This work investigates and reveals the main mechanism(s) responsible for inactivation of E. coli by in-liquid pulsed electrical discharge plasma in low conductivity solutions. Experiments were designed and performed to explore the effects of plasma-emitted UV light, oxidative radicals, and electric field on E. coli inactivation curves, rate of DNA leakage and visual appearance of the treated microorganisms. Results showed that electric field had the main role in inactivation; scanning electron microscopy images revealed that both plasma and the isolated electric field result in extensive cell wall disruptions. While this damage in the case of plasma treatment was extensive and distributed randomly along the envelope, the electric field-induced damage resulted in disruption primarily at the poles of the bacterial rods. Subsequent experiments conducted with an oxidative radical scavenger suggested that plasma-generated radicals do not contribute directly to the inactivation but assist in cell wall deterioration and extension of the ruptures first generated by the electric field.

/pdf/mechanism-of-e-coli-inactivation-by-direct-in-liquid-5l7onllu51.pdf

Mechanism of E. coli Inactivation by Direct-in-liquid Electrical Discharge Plasma in Low Conductivity Solutions.

The paper reviews the state of the art in the field of interaction of low temperature plasmas generated during electrospraying with the liquid cone and jet. Many studies are focused at practical applications of electrospraying, for example to mass spectrometry, electrospinning of nanofibers, thin film deposition, nanoparticle production, ink-jet printing, etc., but the phenomenon of electrically generated plasma due to gas ionization accompanying the electrospraying is frequently ignored. The effect of electrical discharge on the electrospraying process depends on the type of the discharge. When glow corona or onset streamers are generated, the electrospray is stabilized in the classical cone-jet mode, however, for breakdown streamers, sparks, or arc discharges, the electrospraying process is disturbed and irregular modes (spindle, multispindle or ramified jet) occur. The electrospray-discharge interaction phenomena have been studied by photographic recording, electric current measurements, mass spectrometry and optical emission spectroscopy. Some studies show that the current carried by the ions generated in this plasma and flowing through the drift region to the opposite electrode can be higher than the current carried by the electrosprayed droplets. This effect has been proved by separation of both currents using a specially designed device. To prevent the distortion of the electrospray process, various strategies have been developed: modification of the electric field in the vicinity of capillary nozzle, stabilization of the glow corona, reduction of the surface tension of liquid. Recently, the physical processes and phenomena occurring in electrical discharge plasmas during electrospraying of liquids find new application in decontamination of liquids or in material processing. The advantage of coupled electrospray-plasma process is that the liquid atomization is combined with plasma chemical processes within the same device, by using the same power supply applied to the capillary nozzle.

https://iopscience.iop.org/article/10.1088/1361-6463/ab0fdb/pdf

Low temperature plasmas and electrosprays

The synthesis and behavior in water of a set of various cis(Cl,Cl)-[R-tpyRuCl2(NO)](PF6) and trans(Cl,Cl)-[R-tpyRuCl2(NO)](PF6) (R = fluorenyl, phenyl, thiophenyl; tpy = 2,2':6',2''-terpyridine) complexes are presented. In any case, one chlorido ligand is substituted by a hydroxo ligand and the final species arises as a single trans(NO,OH) isomer, whatever the nature of the starting cis/trans(Cl,Cl) complexes. Six X-ray crystal structures are presented for cis(Cl,Cl)-[thiophenyl-tpyRuCl2(NO)](PF6) (cis-3a), trans(Cl,Cl)-[thiophenyl-tpyRuCl2(NO)](PF6) (trans-3a), trans(NO,OH)-[phenyl-tpyRu(Cl)(OH)(NO)](PF6) (4a), trans(NO,OH)-[thiophenyl-tpyRu(Cl)(OH)(NO)](PF6) (4b), trans(NO,OEt)-[phenyl-tpyRu(Cl)(OEt)(NO)](PF6) (5a), and trans(NO,OH)-[phenyl-tpyRu(Cl)(OEt)(NO)](PF6) (5b) compounds. The different cis/trans(Cl,Cl) complexes exhibit an intense low-lying transition in the λ = 330-390 nm range, which appears to be slightly blue-shifted after Cl → OH substitution. In water, both cis/trans(Cl,Cl) isomers are converted to a single trans(NO,OH) isomer in which one chlorido- is replaced by one hydroxo-ligand, which avoids tedious separation workout. The water stable trans(NO,OH)-species all release NO with quantum yields of 0.010 to 0.075 under irradiation at 365 nm. The properties are discussed with computational analysis performed within the framework of Density Functional Theory.

