“Advances in Plasma Oncology toward Clinical Translation”. Lin A, Stapelmann K, Bogaerts A, Cancers 12, 3283 (2020). http://doi.org/10.3390/cancers12113283
Abstract: This Special Issue on “Advances in Plasma Oncology Toward Clinical Translation” aims to bring together cutting-edge research papers within the field in the context of clinical translation and application [...]
Keywords: Editorial; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
DOI: 10.3390/cancers12113283
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“Physical Plasma-Treated Skin Cancer Cells Amplify Tumor Cytotoxicity of Human Natural Killer (NK) Cells”. Clemen R, Heirman P, Lin A, Bogaerts A, Bekeschus S, Cancers 12, 3575 (2020). http://doi.org/10.3390/cancers12123575
Abstract: Skin cancers have the highest prevalence of all human cancers, with the most lethal forms being squamous cell carcinoma and malignant melanoma. Besides the conventional local treatment approaches like surgery and radiotherapy, cold physical plasmas are emerging anticancer tools. Plasma technology is used as a therapeutic agent by generating reactive oxygen species (ROS). Evidence shows that inflammation and adaptive immunity are involved in cancer-reducing effects of plasma treatment, but the role of innate immune cells is still unclear. Natural killer (NK)-cells interact with target cells via activating and inhibiting surface receptors and kill in case of dominating activating signals. In this study, we investigated the effect of cold physical plasma (kINPen) on two skin cancer cell lines (A375 and A431), with non-malignant HaCaT keratinocytes as control, and identified a plasma treatment time-dependent toxicity that was more pronounced in the cancer cells. Plasma treatment also modulated the expression of activating and inhibiting receptors more profoundly in skin cancer cells compared to HaCaT cells, leading to significantly higher NK-cell killing rates in the tumor cells. Together with increased pro-inflammatory mediators such as IL-6 and IL-8, we conclude that plasma treatment spurs stress responses in skin cancer cells, eventually augmenting NK-cell activity.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
DOI: 10.3390/cancers12123575
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“Oxidation of Innate Immune Checkpoint CD47 on Cancer Cells with Non-Thermal Plasma”. Lin A, Razzokov J, Verswyvel H, Privat-Maldonado A, De Backer J, Yusupov M, Cardenas De La Hoz E, Ponsaerts P, Smits E, Bogaerts A, Cancers 13, 579 (2021). http://doi.org/10.3390/cancers13030579
Abstract: Non-thermal plasma (NTP) therapy has been emerging as a promising cancer treatment strategy, and recently, its ability to locally induce immunogenic cancer cell death is being unraveled. We hypothesized that the chemical species produced by NTP reduce immunosuppressive surface proteins and checkpoints that are overexpressed on cancerous cells. Here, 3D in vitro tumor models, an in vivo mouse model, and molecular dynamics simulations are used to investigate the effect of NTP on CD47, a key innate immune checkpoint. CD47 is immediately modulated after NTP treatment and simulations reveal the potential oxidized salt-bridges responsible for conformational changes. Umbrella sampling simulations of CD47 with its receptor, signal-regulatory protein alpha (SIRPα), demonstrate that the induced-conformational changes reduce its binding affinity. Taken together, this work provides new insight into fundamental, chemical NTP-cancer cell interaction mechanisms and a previously overlooked advantage of present NTP cancer therapy: reducing immunosuppressive signals on the surface of cancer cells.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT); Laboratory for Experimental Hematology (LEH); Center for Oncological Research (CORE)
DOI: 10.3390/cancers13030579
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“Cold Atmospheric Plasma Increases Temozolomide Sensitivity of Three-Dimensional Glioblastoma Spheroids via Oxidative Stress-Mediated DNA Damage”. Shaw P, Kumar N, Privat-Maldonado A, Smits E, Bogaerts A, Cancers 13, 1780 (2021). http://doi.org/10.3390/cancers13081780
Abstract: Glioblastoma multiforme (GBM) is the most frequent and aggressive primary malignant brain tumor in adults. Current standard radiotherapy and adjuvant chemotherapy with the alkylating agent temozolomide (TMZ) yield poor clinical outcome. This is due to the stem-like properties of tumor cells and genetic abnormalities in GBM, which contribute to resistance to TMZ and progression. In this study, we used cold atmospheric plasma (CAP) to enhance the sensitivity to TMZ through inhibition of antioxidant signaling (linked to TMZ resistance). We demonstrate that CAP indeed enhances the cytotoxicity of TMZ by targeting the antioxidant specific glutathione (GSH)/glutathione peroxidase 4 (GPX4) signaling. We optimized the threshold concentration of TMZ on five different GBM cell lines (U251, LN18, LN229, U87-MG and T98G). We combined TMZ with CAP and tested it on both TMZ-sensitive (U251, LN18 and LN229) and TMZ-resistant (U87-MG and T98G) cell lines using two-dimensional cell cultures. Subsequently, we used a three-dimensional spheroid model for the U251 (TMZ-sensitive) and U87-MG and T98G (TMZ-resistant) cells. The sensitivity of TMZ was enhanced, i.e., higher cytotoxicity and spheroid shrinkage was obtained when TMZ and CAP were administered together. We attribute the anticancer properties to the release of intracellular reactive oxygen species, through inhibiting the GSH/GPX4 antioxidant machinery, which can lead to DNA damage. Overall, our findings suggest that the combination of CAP with TMZ is a promising combination therapy to enhance the efficacy of TMZ towards the treatment of GBM spheroids.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT); Center for Oncological Research (CORE)
