Protein removal using atmospheric glow discharges: capability and mechanisms

Abstract

Summary form only given. There is well documented evidence of clinical cases that iatrogenic Creutzfeldt-Jakob disease (CJD) were induced by neurosurgical instrument contamination. The associated risk is of particular concern, since infective agents of CJD and indeed the transmissible spongiform encephalopathy are resistant to conventional decontamination procedures. This fundamental healthcare challenge calls for new decontamination strategies that can effectively remove protein from surgical instruments. Given the positive benefits and replacement cost of the current healthcare infrastructure, it is desirable that any new procedure is introduced as an additional step in the conventional cleaning cycle. Technically, this translates to a bio-burden challenge in the form of a minimum surface protein density of 10 mug/cm2 . In this contribution, we present a systematic study of protein removal using an atmospheric glow plasma jet. Bovine serum albumin (BSA) were used as a model protein and coated on surgical-grade stainless-steel disks. Protein was measured using epifluorescence microscopy by labeling BSA with fluorescein isothiocyanate, supplemented with scanning electron microscopy and energy dispersive X-ray spectroscopy. Using He-O2 mixture as the background gas, rapid protein removal was achieved from 100 mug/cm2 to 50 ng/cm2. Greater removal efficiency is highly feasible and can be quantitatively confirmed when the detection limit of our epifluorescence microscope is extended. So atmospheric pressure glow discharges can remove proteins from stainless-steel surfaces. Also presented is a parallel study of possible removal mechanisms using atmospheric glow discharges. Firstly, the protein reduction kinetics is shown to have three phases. Fluorescence images of protein-containing stainless-steel disks were topologically profiled and used to show a preferential removal of sub-areas of the disk surface. To understand possible mechanisms, protein removal experiments were performed under different plasma conditions. Specifically, atmospheric plasma jets in both He-O2 flow and He-N2 flow were used to remove surface proteins. Protein reduction rates are then correlated to intensities of optical emission lines. Systematic comparison between protein reduction with the two different atmospheric plasma jets suggest that oxygen species particularly oxygen atoms were among the main cleaning agents whereas UV photons played a much minor role. These results are valuable in the future development of atmospheric-plasma based decontamination procedures