Quantification of pulsed electric field for the rupture of giant vesicles with various surface charges, cholesterols and osmotic pressures

Electropermeabilization is a promising phenomenon that occurs when pulsed electric field with high frequency is applied to cells/vesicles. We quantify the required values of pulsed electric fields for the rupture of cell-sized giant unilamellar vesicles (GUVs) which are prepared under various surface charges, cholesterol contents and osmotic pressures. The probability of rupture and the average time of rupture are evaluated under these conditions. The electric field changes from 500 to 410 Vcm-1 by varying the anionic lipid mole fraction from 0 to 0.60 for getting the maximum probability of rupture (i.e., 1.0). In contrast, the same probability of rupture is obtained for changing the electric field from 410 to 630 Vcm-1 by varying the cholesterol mole fraction in the membranes from 0 to 0.40. These results suggest that the required electric field for the rupture decreases with the increase of surface charge density but increases with the increase of cholesterol. We also quantify the electric field for the rupture of GUVs containing anionic mole fraction of 0.40 under various osmotic pressures. In the absence of osmotic pressure, the electric field for the rupture is obtained 430 Vcm-1, whereas the field is 300 Vcm-1 in the presence of 17 mOsmL-1, indicating the instability of GUVs at higher osmotic pressures. These investigations open an avenue of possibilities for finding the electric field dependent rupture of cell-like vesicles along with the insight of biophysical and biochemical processes.

Influence of Functional Group Modification on the Toxicity of Nanoplastics

Nanoplastics (NPs) are ubiquitous in harvested organisms at various trophic levels, and more concerns on their diverse responses and wide species-dependent sensitivity are continuously increasing. However, systematic study on the toxic effects of NPs with different functional group modifications is still limited. In this review, we gathered and analyzed the toxic effects of NPs with different functional groups on microorganisms, plants, animals, and mammalian/human cells in vitro. The corresponding toxic mechanisms were also described. In general, most up-to-date relevant studies focus on amino (−NH2) or carboxyl (−COOH)-modified polystyrene (PS) NPs, while research on other materials and functional groups is lacking. Positively charged PS-NH2 NPs induced stronger toxicity than negatively charged PS-COOH. Plausible toxicity mechanisms mainly include membrane interaction and disruption, reactive oxygen species generation, and protein corona and eco-corona formations, and they were influenced by surface charges of NPs. The effects of NPs in the long-term exposure and in the real environment world also warrant further study.

Effect of Permittivity on the Electric-Field-Driven Rotation Dynamics in a Liquid Film

Applying a constant electric field on a suspended film of liquid that carries an electric current, either by the transport of ions or surface charges, induces a rotation in the film. This system is known as “liquid film motor”. So far, the effect of permittivity of the liquid on its rotation has been ignored. We showed that the permittivity of the liquid can significantly affect the dynamics of rotation. Using an experimental approach, we studied the liquid film rotation for a broad range of pure liquids with diverse permittivities and surface tensions. We observed two different regimes of rotation depending on the permittivity of the liquids. We also found that there is no correlation between the surface tension of the liquid and the angular velocity of the rotation. We considered a theoretical framework and suggested scenarios to explain our experimental observations. These results help in better understanding the physics of liquid film motors and suggest opportunities for new flow manipulation techniques at small scales.

Biochemistry Behind Protein Adaptations in Extremophiles

Extremophiles are the mortals that tolerate in the most limiting and aggravating conditions to life. Because of these fantastic ecological criticisms, extremophiles have substituted innumerable intriguing transformations to cell films, proteins, and extracellular metabolites. These stimulatingly regulated usual particles and frameworks as of now play parts in numerous biotechnological fields. Compounds from extremophilic microorganisms as a rule catalyse synthetic responses in non-standard conditions. Such conditions advance accumulation, precipitation, and denaturation, diminishing the movement of most non-extremophilic catalysts, regularly because of the shortfall of adequate hydration. Extremophilic catalysts can go after hydration by means of modifications particularly to their surface through more noteworthy surface charges and expanded sub-atomic movement. These assets have permitted few extremophilic compounds to work within the sight of non-fluid natural solvents, with potential for plan of valuable impetuses.

