The effectiveness of gliding arc discharge plasma in sterilizing artificial seawater contaminated with Vibrio parahaemolyticus.

The rapid proliferation of the halophilic pathogen Vibrio parahaemolyticus poses a severe health hazard to halobios and significantly impedes intensive mariculture. This study aimed to evaluate the potential application of gliding arc discharge plasma (GADP) to control the infection of Vibrio parahaemolyticus in mariculture. This study investigated the inactivation ability of GADP against Vibrio parahaemolyticus in artificial seawater (ASW), changes in the water quality of GADP-treated ASW, and possible inactivation mechanisms of GADP against Vibrio parahaemolyticus in ASW. The results indicate that GADP effectively inactivated Vibrio parahaemolyticus in ASW. As the volume of ASW increased, the time required for GADP sterilization also increased. However, the complete sterilization of 5000 mL of ASW containing Vibrio parahaemolyticus of approximately 1.0 × 104 CFU/mL was achieved within 20 min. Water quality tests of the GADP-treated ASW demonstrated that there were no significant changes in salinity or temperature when Vibrio parahaemolyticus (1.0 ×104 CFU/mL) was completely inactivated. In contrast to the acidification observed in plasma-activated water (PAW) in most studies, the pH of ASW did not decrease after treatment with GADP. The H2O2 concentration in the GADP-treated ASW decreased after post-treatment. The NO2-concentration in the GADP-treated ASW remained unchanged after post-treatment. Further analysis revealed that GADP induced oxidative stress in Vibrio parahaemolyticus, which increased cell membrane permeability and intracellular ROS levels of Vibrio parahaemolyticus. This study provides a viable solution for infection with the halophilic pathogen Vibrio parahaemolyticus and demonstrates the potential of GADP in mariculture.

Uncertainty Quantification and Sensitivity Analysis for the Electrical Impedance Spectroscopy of Changes to Intercellular Junctions Induced by Cold Atmospheric Plasma.

The influence of pertinent parameters of a Cole-Cole model in the impedimetric assessment of cell-monolayers was investigated with respect to the significance of their individual contribution. The analysis enables conclusions on characteristics, such as intercellular junctions. Especially cold atmospheric plasma (CAP) has been proven to influence intercellular junctions which may become a key factor in CAP-related biological effects. Therefore, the response of rat liver epithelial cells (WB-F344) and their malignant counterpart (WB-ras) was studied by electrical impedance spectroscopy (EIS). Cell monolayers before and after CAP treatment were analyzed. An uncertainty quantification (UQ) of Cole parameters revealed the frequency cut-off point between low and high frequency resistances. A sensitivity analysis (SA) showed that the Cole parameters, R0 and α were the most sensitive, while Rinf and τ were the least sensitive. The temporal development of major Cole parameters indicates that CAP induced reversible changes in intercellular junctions, but not significant changes in membrane permeability. Sustained changes of τ suggested that long-lived ROS, such as H2O2, might play an important role. The proposed analysis confirms that an inherent advantage of EIS is the real time observation for CAP-induced changes on intercellular junctions, with a label-free and in situ method manner.

Analysis of microstructural parameters of trabecular bone based on electrical impedance spectroscopy and deep neural networks.

The potential of electrical impedance spectroscopy (EIS) was demonstrated for the investigation of microstructural properties of osseous tissue. Therefore, a deep neural network (DNN) was implemented for a sensitive assessment of different structural features that were derived on the basis of dielectric parameters, especially relative permittivities, recorded over a frequency range from 40 Hz to 5 MHz. The advantages of the developed method over conventional approaches, including equivalent circuit models (ECMs), linear regression and effective medium approximation (EMA), is the comprehensive quantification of bone morphologies by several microstructural parameters simultaneously, such as bone volume fraction (BV/TV), bone surface-volume-ratio (BS/BV), structure model index (SMI), trabecular number (Tb.N) and trabecular thickness (Tb.Th). The comparison of predictions of the DNN with an analysis of µCT-images confirmed a high accuracy for different microstructural parameters, which was indicated by corresponding Pearson correlation coefficients, especially for Tb.Th (r = 0.89) and BS/BV (r = 0.80). Concurrently, the approach was able to unambiguously discriminate anatomically similar bone regions (femoral head, greater trochanter and femoral neck) and therefore was capable to determine the morphological status of osseous tissue in detail. The classification was more discriminative than one based on classical linear discriminant analysis (LDA), due to the distinguishing features extracted by the DNN model. Accordingly, the method and model can serve as a potential tool for evaluating bone quality and bone status.

