The effects of three cold plasma treatments on the osteogenic activity and antibacterial property of PEEK

This study examines the differences in osteogenic activity and antibacterial property among polyetheretherketone (PEEK) treated by three types of cold plasma. Standard PEEK specimens were randomly assigned to four groups, which were named according to the treatment: PEEK-C (untreated), PEEK-A (Ar cold plasma treatment), PEEK-N (N2 cold plasma treatment), and PEEK-AN (90% Ar and 10% N2 mixed cold plasma treatment). Physical and chemical properties of the specimen surfaces were determined by scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and drop shape analyzer (DSA). MC3T3 osteoblasts were used in vitro to determine the osteogenic activity by cell adhesion morphology observation, cell counting-kit 8 (CCK-8) assay, and alkaline phosphatase (ALP) activity assay. Streptococcus mutans and Staphylococcus aureus were used in vitro to determine the antibacterial property by a plate colony-counting method and bacterial adhesion morphology observation. SEM and AFM analysis showed that the PEEK-C surface was smooth, whereas matrix-arranged nanoprotrusions appeared on the surface of the experimental groups: scaly nano-protrusions appeared on the PEEK-A and PEEK-AN surfaces, while dendritic nanoprotrusions appeared on the PEEK-N surface. Among the experimental groups, PEEK-AN had the finest surface nanoprotrusions. The roughness of the experimental groups increased compared with the PEEK-C group: the PEEK-N group was the roughest with a Ra of 192.60 ± 5.89 nm and PEEK-A was the smoothest with a Ra of 99.60 ± 5.43 nm. The hydrophilicity of the experimental groups was significantly enhanced compared with the PEEK-C group, among which, PEEK-N was the strongest and PEEK-A the weakest. The osteogenic activity and antibacterial property of the experimental groups displayed a remarkable increase compared with the PEEK-C group. Among the experimental groups, PEEK-N displayed the best osteogenic activity while PEEK-AN possessed the strongest antibacterial property. The osteogenic activity and antibacterial performance of PEEK-A were the weakest. Among these treatments, the N2 cold plasma treatment was the most suitable modification method for PEEK application in dental implant. Cold plasma treatment is a promising method to improve PEEK osteogenic activity and antibacterial properties. This study provides a theoretical basis for future research on PEEK cold plasma treatment.