The effect of treatment of a Floating-Electrode Dielectric Barrier Discharge (FE-DBD) plasma source on bacteria and skin is researched. The FE-DBD consists of a copper electrode, enclosed in insulating material, and a thin plate of quartz as dielectric; the quartz surface is placed parallel above the to-be-treated surface, which serves as second electrode. Standard settings were: treatment for 30 s, duty cycle of 10%, pulse width of 10µs, pulse frequency of 1500 Hz and distance to sample of 1 mm. A higher pulse frequency (2500-3500 Hz versus 500-1500 Hz) or larger pulse width (tested range: 1-10 µs) were more effective in killing Staphylococcus aureus. Gap distances larger than 1 mm resulted in a weaker or no plasma. Different treatment times (tested range: 5-30 s) showed log reductions of three other staphylococci similar to those of S. aureus. Treatment of S. aureus on human skin resulted in lower log reductions than on glass or agar plates (1 versus 3 for standard settings). Treatment of human skin did not show a clear difference in metabolic activity of the skin cells (determined with the MTT assay). However, histology revealed that one skin sample was damaged, including necrosis in the epidermis, degradation of the basement membrane and changes in collagen in the dermis. The damage was very local and relatively small, which explains the normal metabolic activity. Probably, the damage was due to an uneven skin surface, leading to inhomogeneous discharges on the skin. The effects of the FE-DBD on bacterial inactivation are promising. However, the detrimental effects on skin are cause for concern. We will therefore focus our efforts on optimizing the plasma source for safe use on skin.
|Publication status||Published - 15 Sep 2013|
|Event||2nd Young Professionals Workshop on Plasma Medicine - Kölpinsee, Germany|
Duration: 15 Sep 2013 → 18 Sep 2013
|Conference||2nd Young Professionals Workshop on Plasma Medicine|
|Period||15/09/13 → 18/09/13|