DOI: 10.3390/cancers13081780
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“Covalent Cysteine Targeting of Bruton’s Tyrosine Kinase (BTK) Family by Withaferin-A Reduces Survival of Glucocorticoid-Resistant Multiple Myeloma MM1 Cells”. Logie E, Chirumamilla CS, Perez-Novo C, Shaw P, Declerck K, Palagani A, Rangarajan S, Cuypers B, De Neuter N, Mobashar Hussain Urf Turabe F, Kumar Verma N, Bogaerts A, Laukens K, Offner F, Van Vlierberghe P, Van Ostade X, Berghe WV, Cancers 13, 1618 (2021). http://doi.org/10.3390/cancers13071618
Abstract: Multiple myeloma (MM) is a hematological malignancy characterized by plasma cells’ uncontrolled growth. The major barrier in treating MM is the occurrence of primary and acquired therapy resistance to anticancer drugs. Often, this therapy resistance is associated with constitutive hyperactivation of tyrosine kinase signaling. Novel covalent kinase inhibitors, such as the clinically approved BTK inhibitor ibrutinib (IBR) and the preclinical phytochemical withaferin A (WA), have, therefore, gained pharmaceutical interest. Remarkably, WA is more effective than IBR in killing BTK-overexpressing glucocorticoid (GC)-resistant MM1R cells. To further characterize the kinase inhibitor profiles of WA and IBR in GC-resistant MM cells, we applied phosphopeptidome- and transcriptome-specific tyrosine kinome profiling. In contrast to IBR, WA was found to reverse BTK overexpression in GC-resistant MM1R cells. Furthermore, WA-induced cell death involves covalent cysteine targeting of Hinge-6 domain type tyrosine kinases of the kinase cysteinome classification, including inhibition of the hyperactivated BTK. Covalent interaction between WA and BTK could further be confirmed by biotin-based affinity purification and confocal microscopy. Similarly, molecular modeling suggests WA preferably targets conserved cysteines in the Hinge-6 region of the kinase cysteinome classification, favoring inhibition of multiple B-cell receptors (BCR) family kinases. Altogether, we show that WA’s promiscuous inhibition of multiple BTK family tyrosine kinases represents a highly effective strategy to overcome GC-therapy resistance in MM.
Keywords: A1 Journal article; ADReM Data Lab (ADReM); Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
DOI: 10.3390/cancers13071618
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“Characterization of regulated cancer cell death pathways induced by the different modalities of non-thermal plasma treatment”. Biscop E, Baroen J, De Backer J, Vanden Berghe W, Smits E, Bogaerts A, Lin A, Cell Death Discovery 10, 416 (2024). http://doi.org/10.1038/s41420-024-02178-x
Abstract: Non-thermal plasma (NTP) has shown promising anti-cancer effects, but there is still limited knowledge about the underlying cell death mechanisms induced by NTP and inherent differences between NTP treatment modalities. This study aimed to investigate four major regulated cell death (RCD) pathways, namely apoptosis, pyroptosis, necroptosis, and ferroptosis, in melanoma cancer cells following NTP treatment, and to provide an overview of molecular mechanistic differences between direct and indirect NTP treatment modalities. To discriminate which cell death pathways were triggered after treatment, specific inhibitors of apoptosis, pyroptosis, necroptosis, and ferroptosis were evaluated. RCD-specific molecular pathways were further investigated to validate the findings with inhibitors. Both direct and indirect NTP treatment increased caspase 3/7 and annexin V expression, indicative of apoptosis, as well as lipid peroxidation, characteristic of ferroptosis. Pyroptosis, on the other hand, was only induced by direct NTP treatment, evidenced by increased caspase 1 activity, whereas necroptosis was stimulated in a cell line-dependent manner. These findings highlight the molecular differences and implications of direct and indirect NTP treatment for cancer therapy. Altogether, activation of multiple cell death pathways offers advantages in minimizing treatment resistance and enhancing therapeutic efficacy, particularly in a combination setting. Understanding the mechanisms underlying NTP-induced RCD will enable the development of strategic combination therapies targeting multiple pathways to achieve cancer lethality.
Keywords: A1 Journal Article; Plasma, laser ablation and surface modeling Antwerp (PLASMANT) ;
DOI: 10.1038/s41420-024-02178-x
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“Molecular evidence for feedstock-dependent nucleation mechanisms of CNTs”. Khalilov U, Vets C, Neyts EC, Nanoscale Horizons 4, 674 (2019). http://doi.org/10.1039/C8NH00323H
Abstract: Atomic scale simulations have been shown to be a powerful tool for elucidating the growth mechanisms of carbon nanotubes. The growth picture is however not entirely clear yet due to the gap between current simulations and real experiments. We here simulate for the first time the nucleation and subsequent growth of single-wall carbon nanotubes (SWNTs) from oxygen-containing hydrocarbon feedstocks using the hybrid Molecular Dynamics/Monte Carlo technique. The underlying nucleation mechanisms of Ni-catalysed SWNT growth are discussed in detail. Specifically, we find that as a function of the feedstock, different carbon fractions may emerge as the main growth species, due to a competition between the feedstock decomposition, its rehydroxylation and its contribution to etching of the growing SWNT. This study provides a further understanding of the feedstock effects in SWNT growth in comparison with available experimental evidence as well as with<italic>ab initio</italic>and other simulation data, thereby reducing the simulation–experiment gap.
