“Bacterial inactivation by plasma treated water enhanced by reactive nitrogen species”. Shaw P, Kumar N, Kwak HS, Park JH, Uhm HS, Bogaerts A, Choi EH, Attri P, Scientific reports 8, 11268 (2018). http://doi.org/10.1038/s41598-018-29549-6
Abstract: There is a growing body of literature that recognizes the importance of plasma treated water (PTW)for inactivation of microorganism. However, very little attention has been paid to the role of reactive nitrogen species (RNS) in deactivation of bacteria. The aim of this study is to explore the role of RNS in bacterial killing, and to develop a plasma system with increased sterilization efficiency. To increase the concentration of reactive oxygen and nitrogen species (RONS) in solution, we have used vapor systems (DI water/HNO3 at different wt%) combined with plasma using N2 as working gas. The results show that the addition of the vapor system yields higher RONS contents. Furthermore, PTW produced by N2 + 0.5 wt% HNO3 vapor comprises a large amount of both RNS and ROS, while PTW created by N2 + H2O vapor consists of a large amount of ROS, but much less RNS. Interestingly, we observed more deactivation of E. Coli with PTW created by N2 + 0.5 wt% HNO3 vapor plasma as compared to PTW generated by the other plasma systems. This work provides new insight into the role of RNS along with ROS for deactivation of bacteria.
Keywords: A1 Journal article; Engineering sciences. Technology; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 4.259
Times cited: 17
DOI: 10.1038/s41598-018-29549-6
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“Atomic scale understanding of the permeation of plasma species across native and oxidized membranes”. Razzokov J, Yusupov M, Cordeiro RM, Bogaerts A, Journal of physics: D: applied physics 51, 365203 (2018). http://doi.org/10.1088/1361-6463/aad524
Abstract: Cold atmospheric plasmas (CAPs) have attracted significant interest for their potential benefits in medical applications, including cancer therapy. The therapeutic effects of CAPs are related to reactive oxygen and nitrogen species (ROS and RNS) present in the plasma. The impact of ROS has been extensively studied, but the role of RNS in CAP-treatment remains poorly understood at the molecular level. Here, we investigate the permeation of RNS and ROS across native and oxidized phospholipid bilayers (PLBs) by means of computer simulations. The results reveal significantly lower free energy barriers for RNS (i.e. NO, NO2, N2O4) and O3 compared to hydrophilic ROS, such as OH, HO2 and H2O2. This suggests that the investigated RNS and O3 can permeate more easily through both native and oxidized PLBs in comparison to hydrophilic ROS, indicating their potentially important role in plasma medicine.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 2.588
Times cited: 10
DOI: 10.1088/1361-6463/aad524
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“The effect of reactive oxygen and nitrogen species on the structure of cytoglobin: A potential tumor suppressor”. De Backer J, Razzokov J, Hammerschmid D, Mensch C, Hafideddine Z, Kumar N, van Raemdonck G, Yusupov M, Van Doorslaer S, Johannessen C, Sobott F, Bogaerts A, Dewilde S, Redox Biology 19, 1 (2018). http://doi.org/10.1016/j.redox.2018.07.019
Abstract: Many current anti-cancer therapies rely on increasing the intracellular reactive oxygen and nitrogen species (RONS) contents with the aim to induce irreparable damage, which subsequently results in tumor cell death. A novel tool in cancer therapy is the use of cold atmospheric plasma (CAP), which has been found to be very effective in the treatment of many different cancer cell types in vitro as well as in vivo, mainly through the vast generation of RONS. One of the key determinants of the cell's fate will be the interaction of RONS, generated by CAP, with important proteins, i.e. redox-regulatory proteins. One such protein is cytoglobin (CYGB), a recently discovered globin proposed to be involved in the protection of the cell against oxidative stress. In this study, the effect of plasma-produced RONS on CYGB was investigated through the treatment of CYGB with CAP for different treatment times. Spectroscopic analysis of CYGB showed that although chemical modifications occur, its secondary structure remains intact. Mass spectrometry experiments identified these modifications as oxidations of mainly sulfur-containing and aromatic amino acids. With longer treatment time, the treatment was also found to induce nitration of the heme. Furthermore, the two surface-exposed cysteine residues of CYGB were oxidized upon treatment, leading to the formation of intermolecular disulfide bridges, and potentially also intramolecular disulfide bridges. In addition, molecular dynamics and docking simulations confirmed, and further show, that the formation of an intramolecular disulfide bond, due to oxidative conditions, affects the CYGB 3D structure, thereby opening the access to the heme group, through gate functioning of His117. Altogether, the results obtained in this study (1) show that plasma-produced RONS can extensively oxidize proteins and (2) that the oxidation status of two redox-active cysteines lead to different conformations of CYGB.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT); Molecular Spectroscopy (MolSpec)
Impact Factor: 6.337
DOI: 10.1016/j.redox.2018.07.019
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“Impact of plasma oxidation on structural features of human epidermal growth factor”. Yusupov M, Lackmann J-W, Razzokov J, Kumar S, Stapelmann K, Bogaerts A, Plasma processes and polymers 15, 1800022 (2018). http://doi.org/10.1002/ppap.201800022
Abstract: We perform computer simulations supported by experiments to investigate the oxidation of an important signaling protein, that is, human epidermal growth factor (hEGF), caused by cold atmospheric plasma (CAP) treatment. Specifically, we study the conformational changes of hEGF with different degrees of oxidation, to mimic short and long CAP treatment times. Our results indicate that the oxidized structures become more flexible, due to their conformational changes and breakage of the disulfide bonds, especially at higher oxidation degrees. MM/GBSA calculations reveal that an increasing oxidation level leads to a lower binding free energy of hEGF with its receptor. These results help to understand the fundamentals of the use of CAP for wound healing versus cancer treatment at short and longer treatment times.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 2.846
Times cited: 7
DOI: 10.1002/ppap.201800022
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Mannaerts D, Faes E, Cos P, Briedé, JJ, Gyselaers W, Cornette J, Gorbanev Y, Bogaerts A, Spaanderman M, Van Craenenbroeck E, Jacquemyn Y, Torrens C (2018) Oxidative stress in healthy pregnancy and preeclampsia is linked to chronic inflammation, iron status and vascular function. e0202919
Abstract: Background
During normal pregnancy, placental oxidative stress (OS) is present during all three trimesters and is necessary to obtain normal cell function. However, if OS reaches a certain level, pregnancy complications might arise. In preeclampsia (PE), a dangerous pregnancy specific hypertensive disorder, OS induced in the ischemic placenta causes a systemic inflammatory response and activates maternal endothelial cells. In this study, we aimed to quantify superoxide concentrations (as a measure of systemic OS) using electron paramagnetic resonance (EPR) and correlate them to markers of systemic inflammation, iron status and vascular function.
