The growing prevalence of bacterial infections and the alarming rise of antimicrobial resistance (AMR) have driven the need for innovative antimicrobial coatings for medical implants and biomaterials. However, implant surface properties, such as roughness, chemistry, and reactivity, critically influence biological interactions and must be engineered to ensure biocompatibility, corrosion resistance, and sustained antibacterial activity. This review evaluates three principal categories of antimicrobial agents utilized in surface functionalization: metal/metaloxide nanoparticles, antibiotics, and phytochemical compounds. Metal/metaloxide-based coatings, especially those incorporating silver (Ag), zinc oxide (ZnO), and copper oxide (CuO), offer broad-spectrum antimicrobial efficacy through mechanisms such as reactive oxygen species (ROS) generation and bacterial membrane disruption, with a reduced risk of resistance development. Antibiotic-based coatings enable localized drug delivery but often face limitations related to burst release, cytotoxicity, and diminishing effectiveness against multidrug-resistant (MDR) strains. In contrast, phytochemical-derived coatings—using bioactive plant compounds such as curcumin, eugenol, and quercetin—present a promising, biocompatible, and sustainable alternative. These agents not only exhibit antimicrobial properties but also provide anti-inflammatory, antioxidant, and osteogenic benefits, making them multifunctional tools for implant surface modification. The integration of these antimicrobial strategies aims to reduce bacterial adhesion, inhibit biofilm formation, and enhance tissue regeneration. By leveraging the synergistic effects of metal/metaloxide nanoparticles, antibiotics, and phytochemicals, next-generation implant coatings hold the potential to significantly improve infection control and clinical outcomes in implant-based therapies.

Implant-associated bacterial infections remain a major challenge in biomaterials research, highlighting the need for effective and biocompatible strategies to prevent bacterial colonisation at implant surfaces. This study investigated the antibacterial potential of four phytochemicals-bergenin (B), norbergenin (NB), galloyl-lawsoniaside (GL), and uromyrtoside (U)-isolated from an Australian wet tropical endemic plant and evaluated the potential of bergenin as a biofunctional coating for titanium surfaces. The antibacterial activity of the phytochemicals against Staphylococcus aureus and Pseudomonas aeruginosa was assessed using zone of inhibition (ZOI), optical density (OD₆₀₀), and colony-forming unit (CFU/mL) assays across concentrations of 150-1000 μg mL^-1. All phytochemicals demonstrated concentration-dependent antibacterial activity, with S. aureus generally exhibiting greater susceptibility than P. aeruginosa. Against P. aeruginosa, the estimated IC₅₀ values were 220, 232.4, 240, and 233.1 μg mL^-1 for B, NB, GL, and U, respectively, whereas S. aureus exhibited IC₅₀ values of 150 μg mL^-1 for B, NB, and GL, and 733 μg mL^-1 for U. Among the tested compounds, bergenin demonstrated the strongest antibacterial activity, producing a ZOI of ≥21 mm at 1000 μg mL^-1 and up to 91% inhibition of bacterial growth based on OD₆₀₀ measurements (p < 0.05). CFU analysis further confirmed substantial reductions in bacterial viability, with plant-derived bergenin achieving approximately 95% bacterial reduction and outperforming its commercial counterpart. Importantly, bergenin-functionalised titanium surfaces demonstrated >90% reduction in bacterial viability against S. aureus after 24 h, confirming effective surface-mediated antibacterial activity. Collectively, these findings identify bergenin as a promising plant-derived antibacterial phytochemical and demonstrate its potential as a biofunctional surface modifier for developing infection-resistant titanium biomaterials. This multifunctional approach provides a promising platform for improving the antibacterial performance of titanium implant surfaces while supporting the development of plant-derived strategies for infection prevention.