Germination and Growth of Plasma-Treated Maize Seeds Planted in Fields and Exposed to Realistic Environmental Conditions.

In this study, we applied an inductively coupled, radio frequency oxygen plasma to maize seeds and investigated its effects on seedling emergence, plant number at tasseling, and crop yield of maize in realistic field conditions. Maize seeds of seven different hybrids were treated over two harvest years. In addition to plasma-treated seeds, a control sample, fungicide-treated seeds, an eco-layer, and a plasma and eco-layer combination, were planted. Seedling emergence, plant number at tasseling (plants/m2), and yield (kg/ha), were recorded. In the first harvest year, results were negatively affected by the presence of an insect pest. In the second harvest year, plant number and yield results were more uniform. In both years, for two and three hybrids, respectively, the highest yield arose from plants from plasma-treated seeds, but the differences were only partially significant. Considering our results, plasma treatment of maize seeds appears to have a positive effect on the yield of the plant.

A Method for the Immobilization of Chitosan onto Urinary Catheters.

A method for the immobilization of an antibacterial chitosan coating to polymeric urinary medical catheters is presented. The method comprises a two-step plasma-treatment procedure, followed by the deposition of chitosan from the water solution. In the first plasma step, the urinary catheter is treated with vacuum-ultraviolet radiation to break bonds in the polymer surface film and create dangling bonds, which are occupied by hydrogen atoms. In the second plasma step, polymeric catheters are treated with atomic oxygen to form oxygen-containing surface functional groups acting as binding sites for chitosan. The presence of oxygen functional groups also causes a transformation of the hydrophobic polymer surface to hydrophilic, thus enabling uniform wetting and improved adsorption of the chitosan coating. The wettability was measured by the sessile-drop method, while the surface composition and structure were measured by X-ray photoelectron spectroscopy and Fourier-transform infrared spectroscopy. Non-treated samples did not exhibit successful chitosan immobilization. The effect of plasma treatment on immobilization was explained by noncovalent interactions such as electrostatic interactions and hydrogen bonds.

Effect of Oxygen Plasma Treatment on Wheat Emergence and Yield in the Field.

This paper investigates the effects of an inductively coupled, radio frequency oxygen plasma on the plant emergence and crop yield of wheat in field growth conditions. Wheat seeds of eight different cultivars were plasma-treated using conditions selected based on preliminary experiments. Additionally, a control sample, as well as seeds treated with fungicide, an eco-layer, or a plasma + eco-layer combination, were planted in parallel. Four cultivars per harvest year were used. Plant emergence (plants/m2) and yield (kg/ha) were followed. There was little variation among the control and the various treatments regarding plant emergence. Regarding yield, there were statistically significant differences, but no discernible trend was seen when comparing the individual treatments. In the case of several cultivars, plasma-treated seeds performed as well as the control, but there was a significant increase in yield only in the case of cultivar 88.5 R. In several cases, yield of plants for plasma-treated seeds was also lower than the control. Our results demonstrate that the response of wheat yield to plasma treatment, as well as to other seed treatments, differs depending on the wheat cultivar.

Surface Modifications of Wheat Cultivar Bologna upon Treatment with Non-Equilibrium Gaseous Plasma.

Seeds of wheat cultivar Bologna were treated with a low-pressure, inductively coupled, radio frequency oxygen plasma. E-mode and H-mode plasma at the real powers of 25 and 275 W, respectively, was used at treatment times of 0.1-300 s. Plasma affected seed surface chemistry, determined by XPS, and surface topography, visualized by SEM. The combined effects of functionalization and etching modified seed surface wettability. The water contact angle (WCA) exponentially decreased with treatment time and correlated with the product of discharge power and treatment time well. Super-hydrophilicity was seen at a few 1000 Ws, and the necessary condition was over 35 at.% of surface oxygen. Wettability also correlated well with O-atom dose, where super-hydrophilicity was seen at 1024-1025 m-2. A relatively high germination percentage was seen, up to 1000 Ws (O-atom dose 1023-1024 m-2), while seed viability remained unaffected only up to about 100 Ws. Extensively long treatments decreased germination percentage and viability.

