Boosting Titanium Surfaces with Positive Charges: Newly Developed Cationic Coating Combines Anticorrosive and Bactericidal Properties for Implant Application

Along with poor implant-bone integration, peri-implantdiseasesare the major causes of implant failure. Although such diseases areprimarily triggered by biofilm accumulation, a complex inflammatoryprocess in response to corrosive-related metallic ions/debris hasalso been recognized as a risk factor. In this regard, by boostingthe titanium (Ti) surface with silane-based positive charges, cationiccoatings have gained increasing attention due to their ability tokill pathogens and may be favorable for corrosion resistance. Nevertheless,the development of a cationic coating that combines such propertiesin addition to having a favorable topography for implant osseointegrationis lacking. Because introducing hydroxyl (-OH) groups to Tiis essential to increase chemical bonds with silane, Ti pretreatmentis of utmost importance to achieve such polarization. In this study,plasma electrolytic oxidation (PEO) was investigated as a new routeto pretreat Ti with OH groups while providing favorable propertiesfor implant application compared with traditional hydrothermal treatment(HT). To produce bactericidal and corrosion-resistant cationic coatings,after pretreatment with PEO or HT (Step 1), surface silanization wassubsequently performed via immersion-based functionalization with3-aminopropyltriethoxysilane (APTES) (Step 2). In the end, five groupswere assessed: untreated Ti (Ti), HT, PEO, HT+APTES, and PEO+APTES.PEO created a porous surface with increased roughness and better mechanicaland tribological properties compared with HT and Ti. The introductionof -OH groups by HT and PEO was confirmed by Fourier transforminfrared spectroscopy and the increase in wettability producing superhydrophilicsurfaces. After silanization, the surfaces were polarized to hydrophobicones, and an increase in the amine functional group was observed byX-ray photoelectron spectroscopy, demonstrating a considerable amountof positive ions. Such protonation may explain the enhanced corrosionresistance and dead bacteria (Streptococcus aureus and Escherichia coli) found for PEO+APTES.All groups presented noncytotoxic properties with similar blood plasmaprotein adsorption capacity vs the Ti control. Our findings providenew insights into developing next-generation cationic coatings bysuggesting that a tailorable porous and oxide coating produced byPEO has promise in designing enhanced cationic surfaces targetingbiomedical and dental implant applications.