Keywords: A1 Journal article; Engineering sciences. Technology; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Times cited: 1
DOI: 10.1039/C8NH00323H
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“Engineering the electronic properties of silicene by tuning the composition of MoX2 and GaX (X = S,Se,Te) chalchogenide templates”. Scalise E, Houssa M, Cinquanta E, Grazianetti C, van den Broek B, Pourtois G, Stesmans A, Fanciulli M, Molle A, 2D materials 1, 011010 (2014). http://doi.org/10.1088/2053-1583/1/1/011010
Abstract: By using first-principles simulations, we investigate the interaction of a 2D silicon layer with two classes of chalcogenide-layered compounds, namely MoX2 and GaX (X = S, Se, Te). A rather weak (van der Waals) interaction between the silicene layers and the chalcogenide layers is predicted. We found that the buckling of the silicene layer is correlated to the lattice mismatch between the silicene layer and the MoX2 or GaX template. The electronic properties of silicene on these different templates largely depend on the buckling of the silicene layer: highly buckled silicene on MoS2 is predicted to be metallic, while low buckled silicene on GaS and GaSe is predicted to be semi-metallic, with preserved Dirac cones at the K points. These results indicate new routes for artificially engineering silicene nanosheets, providing tailored electronic properties of this 2D layer on non-metallic substrates. These non-metallic templates also open the way to the possible integration of silicene in future nanoelectronic devices.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 6.937
Times cited: 49
DOI: 10.1088/2053-1583/1/1/011010
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“Two-dimensional hexagonal tin : ab initio geometry, stability, electronic structure and functionalization”. van den Broek B, Houssa M, Scalise E, Pourtois G, Afanas'ev VV, Stesmans A, 2D materials 1, 021004 (2014). http://doi.org/10.1088/2053-1583/1/2/021004
Abstract: We study the structural, mechanical and electronic properties of the two-dimensional (2D) allotrope of tin: tinene/stanene using first-principles calculation within density functional theory, implemented in a set of computer codes. Continuing the trend of the group-IV 2D materials graphene, silicene and germanene; tinene is predicted to have a honeycomb lattice with lattice parameter of a(0) = 4.62 angstrom and a buckling of d(0) = 0.92 angstrom. The electronic dispersion shows a Dirac cone with zero gap at the Fermi energy and a Fermi velocity of v(F) = 0.97 x 10(6) m s(-1); including spin-orbit coupling yields a bandgap of 0.10 eV. The monolayer is thermally stable up to 700 K, as indicated by first-principles molecular dynamics, and has a phonon dispersion without imaginary frequencies. We explore applied electric field and applied strain as functionalization mechanisms. Combining these two mechanisms allows for an induced bandgap up to 0.21 eV, whilst retaining the linear dispersion, albeit with degraded electronic transport parameters.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 6.937
Times cited: 58
DOI: 10.1088/2053-1583/1/2/021004
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“Functional silicene and stanene nanoribbons compared to graphene: electronic structure and transport”. van den Broek B, Houssa M, Iordanidou K, Pourtois G, Afanas'ev VV, Stesmans A, 2D materials 3, 015001 (2016). http://doi.org/10.1088/2053-1583/3/1/015001
Abstract: Since the advent of graphene, other 2D materials have garnered interest; notably the single element materials silicene, germanene, and stanene. Weinvestigate the ballistic current-voltage (I-V) characteristics of armchair silicene and stanene armchair nanoribbons (AXNRs with X = Si, Sn) using a combination of density functional theory and non-equilibrium Green's functions. The impact of out-of-plane electric field and in-plane uniaxial strain on the ribbon geometries, electronic structure, and (I-V)s are considered and contrasted with graphene. Since silicene and stanene are sp(2)/sp(3) buckled layers, the electronic structure can be tuned by an electric field that breaks the sublattice symmetry, an effect absent in graphene. This decreases the current by similar to 50% for Sn, since it has the largest buckling. Uniaxial straining of the ballistic channel affects the AXNR electronic structure in multiple ways: it changes the bandgap and associated effective carrier mass, and creates a local buckling distortion at the lead-channel interface which induces a interface dipole. Due to the increasing sp(3) hybridization character with increasing element mass, large reconstructions rectify the strained systems, an effect absent in sp(2) bonded graphene. This results in a smaller strain effect on the current: a decrease of 20% for Sn at 15% tensile strain compared to a similar to 75% decrease for C.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 6.937
Times cited: 19
DOI: 10.1088/2053-1583/3/1/015001
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“A route towards the fabrication of 2D heterostructures using atomic layer etching combined with selective conversion”. Heyne MH, Marinov D, Braithwaite N, Goodyear A, de Marneffe J-F, Cooke M, Radu I, Neyts EC, De Gendt S, 2D materials 6, 035030 (2019). http://doi.org/10.1088/2053-1583/AB1BA7
Abstract: Heterostructures of low-dimensional semiconducting materials, such as transition metal dichalcogenides (MX2), are promising building blocks for future electronic and optoelectronic devices. The patterning of one MX2 material on top of another one is challenging due to their structural similarity. This prevents an intrinsic etch stop when conventional anisotropic dry etching processes are used. An alternative approach consist in a two-step process, where a sacrificial silicon layer is pre-patterned with a low damage plasma process, stopping on the underlying MoS2 film. The pre-patterned layer is used as sacrificial template for the formation of the top WS2 film. This study describes the optimization of a cyclic Ar/Cl-2 atomic layer etch process applied to etch silicon on top of MoS2, with minimal damage, followed by a selective conversion of the patterned Si into WS2. The impact of the Si atomic layer etch towards the MoS2 is evaluated: in the ion energy range used for this study, MoS2 removal occurs in the over-etch step over 1-2 layers, leading to the appearance of MoOx but without significant lattice distortions to the remaining layers. The combination of Si atomic layer etch, on top of MoS2, and subsequent Si-to-WS2 selective conversion, allows to create a WS2/MoS2 heterostructure, with clear Raman signals and horizontal lattice alignment. These results demonstrate a scalable, transfer free method to achieve horizontally individually patterned heterostacks and open the route towards wafer-level processing of 2D materials.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 6.937
