Sulfobetaine interfaces on titanium through stepwise surface engineering: a strategy to reduce bacterial biofilm formation

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Titanium is extensively employed in implantable medical devices owing to its excellent mechanical properties, corrosion resistance, and biocompatibility. Nevertheless, its native oxide layer does not prevent bacterial adhesion and subsequent biofilm formation, making implant-associated infections a persistent clinical challenge. Herein, we report a stepwise covalent surface engineering strategy to generate sulfobetaine-based zwitterionic interfaces on titanium as a covalent approach to mitigate bacterial colonization. Surface modification was achieved through sequential hydroxylation, APTES silanization, sulfonation with 1,3-propane sultone, and final quaternization, yielding permanently charged zwitterionic moieties covalently anchored to the titanium substrate. The evolution of surface chemistry and morphology was investigated by ATR-FTIR, SEM–EDX, profilometry, and wettability analyses. Spectroscopic and elemental mapping results confirmed the successful formation of sulfonate and quaternary ammonium functionalities, while contact angle measurements substantial changes in surface wettability throughout the functionalization sequence. The zwitterionic surface reduced the growth of Staphylococcus aureus ATCC 29213 by 70%, while no significant effect was observed for Pseudomonas aeruginosa. The biofilm formation of P. aeruginosa and S. aureus was greatly reduced by sulfonated surfaces and zwitterionic surfaces suggesting that the presence of charged chemical group and hydration effectively interfere to bacterial adhesion. These findings support the potential of surface-functionalized titanium as a strategy to reduce bacterial biofilm formation on titanium-based biomaterials.