/pdf/chemical-and-photochemical-behavior-of-ruthenium-nitrosyl-4eppb5p19b.pdf

Chemical and photochemical behavior of ruthenium nitrosyl complexes with terpyridine ligands in aqueous media

The synthesis of new types of mono- and polynuclear ruthenium nitrosyl complexes is driving progress in the field of NO generation for a variety of applications. Light-induced Ru-NO bond dissociation...

Ruthenium-nitrosyl complexes as NO-releasing molecules and potential anticancer drugs

The synthesis of new types of mono- and polynuclear ruthenium nitrosyl complexes is driving progress in the field of NO generation for a variety of applications. Light-induced Ru-NO bond dissociation in solution may involve transient linkage isomers MS1 (Ru-ON) and MS2 (Ru-η2-NO), which can be detected spectroscopically and analyzed computationally. The investigation of photoisomerization processes in the solid state may be useful for potential application of such complexes for data storage, photochromic or photomagnetic materials or even non-linear optics. Herein we describe the major developments in the synthesis of ruthenium nitrosyl complexes, their photoinduced linkage isomerization (PLI) processes, their NO release both in the solid state and in solution, and their application as potential anticancer drugs. Illustrative examples of such innovations made mainly in the last decade are provided.

/pdf/ruthenium-nitrosyl-complexes-as-no-releasing-molecules-3qfww6ut.pdf

Ruthenium-nitrosyl complexes as NO-releasing molecules, potential anticancer drugs, and photoswitches based on linkage isomerism.

Antibiotic resistance is becoming a global scourge with 700,000 deaths each year and could cause up to 10 million deaths by 2050. As an example, Staphylococcus epidermidis has emerged as a causative agent of infections often associated with implanted medical devices. S. epidermidis can form biofilms, which contribute to its pathogenicity when present in intravascular devices. These staphylococci, embedded in the biofilm matrix, are resistant to methicillin, which had long been the recommended therapy and which has nowadays been replaced by less toxic and more stable therapeutic agents. Moreover, current reports indicate that 75 to 90% of Staphylococcus epidermidis isolates from nosocomial infections are methicillin-resistant strains. The challenge of successfully combating antibiotics resistance in biofilms requires the use of compounds with a controlled mode of action that can act in combination with antibiotics. Ruthenium nitrosyl complexes are potential systems for NO release triggered by light. The influence of trans(NO, OH)-[RuFT(Cl)(OH)NO](PF6) on Staphylococcus epidermidis resistant to methicillin is described. The results show a 50% decrease in cell viability in bacteria treated with low concentrations of NO. When combined with methicillin, this low dose of NO dramatically decreases bacterial resistance and makes bacteria 100-fold more sensitive to methicillin.

/pdf/effect-of-trans-no-oh-ruft-cl-oh-no-pf6-ruthenium-nitrosyl-3dtkqwgpn2.pdf

Effect of trans(NO, OH)-[RuFT(Cl)(OH)NO](PF6) ruthenium nitrosyl complex on methicillin-resistant Staphylococcus epidermidis.

Bacterial spores are one of the most resilient life forms on earth and are involved in many human diseases, such as infectious diarrhea, fatal paralytic illnesses and respiratory infections. Here, we investigated the mechanisms involved in the death of Bacillus pumilus spores after exposure to electric arcs in water. Cutting-edge microscopies at the nanoscale did not reveal any structural disorganization of spores exposed to electric arcs. This result suggested the absence of physical destruction by a propagating shock wave or an exposure to an electric field. However, Pulsed-Field Gel Electrophoresis (PFGE) revealed genomic DNA damage induced by UV radiation and Reactive Oxygen Species (ROS). UV induced single-strand DNA breaks and thymine dimers while ROS were mainly involved in base exci-sion. Our findings revealed a correlation between DNA damage and the treatment of spores with electrical discharges.

/pdf/electrical-discharges-in-water-induce-spores-dna-damage-28o0xhmfnl.pdf

Electrical discharges in water induce spores' DNA damage.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

/pdf/author-correction-effect-of-trans-no-oh-ruft-cl-oh-no-pf-6-3mbps0yopf.pdf

Charlotte Da Silva

Papers

Effect of trans(NO, OH)-[RuFT(Cl)(OH)NO](PF6) ruthenium nitrosyl complex on methicillin-resistant Staphylococcus epidermidis.

Electrical discharges in water induce spores' DNA damage.

Author Correction: Effect of trans(NO, OH)-[RuFT(Cl)(OH)NO](PF 6 ) ruthenium nitrosyl complex on methicillin-resistant Staphylococcus epidermidis