DOI: 10.1088/2053-1583/AB1BA7
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“Multilayer MoS2 growth by metal and metal oxide sulfurization”. Heyne MH, Chiappe D, Meersschaut J, Nuytten T, Conard T, Bender H, Huyghebaert C, Radu IP, Caymax M, de Marneffe JF, Neyts EC, De Gendt S;, Journal of materials chemistry C : materials for optical and electronic devices 4, 1295 (2016). http://doi.org/10.1039/c5tc04063a
Abstract: We investigated the deposition of MoS2 multilayers on large area substrates. The pre-deposition of metal or metal oxide with subsequent sulfurization is a promising technique to achieve layered films. We distinguish a different reaction behavior in metal oxide and metallic films and investigate the effect of the temperature, the H2S/H-2 gas mixture composition, and the role of the underlying substrate on the material quality. The results of the experiments suggest a MoS2 growth mechanism consisting of two subsequent process steps. At first, the reaction of the sulfur precursor with the metal or metal oxide occurs, requiring higher temperatures in the case of metallic film compared to metal oxide. At this stage, the basal planes assemble towards the diffusion direction of the reaction educts and products. After the sulfurization reaction, the material recrystallizes and the basal planes rearrange parallel to the substrate to minimize the surface energy. Therefore, substrates with low roughness show basal plane assembly parallel to the substrate. These results indicate that the substrate character has a significant impact on the assembly of low dimensional MoS2 films.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 5.256
DOI: 10.1039/c5tc04063a
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“The conversion mechanism of amorphous silicon to stoichiometric WS2”. Heyne MH, de Marneffe J-F, Nuytten T, Meersschaut J, Conard T, Caymax M, Radu I, Delabie A, Neyts EC, De Gendt S, Journal of materials chemistry C : materials for optical and electronic devices 6, 4122 (2018). http://doi.org/10.1039/C8TC00760H
Abstract: The deposition of ultra-thin tungsten films and their related 2D chalcogen compounds on large area dielectric substrates by gas phase reactions is challenging. The lack of nucleation sites complicates the adsorption of W-related precursors and subsequent sulfurization usually requires high temperatures. We propose here a technique in which a thin solid amorphous silicon film is used as reductant for the gas phase precursor WF6 leading to the conversion to metallic W. The selectivity of the W conversion towards the underlying dielectric surfaces is demonstrated. The role of the Si surface preparation, the conversion temperature, and Si thickness on the formation process is investigated. Further, the in situ conversion of the metallic tungsten into thin stoichiometric WS2 is achieved by a cyclic approach based on WF6 and H2S pulses at the moderate temperature of 450 1C, which is much lower than usual oxide sulfurization processes.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 5.256
Times cited: 4
DOI: 10.1039/C8TC00760H
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“Does non-thermal plasma modify biopolymers in solution? A chemical and mechanistic study for alginate”. Tampieri F, Espona-Noguera A, Labay C, Ginebra M-P, Yusupov M, Bogaerts A, Canal C, Biomaterials Science (2023). http://doi.org/10.1039/D3BM00212H
Abstract: In the last decades, non-thermal plasma has been extensively investigated as a relevant tool for various biomedical applications, ranging from tissue decontamination to regeneration and from skin treatment to tumor therapies. This high versatility is due to the different kinds and amount of reactive oxygen and nitrogen species that can be generated during a plasma treatment and put in contact with the biological target. Some recent studies report that solutions of biopolymers with the ability to generate hydrogels, when treated with plasma, can enhance the generation of reactive species and influence their stability, resulting thus in the ideal media for indirect treatments of biological targets. The direct effects of the plasma treatment on the structure of biopolymers in water solution, as well as the chemical mechanisms responsible for the enhanced generation of RONS, are not yet fully understood. In this study, we aim at filling this gap by investigating, on the one hand, the nature and extent of the modifications induced by plasma treatment in alginate solutions, and, on the other hand, at using this information to explain the mechanisms responsible for the enhanced generation of reactive species as a consequence of the treatment. The approach we use is twofold: (i) investigating the effects of plasma treatment on alginate solutions, by size exclusion chromatography, rheology and scanning electron microscopy and (ii) study of a molecular model (glucuronate) sharing its chemical structure, by chromatography coupled with mass spectrometry and by molecular dynamics simulations. Our results point out the active role of the biopolymer chemistry during direct plasma treatment. Short-lived reactive species, such as OH radicals and O atoms, can modify the polymer structure, affecting its functional groups and causing partial fragmentation. Some of these chemical modifications, like the generation of organic peroxide, are likely responsible for the secondary generation of long-lived reactive species such as hydrogen peroxide and nitrite ions. This is relevant in view of using biocompatible hydrogels as vehicles for storage and delivery reactive species for targeted therapies.