Methods
Fifty-nine women with a healthy pregnancy (HP), 10 non-pregnant controls (NP) and 28 PE patients (32±3.3weeks) were included. During HP, blood samples for superoxide, neutrophil to lymphocyte ratio (NLR), mean platelet volume (MPV) and iron status were taken at 10, 25 and 39 weeks. Vascular measurements for arterial stiffness (carotid-femoral pulse wave velocity (CF-PWV), augmentation index (AIx), augmentation Pressure (AP)) and microvascular endothelial function (reactive hyperemia index (RHI)) were performed at 35 weeks. In PE, all measurements were performed at diagnosis. CMH (1-hydroxy-3-methoxycarbonyl-2,2,5,5-tetramethylpyrrolidine) was used as spin probe for EPR, since the formed CM radical
corresponds to the amount of superoxide.
Results
Superoxide concentration remains stable during pregnancy (p = 0.92), but is significantly higher compared to the NP controls (p<0.0001). At 25 weeks, there is a significant positive correlation between superoxide and ferritin concentration. (p = 0.04) In PE, superoxide, systemic inflammation and iron status are much higher compared to HP (all p<0.001). During HP, superoxide concentrations correlate significantly with arterial stiffness (all p<0.04), while in PE superoxide is significantly correlated to microvascular endothelial function (p = 0.03).
Conclusions
During HP there is an increased but stable oxidative environment, which is correlated to ferritin concentration. If superoxide levels increase, there is an augmentation in arterial stiffness. In PE pregnancies, systemic inflammation and superoxide concentrations are higher and result in a deterioration of endothelial function. Together, these findings support the hypothesis that vascular function is directly linked to the amount of OS and that measurement of OS in combination with vascular function tests might be used in the prediction of PE.
Keywords: University Hospital Antwerp; A1 Journal article; Engineering sciences. Technology; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT); Antwerp Surgical Training, Anatomy and Research Centre (ASTARC); Translational Pathophysiological Research (TPR)
Impact Factor: 2.806
Times cited: 15
DOI: 10.1371/journal.pone.0202919
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“White paper on the future of plasma science in environment, for gas conversion and agriculture”. Brandenburg R, Bogaerts A, Bongers W, Fridman A, Fridman G, Locke BR, Miller V, Reuter S, Schiorlin M, Verreycken T, Ostrikov KK, Plasma processes and polymers 16, 1700238 (2019). http://doi.org/10.1002/ppap.201700238
Abstract: Climate change, environmental pollution control, and resource utilization efficiency, as well as food security, sustainable agriculture, and water supply are among the main challenges facing society today. Expertise across different academic fields, technologies,anddisciplinesisneededtogeneratenewideastomeetthesechallenges. This “white paper” aims to provide a written summary by describing the main aspects and possibilities of the technology. It shows that plasma science and technology can make significant contributions to address the mentioned issues. The paper also addresses to people in the scientific community (inside and outside plasma science) to give inspiration for further work in these fields.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 2.846
Times cited: 19
DOI: 10.1002/ppap.201700238
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“Characterization of a nitrogen gliding arc plasmatron using optical emission spectroscopy and high-speed camera”. Gröger S, Ramakers M, Hamme M, Medrano JA, Bibinov N, Gallucci F, Bogaerts A, Awakowicz P, Journal of physics: D: applied physics 52, 065201 (2019). http://doi.org/10.1088/1361-6463/aaefe4
Abstract: A gliding arc plasmatron (GAP), which is very promising for purification and gas conversion,
is characterized in nitrogen using optical emission spectroscopy and high-speed photography,
because the cross sections of electron impact excitation of N 2 are well known. The gas
temperature (of about 5500 K), the electron density (up to 1.5 × 10 15 cm −3 ) and the reduced
electric field (of about 37 Td) are determined using an absolutely calibrated intensified charge-
coupled device (ICCD) camera, equipped with an in-house made optical arrangement for
simultaneous two-wavelength diagnostics, adapted to the transient behavior of a GA channel
in turbulent gas flow. The intensities of nitrogen molecular emission bands, N 2 (C–B,0–0) as
well as N +
2 (B–X,0–0), are measured simultaneously. The electron density and the reduced
electric field are determined at a spatial resolution of 30 µm, using numerical simulation and
measured emission intensities, applying the Abel inversion of the ICCD images. The temporal
behavior of the GA plasma channel and the formation of plasma plumes are studied using a
high-speed camera. Based on the determined plasma parameters, we suggest that the plasma
plume formation is due to the magnetization of electrons in the plasma channel of the GAP by
an axial magnetic field in the plasma vortex.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 2.588
Times cited: 7
DOI: 10.1088/1361-6463/aaefe4
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“Three-dimensional modeling of energy transport in a gliding arc discharge in argon”. Kolev S, Bogaerts A, Plasma Sources Science &, Technology 27, 125011 (2018). http://doi.org/10.1088/1361-6595/aaf29c
Abstract: In this work we study energy transport in a gliding arc discharge with two diverging flat
electrodes in argon gas at atmospheric pressure. The discharge is ignited at the shortest electrode
gap and it is pushed downstream by a forced gas flow. The current values considered are
relatively low and therefore a non-equilibrium plasma is produced. We consider two cases, i.e.