Biocompatibility and Mechanical Stability of Nanopatterned Titanium Films on Stainless Steel Vascular Stents.

Nanoporous ceramic coatings such as titania are promoted to produce drug-free cardiovascular stents with a low risk of in-stent restenosis (ISR) because of their selectivity towards vascular cell proliferation. The brittle coatings applied on stents are prone to cracking because they are subjected to plastic deformation during implantation. This study aims to overcome this problem by using a unique process without refraining from biocompatibility. Accordingly, a titanium film with 1 µm thickness was deposited on 316 LVM stainless-steel sheets using magnetron sputtering. Then, the samples were anodized to produce nanoporous oxide. The nanoporous oxide was removed by ultrasonication, leaving an approximately 500 nm metallic titanium layer with a nanopatterned surface. XPS studies revealed the presence of a 5 nm-thick TiO2 surface layer with a trace amount of fluorinated titanium on nanopatterned surfaces. Oxygen plasma treatment of the nanopatterned surface produced an additional 5 nm-thick fluoride-free oxide layer. The samples did not exhibit any cracking or spallation during plastic deformation. Cell viability studies showed that nanopatterned surfaces stimulate endothelial cell proliferation while reducing the proliferation of smooth muscle cells. Plasma treatment further accelerated the proliferation of endothelial cells. Activation of blood platelets did not occur on oxygen plasma-treated, fluoride-free nanopatterned surfaces. The presented surface treatment method can also be applied to other stent materials such as CoCr, nitinol, and orthopedic implants.

Approaches to Inactivating Aflatoxins-A Review and Challenges.

According to the World Health Organization, the contamination of crops with aflatoxins poses a significant economic burden, estimated to affect 25% of global food crops. In the event that the contaminated food is processed, aflatoxins enter the general food supply and can cause serious diseases. Aflatoxins are distributed unevenly in food or feedstock, making eradicating them both a scientific and a technological challenge. Cooking, freezing, or pressurizing have little effect on aflatoxins. While chemical methods degrade toxins on the surface of contaminated food, the destruction inside entails a slow process. Physical techniques, such as irradiation with ultraviolet photons, pulses of extensive white radiation, and gaseous plasma, are promising; yet, the exact mechanisms concerning how these techniques degrade aflatoxins require further study. Correlations between the efficiency of such degradation and the processing parameters used by various authors are presented in this review. The lack of appropriate guidance while interpreting the observed results is a huge scientific challenge.

Germination of Phaseolus vulgaris L. Seeds after a Short Treatment with a Powerful RF Plasma.

Seeds of common bean (Phaseolus vulgaris L.), of the Etna variety, were treated with low-pressure oxygen plasma sustained by an inductively coupled radiofrequency discharge in the H-mode for a few seconds. The high-intensity treatment improved seed health in regard to fungal contamination. Additionally, it increased the wettability of the bean seeds by altering surface chemistry, as established by X-ray photoelectron spectroscopy, and increasing surface roughness, as seen with a scanning electron microscope. The water contact angle at the seed surface dropped to immeasurably low values after a second of plasma treatment. Hydrophobic recovery within a month returned those values to no more than half of the original water contact angle, even for beans treated for the shortest time (0.5 s). Increased wettability resulted in accelerated water uptake. The treatment increased the bean radicle length, which is useful for seedling establishment in the field. These findings confirm that even a brief plasma treatment is a useful technique for the disinfection and stimulation of radicle growth. The technique is scalable to large systems due to the short treatment times.

Intracellular Responses Triggered by Cold Atmospheric Plasma and Plasma-Activated Media in Cancer Cells.

Cold atmospheric plasma (CAP), an ionized gas operating at room temperature, has been increasingly studied with respect to its potential use in medicine, where its beneficial effects on tumor reduction in oncology have been demonstrated. This review discusses the cellular changes appearing in cell membranes, cytoplasm, various organelles, and DNA content upon cells' direct or indirect exposure to CAP or CAP-activated media/solutions (PAM), respectively. In addition, the CAP/PAM impact on the main cellular processes of proliferation, migration, protein degradation and various forms of cell death is addressed, especially in light of CAP use in the oncology field of plasma medicine.