Keywords: A1 Journal Article; Plasma, laser ablation and surface modeling Antwerp (PLASMANT) ;
Impact Factor: 6.6
DOI: 10.1039/D3BM00212H
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“Plasma-based dry reforming : improving the conversion and energy efficiency in a dielectric barrier discharge”. Snoeckx R, Zeng YX, Tu X, Bogaerts A, RSC advances 5, 29799 (2015). http://doi.org/10.1039/C5RA01100K
Abstract: Dry reforming of methane has gained significant interest over the years. A novel reforming technique with great potential is plasma technology. One of its drawbacks, however, is energy consumption. Therefore, we performed an extensive computational study, supported by experiments, aiming to identify the influence of the operating parameters (gas mixture, power, residence time and frequency) of a dielectric barrier discharge plasma on the conversion and energy efficiency, and to investigate which of these parameters lead to the most promising results and whether these are eventually sufficient for industrial implementation. The best results, in terms of both energy efficiency and conversion, are obtained at a specific energy input (SEI) of 100 J cm−3, a 1090 CH4CO2 ratio, 10 Hz, a residence time of 1 ms, resulting in a total conversion of 84% and an energy efficiency of 8.5%. In general, increasing the CO2 content in the gas mixture leads to a higher conversion and energy efficiency. The SEI couples the effect of the power and residence time, and increasing the SEI always results in a higher conversion, but somewhat lower energy efficiencies. The effect of the frequency is more complicated: we observed that the product of frequency (f) and residence time (τ), being a measure for the total number of micro-discharge filaments which the gas molecules experience when passing through the reactor, was critical. For most cases, a higher number of filaments yields higher values for conversion and energy efficiency. To benchmark our model predictions, we also give an overview of measured conversions and energy efficiencies reported in the literature, to indicate the potential for improvement compared to the state-of-the art. Finally, we identify the limitations as well as the benefits and future possibilities of plasma technology.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 3.108
Times cited: 67
DOI: 10.1039/C5RA01100K
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“Sulfur-alloyed Cr2O3: a new p-type transparent conducting oxide host”. Dabaghmanesh S, Saniz R, Neyts E, Partoens B, RSC advances 7, 4453 (2017). http://doi.org/10.1039/C6RA27852C
Abstract: Doped Cr2O3 has been shown to be a p-type transparent conducting oxide (TCO). Its conductivity, however, is low. As for most p-type TCOs, the main problem is the high effective hole mass due to flat valence bands. We use first-principles methods to investigate whether one can increase the valence band dispersion (i.e. reduce the hole mass) by anion alloying with sulfur, while keeping the band gap large enough for transparency. The alloying concentrations considered are given by Cr(4)SxO(6-x), with x = 1-5. To be able to describe the electronic properties of these materials accurately, we first study Cr2O3, examining critically the accuracy of different density functionals and methods, including PBE, PBE+U, HSE06, as well as perturbative approaches within the GW approximation. Our results demonstrate that Cr4S2O4 has an optical band gap of 3.08 eV and an effective hole mass of 1.8 m(e). This suggests Cr4S2O4 as a new p-type TCO host candidate.
Keywords: A1 Journal article; Condensed Matter Theory (CMT); Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 3.108
Times cited: 9
DOI: 10.1039/C6RA27852C
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“Enhancement of cellular glucose uptake by reactive species: a promising approach for diabetes therapy”. Kumar N, Shaw P, Razzokov J, Yusupov M, Attri P, Uhm HS, Choi EH, Bogaerts A, RSC advances 8, 9887 (2018). http://doi.org/10.1039/C7RA13389H
Abstract: It is generally known that antidiabetic activity is associated with an increased level of glucose uptake in adipocytes and skeletal muscle cells. However, the role of exogenous reactive oxygen and nitrogen species (RONS) in muscle development and more importantly in glucose uptake is largely unknown. We investigate the effect of RONS generated by cold atmospheric plasma (CAP) in glucose uptake. We show that the glucose uptake is significantly enhanced in differentiated L6 skeletal muscle cells after CAP treatment. We also observe a significant increase of the intracellular Ca++ and ROS level, without causing toxicity. One of the possible reasons for an elevated level of glucose uptake as well as intracellular ROS and Ca++ ions is probably the increased oxidative stress leading to glucose transport.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 3.108
Times cited: 1
DOI: 10.1039/C7RA13389H
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“The role of WOx and dopants (ZrO₂, and SiO₂) on CeO₂-based nanostructure catalysts in the selective oxidation of benzyl alcohol to benzaldehyde under ambient conditions”. Bathula G, Rana S, Bandalla S, Dosarapu V, Mavurapu S, Rajeevan VVA, Sharma B, Jonnalagadda SB, Baithy M, Vasam CS, RSC advances 13, 36242 (2023). http://doi.org/10.1039/D3RA06828E
Abstract: Herein, the efficacy of WOx-promoted CeO2-SiO2 and CeO2-ZrO2 mixed oxide catalysts in the solvent-free selective oxidation of benzyl alcohol to benzaldehyde using molecular oxygen as an oxidant is reported. We evaluated the effects of the oxidant and catalyst concentration, reaction duration, and temperature on the reaction with an aim to optimize the reaction conditions. The as-prepared CeO2, CeO2-ZrO2, CeO2-SiO2, WOx/CeO2, WOx/CeO2-ZrO2, and WOx/CeO2-SiO2 catalysts were characterized by X-ray diffraction (XRD), N-2 adsorption-desorption, Raman spectroscopy, temperature-programmed desorption of ammonia (TPD-NH3), X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM). These characterisation results indicated that the WOx/CeO2-SiO2 catalyst possessed improved physicochemical (i.e., structural, textural, and acidic) properties owing to the strong interactivity between WOx and CeO2-SiO2. A higher number of Ce3+ ions (I-u '''/I-Total) were created with the WOx/CeO2-SiO2 catalyst than those with the other catalysts in this work, indicating the generation of a high number of oxygen vacancies. The WOx/CeO2-SiO2 catalyst exhibited a high conversion of benzyl alcohol (>99%) and a high selectivity (100%) toward benzaldehyde compared to the other promoted catalysts (i.e., WOx/CeO2 and WOx/CeO2-ZrO2), which is attributed to the smaller particle size of the WOx and CeO2 and their high specific surface area, more significant number of acidic sites, and superior number of oxygen vacancies. The WOx/CeO2-SiO2 catalyst could be quickly recovered and utilized at least five times without suffering any appreciable activity loss.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 3.9
DOI: 10.1039/D3RA06828E
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“A comparative study for the inactivation of multidrug resistance bacteria using dielectric barrier discharge and nano-second pulsed plasma”. Hoon Park J, Kumar N, Hoon Park D, Yusupov M, Neyts EC, Verlackt CCW, Bogaerts A, Ho Kang M, Sup Uhm H, Ha Choi E, Attri P;, Scientific reports 5, 13849 (2015). http://doi.org/10.1038/srep13849
Abstract: Bacteria can be inactivated through various physical and chemical means, and these have always been the focus of extensive research. To further improve the methodology for these ends, two types of plasma systems were investigated: nano-second pulsed plasma (NPP) as liquid discharge plasma and an Argon gas-feeding dielectric barrier discharge (Ar-DBD) as a form of surface plasma. To understand the sterilizing action of these two different plasma sources, we performed experiments with Staphylococcus aureus (S. aureus) bacteria (wild type) and multidrug resistant bacteria (Penicillum-resistant, Methicillin-resistant and Gentamicin-resistant). We observed that both plasma sources can inactivate both the wild type and multidrug-resistant bacteria to a good extent. Moreover, we observed a change in the surface morphology, gene expression and β-lactamase activity. Furthermore, we used X-ray photoelectron spectroscopy to investigate the variation in functional groups (C-H/C-C, C-OH and C=O) of the peptidoglycan (PG) resulting from exposure to plasma species. To obtain atomic scale insight in the plasma-cell interactions and support our experimental observations, we have performed molecular dynamics simulations to study the effects of plasma species, such as OH, H2O2, O, O3, as well as O2 and H2O, on the dissociation/formation of above mentioned functional groups in PG.