Gold-Polymer Nanocomposites for Future Therapeutic and Tissue Engineering Applications

Gold nanoparticles (AuNPs) have been extensively investigated for their use in various biomedical applications. Owing to their biocompatibility, simple surface modifications, and electrical and unique optical properties, AuNPs are considered promising nanomaterials for use in in vitro disease diagnosis, in vivo imaging, drug delivery, and tissue engineering applications. The functionality of AuNPs may be further expanded by producing hybrid nanocomposites with polymers that provide additional functions, responsiveness, and improved biocompatibility. Polymers may deliver large quantities of drugs or genes in therapeutic applications. A polymer alters the surface charges of AuNPs to improve or modulate cellular uptake efficiency and their biodistribution in the body. Furthermore, designing the functionality of nanocomposites to respond to an endo- or exogenous stimulus, such as pH, enzymes, or light, may facilitate the development of novel therapeutic applications. In this review, we focus on the recent progress in the use of AuNPs and Au-polymer nanocomposites in therapeutic applications such as drug or gene delivery, photothermal therapy, and tissue engineering.

Metal-wire-embedded alumina insulating material using micro and nanoscale 3D printing for surface flashover mitigation in vacuum

Micro and nanoscale 3D printing technic is applied to fabricate functional insulating material which mitigates surface discharge in vacuum based on the microscopic electron multipactor suppression. The proposed alumina ceramic insulator design consists surface-embedded thin metal wires which introduce a local gradient of secondary electron emission yield, such that the trajectories of multipactor electrons are distorted by accumulated negative surface charges and the secondary electron emission avalanche across the insulator surface is intermitted. Considerable increases of surface flashover threshold and surface charging reduction are verified by experiment. Also, additional efforts are made to determine the optimal size and spatial distribution of the metal wire. A convex-shape flashover voltage trace is observed when increasing the wire width, suggesting a trade-off between the multipactor mitigation and the insulator strength. Wire position between the adjacency of cathode triple junction and middle of the insulator is proved to be favorable for flashover mitigation. The physical details of surface flashover mitigation by the proposed insulator design are revealed by an ab initio particle-in-cell (PIC) simulation code, corroborating the experiment from microscopic aspect.

Manganese Assisted Waterflooding Processes for Enhanced Oil Recovery in Carbonates

Modifying the wettability of carbonate formations through divalent foreign metal incorporation can become a cost-effective practical method for enhanced oil recovery (EOR) applications. The addition of manganese ions to both high salinity water (HSW) and tailored SmartWater at dilute concentrations is exploited in this study to maximize the interfacial potential and promote water-wet conditions in carbonate reservoirs. In this experimental investigation, the impact of manganese ions on zeta-potentials at calcite/brine and crude oil/brine interfaces is first determined by measuring zeta-potentials in calcite suspensions and oil emulsions. Two different water chemistries representative of HSW (~60,000 ppm TDS) and a low salinity tailored SmartWater (~6,000 ppm TDS) were used. The measurements were then extended to carbonate rocks and reservoir cores by performing contact angle and spontaneous imbibition tests at reservoir conditions. The oil-water interfacial tensions are also measured to understand the interactions of manganese ions at the oil/brine interface. The zeta potential results showed a positive consistent trend, with the addition of 100-1,000 ppm of Mn+2 ions in the form of MnSO4 to the high salinity water, to impact the wetting transition towards water-wet conditions in carbonates. The addition of Mn+2 ions at a concentration of 100-1,000 ppm to HSW enhanced the electrokinetic interactions to favorably alter surface charges at both oil/brine and calcite/brine interfaces. These findings based on eletrokinetic interactions demonstrated good agreement with contact angle data wherein manganese ions in HSW were able to drastically decrease the contact angles from 156 to 88°. Conversely, insignificant changes in oil-water interfacial tensions were observed due to manganese ions. The manganese assisted spontaneous imbibition oil recoveries were increased by about 10% in HSW. Mn+2 ions showed the ability to increase the negative potentials at both calcite/brine and oil/brine interfaces. The obvious trend of such enhanced electrical potential due to Mn+2 addition at the calcite interface supports the claim that Mn+2 selectively gets incorporated into the calcite crystal to modify its surface chemistry. This is expected to increase the surface charges of same polarity at the two opposing interfaces and promote the electrostatic repulsion to inherently change the surface preference towards water-wet conditions. This work for the first time identified the favorable impact of incorporating Mn+2 ions under optimized conditions to enhance the wetting transition in carbonate reservoirs. Such new knowledge gained from this experimental study highlights the practical significance of Mn+2 ions as cheap and sustainable wettability modifiers for EOR applications in carbonate reservoirs.