Cold atmospheric plasma induces stress granule formation via an eIF2α-dependent pathway.

Cold atmospheric plasma is an ionized gas that shows promise in regenerative medical treatments, yet the mechanisms underlying its effects are still poorly understood. Plasma treatment promotes cell growth or cell death depending on the cell type and exposure parameters. To date, no early cell response to plasma, such as stress granule (SG) formation has been addressed. Cytoplasmic SGs are formed as an immediate cell response to acute stress stimuli by recruitment of over 140 proteins intertwined with cytoplasmic RNAs that leads to transient suspension of protein translation. Encouraged by the plasma effects in regenerative medicine and oncology, the atmospheric pressure plasma jet with argon gas flow is being utilized to treat SH-SY5Y cells with an inducible expression of the stress granule marker G3BP1, to gain an insight into early cell response to plasma and SG formation dynamics. Plasma effectively induces SG formation in the exposed cells in a flow/time-dependent manner, with the SG assembly clearly prompted by plasma-induced oxidative stress. Plasma causes SG formation via eIF2α-signaling, which is repressed with the SG formation inhibitor ISRIB. This insight into the early cell response to plasma treatment may lead to improved therapies in regenerative medicine and cancer treatment.

Chemo-Radiative Stress of Plasma as a Modulator of Charge-Dependent Nanodiamond Cytotoxicity.

Efficient and selective internalization of nanoscale diamonds (also termed nanodiamonds, NDs) by living cells is of fundamental importance for their bionanotechnological applications. The biocompatibility of NDs is well established and has been suggested to arise from the limited membrane perturbation during their cellular translocation. However, the latter may be affected when cells are subjected to external stress. This study shows that the oxidative stress generated by atmospheric pressure cold plasmas (APCP) alters cell sensitivity to NDs, and their cytotoxicity profile. Both positively and negatively charged NDs are nontoxic to cells, here Saccharomyces cerevisiae and human cell lines, i.e., near-normal human mammary epithelial cells (MCF-10A) and breast cancer cells (MDA-MB-468 and T47D), unless the APCP stress is introduced. A brief exposure of the cells to APCP leads to a significant increase in their ND affinity (uptake and/or surface attachment) and intracellular ROS accumulation, particularly for positively charged NDs and both yeast and cancer cells. A concomitant decrease in cell viability and yeast cell growth, reflected by longer lag phases and lower cell density after 24 h of incubation, demonstrates a considerably enhanced ND toxicity to these cells. These results suggest that chemo-radiative stress, such as that produced by plasma, may influence the toxicity of nanoparticles to different cells, with specificity achieved through controlling particle charges. Moreover, since oxidative stress is not only associated with the use of APCP but can arise unintentionally within an organism and/or in the environment, these findings may have broader implications for the use of nontoxic nanoparticles in bionanotechnology in general.

Biocompatibility of Plasma-Treated Polymeric Implants.

Cardiovascular diseases are one of the main causes of mortality in the modern world. Scientist all around the world are trying to improve medical treatment, but the success of the treatment significantly depends on the stage of disease progression. In the last phase of disease, the treatment is possible only by implantation of artificial graft. Most commonly used materials for artificial grafts are polymer materials. Despite different industrial procedures for graft fabrication, their properties are still not optimal. Grafts with small diameters (<6 mm) are the most problematic, because the platelets are more likely to re-adhere. This causes thrombus formation. Recent findings indicate that platelet adhesion is primarily influenced by blood plasma proteins that adsorb to the surface immediately after contact of a synthetic material with blood. Fibrinogen is a key blood protein responsible for the mechanisms of activation, adhesion and aggregation of platelets. Plasma treatment is considered as one of the promising methods for improving hemocompatibility of synthetic materials. Another method is endothelialization of materials with Human Umbilical Vein Endothelial cells, thus forming a uniform layer of endothelial cells on the surface. Extensive literature review led to the conclusion that in this area, despite numerous studies there are no available standardized methods for testing the hemocompatibility of biomaterials. In this review paper, the most promising methods to gain biocompatibility of synthetic materials are reported; several hypotheses to explain the improvement in hemocompatibility of plasma treated polymer surfaces are proposed.

