Purpose: To evaluate the antibacterial and anti-inflammatory properties of SiOx:H nanocoatings using a plasma-deposition technique.
Materials and Methods: Four groups of SiOx:H nanocoatings were prepared by plasma nanocoating technique using different deposition gases and durations, specifically trimethylsilane (TMS) for groups A1 and A2 and a mixture of TMS and oxygen for groups B1 and B2. Changes in surface chemistry and physical properties were measured. Staphylococcus aureus  and Streptococcus mutans  were cultured on plasma SiOx:H nanocoatings to evaluate antibacterial and antibiofilm formation activities. Human gingival fibroblasts (HGFs) and HaCaT human keratinocytes were cultured and stimulated with tumor necrosis factor-α (TNF-α). Cell viability was measured using a Cell Counting Kit-8 (CCK-8) assay. Quantitative real-time polymerase chain reaction (qRT-PCR) and enzyme-linked immunosorbent assay (ELISA) were used to evaluate anti-inflammatory properties, including the mRNA and protein levels of inflammatory mediators and proinflammatory cytokines.
Results: The carbon content was dominant in group A nanocoatings and the oxygen and silicon elements were dominant in group B nanocoatings. Groups A2 and B2 were approximately threefold thicker than groups A1 and B1. The plasma SiO_x:H nanocoatings decreased bacterial growth and biofilm formation by 30– 70% (p < 0.05). Scanning electron microscopy (SEM) revealed damaged biofilm structures. Moreover, the antibacterial properties of group B were greater than group A, and the antibacterial properties of groups A2 and B2 were more effective than A1 and B1, respectively. CCK-8 assays revealed the plasma SiOx:H nanocoatings had good biocompatibility. Furthermore, under TNF-α-induced inflammation, the mRNA and protein levels of interleukin-6, interleukin-8, cyclooxygenase-2, and monocyte chemoattractant protein-1 were downregulated in the plasma SiOx:H nanocoating groups (p < 0.05).
Conclusion: Plasma SiOx:H nanocoatings exerted antibacterial and anti-inflammatory effects with excellent biocompatibility. Therefore, the plasma SiOx:H nanocoating technique has potential for implant materials and other medical devices.
Keywords: plasma SiOx:H nanocoating technique, biomaterial-related infection, bacterial adhesion, biofilm formation, anti-inflammation