Changes In Electrical Impedance Research Articles

Phosphorylation-amplified synchronized droplet microfluidics sensitizes bacterial growth kinetic real-time monitoring

The necessity for rapid and accurate bacterial growth monitoring is imperative across various domains, including healthcare and environmental safety. We introduce the self-synchronized droplet-amplified electrical screening cytometry (SYNC) system, a novel meld of droplet microfluidics and electrochemical amplification tailored for precise bacterial growth kinetic monitoring. SYNC encapsulates single bacteria in picolitre droplets, enabling real-time, fluorescence-free electrochemical monitoring. A specially devised phosphorylation-amplified culture medium translates bacterial metabolic activity into discernible electrical impedance changes. The dual-channel design and a rail-based structure in SYNC facilitate parallel screening and self-synchronization of droplets, addressing the limitations of conventional impedance cytometry. SYNC showcases a 5-fold enhancement in detection sensitivity and reduces 50% of the detection time compared to traditional approaches. Notably, SYNC is pioneering in providing exact initial bacterial concentrations, achieve to 104 bacteria/ml, a capability unmatched by existing real-time techniques measuring electrochemical variations. Along with its robust performance, this earmarks SYNC as a powerful tool for applications such as antibiotic susceptibility testing, food quality monitoring, and real-time water bacteria monitoring, paving the way for enhanced microbial process management and infection control.

The effectiveness of cervical mucus electrical impedance compared to basal body temperature to determine fertility window

BackgroundSerial serum hormone measurements and transvaginal ultrasound are reliable measures to predict ovulation. These measures are inconvenient and expensive therefore, basal body temperature charting (BBT) and urine ovulation predictor kits (OPK) for luteinizing hormone are often used to determine the 6-day fertile window. However, BBT does not clearly change until 1–2 days after ovulation. Additionally, while OPK can indicate positivity prior to ovulation, false readings are common. A novel alternative approach involves measuring electrolyte trends in cervical mucus using electrical impedance spectroscopy. Cervical mucus electrolyte measurements are associated with hormone level changes during the menstrual cycle. The purpose of this study was to compare the effectiveness of cervical mucus electrical impedance and basal body temperature. We sought to determine if cervical mucus electrolyte measurements provided improved detection of the ovulation day and therefore, improve fertility timing for women.Methods14 healthy women between 18 and 44 years of age with normal menstrual cycles were enrolled in the Observational Study. Participants measured BBT and cervical mucus electrical impedance daily for 3 menstrual cycles using Kegg (Lady Technologies Inc. San Francisco, California, USA). Ovulation date for each cycle was confirmed by measuring hormone levels in urine and serum, and by vaginal ultrasound.ResultsElectrical impedance was significantly different between the follicular phase versus ovulatory date (p = 0.007) and between the luteal phase versus the ovulatory date (p = 0.007). A significant difference in the rate of change of cervical impedance measurements in the pre-ovulatory follicular phase was found compared to BBT (p = 0.0225). The sensitivity (+ 7.14%), specificity (+ 20.35%), and accuracy (+ 17.59) to determine the 1-day fertility window was significantly higher using cervical mucus impedance compared to BBT.ConclusionsBBT is considered unreliable for evaluating ovulatory function. Cervical mucus electrical impedance offers a novel measure of electrolyte changes associated with hormone levels. We report that pre-ovulatory electrical impedance patterns demonstrated higher sensitivity, specificity, and accuracy for determining the fertility window when compared to BBT. These findings suggest that changes in electrical impedance may provide an accurate method for predicting ovulation and for measuring ovulatory function.

Saccharomyces Cerevisiae as a Model Organism for Retrospective Impedance Biodosimetry.