Improved fermentation efficiency of S. cerevisiae by changing glycolytic metabolic pathways with plasma agitation.

Production of ethanol by the yeast Saccharomyces cerevisiae is a process of global importance. In these processes, productivities and yields are pushed to their maximum possible values leading to cellular stress. Transient and lasting enhancements in tolerance and performance have been obtained by genetic engineering, forced evolution, and exposure to moderate levels of chemical and/or physical stimuli, yet the drawbacks of these methods include cost, and multi-step, complex and lengthy treatment protocols. Here, plasma agitation is shown to rapidly induce desirable phenotypic changes in S. cerevisiae after a single treatment, resulting in improved conversion of glucose to ethanol. With a complex environment rich in energetic electrons, highly-reactive chemical species, photons, and gas flow effects, plasma treatment simultaneously mimics exposure to multiple environmental stressors. A single treatment of up to 10 minutes performed using an atmospheric pressure plasma jet was sufficient to induce changes in cell membrane structure, and increased hexokinase 2 activity and secondary metabolite production. These results suggest that plasma treatment is a promising strategy that can contribute to improving metabolic activity in industrial microbial strains, and thus the practicality and economics of industrial fermentations.

Cell Proliferation on Polyethylene Terephthalate Treated in Plasma Created in SO2/O2 Mixtures.

Samples of polymer polyethylene terephthalate were exposed to a weakly ionized gaseous plasma to modify the polymer surface properties for better cell cultivation. The gases used for treatment were sulfur dioxide and oxygen of various partial pressures. Plasma was created by an electrodeless radio frequency discharge at a total pressure of 60 Pa. X-ray photoelectron spectroscopy showed weak functionalization of the samples' surfaces with the sulfur, with a concentration around 2.5 at %, whereas the oxygen concentration remained at the level of untreated samples, except when the gas mixture with oxygen concentration above 90% was used. Atomic force microscopy revealed highly altered morphology of plasma-treated samples; however, at high oxygen partial pressures this morphology vanished. The samples were then incubated with human umbilical vein endothelial cells. Biological tests to determine endothelialization and possible toxicity of the plasma-treated polyethylene terephthalate samples were performed. Cell metabolic activity (MTT) and in vitro toxic effects of unknown compounds (TOX) were assayed to determine the biocompatibility of the treated substrates. The biocompatibility demonstrated a well-pronounced maximum versus gas composition which correlated well with development of the surface morphology.

Microplasma Induced Cell Morphological Changes and Apoptosis of Ex Vivo Cultured Human Anterior Lens Epithelial Cells - Relevance to Capsular Opacification.

Inducing selective or targeted cell apoptosis without affecting large number of neighbouring cells remains a challenge. A plausible method for treatment of posterior capsular opacification (PCO) due to remaining lens epithelial cells (LECs) by reactive chemistry induced by localized single electrode microplasma discharge at top of a needle-like glass electrode with spot size ~3 µm is hereby presented. The focused and highly-localized atmospheric pressure microplasma jet with electrode discharge could induce a dose-dependent apoptosis in selected and targeted individual LECs, which could be confirmed by real-time monitoring of the morphological and structural changes at cellular level. Direct cell treatment with microplasma inside the medium appeared more effective in inducing apoptosis (caspase 8 positivity and DNA fragmentation) at a highly targeted cell level compared to treatment on top of the medium (indirect treatment). Our results show that single cell specific micropipette plasma can be used to selectively induce demise in LECs which remain in the capsular bag after cataract surgery and thus prevent their migration (CXCR4 positivity) to the posterior lens capsule and PCO formation.

Degradation of Albumin on Plasma-Treated Polystyrene by Soft X-ray Exposure.