with high and low discharge current (28 mA and 2.8mA), and a constant gas flow of 10 lmin −1 ,
with a significant turbulent component to the velocity. The study presents an analysis of the
various energy transport mechanisms responsible for the redistribution of Joule heating to the
plasma species and the moving background gas. The objective of this work is to provide a
general understanding of the role of the different energy transport mechanisms in arc formation
and sustainment, which can be used to improve existing or new discharge designs. The work is
based on a three-dimensional numerical model, combining a fluid plasma model, the shear stress
transport Reynolds averaged Navier–Stokes turbulent gas flow model, and a model for gas
thermal balance. The obtained results show that at higher current the discharge is constricted
within a thin plasma column several hundred kelvin above room temperature, while in the low-
current discharge the combination of intense convective cooling and low Joule heating prevents
discharge contraction and the plasma column evolves to a static non-moving diffusive plasma,
continuously cooled by the flowing gas. As a result, the energy transport in the two cases is
determined by different mechanisms. At higher current and a constricted plasma column, the
plasma column is cooled mainly by turbulent transport, while at low current and an unconstricted
plasma, the major cooling mechanism is energy transport due to non-turbulent gas convection. In
general, the study also demonstrates the importance of turbulent energy transport in
redistributing the Joule heating in the arc and its significant role in arc cooling and the formation
of the gas temperature profile. In general, the turbulent energy transport lowers the average gas
temperature in the arc, thus allowing additional control of thermal non-equilibrium in the
discharge.
Keywords: A1 Journal Article; gliding arc discharge, sliding arc discharge, energy transport, fluid plasma model, atmospheric pressure plasmas; Plasma, laser ablation and surface modeling Antwerp (PLASMANT) ;
Impact Factor: 3.302
DOI: 10.1088/1361-6595/aaf29c
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“Supersonic Microwave Plasma: Potential and Limitations for Energy-Efficient CO2Conversion”. Vermeiren V, Bogaerts A, Journal Of Physical Chemistry C 122, 25869 (2018). http://doi.org/10.1021/acs.jpcc.8b08498
Abstract: Supersonic flows provide a high thermodynamic
nonequilibrium, which is crucial for energy-efficient conversion of
CO 2 in microwave plasmas and are therefore of great interest.
However, the effect of the flow on the chemical reactions is poorly
understood. In this work, we present a combined flow and plasma
chemical kinetics model of a microwave CO 2 plasma in a Laval
nozzle setup. The effects of the flow field on the different dissociation
and recombination mechanisms, the vibrational distribution, and the
vibrational transfer mechanism are discussed. In addition, the effect
of experimental parameters, like position of power deposition, outlet
pressure, and specific energy input, on the CO 2 conversion and
energy efficiency is examined. The short residence time of the gas in
the plasma region, the shockwave, and the maximum critical heat,
and thus power, that can be added to the flow to avoid thermal
choking are the main obstacles to reaching high energy efficiencies.
Keywords: A1 Journal Article; Plasma, laser ablation and surface modeling Antwerp (PLASMANT) ;
Impact Factor: 4.536
Times cited: 5
DOI: 10.1021/acs.jpcc.8b08498
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“Capacitive electrical asymmetry effect in an inductively coupled plasma reactor”. Zhang Q-Z, Bogaerts A, Plasma Sources Science &, Technology 27, 105019 (2018). http://doi.org/10.1088/1361-6595/aad796
Abstract: The electrical asymmetry effect is realized by applying multiple frequency power sources
(13.56 MHz and 27.12 MHz) to a capacitively biased substrate electrode in a specific inductively
coupled plasma reactor. On the one hand, by adjusting the phase angle θ between the multiple
frequency power sources, an almost linear self-bias develops on the substrate electrode, and
consequently the ion energy can be well modulated, while the ion flux stays constant within a
large range of θ. On the other hand, the plasma density and ion flux can be significantly
modulated by tuning the inductive power supply, while only inducing a small change in the self-
bias. Independent control of self-bias/ion energy and ion flux can thus be realized in this specific
inductively coupled plasma reactor.