Previous studies have shown that measuring changes in electrical impedance that follow radiation-induced suppression of metabolic activity in irradiated yeast cells can be used to determine radiation dose. The current work investigates the radiation response of Saccharomyces cerevisiae cells by using metabolic activity of cells as a damage indicator. Impedance biodosimetry was examined as a method to evaluate the radiation response of yeast cells. Active lab-grade dry yeast cells were used as the biological material as these samples are simple to handle and have a long shelf-life. A novel dosimeter design has been developed with a strict fabrication method and measurement procedure to ensure reproducible measurements are possible. Prepared yeast samples were irradiated to doses from 0.5 to 8 Gy using a 137Cs source, and a dose response curve was developed that showed a linear relationship of dose with changes in impedance measurements. Fading of the impedance signal was also investigated, and it was shown that there was no noticeable fading of the impedance signal over a period of 7 mo. Finally, the lowest detectable limit measured using this methodology was determined to be 300 mGy. This work presents an alternative retrospective dosimetry technique that can be used at a high scale and low cost following large-scale radiological accidents.

Giant magnetoimpedance effect and spin accumulation in conjugated polymeric networks with inhomogeneity

The magnetoimpedance effect allows us to estimate the extent of spin dependent scattering in disordered solids. The change in impedance with respect to applied magnetic field manifests through local change in permeability on the surface and it amplifies at defect sites. The local electrical inhomogeneities are expected to aid this effect through spin dependent scattering. The organic conjugated electrical networks provide scope for producing such inhomogeneities formed by path defects and protonic charge accumulation leading to spin dependent scattering. This hypothesis is investigated in the present work taking polyaniline as a prototype network. The electrical inhomogeneities in the network were controlled by selective oxidation and aging in polyaniline. The Giant Magnetoimpedance (GMI) was observed in the electrically inhomogeneous network with the change in electrical impedance of the order of 50%–60% for lower frequencies with prominent capacitive coupling and a change of the order of 200% at higher frequencies with prominent inductive coupling with the application of magnetic field. However, no spin accumulation was observed in the insulating networks formed by a modified oxidative process. This study is expected to serve as a tool to develop frequency selective spin accumulation based magnetic field sensors and oscillator networks.

Transepithelial Electrical Impedance Increase Following Porous Substrate Electroporation Enables Label-Free Delivery.

Porous substrate electroporation (PSEP) is a promising new method for intracellular delivery, yet fundamentals of PSEP are not well understood, especially the intermediate processes leading to delivery. PSEP is an electrical method, yet the relationship between PSEP and electrical impedance remains underexplored. In this study, a device capable of measuring impedance and performing PSEP is developed and the changes in transepithelial electrical impedance (TEEI) are monitored. These measurements show TEEI increases following PSEP, unlike other electroporation methods. The authors then demonstrate how cell culture conditions and electrical waveforms influence this response. More importantly, TEEI response features are correlated with viability and delivery efficiency, allowing prediction of outcomes without fluorescent cargo, imaging, or image processing. This label-free delivery also allows improved temporal resolution of transient processes following PSEP, which the authors expect will aid PSEP optimization for new cell types and cargos.

Amyloid-β Oligomer-Induced Electrophysiological Mechanisms and Electrical Impedance Changes in Neurons.

Amyloid plays a critical role in the pathogenesis of Alzheimer's disease (AD) and can aggregate to form oligomers and fibrils in the brain. There is increasing evidence that highly toxic amyloid-β oligomers (AβOs) lead to tau protein aggregation, hyperphosphorylation, neuroinflammation, neuronal loss, synaptic loss, and dysfunction. Although the effects of AβOs on neurons have been investigated using conventional biochemical experiments, there are no established criteria for electrical evaluation. To this end, we explored electrophysiological changes in mouse hippocampal neurons (HT22) following exposure to AβOs and/or naringenin (Nar, a flavonoid compound) using electrical impedance spectroscopy (EIS). AβO-induced HT22 showed a decreased impedance amplitude and increased phase angle, and the addition of Nar reversed these changes. The characteristic frequency was markedly increased with AβO exposure, which was also reversed by Nar. The AβOs decreased intranuclear and cytoplasmic resistance and increased nucleus resistance and extracellular capacitance. Overall, the innovative construction of the eight-element CPE-equivalent circuit model further reflects that the pseudo-capacitance of the cell membrane and cell nucleus was increased in the AβO-induced group. This study conclusively revealed that AβOs induce cytotoxic effects by disrupting the resistance characteristics of unit membranes. The results further support that EIS is an effective technique for evaluating AβO-induced neuronal damage and microscopic electrical distinctions in the sub-microscopic structure of reactive cells.