Electrically Conductive and 3D-Printable Oxidized Alginate-Gelatin Polypyrrole:PSS Hydrogels for Tissue Engineering.

Electroactive hydrogels can be used to influence cell response and maturation by electrical stimulation. However, hydrogel formulations which are 3D printable, electroactive, cytocompatible, and allow cell adhesion, remain a challenge in the design of such stimuli-responsive biomaterials for tissue engineering. Here, a combination of pyrrole with a high gelatin-content oxidized alginate-gelatin (ADA-GEL) hydrogel is reported, offering 3D-printability of hydrogel precursors to prepare cytocompatible and electrically conductive hydrogel scaffolds. By oxidation of pyrrole, electroactive polypyrrole:polystyrenesulfonate (PPy:PSS) is synthesized inside the ADA-GEL matrix. The hydrogels are assessed regarding their electrical/mechanical properties, 3D-printability, and cytocompatibility. It is possible to prepare open-porous scaffolds via bioplotting which are electrically conductive and have a higher cell seeding efficiency in scaffold depth in comparison to flat 2D hydrogels, which is confirmed via multiphoton fluorescence microscopy. The formation of an interpenetrating polypyrrole matrix in the hydrogel matrix increases the conductivity and stiffness of the hydrogels, maintaining the capacity of the gels to promote cell adhesion and proliferation. The results demonstrate that a 3D-printable ADA-GEL can be rendered conductive (ADA-GEL-PPy:PSS), and that such hydrogel formulations have promise for cell therapies, in vitro cell culture, and electrical-stimulation assisted tissue engineering.

Toward a Quantitative Relationship between Nanoscale Spatial Organization and Hybridization Kinetics of Surface Immobilized Hairpin DNA Probes.

Hybridization of DNA probes immobilized on a solid support is a key process for DNA biosensors and microarrays. Although the surface environment is known to influence the kinetics of DNA hybridization, so far it has not been possible to quantitatively predict how hybridization kinetics is influenced by the complex interactions of the surface environment. Using spatial statistical analysis of probes and hybridized target molecules on a few electrochemical DNA (E-DNA) sensors, functioning through hybridization-induced conformational change of redox-tagged hairpin probes, we developed a phenomenological model that describes how the hybridization rates for single probe molecules are determined by the local environment. The predicted single-molecule rate constants, upon incorporation into numerical simulation, reproduced the overall kinetics of E-DNA sensor surfaces at different probe densities and different degrees of probe clustering. Our study showed that the nanoscale spatial organization is a major factor behind the counterintuitive trends in hybridization kinetics. It also highlights the importance of models that can account for heterogeneity in surface hybridization. The molecular level understanding of hybridization at surfaces and accurate prediction of hybridization kinetics may lead to new opportunities in development of more sensitive and reproducible DNA biosensors and microarrays.

Experimental Investigation of the Pressure Decay Characteristics of Oil Reservoirs after Fracturing Operations.

Field experience shows that extending shut-in periods are conducive to increasing tight oil production after fracturing operations. Understanding the regularity of pressure decay is helpful to establish an appropriate shut-in time. However, the characteristics and influencing factors of pressure decay are unclear. This paper studies the porosity, permeability, mineral composition, and pore structure of samples in six different blocks. The pressure decay regularity is tested according to an independently designed indoor shut-in experimental device, and the oil distribution of experimental samples is monitored using nuclear magnetic resonance technology. The results show that the fracturing fluid enters the matrix pores under the action of percolation to slowly drive out the oil, causing the well pressure to decay over time. There are three types of pressure decay characteristics: concave type, fluctuation type, and quadratic type. Compared with conventional sandstone, the pressure decay rate of tight reservoirs is slower, and the pressure decay characteristics are more complicated. Clay mineral-rich reservoirs will swell when exposed to water. As a result, the strength of the framework will be weakened and collapsed. What's more, it will cause blockage of the throat, blocking the flow of oil and the decay of pressure. In addition, the rate of pressure decay is also related to the volume of fracturing fluid, initial borehole pressure, and formation closure stress. At a certain proppant thickness (fracture width), the larger the fracturing fluid volume, the larger the fracture surface area and the faster the pressure decay rate; Moreover, the greater the initial shut-in pressure, the greater the pressure difference and the faster the decay rate; the formation closure stress causes the core porosity and the permeability to decrease, resulting in a decrease in the decay rate. The experimental results are of great significance for establishing a proper shut-in time and enhancing the oil recovery of tight reservoirs.