Keywords: A1 Journal Article; electrical asymmetry effect, inductively coupled plasma, self-bias, independent control of the ion fluxes and ion energy; Plasma, laser ablation and surface modeling Antwerp (PLASMANT) ;
Impact Factor: 3.302
Times cited: 1
DOI: 10.1088/1361-6595/aad796
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“Plasma streamer propagation in structured catalysts”. Zhang Q-Z, Bogaerts A, Plasma Sources Science &, Technology 27, 105013 (2018). http://doi.org/10.1088/1361-6595/aae430
Abstract: Plasma catalysis is gaining increasing interest for various environmental applications. Catalytic
material can be inserted in different shapes in the plasma, e.g., as pellets, (coated) beads, but also
as honeycomb monolith and 3DFD structures, also called ‘structured catalysts’, which have high
mass and heat transfer properties. In this work, we examine the streamer discharge propagation
and the interaction between plasma and catalysts, inside the channels of such structured catalysts,
by means of a two-dimensional particle-in-cell/Monte Carlo collision model. Our results reveal
that plasma streamers behave differently in various structured catalysts. In case of a honeycomb
structure, the streamers are limited to only one channel, with low or high plasma density when
the channels are parallel or perpendicular to the electrodes, respectively. In contrast, in case of a
3DFD structure, the streamers can distribute to different channels, causing discharge
enhancement due to surface charging on the dielectric walls of the structured catalyst, and
especially giving rise to a broader plasma distribution. The latter should be beneficial for plasma
catalysis applications, as it allows a larger catalyst surface area to be exposed to the plasma.
Keywords: A1 Journal Article; plasma catalysis, streamer propagation, 3D structures, PIC/MCC; Plasma, laser ablation and surface modeling Antwerp (PLASMANT) ;
Impact Factor: 3.302
Times cited: 3
DOI: 10.1088/1361-6595/aae430
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“Plasma-based multi-reforming for Gas-To-Liquid: tuning the plasma chemistry towards methanol”. Snoeckx R, Wang W, Zhang X, Cha MS, Bogaerts A, Scientific reports 8, 15929 (2018). http://doi.org/10.1038/s41598-018-34359-x
Abstract: Because of its unique properties, plasma technology has gained much prominence in the
microelectronics industry. Recently, environmental and energy applications of plasmas have gained a lot of attention. In this area, the focus is on converting CO 2 and reforming hydrocarbons, with the goal of developing an efficient single-step ‘gas-to-liquid’ (GTL) process. Here we show that applying tri-reforming principles to plasma—further called ‘plasma-based multi-reforming’—allows us to better control the plasma chemistry and thus the formed products. To demonstrate this, we used chemical kinetics calculations supported by experiments and reveal that better control of the plasma chemistry can be achieved by adding O 2 or H 2 O to a mixture containing CH 4 and CO 2 (diluted in N 2 ). Moreover, by adding O 2 and H 2 O simultaneously, we can tune the plasma chemistry even further, improving the conversions, thermal efficiency and methanol yield. Unlike thermocatalytic reforming, plasma-based reforming is capable of producing methanol in a single step; and compared with traditional plasma-based dry reforming, plasma-based multi-reforming increases the methanol yield by more than seven times and the thermal efficiency by 49%, as revealed by our model calculations. Thus, we believe that by using plasma-based multi-reforming, ‘gas-to-liquid’ conversion may be made efficient and scalable.
Keywords: A1 Journal article; Engineering sciences. Technology; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 4.259
DOI: 10.1038/s41598-018-34359-x
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“Reduction of Human Glioblastoma Spheroids Using Cold Atmospheric Plasma: The Combined Effect of Short- and Long-Lived Reactive Species”. Privat-Maldonado A, Gorbanev Y, Dewilde S, Smits E, Bogaerts A, Cancers 10, 394 (2018). http://doi.org/10.3390/cancers10110394
Abstract: Cold atmospheric plasma (CAP) is a promising technology against multiple types of cancer. However, the current findings on the effect of CAP on two-dimensional glioblastoma cultures do not consider the role of the tumour microenvironment. The aim of this study was to determine the ability of CAP to reduce and control glioblastoma spheroid tumours in vitro . Three-dimensional glioblastoma spheroid tumours (U87-Red, U251-Red) were consecutively treated directly and indirectly with a CAP using dry He, He + 5% H 2 O or He + 20% H 2 O. The cytotoxicity and spheroid shrinkage were monitored using live imaging. The reactive oxygen and nitrogen species produced in phosphate buffered saline (PBS) were measured by electron paramagnetic resonance (EPR) and colourimetry. Cell migration was also assessed. Our results demonstrate that consecutive CAP treatments (He + 20% H 2 O) substantially shrank U87-Red spheroids and to a lesser degree, U251-Red spheroids. The cytotoxic effect was due to the short- and long-lived species delivered by CAP: they inhibited spheroid growth, reduced cell migration and decreased proliferation in CAP-treated spheroids. Direct treatments were more effective than indirect treatments, suggesting the importance of CAP-generated, short-lived species for the growth inhibition and cell cytotoxicity of solid glioblastoma tumours. We concluded that CAP treatment can effectively reduce glioblastoma tumour size and restrict cell migration, thus demonstrating the potential of CAP therapies for glioblastoma.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
DOI: 10.3390/cancers10110394
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“Impact of the Particle Diameter on Ion Cloud Formation from Gold Nanoparticles in ICPMS”. Fuchs J, Aghaei M, Schachel TD, Sperling M, Bogaerts A, Karst U, Analytical chemistry 90, 10271 (2018). http://doi.org/10.1021/acs.analchem.8b02007
