Direct Treatment of Liquids Using Low-Current Arc in Ambient Air for Biomedical Applications

A, Boopathy B, Chatterjee R, M. H, Chakravortty D, Rao L. Generation of neutral pH high‐strength plasma‐activated water from a pin to water discharge and its bactericidal activity on multidrug‐resistant pathogens

Plasma‐activated water (PAW) is emerging as a green alternative technology in biomedicine due to its rich and diverse aqueous reactive nitrogen and oxygen species (RONS). This study explores how to configure a pin to water (P2W) discharge to generate neutral pH high‐strength plasma‐activated water (hs‐PAW) and its bactericidal activity on hypervirulent multidrug resistance (MDR) pathogens. The factors affecting the strength of PAW, namely: water type, PAW temperature, plasma enclosure, and activation time, were studied and optimized to generate hs‐PAW having 650 ± 40 mg/l of and 215 ± 15 mg/l of H2O2 at a pH of 7. This study demonstrates a simple P2W discharge set up to handle the MDR pathogens and can be easily scalable for real‐world medical applications.

The Effect of Gap Distance between a Pin and Water Surface on the Inactivation of Escherichia coli Using a Pin-to-Water Plasma

Atmospheric plasmas have been applied for the inactivation of microorganisms. Industrials demand to investigate the relation of the key reactive species induced by plasmas and the operating parameters including boundary conditions in order to control plasma treatment processes. In this study, we investigated the effect of gap distance between a pin-electrode and water surface on inactivation efficacy. When the gap distance decreased from 5 mm to 1 mm, the reduction of Escherichia coli (E. coli) was increased to more than 4 log CFU/mL. The reactive oxygen species measured optically and spectrophotometrically were influenced by gap distance. The results from electron spin resonance (ESR) analysis showed that the pin-to-water plasma generated hydroxyl radical (OH•) and singlet oxygen (¹O₂) in the water and superoxide radical (O₂⁻•) served as a precursor of OH•. The inactivation of E. coli was significantly alleviated by sodium azide (¹O₂ scavenger), indicating that ¹O₂ contributes the most to bacterial inactivation. These findings provide a potentially effective strategy for bacterial inactivation using a pin-to-water plasma.

Antimicrobial Effect of Plasma-Activated Tap Water on Staphylococcus aureus, Escherichia coli, and Candida albicans

In this study, the potential antimicrobial activity of plasma-activated tap water (PAW) was evaluated against Staphylococcus aureus, Escherichia coli, and Candida albicans. For this, PAW was prepared in a gliding arc plasma system using two treatment conditions: stagnant water and water stirring by a magnetic stirrer, called moving water. Subsequently, their oxidation-reduction potential (ORP), pH, electrical conductivity (σ), and total dissolved solids (TDS) were monitored in different areas of the sample divided according to the depth of the beaker. It was observed that PAW obtained in dynamic conditions showed a more uniform acidity among the evaluated areas with pH 3.53 and ORP of 215 mV. Finally, standardized suspensions of Staphylococcus aureus (ATCC 6538), Escherichia coli (ATCC 10799), and Candida albicans (SC 5314) were treated with PAW, and the reduction of viable cells determined the antimicrobial effect. Our results indicate that the tap water, activated by plasma treatment using gliding arc, is an excellent inactivation agent in the case of Staphylococcus aureus and Escherichia coli. On the other hand, no significant antimicrobial activity was achieved for Candida albicans.

Special Issue “Plasma Technology for Biomedical Applications”

The use of plasmas for biomedical applications in encountering a growing interest, especially in the framework of so-called “plasma medicine”, which aims at exploiting the action of low-power, atmospheric pressure plasmas for therapeutic purposes [...]

Scalable Treatment of Flowing Organic Liquids Using Ambient-Air Glow Discharge for Agricultural Applications

In this work, we developed a portable device with low production and operation costs for generating ambient-air glow discharge (AAGD) that is transferred to the surface of flowing liquid and demonstrated its applicability to practical use in agriculture. An experiment procedure that ensured the stable treatment of various liquids was established. Additionally, it was found that humidity did not have a significant effect on the treatment process, which makes the use of the developed device possible in various locations. It was found that an L-phenylalanine solution treated with AAGD allows simultaneous 40% hydroponic radish-sprout growth promotion with a bactericidal effect. Further, scalability and practical-application possibilities in hydroponic plant growth were discussed.