Comparative Evaluation of Microbial Growth on Unfilled and Filled Polyetheretherketone (PEEK) With and Without Surface Treatments: An In Vitro Study

Aims and background: Polyetheretherketone (PEEK) is a high-performance thermoplastic polymer used in biomedical applications due to its biocompatibility, mechanical strength, and chemical resistance. However, its inherent hydrophobicity and bio-inertness promote microbial adhesion and biofilm formation, limiting its effectiveness. This study evaluates the effects of laser and plasma surface treatments on the surface characteristics and microbial adhesion of PEEK. Materials and methods: PEEK samples, both unfilled and glass-filled, were subjected to laser (neodymium-doped yttrium aluminum garnet (Nd:YAG), 1064 nm) and argon plasma treatments. Surface morphology was analysed using scanning electron microscopy (SEM). Bacterial adhesion and biofilm formation were evaluated using crystal violet staining and spectrophotometric analysis at 570 nm. Live/dead staining was performed to determine bacterial viability. Results: Laser surface treatment produced uniform microstructures and significantly reduced bacterial adhesion and biofilm formation across all tested strains (E. coli, S. mutans, and S. oralis). Plasma treatment enhanced the surface wettability and reduced the microbial adhesion, to a lesser extent compared to laser surface treatment. Filled PEEK demonstrated higher roughness but lower microbial growth due to the antimicrobial effects of embedded glass fibers. Statistical analysis confirmed that biofilm formation was significantly lower in surface-treated groups (p < 0.001), exhibiting the antimicrobial performance. Conclusion: Laser surface treatment with an Nd:YAG laser was the most effective in reducing bacterial viability and biofilm formation, making it a promising technique for biomedical applications where infection control is essential. Plasma treatment remains a viable alternative for surface functionalization and biocompatibility enhancement. The findings emphasise the importance of surface modifications in improving the antimicrobial properties of PEEK for medical applications. Clinical significance: Surface modifications of PEEK via laser and plasma treatments provide promising strategies for reducing bacterial adhesion and biofilm formation, improving the material's suitability for biomedical implants and prosthetic applications.