Abstract: The unique capabilities of microsecond dwell time (DT) single-particle inductively coupled plasma mass spectrometry (spICPMS) were utilized to characterize the cloud of ions generated from the introduction of suspensions of gold nanoparticles (AuNPs) into the plasma. A set of narrowly distributed particles with diameters ranging from 15.4 to 100.1 nm was synthesized and characterized according to established protocols. Statistically significant numbers of the short transient spICPMS events were evaluated by using 50 μs DT for their summed intensity, maximum intensity, and duration, of which all three were found to depend on the particle diameter. The summed intensity increases from 10 to 1661 counts and the maximum intensity from 6 to 309 counts for AuNPs with diameters from 15.4 to 83.2 nm. The event duration rises from 322 to 1007 μs upon increasing AuNP diameter. These numbers represent a comprehensive set of key data points of the ion clouds generated in ICPMS from AuNPs. The extension of event duration is of high interest to appoint the maximum possible particle number concentration at which separation of consecutive events in spICPMS can still be achieved. Moreover, the combined evaluation of all above-mentioned ion cloud characteristics can explain the regularly observed prolonged single-particle events. The transport and ionization behavior of AuNPs in the ICP was also computationally modeled to gain insight into the size-dependent signal generation. The simulated data reveals that the plasma temperature, and therefore the point of ionization of the particles, is the same for all diameters. However, the maximum number density of Au+, as well as the extent of the ion cloud, depends on the particle diameter, in agreement with the experimental data, and it provides an adequate explanation for the observed ion cloud characteristics.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 6.32
Times cited: 5
DOI: 10.1021/acs.analchem.8b02007
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“Ammonia Synthesis by Radio Frequency Plasma Catalysis: Revealing the Underlying Mechanisms”. Shah J, Wang W, Bogaerts A, Carreon ML, ACS applied energy materials 1, 4824 (2018). http://doi.org/10.1021/acsaem.8b00898
Abstract: Nonthermal plasma is a promising alternative for ammonia synthesis at gentle conditions. Metal meshes of Fe, Cu, Pd, Ag, and Au were employed as catalysts in radio frequency plasma for ammonia synthesis. The energy yield for all these transition metal catalysts ranged between 0.12 and 0.19 g-NH3/kWh at 300 W and, thus, needs further improvement. In addition, a semimetal, pure gallium, was used for the first time as catalyst for ammonia synthesis, with energy yield of 0.22 g-NH3/kWh and with a maximum yield of ∼10% at 150 W. The emission spectra, as well as computer simulations, revealed hydrogen recombination as a primary governing parameter, which depends on the concentration or flux of H atoms in the plasma and on the catalyst surface. The simulations helped to elucidate the underlying mechanism, implicating the dominance of surface reactions and surface adsorbed species. The rate limiting step appears to be NH2 formation on the surface of the reactor wall and on the catalyst surface, which is different from classical catalysis.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
DOI: 10.1021/acsaem.8b00898
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“Novel power-to-syngas concept for plasma catalytic reforming coupled with water electrolysis”. Li K, Liu J-L, Li X-S, Lian H-Y, Zhu X, Bogaerts A, Zhu A-M, Chemical engineering journal 353, 297 (2018). http://doi.org/10.1016/j.cej.2018.07.111
Abstract: We propose a novel Power to Synthesis Gas (P2SG) approach, composed of two high-efficiency and renewable electricity-driven units, i.e., plasma catalytic reforming (PCR) and water electrolysis (WE), to produce high quality syngas from CH4, CO2 and H2O. As WE technology is already commercial, we mainly focus on the PCR unit, consisting of gliding arc plasma and Ni-based catalyst, for oxidative dry reforming of methane. An energy efficiency of 78.9% and energy cost of 1.0 kWh/Nm3 at a CH4 conversion of 99% and a CO2 conversion of 79% are obtained. Considering an energy efficiency of 80% for WE, the P2SG system yields an overall energy efficiency of 79.3% and energy cost of 1.8 kWh/Nm3. High-quality syngas is produced without the need for posttreatment units, featuring the ideal stoichiometric number of 2, with concentration of 94.6 vol%, and a desired CO2 fraction of 1.9 vol% for methanol synthesis. The PCR unit has the advantage of fast response to adapting to fluctuation of renewable electricity, avoiding local hot spots in the catalyst bed and coking, in contrast to conventional catalytic processes. Moreover, pure O2 from the WE unit is directly utilized by the PCR unit for oxidative dry reforming of methane, and thus, no air separation unit, like in conventional processes, is required. This work demonstrates the viability of the P2SG approach for large-scale energy storage of renewable electricity via electricity-to-fuel conversion.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 6.216
Times cited: 7
DOI: 10.1016/j.cej.2018.07.111
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“Analysis of Short-Lived Reactive Species in Plasma–Air–Water Systems: The Dos and the Do Nots”. Gorbanev Y, Privat-Maldonado A, Bogaerts A, Analytical Chemistry 90, 13151 (2018). http://doi.org/10.1021/acs.analchem.8b03336
Abstract: This Feature addresses the analysis of the reactive species generated by nonthermal atmospheric
pressure plasmas, which are widely employed in industrial and biomedical research, as well as first
clinical applications. We summarize the progress in detection of plasma-generated short-lived
reactive oxygen and nitrogen species in aqueous solutions, discuss the potential and limitations of
various analytical methods in plasma−liquid systems, and provide an outlook on the possible future
research goals in development of short-lived reactive species analysis methods for a general
nonspecialist audience.
Keywords: A1 Journal Article; Plasma, laser ablation and surface modeling Antwerp (PLASMANT) ;
Impact Factor: 6.32
Times cited: 17
DOI: 10.1021/acs.analchem.8b03336
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“Non‐Thermal Plasma as a Unique Delivery System of Short‐Lived Reactive Oxygen and Nitrogen Species for Immunogenic Cell Death in Melanoma Cells”. Lin A, Gorbanev Y, De Backer J, Van Loenhout J, Van Boxem W, Lemière F, Cos P, Dewilde S, Smits E, Bogaerts A, Advanced Science 6, 1802062 (2019). http://doi.org/10.1002/advs.201802062
Keywords: A1 Journal article; Engineering sciences. Technology; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT); Center for Oncological Research (CORE)
Impact Factor: 9.034
Times cited: 39
DOI: 10.1002/advs.201802062
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“Editorial Catalysts: Special Issue on Plasma Catalysis”. Bogaerts A, Catalysts 9, 196 (2019). http://doi.org/10.3390/catal9020196
Abstract: Plasma catalysis is gaining increasing interest for various gas conversion applications, such as CO2 conversion into value-added chemicals and fuels, N2 fixation for the synthesis of NH3 or NOx, and CH4 conversion into higher hydrocarbons or oxygenates [...]