Variation of electrical impedance over 5 years post-implantation and relationship with the maximum comfort level (MCL) in adults with cochlear implants

IntroductionThe maximum comfort level (MCL), threshold level (THR) and electrical impedance change in the postoperative period of the cochlear implant for months until they stabilize. The objective of this article is to establish the variation during 5 post-surgical years of impedance, and its relationship with MCL in unilaterally implanted adults. MethodsRetrospective study over 5 years, with 78 adult patients implanted with MED-EL in a tertiary hospital from the year 2000 to 2015. The variation in impedance, MCL and the relationship between them were analyzed in basal (9–12), medial (5–8) and apical electrodes (1–4), performing an inferential ANOVA analysis of repeated measures with comparisons between consecutive times, corrected with Bonferroni criteria. Results33 men (42.3%) and 45 women (57.7%), with a mean age of 52.7±14.6 years. “Stability” was considered the time of follow-up without statistically significant differences between one visit and the next. Changes in impedance in medial electrodes ceased to be statistically significant at 3 months, and in apicals at 6 months, with mean values of 5.84 and 6.43kΩ. MCL stabilized at 2 years in basal and apical electrodes, and at 3 years in medial, with mean values of 24.9, 22.7, and 25.6qu. There was a correlation between MCL and impedance in medium electrodes up to 3 months and in apical ones up to one year. ConclusionsElectrical impedance drops significantly in medial and apical electrodes up to 3 and 6 months. MCL increases significantly up to two years. Impedance is related to MCL up to 6 months.

A Miniaturized, Rapid Technique for Measuring Red Blood Cell-Mediated Microcapillary Occlusion in HbAS, HbSC, and HbSS Sickle Cell Disease Genotypes

