The effect of atmospheric pressure plasma jet on macrophage activation

Titanium (Ti) and hydroxyapatite are used successfully as a bone substitute materials. However, sometimes such biomaterials are recognized as foreign bodies in the host, show undesirable effects. These unsuitable host immune response leads to inflammatory fibrotic capsule surround the implant. In the immune response, macrophages play a critical role. Nevertheless, the effect of macrophage on biomaterial-induced immune response is poorly understood. A non-thermal atmospheric pressure plasma jet (NTAPPJ) treatment on Ti could be applied to enhance initial cell attachment and osteogenic differentiation. However, research on macrophage polarization by NTAPPJ does not yet. Therefore, this study was performed to investigate the effect of NTAPPJ on expression of inflammatory cytokines of macrophage. Immortalized mouse bone marrow-derived macrophage, named IMBMM, was used in this study. The suspended IMBMMs in culture medium were plated on Ti disc with nitrogen-based NTAPPJ treatment for 0.5, 2 and 10 min. For evaluation of cytotoxicity on NTAPPJ treatment, the WST-1 assay of IMBMMs was conducted after 24 hours of culture. The influence of NTAPPJ treatment associated with inflammatory cytokine secretion was investigated by analysis of specific gene (IL-1β, IL-6 and so on) expression levels using quantitative RT-PCR. For quantitative RT-PCR, after 24 hours of NTAPPJ treatment on plated IMBMMs with/without lipopolysaccharide (LPS; 0.5 mug / ml) which is an essential role in secretion of pro-inflammatory cytokine on macrophage, the IMBMMs were harvested to RNA isolation and cDNA synthesis. The statistical differences were identified using analysis of one-way ANOVA and the statistical significance was accepted at confidence level of 95 % (p <; 0.05) by Tukey´s test. As a result, no significant differences were showed between NTAPPJ treatment group and non-NTAPPJ treatment group in WST-1 assay (p > 0.05). For cytokines secretion analysis of LPSstimulated IMBMMs- the expression of IL-1β and IL-6 were significantly downregulated on NTAPPJ-10 min treatment group comparing with non-NTAPPJ treatment group (p <; 0.05). Furthermore, pro-inflammatory gene expression (IL-1β, IL-6 and TNFα) of all NTAPPJ-treated groups was lower than non-NTAPPJ treatment group, though there was no statistical significant (p > 0.05). These finding provided a conclusion that the NTAPPJ treatment on Ti effectively reduced a pro-inflammatory cytokine expression of macrophages. This study could be applied to enhance a success rate of bone replacement surgery with suppressing the fibrosis response caused by excessive inflammation.