Keywords: Editorial; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 3.082
Times cited: 1
DOI: 10.3390/catal9020196
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“Reaction of chloride anion with atomic oxygen in aqueous solutions: can cold plasma help in chemistry research?”.Gorbanev Y, Van der Paal J, Van Boxem W, Dewilde S, Bogaerts A, Physical chemistry, chemical physics 21, 4117 (2019). http://doi.org/10.1039/C8CP07550F
Abstract: Cold atmospheric plasma in contact with solutions has many applications, but its chemistry contains many unknowns such as the undescribed reactions with solutes. By combining experiments and modelling, we report the first direct demonstration of the reaction of chloride with oxygen atoms in aqueous solutions exposed to cold plasma.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 4.123
Times cited: 4
DOI: 10.1039/C8CP07550F
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“How process parameters and packing materials tune chemical equilibrium and kinetics in plasma-based CO2 conversion”. Uytdenhouwen Y, Bal Km, Michielsen I, Neyts Ec, Meynen V, Cool P, Bogaerts A, Chemical engineering journal 372, 1253 (2019). http://doi.org/10.1016/j.cej.2019.05.008
Abstract: Plasma (catalysis) reactors are increasingly being used for gas-based chemical conversions, providing an alternative method of energy delivery to the molecules. In this work we explore whether classical concepts such as
equilibrium constants, (overall) rate coefficients, and catalysis exist under plasma conditions. We specifically
investigate the existence of a so-called partial chemical equilibrium (PCE), and how process parameters and
packing properties influence this equilibrium, as well as the overall apparent rate coefficient, for CO2 splitting in
a DBD plasma reactor. The results show that a PCE can be reached, and that the position of the equilibrium, in
combination with the rate coefficient, greatly depends on the reactor parameters and operating conditions (i.e.,
power, pressure, and gap size). A higher power, higher pressure, or smaller gap size enhance both the equilibrium constant and the rate coefficient, although they cannot be independently tuned. Inserting a packing
material (non-porous SiO2 and ZrO2 spheres) in the reactor reveals interesting gap/material effects, where the
type of material dictates the position of the equilibrium and the rate (inhibition) independently. As a result, no
apparent synergistic effect or plasma-catalytic behaviour was observed for the non-porous packing materials
studied in this reaction. Within the investigated parameters, equilibrium conversions were obtained between 23
and 71%, while the rate coefficient varied between 0.027 s−1 and 0.17 s−1. This method of analysis can provide
a more fundamental insight in the overall reaction kinetics of (catalytic) plasma-based gas conversion, in order
to be able to distinguish plasma effects from true catalytic enhancement.
Keywords: A1 Journal article; Laboratory of adsorption and catalysis (LADCA); Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 6.216
Times cited: 3
DOI: 10.1016/j.cej.2019.05.008
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“Plasma for cancer treatment: How can RONS penetrate through the cell membrane? Answers from computer modeling”. Bogaerts A, Yusupov M, Razzokov J, Van der Paal J, Frontiers of Chemical Science and Engineering (2019). http://doi.org/10.1007/s11705-018-1786-8
Abstract: Plasma is gaining increasing interest for cancer
treatment, but the underlying mechanisms are not yet fully
understood. Using computer simulations at the molecular
level, we try to gain better insight in how plasma-generated
reactive oxygen and nitrogen species (RONS) can
penetrate through the cell membrane. Specifically, we
compare the permeability of various (hydrophilic and
hydrophobic) RONS across both oxidized and nonoxidized cell membranes. We also study pore formation,
and how it is hampered by higher concentrations of
cholesterol in the cell membrane, and we illustrate the
much higher permeability of H2O2 through aquaporin
channels. Both mechanisms may explain the selective
cytotoxic effect of plasma towards cancer cells. Finally, we
also discuss the synergistic effect of plasma-induced
oxidation and electric fields towards pore formation.
Keywords plasma medicine, cancer treatment, computer
modelling, cell membrane, reactive oxygen and nitrogen
species
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 1.712
Times cited: 5
DOI: 10.1007/s11705-018-1786-8
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“Combining CO2 conversion and N2 fixation in a gliding arc plasmatron”. Ramakers M, Heijkers S, Tytgat T, Lenaerts S, Bogaerts A, Journal of CO2 utilization 33, 121 (2019). http://doi.org/10.1016/j.jcou.2019.05.015
Abstract: Industry needs a flexible and efficient technology to convert CO2 into useful products, which fits in the Carbon Capture and Utilization (CCU) philosophy. Plasma technology is intensively being investigated for this purpose. A promising candidate is the gliding arc plasmatron (GAP). Waste streams of CO2 are often not pure and contain N2 as important impurity. Therefore, in this paper we provide a detailed experimental and computational study of the combined CO2 and N2 conversion in a GAP. Is it possible to take advantage of the presence of N2 in the mixture and to combine CO2 conversion with N2 fixation? Our experiments and simulations reveal that N2 actively contributes to the process of CO2 conversion, through its vibrational levels. In addition, NO and NO2 are formed, with concentrations around 7000 ppm, which is slightly too low for valorization, but by improving the reactor design it must be possible to further increase their concentrations. Other NO-based molecules, in particular the strong greenhouse gas N2O, are not formed in the GAP, which is an important result. We also compare our results with those obtained in other plasma reactors to clarify the differences in underlying plasma processes, and to demonstrate the superiority of the GAP.