Keywords: A1 Journal article; Engineering sciences. Technology; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 4.259
Times cited: 32
DOI: 10.1038/srep13849
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“Structural modification of P-glycoprotein induced by OH radicals: Insights from atomistic simulations”. Khosravian N, Kamaraj B, Neyts EC, Bogaerts A, Scientific reports 6, 19466 (2016). http://doi.org/10.1038/srep19466
Abstract: This study reports on the possible effects of OH radical impact on the transmembrane domain 6 of P-glycoprotein, TM6, which plays a crucial role in drug binding in human cells. For the first time, we employ molecular dynamics (MD) simulations based on the self-consistent charge density functional tight binding (SCC-DFTB) method to elucidate the potential sites of fragmentation and mutation in this domain upon impact of OH radicals, and to obtain fundamental information about the underlying reaction mechanisms. Furthermore, we apply non-reactive MD simulations to investigate the long-term effect of this mutation, with possible implications for drug binding. Our simulations indicate that the interaction of OH radicals with TM6 might lead to the breaking of C-C and C-N peptide bonds, which eventually cause fragmentation of TM6. Moreover, according to our simulations, the OH radicals can yield mutation in the aromatic ring of phenylalanine in TM6, which in turn affects its structure. As TM6 plays an important role in the binding of a range of cytotoxic drugs with P-glycoprotein, any changes in its structure are likely to affect the response of the tumor cell in chemotherapy. This is crucial for cancer therapies based on reactive oxygen species, such as plasma treatment.
Keywords: A1 Journal article; Engineering sciences. Technology; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 4.259
Times cited: 7
DOI: 10.1038/srep19466
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“Mechanism and comparison of needle-type non-thermal direct and indirect atmospheric pressure plasma jets on the degradation of dyes”. Attri P, Yusupov M, Park JH, Lingamdinne LP, Koduru JR, Shiratani M, Choi EH, Bogaerts A, Scientific reports 6, 34419 (2016). http://doi.org/10.1038/srep34419
Abstract: Purified water supply for human use, agriculture and industry is the major global priority nowadays. The advanced oxidation process based on atmospheric pressure non-thermal plasma (NTP) has been used for purification of wastewater, although the underlying mechanisms of degradation of organic pollutants are still unknown. In this study we employ two needle-type atmospheric pressure non-thermal plasma jets, i.e., indirect (ID-APPJ) and direct (D-APPJ) jets operating at Ar feed gas, for the treatment of methylene blue, methyl orange and congo red dyes, for two different times (i.e., 20 min and 30 min). Specifically, we study the decolorization/degradation of all three dyes using the above mentioned plasma sources, by means of UV-Vis spectroscopy, HPLC and a density meter. We also employ mass spectroscopy to verify whether only decolorization or also degradation takes place after treatment of the dyes by the NTP jets. Additionally, we analyze the interaction of OH radicals with all three dyes using reactive molecular dynamics simulations, based on the density functional-tight binding method. This investigation represents the first report on the degradation of these three different dyes by two types of NTP setups, analyzed by various methods, and based on both experimental and computational studies.
Keywords: A1 Journal article; Engineering sciences. Technology; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 4.259
Times cited: 23
DOI: 10.1038/srep34419
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“Hampering Effect of Cholesterol on the Permeation of Reactive Oxygen Species through Phospholipids Bilayer: Possible Explanation for Plasma Cancer Selectivity”. Van der Paal J, Verheyen C, Neyts EC, Bogaerts A, Scientific reports 7, 39526 (2017). http://doi.org/10.1038/srep39526
Abstract: In recent years, the ability of cold atmospheric pressure plasmas (CAPS) to selectively induce cell death in cancer cells has been widely established. This selectivity has been assigned to the reactive oxygen and nitrogen species (RONS) created in CAPs. To provide new insights in the search for an explanation
for the observed selectivity, we calculate the transfer free energy of multiple ROS across membranes containing a varying amount of cholesterol. The cholesterol fraction is investigated as a selectivity parameter because membranes of cancer cells are known to contain lower fractions of cholesterol compared to healthy cells. We find that cholesterol has a significant effect on the permeation of
reactive species across a membrane. Indeed, depending on the specific reactive species, an increasing cholesterol fraction can lead to (i) an increase of the transfer free energy barrier height and width, (ii) the formation of a local free energy minimum in the center of the membrane and (iii) the creation of extra free energy barriers due to the bulky sterol rings. In the context of plasma oncology, these observations suggest that the increased ingress of RONS in cancer cells can be explained by the decreased cholesterol fraction of their cell membrane.