Application of bioimpedance spectroscopy to characterize chemoresistant tumor cell selectivity of nanosecond pulse stimulation.

The discriminating effects of nanosecond pulsed electric fields (nsPEFs) between chemoresistant tumor cells (CRTCs) and their respective homologous chemosensitive tumor cells (CSTCs) were investigated based on bioimpedance spectroscopy (BIS). The electrical properties of individual untreated cells were determined by fitting the impedance spectra to an equivalent circuit model and then using aided simulations to calculate the nuclear envelope transmembrane potential (nTMP) and electroporation area on the nuclear envelope. Additionally, fluorescence staining assays of cell monolayers after nanopulse stimulation (80 pulses, 200 ns, 3 kV) were conducted to validate the simulation results. The staining results indicated that CRTCs showed a larger ablation area and lower lethal threshold compared to CSTCs after exposure to the same nsPEF energy, which was in accordance with the higher nTMP and larger electroporation area calculated for CRTCs. The increase in the lethal effects of nsPEFs on CRTCs compared to CSTCs mainly resulted from the superposition of the changes in the electrical properties and nuclear size. The work shows that BIS can distinguish CRTCs and CSTCs and the corresponding nsPEF effects, suggesting potential applications for the optimization of novel anti-chemoresistance methods, including nsPEF-treatments.

Enhanced resolution impedimetric analysis of cell responses from the distribution of relaxation times.

A universal strategy for the sensitive investigation of cell responses to external stimuli, in particular nanosecond pulsed electric fields (nsPEFs), was developed based on electrical impedance spectroscopy (EIS) in combination with a multi-peak analysis for the distribution of relaxation times (DRT). The DRT method provides high resolution for the identification of different polarization processes without a priori assumptions, as they are needed by more conventional approaches, such as an evaluation by equivalent circuit models. Accordingly, the physical properties of cells and their changes due to external stimuli can be uncovered and visualized and dispersion mechanisms introduced by Schwan et al. clearly identified. These are in particular relaxation processes at about 100 kHz that are associated with cell membrane characteristics and dominating respective changes of the distribution function for epithelial cell monolayers after exposure. A relatively moderate evolution at about 10 kHz may represent the polarization of extracellular matrices. Relaxation processes at around 1 MHz were suggested to be associated with intracellular changes. Conversely, the distribution of relaxation times can aid the optimization of the experimental design with respect to intended responses by an external stimulus.

Bioimpedance Analysis of Epithelial Monolayers after Exposure to Nanosecond Pulsed Electric Fields.

Exposures to pulsed electric fields (PEFs) are known to affect cell membranes and consequently also cell-cell interactions as well as associated characteristics. Bioimpedance analysis offers direct and non-invasive insights into structural and functional changes of cell membranes and extracellular matrices through a rigorous evaluation of electrical parameters. Accordingly, the multi-frequency impedance of confluent monolayers of rat liver epithelial WB-F344 cells was monitored in situ before and after exposure to nanosecond PEFs (nsPEFs). The results were fitted by two Cole models in series to obtain the Cole parameters for the monolayer. For an interpretation of the results, dielectric parameters, were correlated with changes of the TJ protein zonula occludens (ZO-1) and the paracellular permeability of the monolayer Cole parameters in general change as a function of pulse number and time. The findings demonstrate that impedance analysis is an effective method to monitor changes of TJs cell-cell contacts and paracellular permeability and relate them to exposure parameters.