Keywords: A1 Journal article; Engineering sciences. Technology; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT); Sustainable Energy, Air and Water Technology (DuEL)
Impact Factor: 4.292
Times cited: 3
DOI: 10.1016/j.jcou.2019.05.015
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“Nanosecond Pulsed Discharge for CO2Conversion: Kinetic Modeling To Elucidate the Chemistry and Improve the Performance”. Heijkers S, Martini LM, Dilecce G, Tosi P, Bogaerts A, The journal of physical chemistry: C : nanomaterials and interfaces 123, 12104 (2019). http://doi.org/10.1021/acs.jpcc.9b01543
Abstract: We study the mechanisms of CO2 conversion in a nanosecond repetitively pulsed (NRP) discharge, by means of a chemical kinetics model. The calculated conversions and energy efficiencies are in reasonable agreement with experimental results over a wide range of specific energy input values, and the same applies to the evolution of gas temperature and CO2 conversion as a function of time in the afterglow, indicating that our model provides a realistic picture of the underlying mechanisms in the NRP discharge and can be used to identify its limitations and thus to suggest further improvements. Our model predicts that vibrational excitation is very important in the NRP discharge, explaining why this type of plasma yields energy-efficient CO2 conversion. A significant part of the CO2 dissociation occurs by electronic excitation from the lower vibrational levels toward repulsive electronic states, thus resulting in dissociation. However, vibration−translation (VT) relaxation (depopulating the higher vibrational levels) and CO + O recombination (CO + O + M → CO2 + M), as well as mixing of the converted gas with fresh gas entering the plasma in between the pulses, are limiting factors for the conversion and energy efficiency. Our model predicts that extra cooling, slowing down the rate of VT relaxation and of the above recombination reaction, thus enhancing the contribution of the highest vibrational levels to the overall CO2 dissociation, can further improve the performance of the NRP discharge for energy-efficient CO2 conversion.
Keywords: A1 Journal article; Engineering sciences. Technology; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 4.536
Times cited: 4
DOI: 10.1021/acs.jpcc.9b01543
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“Transport of Reactive Oxygen and Nitrogen Species across Aquaporin: A Molecular Level Picture”. Yusupov M, Razzokov J, Cordeiro RM, Bogaerts A, Oxidative medicine and cellular longevity 2019, 1 (2019). http://doi.org/10.1155/2019/2930504
Abstract: Aquaporins (AQPs) are transmembrane proteins that conduct not only water molecules across the cell membrane but also other solutes, such as reactive oxygen and nitrogen species (RONS), produced (among others) by cold atmospheric plasma (CAP). These RONS may induce oxidative stress in the cell interior, which plays a role in cancer treatment. The underlying mechanisms of the transport of RONS across AQPs, however, still remain obscure. We apply molecular dynamics simulations to investigate the permeation of both hydrophilic (H<sub>2</sub>O<sub>2</sub>and OH) and hydrophobic (NO<sub>2</sub>and NO) RONS through AQP1. Our simulations show that these RONS can all penetrate across the pores of AQP1. The permeation free energy barrier of OH and NO is lower than that of H<sub>2</sub>O<sub>2</sub>and NO<sub>2</sub>, indicating that these radicals may have easier access to the pore interior and interact with the amino acid residues of AQP1. We also study the effect of RONS-induced oxidation of both the phospholipids and AQP1 (i.e., sulfenylation of Cys<sub>191</sub>) on the transport of the above-mentioned RONS across AQP1. Both lipid and protein oxidation seem to slightly increase the free energy barrier for H<sub>2</sub>O<sub>2</sub>and NO<sub>2</sub>permeation, while for OH and NO, we do not observe a strong effect of oxidation. The simulation results help to gain insight in the underlying mechanisms of the noticeable rise of CAP-induced RONS in cancer cells, thereby improving our understanding on the role of AQPs in the selective anticancer capacity of CAP.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 4.593
Times cited: 5
DOI: 10.1155/2019/2930504
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“Oxidation destabilizes toxic amyloid beta peptide aggregation”. Razzokov J, Yusupov M, Bogaerts A, Scientific reports 9, 5476 (2019). http://doi.org/10.1038/s41598-019-41931-6
Abstract: The aggregation of insoluble amyloid beta (Aβ) peptides in the brain is known to trigger the onset of neurodegenerative diseases, such as Alzheimer’s disease. In spite of the massive number of investigations, the underlying mechanisms to destabilize the Aβ aggregates are still poorly understood. Some studies indicate the importance of oxidation to destabilize the Aβ aggregates. In particular, oxidation induced by cold atmospheric plasma (CAP) has demonstrated promising results in eliminating these toxic aggregates. In this paper, we investigate the effect of oxidation on the stability of an Aβ pentamer. By means of molecular dynamics simulations and umbrella sampling, we elucidate the conformational changes of Aβ pentamer in the presence of oxidized residues, and we estimate the dissociation free energy of the terminal peptide out of the pentamer form. The calculated dissociation free energy of the terminal peptide is also found to decrease with increasing oxidation. This indicates that Aβ pentamer aggregation becomes less favorable upon oxidation. Our study contributes to a better insight in one of the potential mechanisms for inhibition of toxic Aβ peptide aggregation, which is considered to be the main culprit to Alzheimer’s disease.
