Bioinspired strong-adhesion hydrogel coatings via synergistic mechanical interlocking and physicochemical bonding for lubricious antibacterial titanium alloys

Ti6Al4V is widely used in load-bearing orthopedic implants, but insufficient surface lubricity, wear-debris generation and bacterial adhesion remain major causes of implant failure. Inspired by the hydration lubrication and hierarchical molecular network of natural articular cartilage, we develop a strongly adhesive sodium alginate/poly (acrylic acid-co-acrylamide) (SA/P(AA-co-AM)) hydrogel coating on Ti6Al4V. Surface hydroxylation of Ti6Al4V, followed by in situ UV-initiated polymerization, creates an integrated interfacial anchoring strategy that couples mechanical interlocking with physicochemical bonding. The optimized coating achieves a maximum adhesion strength of 280.33 kPa, while its hydrated polymer network reduces the coefficient of friction by 94.23%. The highly hydrated coating also suppresses the adhesion and aggregation of Escherichia coli and Staphylococcus aureus , thereby providing antibacterial surface protection without relying on leachable bactericides. This work presents a cartilage-inspired route to integrate strong adhesion, hydration lubrication and bacterial-repellent functionality on titanium alloy implants, offering a promising surface-engineering strategy for next-generation artificial joints.