Proliferation promotion of fibroblast cells using atmospheric-pressure radical source.*

Recently, biological applications of atmospheric-pressure plasmas have been extensively researched. In this study, we investigated that the proliferation promotion of fibroblast cells in phosphate buffered saline (PBS) using a non-equilibrium radical source which selectively supplies electrically neutral radicals. The radical source was driven with Ar, O$_{\mathrm{2}}$ and N$_{\mathrm{2}}$ gases. The flow rate of Ar was fixed at 4 slm and the flow ratio of N$_{\mathrm{2}}$ against the sum of N$_{\mathrm{2}}$ and O$_{\mathrm{2}}$, hereafter N$_{\mathrm{2}}$/(N$_{\mathrm{2}}+$O$_{\mathrm{2}})$, was varied within 1 slm. The species and densities of supplied neutral radicals were investigated using a mass spectrometer (Hiden Analytical). As a result, N\textbullet , O\textbullet , NO\textbullet , NO$_{\mathrm{2}}$\textbullet and O$_{\mathrm{3}}$ were found to be major species. 3ml PBS with fibroblast cells were placed in a dish and the sample was treated for 10, 15, 20 and 30 s using the radical source with N$_{\mathrm{2}}$/(N$_{\mathrm{2}}+$O$_{\mathrm{2}})$ of 60, 70 and 80 {\%}. Cell viability was promoted compared to untreated samples with various exposure times and N$_{\mathrm{2}}$/(N$_{\mathrm{2}}+$O$_{\mathrm{2}})$, and the maximum promotion ratio was 34{\%} at a N$_{\mathrm{2}}$/(N$_{\mathrm{2}}+$O$_{\mathrm{2}})$ of 70{\%} and 15 s exposure. Also, the promotion ratio showed strong dependency only on the NO\textbullet dose. This result strongly suggests that NO\textbullet is the responsible factor for the proliferation promotion of fibroblast cells using atmospheric-pressure plasmas.