Enhanced Antibacterial and Antioxidant Properties of Chitosan Films Blended with Gallic Acid and Incorporated with Thymol Silver Nanoparticles

In the present study, an attempt has been made to build and evaluate Chitosan+Glycerol/Gallic acid/Thymol-silver nanoparticles or chitosan blended (C+G/GA/T-SNPs) film to significantly improve antioxidant and antibacterial activity for accelerated wound healing. Methanolic Gallic acid is used for the first time in antibacterial chitosan control (C+G) films. All developed films, compounds was Thymol and Gallic acid and their synthesized Thymol silver nanoparticles (T-SNPs) and Gallic acid silver nanoparticles (GA-SNPs) were characterized by Fourier-transform infrared spectroscopy (FT-IR), Scanning electron microscopy (SEM), X-Ray diffraction (XRD), Zeta potential (ZP), Dynamic light scattering (DLS), and UV-Vis spectroscopy. T-SNPs and GA-SNPs are rod and spherical in shape and were sufficient to reduce, capped, and stabilize. T-SNPs and GA-SNPs were measured Dynamic Light scattering and found to be 123.2 nm and 121.1 nm with surface charges of -19.7 and -20.3 respectively. The incorporation of methanolic Gallic acid and T-SNPs into chitosan films, as predicted, effectively enhanced antioxidant and antimicrobial activity. The antimicrobial activity of Thymol, T-SNPs and C+G/GA/T-SNPs film showed more zone of inhibition than Gallic acid, GA-SNPs and C+G film. The elasticity, texture and folding endurance of the C+G film and C+G/GA/T-SNPs films have been substantially improved. The ecological quality of the generated C+G and C+G/GA/T-SNPs film was determined by the assessment of soil degradation and water degradation parameters. These findings lead to the conclusion that the C+G/GA/T-SNPs film produced with Gallic acid and T-SNPs can improve wound healing. Keywords: Chitosan, Gallic Acid, Thymol Silver Nanoparticles, Antibacterial and Antioxidant Properties.

Study and Optimization of Field Limiting Rings for 10kV SiC Insulated Gate Bipolar Transistor

A 10kV-level silicon carbide (SiC) insulated gate bipolar transistor (IGBT) with field limiting rings (FLRs) is designed and simulated with Sentaurus TCAD, the detailed optimization method and comparisons are presented in this paper. Linearly varying spacing between rings is introduced to SiC IGBT and adjustment is performed on width of rings, the final structure achieves a breakdown voltage over 12kV with a termination length of 164.5 µm , which is 69.93% lower than that of conventional structure with a fixed ring spacing. Moreover, the final design can decrease the sensitivity to the interface charges, the tolerance to positive surface charges exceeds 8 × 10 11 cm − 2 , which is 3.5 times that of the conventional structure. Besides, double pulse measurements prove no degradation of conduction and switching characteristics.

Distribution and evolution of surface charge in surface dielectric barrier discharge driven by AC and pulse dual power supply

The evolution of surface charge in surface dielectric barrier discharge (SDBD) is observed by using Pockels effect. SDBD is driven by sine AC and pulse dual-power supply voltage. The filamentary discharge and glow-like discharge are enhanced by superimposing positive pulse on sine trough and negative pulse on sine crest, respectively. The interval of enhanced discharge is adjusted by pulse repetition rate (PRF). The formation and decay of surface charges are analyzed at low PRF, and the accumulation effect is analyzed at high PRF. The results showed that the decay rates of charges decrease with increasing distance from the exposed electrode. When a positive pulse is superimposed on sine trough, the traces of positive charges are filaments with long extending lengths, which are the footprints of discharge channels. The lifetime of positive charges is hundreds of AC cycles (tens of milliseconds). Under certain conditions, subsequent glow-like discharge evolves as “flying” above the dielectric surface (3D propagation). Most of the negative charges are neutralized in subsequent filamentary discharge. Some negative charges accumulate downstream and exist longer than positive charges. In the case of negative pulses superimposed on sine crest, the enhanced glow-like discharge appears 3D propagation. The propagation distance is much smaller than that of positive pulse. Most of the negative charges are uniformly distributed near the exposed electrodes with a short lifetime (a few hundred microseconds) and are quickly neutralized in subsequent discharges. The occurrence of 3D propagation requires certain conditions and the mechanism needs further research.