proliferation. This multifunctional coating provides a simple strategy for constructing antibacterial and cytocompatible interfaces on titanium implants.