Keywords: A1 Journal article; Engineering sciences. Technology; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 4.259
Times cited: 5
DOI: 10.1038/s41598-019-41931-6
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“Transport of cystine across xC-antiporter”. Ghasemitarei M, Yusupov M, Razzokov J, Shokri B, Bogaerts A, Archives of biochemistry and biophysics 664, 117 (2019). http://doi.org/10.1016/j.abb.2019.01.039
Abstract: Extracellular cystine (CYC) uptake by xC antiporter is important for the cell viability. Especially in cancer cells, the upregulation of xC activity is observed, which protects these cells from intracellular oxidative stress. Hence, inhibition of the CYC uptake may eventually lead to cancer cell death. Up to now, the molecular level mechanism of the CYC uptake by xC antiporter has not been studied in detail. In this study, we applied several different simulation techniques to investigate the transport of CYC through xCT, the light subunit of the xC antiporter, which is responsible for the CYC and glutamate translocation. Specifically, we studied the permeation of CYC across three model systems, i.e., outward facing (OF), occluded (OCC) and inward facing (IF) configurations of xCT. We also investigated the effect of mutation of Cys327 to Ala within xCT, which was also studied experimentally in literature. This allowed us to qualitatively compare our computation results with experimental observations, and thus, to validate our simulations. In summary, our simulations provide a molecular level mechanism of the transport of CYC across the xC antiporter, more specifically, which amino acid residues in the xC antiporter play a key role in the uptake, transport and release of CYC.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 3.165
Times cited: 3
DOI: 10.1016/j.abb.2019.01.039
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“Suppressing the formation of NOxand N2O in CO2/N2dielectric barrier discharge plasma by adding CH4: scavenger chemistry at work”. Snoeckx R, Van Wesenbeeck K, Lenaerts S, Cha MS, Bogaerts A, Sustainable Energy &, Fuels 3, 1388 (2019). http://doi.org/10.1039/C8SE00584B
Abstract: The need for carbon negative technologies led to the development of a wide array of novel CO<sub>2</sub>conversion techniques. Most of them either rely on high temperatures or generate highly reactive O species, which can lead to the undesirable formation of NO<sub>x</sub>and N<sub>2</sub>O when the CO<sub>2</sub>feeds contain N<sub>2</sub>. Here, we show that, for plasma-based CO<sub>2</sub>conversion, adding a hydrogen source, as a chemical oxygen scavenger, can suppress their formation,<italic>in situ</italic>. This allows the use of low-cost N<sub>2</sub>containing (industrial and direct air capture) feeds, rather than expensive purified CO<sub>2</sub>. To demonstrate this, we add CH<sub>4</sub>to a dielectric barrier discharge plasma used for converting impure CO<sub>2</sub>. We find that when adding a stoichiometric amount of CH<sub>4</sub>, 82% less NO<sub>2</sub>and 51% less NO are formed. An even higher reduction (96 and 63%) can be obtained when doubling this amount. However, in that case the excess radicals promote the formation of by-products, such as HCN, NH<sub>3</sub>and CH<sub>3</sub>OH. Thus, we believe that by using an appropriate amount of chemical scavengers, we can use impure CO<sub>2</sub>feeds, which would bring us closer to ‘real world’ conditions and implementation.
Keywords: A1 Journal article; Engineering sciences. Technology; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT); Sustainable Energy, Air and Water Technology (DuEL)
DOI: 10.1039/C8SE00584B
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“Perspectives of Plasma-treated Solutions as Anticancer Drugs”. Attri P, Bogaerts A, Anti-cancer agents in medicinal chemistry 19, 436 (2019). http://doi.org/10.2174/187152061904190521102345
Keywords: A1 Journal article; Pharmacology. Therapy; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 2.598
Times cited: 2
DOI: 10.2174/187152061904190521102345
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“Synergistic Effects of Melittin and Plasma Treatment: A Promising Approach for Cancer Therapy”. Shaw P, Kumar N, Hammerschmid D, Privat-Maldonado A, Dewilde S, Bogaerts A, Cancers 11, 1109 (2019). http://doi.org/10.3390/cancers11081109
Abstract: Melittin (MEL), a small peptide component of bee venom, has been reported to exhibit anti-cancer effects in vitro and in vivo. However, its clinical applicability is disputed because of its non-specific cytotoxicity and haemolytic activity in high treatment doses. Plasma-treated phosphate buffered saline solution (PT-PBS), a solution rich in reactive oxygen and nitrogen species (RONS) can disrupt the cell membrane integrity and induce cancer cell death through oxidative stress-mediated pathways. Thus, PT-PBS could be used in combination with MEL to facilitate its access into cancer cells and to reduce the required therapeutic dose. The aim of our study is to determine the reduction of the effective dose of MEL required to eliminate cancer cells by its combination with PT-PBS. For this purpose, we have optimised the MEL threshold concentration and tested the combined treatment of MEL and PT-PBS on A375 melanoma and MCF7 breast cancer cells, using in vitro, in ovo and in silico approaches. We investigated the cytotoxic effect of MEL and PT-PBS alone and in combination to reveal their synergistic cytological effects. To support the in vitro and in ovo experiments, we showed by computer simulations that plasma-induced oxidation of the phospholipid bilayer leads to a decrease of the free energy barrier for translocation of MEL in comparison with the non-oxidized bilayer, which also suggests a synergistic effect of MEL with plasma induced oxidation. Overall, our findings suggest that MEL in combination with PT-PBS can be a promising combinational therapy to circumvent the non-specific toxicity of MEL, which may help for clinical applicability in the future.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Times cited: 1
DOI: 10.3390/cancers11081109
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