Keywords: A1 Journal article; Engineering sciences. Technology; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 4.259
Times cited: 27
DOI: 10.1038/srep39526
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“Effect of head group and lipid tail oxidation in the cell membrane revealed through integrated simulations and experiments”. Yusupov M, Wende K, Kupsch S, Neyts EC, Reuter S, Bogaerts A, Scientific reports 7, 5761 (2017). http://doi.org/10.1038/s41598-017-06412-8
Abstract: We report on multi-level atomistic simulations for the interaction of reactive oxygen species (ROS) with the head groups of the phospholipid bilayer, and the subsequent effect of head group and lipid tail oxidation on the structural and dynamic properties of the cell membrane. Our simulations are validated by experiments using a cold atmospheric plasma as external ROS source. We found that plasma treatment leads to a slight initial rise in membrane rigidity, followed by a strong and persistent increase in fluidity, indicating a drop in lipid order. The latter is also revealed by our simulations. This study is important for cancer treatment by therapies producing (extracellular) ROS, such as plasma treatment. These ROS will interact with the cell membrane, first oxidizing the head groups, followed by the lipid tails. A drop in lipid order might allow them to penetrate into the cell interior (e.g., through pores created due to oxidation of the lipid tails) and cause intracellular oxidative damage, eventually leading to cell death. This work in general elucidates the underlying mechanisms of ROS interaction with the cell membrane at the atomic level.
Keywords: A1 Journal article; Engineering sciences. Technology; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 4.259
Times cited: 27
DOI: 10.1038/s41598-017-06412-8
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“Anti-cancer capacity of plasma-treated PBS: effect of chemical composition on cancer cell cytotoxicity”. Van Boxem W, Van der Paal J, Gorbanev Y, Vanuytsel S, Smits E, Dewilde S, Bogaerts A, Scientific reports 7, 16478 (2017). http://doi.org/10.1038/s41598-017-16758-8
Abstract: We evaluate the anti-cancer capacity of plasma-treated PBS (pPBS), by measuring the concentrations of NO2 − and H2O2 in pPBS, treated with a plasma jet, for different values of gas flow rate, gap and plasma treatment time, as well as the effect of pPBS on cancer cell cytotoxicity, for three different glioblastoma cancer cell lines, at exactly the same plasma treatment conditions. Our experiments reveal that pPBS is cytotoxic for all conditions investigated. A small variation in gap between plasma jet and liquid surface (10 mm vs 15 mm) significantly affects the chemical composition of pPBS and its anti-cancer capacity, attributed to the occurrence of discharges onto the liquid. By correlating the effect of gap, gas flow rate and plasma treatment time on the chemical composition and anti-cancer capacity of pPBS, we may conclude that H2O2 is a more important species for the anti-cancer capacity of pPBS than NO2 −. We also used a 0D model, developed for plasma-liquid interactions, to elucidate the most important mechanisms for the generation of H2O2 and NO2 −. Finally, we found that pPBS might be more suitable for practical applications in a clinical setting than (commonly used) plasma-activated media (PAM), because of its higher stability.
Keywords: A1 Journal article; Engineering sciences. Technology; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 4.259
Times cited: 40
DOI: 10.1038/s41598-017-16758-8
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“Elucidation of plasma-induced chemical modifications on glutathione and glutathione disulphide”. Klinkhammer C, Verlackt C, Smilowicz D, Kogelheide F, Bogaerts A, Metzler-Nolte N, Stapelmann K, Havenith M, Lackmann J-W, Scientific reports 7, 13828 (2017). http://doi.org/10.1038/S41598-017-13041-8
Abstract: Cold atmospheric pressure plasmas are gaining increased interest in the medical sector and clinical trials to treat skin diseases are underway. Plasmas are capable of producing several reactive oxygen and nitrogen species (RONS). However, there are open questions how plasma-generated RONS interact on a molecular level in a biological environment, e.g. cells or cell components. The redox pair glutathione (GSH) and glutathione disulphide (GSSG) forms the most important redox buffer in organisms responsible for detoxification of intracellular reactive species. We apply Raman spectroscopy, mass spectrometry, and molecular dynamics simulations to identify the time-dependent chemical modifications on GSH and GSSG that are caused by dielectric barrier discharge under ambient conditions. We find GSSG, S-oxidised glutathione species, and S-nitrosoglutathione as oxidation products with the latter two being the final products, while glutathione sulphenic acid, glutathione sulphinic acid, and GSSG are rather reaction intermediates. Experiments using stabilized pH conditions revealed the same main oxidation products as were found in unbuffered solution, indicating that the dominant oxidative or nitrosative reactions are not influenced by acidic pH. For more complex systems these results indicate that too long treatment times can cause difficult-to-handle modifications to the cellular redox buffer which can impair proper cellular function.
