Antibiofilm and osteogenic nanocoatings: a comparative study of self-assembled layers of the isomers carvacrol and thymol on titanium biomaterials

Abstract

The rise of multidrug-resistant bacterial biofilms presents a significant challenge in biomedical applications, demanding innovative and eco-friendly solutions. In this study, bactericidal nanolayers (NLs) were engineered on titanium (Ti) surfaces using two isomeric phytocompounds: carvacrol (Carv-Ti-NL) and thymol (TOH-Ti-NL). These NLs were fabricated via a simple, one-step self-assembly process. Both exhibited strong anti-biofilm and bactericidal activity against Staphylococcus aureus. TOH-Ti-NL proved superior for osteogenesis, while fibroblasts showed reduced adhesion on TOH-Ti-NL but enhanced proliferation on Carv-Ti-NL. Attenuated total reflectance Fourier-transform infrared spectroscopy (ATR-FTIR) spectroscopy confirmed spontaneous oxidation of Carv and TOH on Ti into ketonic structures. TOH-Ti-NL also displayed higher surface roughness, linked to improved osseointegration, and a higher release rate than Carv-Ti-NL. Both coatings eradicated bacteria within 24 h. Their early effectiveness underscores their potential for infection prevention on Ti implants. Thus, TOH-Ti-NL shows promise for bone-related applications, whereas Carv-Ti-NL may be better suited for fibroblast growth, offering tailored properties for diverse biomedical applications.