Application of a bifilar helix discharge in endoscope biopsy channels for plasma decontamination and biomedical aspects

Summary form only given. In modern medicine endoscopes are essential diagnostic and therapeutic tools. Due to their complex geometry, the thermolability of the used materials and the integrated sensitive electronics only a few sterilization techniques are applicable for this high cost medical product, e.g. sterilization with ethylene oxide (ETO) or the low temperature steam sterilization with formaldehyde. However, these techniques use carcinogenic chemicals and therefore need long outgas-times or operate at low pressure, which is technically demanding. Furthermore, the long and narrow flexible tubes inside the endoscopes are challenging. Cold atmospheric pressure plasmas have a huge potential for the sterilization of such complex medical devices and therefore are of great scientific and hygienic interest. In our contribution we will present a bifilar helix discharge setup to generate an atmospheric pressure dielectric barrier discharge (APDBD) at room temperature inside a long and narrow tube (length >; 5 m, inner diameter <; 2 mm), which is specially designed for replacing conventional biopsy channels in endoscopes. Moreover, a special electrode design at the tube end provides the generation of a stable and reproducible jet-like plasma for therapeutic applications inside the body or other plasma medical purposes. This effluent plasma has a typical axial expansion of 1 to 2 cm when a moderate gas flow rate of 1 standard liter per minute (slm) is applied. But even for a very low gas flow rate of 0.1 slm a 0.5 cm long jet-like plasma is generated. To characterize the inside tube and the effluent plasma experimentally optical emission spectroscopy (OES) in the UV and VUV spectral range as well as absorption spectroscopy is performed. Furthermore, the antimicrobial effect of both plasmas is proofed for different gas mixtures using Bacillus atrophaeus spores. In an additional experiment the effect of the effluent plasma on eukaryotic cells is investigated.