Depyrogenation using Plasmas: A Novel Approach for Endotoxin Deactivation Using a Dielectric Barrier Discharge at Atmospheric Pressure

Developing a low-cost depyrogenation process is vital in extending medical applicability of polymers that can be used in medicine. We present an overview of the plasma-based depyrogenation literature and address the need to develop a non-thermal plasma-based depyrogenation process for delicate materials such as chitosan. We present a low-cost plasma apparatus to treat chitosan powder in hermetically sealed bags. We decouple the experiments into two; depyrogenation experiments for dried standard endotoxin on glass slides, and chitosan modifications analysis through FTIR spectroscopy. We demonstrate depyrogenation efficacy with up to a 4-log reduction in endotoxin levels and discuss minor changes observed in plasma-treated chitosan.

Performance evaluation of bactericidal effect and endotoxin inactivation by low-temperature ozone/hydrogen peroxide mixed gas exposure

This study evaluated the performance of a new O₃ /H₂ O₂ mixed gas sterilization instrument for killing microorganisms and inactivating bacterial endotoxin at low temperatures. Sterility assurance level was achieved by an over 6-log reduction of Geobacillus stearothermophilus ATCC 12980, and the decimal reduction value was 0.77 min in sterilization mode. A reduction of over 3 logs in Limulus amebocyte lysate coagulation activity of purified endotoxin from Escherichia coli was observed after treatment in endotoxin-inactivation mode. The same inactivation ability was observed when treating dried bacterial cells. Biomaterials made of polymer or metal did not exhibit cytotoxicity after gas exposure at O₃ concentrations below 200 ppm. As the results of human cell-based pyrogen testing, significant amounts of endotoxin that were over the limit for medical devices contacting cerebrospinal fluid (2.15 EU/device) were detected on scissors washed with a washer-disinfector and sterilized with ethylene oxide or autoclaving. In contrast, endotoxin decreased to 0.29 ± 0.05 EU/device after O₃ /H₂ O₂ mixed gas sterilization in endotoxin-inactivation mode. Compared to conventional gas sterilization methods, O₃ /H₂ O₂ mixed gas has high sterilization ability and a strong capacity to inactivate endotoxin. It is expected that this sterilization technology will improve the safety of reusable medical devices and utensils for regenerative medicine.

Atmospheric pressure non-thermal plasma exposure reduces Pseudomonas aeruginosa lipopolysaccharide toxicity in vitro and in vivo

Lipopolysaccharide (LPS) is an endotoxin composed of a polysaccharide and lipid component. It is intrinsically responsible for the pathogenicity of Gram-negative bacteria and is involved in the development of bacterial sepsis. Atmospheric pressure non-thermal plasma is proposed as a potential new approach for the treatment of infected tissue such as chronic wounds, with both antibacterial and wound-healing activities extensively described. Using both the RAW264.7 murine macrophage cell line in vitro assays and the Galleria mellonella insect in vivo toxicity model, the effect non-thermal plasma exposure on LPS-mediated toxicity has been characterised. Short (60 s) non-thermal plasma exposures of Pseudomonas aeruginosa conditioned growth media, membrane lysates and purified P. aeruginosa LPS, resulted in a substantial detoxification and reduction of LPS-induced cytotoxicity in RAW264.7 murine macrophages. Non-thermal plasma exposure (60 s) of purified P. aeruginosa LPS led to a significant (p < 0.05) improvement in the G. mellonella health index (GHI) score, a measure of in vivo toxicity. These findings demonstrate the ability of short plasma exposures to significantly reduce LPS-induced cytotoxicity both in vitro and in vivo; attenuating the toxicity of this important virulence factor intrinsic to the pathogenicity of Gram-negative bacteria.

Endotoxin contamination: a key element in the interpretation of nanosafety studies

The study of toxicity and potential risks of engineered nanoparticles is of particular importance in nanomedicine. Endotoxin, a common contaminant of bacterial origin, has biological effects that can mask the true biological effects of nanoparticles, if its presence is overlooked. In this review, we report the features of nanoparticle contamination by endotoxin, and the different biological effects of endotoxin-contaminated nanoparticles. We will describe different methods for endotoxin detection applied to nanoparticles, and discuss their pros and cons. Eventually, we describe various methods for eliminating endotoxin contamination in nanoparticles. Although there is no universal technique for efficiently removing endotoxin from nanoparticles, specific solutions can be found case by case, which can allow us to perform nanosafety studies in biologically relevant conditions.

Elimination of biological contaminations from surfaces by plasma discharges: chemical sputtering

Plasma treatment of surfaces as a sterilisation or decontamination method is a promising approach to overcome limitations of conventional techniques. The precise characterisation of the employed plasma discharges, the application of sensitive surface diagnostic methods and targeted experiments to separate the effects of different agents, have led to rapid progress in the understanding of different relevant elementary processes. This contribution provides an overview of the most relevant and recent results, which reveal the importance of chemical sputtering as one of the most important processes for the elimination of biological residuals. Selected studies on the interaction of plasmas with bacteria, proteins and polypeptides are highlighted, and investigations employing beams of atoms and ions confirming the prominent role of chemical sputtering are presented. With this knowledge, it is possible to optimize the plasma treatment for decontamination/sterilisation purposes in terms of discharge composition, density of active species and UV radiation intensity.

Use of a low-pressure plasma discharge for the decontamination and sterilization of medical devices

Nonequilibrium low-pressure plasma discharges are extensively studied for their applications in the field of decontamination and sterilization of medical devices. The aim of this contribution is to discuss and demonstrate feasibility of oxygen low-pressure inductively coupled plasma (ICP) discharges for removal of various kinds of biological contamination. We demonstrate the ability of ICP discharges for the sterilization of bacterial spores and the removal of biological contamination from proteins and pyrogens.