Thin films of human serum albumin (HSA) were immobilized on polystyrene (PS) substrates previously functionalized either with polar or nonpolar functional groups. The functionalization was performed by treatment with cold gaseous plasma created in pure oxygen and tetrafluoromethane (CF4) plasmas, respectively. Samples were examined with soft X-rays in the photon energy range of 520 to 710 eV in the ANTARES beam line at SOLEIL Synchrotron. NEXAFS spectra of O K-edge and F K-edge were collected at different spots of the sample, and measurements at each spot were repeated many times. A strong degradation of the HSA protein was observed. The weakly irradiated samples exhibited strong absorption at 531.5 eV associated with the O 1s→π*amide transitions, and a broad non distinctive peak at 540 eV was attributed to the O 1s→σ*C⁻O transitions. Both peaks decreased with increasing irradiation time until they were completely replaced by a broad non-distinctive peak at around 532 eV, indicating the destruction of the original protein conformation. The shortage of the amide groups indicated breakage of the peptide bonds.

Effect of cold plasma on glial cell morphology studied by atomic force microscopy.

The atomic force microscope (AFM) is broadly used to study the morphology of cells. The morphological characteristics and differences of the cell membrane between normal human astrocytes and glial tumor cells are not well explored. Following treatment with cold atmospheric plasma, evaluation of the selective effect of plasma on cell viability of tumor cells is poorly understood and requires further evaluation. Using AFM we imaged morphology of glial cells before and after cold atmospheric plasma treatment. To look more closely at the effect of plasma on cell membrane, high resolution imaging was used. We report the differences between normal human astrocytes and human glioblastoma cells by considering the membrane surface details. Our data, obtained for the first time on these cells using atomic force microscopy, argue for an architectural feature on the cell membrane, i.e. brush layers, different in normal human astrocytes as compared to glioblastoma cells. The brush layer disappears from the cell membrane surface of normal E6/E7 cells and is maintained in the glioblastoma U87 cells after plasma treatment.

Oxygen-rich coating promotes binding of proteins and endothelialization of polyethylene terephthalate polymers.

The formation of endothelial cell monolayer on prosthetic implants has not sufficiently explored. The main reasons leading to the development of thrombosis and/or intimal hyperplasia is the lack of endothelialization. In the present work, we have studied the influence of oxygen and fluorine plasma treatment of polyethylene terephthalate (PET) polymers on human microvascular endothelial cell adhesion and proliferation. We characterized the polymer surface, wettability, and oxidation potential upon plasma treatment. Moreover, binding of serum and media compounds on PET surface was monitored by Quartz crystal microbalance method, X-ray photoelectron spectroscopy, and atomic force microscopy. Cell adhesion and morphology was assessed by light and scanning electron microscopy. The influence of plasma treatment on induction of cellular oxidative stress and cell proliferation was evaluated. The results obtained showed that treatment with oxygen plasma decreased the oxidation potential of the PET surface and revealed the highest affinity for binding of serum components. Accordingly, the cells reflected the best adhesion and morphological properties on oxygen-treated PET polymers. Moreover, treatment with oxygen plasma did not induce intracellular reactive oxygen species production while it stimulated endothelial cell proliferation by 25% suggesting the possible use of oxygen plasma treatment to enhance endothelialization of synthetic vascular grafts.

Protein adsorption on various plasma-treated polyethylene terephthalate substrates.

Protein adhesion and cell response to plasma-treated polymer surfaces were studied. The polymer polyethylene terephthalate (PET) was treated in either an oxygen plasma to make the surface hydrophilic, or a tetrafluoromethane CF(4) plasma to make the surface hydrophobic. The plasma source was radiofrequency (RF) discharge. The adsorption of albumin and other proteins from a cell-culture medium onto these surfaces was studied using a quartz crystal microbalance (QCM), X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). The cellular response to plasma-treated surfaces was studied as well using an MTT assay and scanning electron microscopy (SEM). The fastest adsorption rate was found on the hydrophilic oxygen plasma-treated sample, and the lowest was found on the pristine untreated sample. Additionally, the amount of adsorbed proteins was higher for the oxygen-plasma-treated surface, and the adsorbed layer was more viscoelastic. In addition, cell adhesion studies support this finding because the best cell adhesion was observed on oxygen-plasma-treated substrates.