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/S41598-017-13041-8
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“Chemical fingerprints of cold physical plasmas &ndash, an experimental and computational study using cysteine as tracer compound”. Lackmann J-W, Wende K, Verlackt C, Golda J, Volzke J, Kogelheide F, Held J, Bekeschus S, Bogaerts A, Schulz-von der Gathen V, Stapelmann K, Scientific reports 8, 7736 (2018). http://doi.org/10.1038/s41598-018-25937-0
Abstract: Reactive oxygen and nitrogen species released by cold physical plasma are being proposed as effectors in various clinical conditions connected to inflammatory processes. As these plasmas can be tailored in a wide range, models to compare and control their biochemical footprint are desired to infer on the molecular mechanisms underlying the observed effects and to enable the discrimination between different plasma sources. Here, an improved model to trace short-lived reactive species is presented. Using FTIR, high-resolution mass spectrometry, and molecular dynamics computational simulation, covalent modifications of cysteine treated with different plasmas were deciphered and the respective product pattern used to generate a fingerprint of each plasma source. Such, our experimental model allows a fast and reliable grading of the chemical potential of plasmas used for medical purposes. Major reaction products were identified to be cysteine sulfonic acid, cystine, and cysteine fragments. Less abundant products, such as oxidized cystine derivatives or S-nitrosylated cysteines, were unique to different plasma sources or operating conditions. The data collected point at hydroxyl radicals, atomic O, and singlet oxygen as major contributing species that enable an impact on cellular thiol groups when applying cold plasma in vitro or in vivo.
Keywords: A1 Journal article; Engineering sciences. Technology; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 4.259
Times cited: 19
DOI: 10.1038/s41598-018-25937-0
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“Molecular Insights into the Interaction of RONS and Thieno[3,2-c]pyran Analogs with SIRT6/COX-2: A Molecular Dynamics Study”. Yadav DK, Kumar S, Saloni, Misra S, Yadav L, Teli M, Sharma P, Chaudhary S, Kumar N, Choi EH, Kim HS, Kim M-hyun, Scientific reports 8, 4777 (2018). http://doi.org/10.1038/S41598-018-22972-9
Abstract: SIRT6 and COX-2 are oncogenes target that promote the expression of proinflammatory and pro-survival proteins through a signaling pathway, which leads to increased survival and proliferation of tumor cells. However, COX-2 also suppresses skin tumorigenesis and their relationship with SIRT6, making it an interesting target for the discovery of drugs with anti-inflammatory and anti-cancer properties. Herein, we studied the interaction of thieno[3,2-c] pyran analogs and RONS species with SIRT6 and COX-2 through the use of molecular docking and molecular dynamic simulations. Molecular docking studies revealed the importance of hydrophobic and hydrophilic amino acid residues for the stability. The molecular dynamics study examined conformational changes in the enzymes caused by the binding of the substrates and how those changes affected the stability of the protein-drug complex. The average RMSD values of the backbone atoms in compounds 6 and 10 were calculated from 1000 ps to 10000 ps and were found to be 0.13 nm for both compounds. Similarly, the radius of gyration values for compounds 6 and 10 were found to be 1.87 +/- 0.03 nm and 1.86 +/- 0.02 nm, respectively. The work presented here, will be of great help in lead identification and optimization for early drug discovery.
Keywords: A1 Journal article; Engineering sciences. Technology; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 4.259
Times cited: 10
DOI: 10.1038/S41598-018-22972-9
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“Study of an AC dielectric barrier single micro-discharge filament over a water film”. Vanraes P, Nikiforov A, Bogaerts A, Leys C, Scientific reports 8, 10919 (2018). http://doi.org/10.1038/s41598-018-29189-w
Abstract: In the last decades, AC powered atmospheric dielectric barrier discharges (DBDs) in air with a liquid electrode have been proposed as a promising plasma technology with versatile applicability in medicine agriculture and water treatment. The fundamental features of the micro-discharge filaments that make up this type of plasma have, however, not been studied yet in sufficient detail. In order to address this need, we investigated a single DBD micro-discharge filament over a water film in a sphere-to-sphere electrode configuration, by means of ICCD imaging and optical emission spectroscopy. When the water film temporarily acts as the cathode, the plasma duration is remarkably long and shows a clear similarity with a resistive barrier discharge, which we attribute to the resistive nature of the water film and the formation of a cathode fall. As another striking difference to DBD with solid electrodes, a constant glow-like plasma is observed at the water surface during the entire duration of the applied voltage cycle, indicating continuous plasma treatment of the liquid. We propose several elementary mechanisms that might underlie the observed unique behavior, based on the specific features of a water electrode.
Keywords: A1 Journal article; Engineering sciences. Technology; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 4.259
Times cited: 3
DOI: 10.1038/s41598-018-29189-w
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“CAP modifies the structure of a model protein from thermophilic bacteria: mechanisms of CAP-mediated inactivation”. Attri P, Han J, Choi S, Choi EH, Bogaerts A, Lee W, Scientific reports 8, 10218 (2018). http://doi.org/10.1038/s41598-018-28600-w
Abstract: Cold atmospheric plasma (CAP) has great potential for sterilization in the food industry, by deactivation of thermophilic bacteria, but the underlying mechanisms are largely unknown. Therefore, we investigate here whether CAP is able to denature/modify protein from thermophilic bacteria. We focus on MTH1880 (MTH) from Methanobacterium thermoautotrophicum as model protein, which we treated with dielectric barrier discharge (DBD) plasma operating in air for 10, 15 and 20 mins. We analysed the structural changes of MTH using circular dichroism, fluorescence and NMR spectroscopy, as well as the thermal and chemical denaturation, upon CAP treatment. Additionally, we performed molecular dynamics (MD) simulations to determine the stability, flexibility and solvent accessible surface area (SASA) of both the native and oxidised protein.
Keywords: A1 Journal article; Engineering sciences. Technology; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 4.259
Times cited: 6
DOI: 10.1038/s41598-018-28600-w
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“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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