Sustainable Plant-Derived Coatings for Titanium Implants: Dual Drug and Ion Release Capabilities

In this study, hybrid coatings for titanium implants were developed based on strontium titanate layers further functionalized with polyphenols derived from mint, nettle, and sage extracts. The coatings were additionally loaded with ciprofloxacin as an antibacterial agent through interactions with Mg2+ ions present in the polyphenolic part of the layer. The obtained materials were comprehensively characterized using SEM, AFM, FT-IR, zeta potential analysis, water contact angle measurements, corrosion resistance tests, and adhesion studies. The results demonstrated that the type of plant extract significantly influenced the composition and thickness of the polyphenolic layer, which in turn affected ciprofloxacin sorption and release profiles. All coatings enabled a rapid therapeutic release of the antibiotic within the first hour, followed by a sustained release lasting up to 8-10 h. Simultaneously, Mg2+ and Sr2+ ions were released in biologically relevant concentrations, supporting bone tissue regeneration. The hybrid layers markedly enhanced hydrophilicity, corrosion resistance, and adhesion to the Ti6Al4V substrate. These findings highlight the potential of the proposed strategy as a dual-function surface modification, providing both antibacterial protection and osteogenic stimulation, and thus represent a promising approach for next-generation titanium implants. Moreover, the use of plant-derived polyphenols obtained from renewable herbal sources introduces a sustainable and environmentally friendly alternative to synthetic coating agents. The proposed fabrication process relies on aqueous, low-temperature conditions and avoids toxic reagents, aligning with the principles of green chemistry.