Introduction Sickle cell disease (SCD) is caused by a genetic mutation that produces sickle hemoglobin (HbS). HbS polymerizes upon deoxygenation, causing red blood cells (RBCs) to become sickle-shaped and poorly deformable. Stiff sickle RBCs contribute to microvascular occlusion and organ damage. Previous studies have developed microfluidic devices for assessing RBC-mediated occlusion under hypoxia, but the complexity of the setup and data acquisition limits their adoption. A rapid, easy-to-use, point-of-care assay for assessing RBC-mediated occlusion could increase throughput and aid in determining outcomes of novel therapies, including gene therapies, for SCD. Here, we induced RBC sickling using a chemical method in a simplified workflow to study hypoxic RBC-mediated microcapillary occlusion for healthy (HbAA), sickle cell trait (HbAS), hemoglobin SC disease (HbSC), and homozygous SCD (HbSS) RBCs. Additionally, a custom miniaturized impedance analyzer (MIA) was developed to provide a rapid and fully electronic measurement of occlusion within 10 minutes of sample perfusion. Methods Microfluidic devices were fabricated using standard photolithography and polydimethylsiloxane (PDMS) micro-molding protocols. Glass slides were coated with gold electrodes by sputter deposition and bound to the PDMS microfluidic devices using oxygen plasma. The microfluidic devices comprised six microcapillary arrays of widths 12, 10, 8, 6, 4, and 3 μm, with each array coupled with a pair of gold electrodes [3]. The MIA included an ADALM2000 software-defined instrument module, a custom-designed front-end interface board, and a Raspberry Pi single-board computing module. The ADALM2000 was used to generate and acquire a 10-kHz measurement signal, while the front-end interface board handled signal amplification and multiplexed signal routing through the microcapillary arrays. A custom graphical user interface on the Raspberry Pi allowed users to set experimental parameters and monitor data in real time. Venous blood samples were collected in EDTA tubes from participants with HbAS (n=9), HbSC (n=9), HbSS (n=13), and HbAA (n=6) under an IRB-approved protocol. To induce hypoxia, washed RBCs were suspended at 20% hematocrit in a 1.5% (w/v) sodium metabisulphite in 1× PBS buffer and incubated for 3 minutes at room temperature. For normoxia, RBCs from the same donors were suspended at 20% hematocrit in PBS and incubated with the same conditions. Samples were then perfused through the microfluidic device at a constant inlet pressure. After 10 minutes of perfusion, the change in electrical impedance across each array was used to calculate an occlusion index (OI), representing the percent occlusion of the capillary network. Results Normoxic OI for HbSS and HbSC was significantly higher than HbAA but there were no statistical differences in HbAA vs. HbAS and HbSC vs. HbSS (Figure 1A). HbAS, HbSC, and HbSS RBCs had significantly higher occlusion under hypoxia than in normoxia (Figure 1A, 1.46 ± 1.67% vs. 8.43 ± 2.78%, P = 0.004 for HbAS, 4.56 ± 2.77% vs. 27.1 ± 17.0%, P = 0.004 for HbSC, and 8.01 ± 6.26% vs. 58.3 ± 26.2%, P = 0.0002 for HbSS). Occlusion of HbAA RBCs remained low in both normoxia and hypoxia (2.70 ± 0.643% vs. 4.72 ± 0.953%, P = 0.0625). Hypoxic OI was significantly different between HbAA vs. HbAS (P = 0.017), HbAS vs. HbSC (P = 0.004), and HbSC vs. HbSS (P = 0.007). Hypoxic OI in HbSC and HbSS was associated with elevated markers of RBC hemolysis - absolute reticulocyte count (ARC, P = 0.0061) and lactate dehydrogenase (LDH, P < 0.0001, Figure 1B). Conclusion In normoxia, HbSC had comparable OI to HbSS likely due to HbC induced efflux of potassium ions and water resulting in cellular dehydration and poor RBC deformability. The hypoxic assay, however, unmasked the greater severity of HbSS. Further, elevated hypoxic OI in HbAS may be linked to higher risk of organ damage in this genotype. Chemically-induced hypoxia combined with electrical impedance-based measurement of RBC-mediated microcapillary occlusion offers a new technique for rapidly assessing RBC health and function in a low-oxygen environment. This approach eliminates the need for expensive, high-resolution microscopes and complex gas-exchange chambers. This may serve as a new standard for assessing the clinical efficacy of new treatments that improve RBC deformability and identifying at-risk patients in otherwise mild SCD genotypes.

Modified Impedance Sensing System Determination of Virulence Characteristics of Pathogenic Bacteria Klebsiella Species.

An impedance sensing system is a family of biosensors that measure changes in electrical impedance to perform their functions. Physical and chemical changes in the impedance of the sensing element, such as changes in the concentration of a target analyte or changes in the physical properties of the sensing element, can result in changes in the impedance of the sensing element. Many impedance biosensors have been developed for the detection of pathogens in the past few decades. Several types of biosensors have been developed for the detection of infections, including transduction elements, biorecognition components, and electrochemical approaches. In this review, we discuss the characteristics and pathogenic factors associated with 2,3-butanediol-producing Klebsiella pneumoniae collected using impedance sensors. An impedance sensing system was introduced as a great method for monitoring the virulence factors of Klebsiella spp. in situ. Klebsiella pneumoniae produces virulence factors, including capsules, lipopolysaccharides, fimbriae, and siderophores, as part of its pathogenesis. It is possible to examine virulence factors' pathogenic characteristics in vitro and in vivo using real tissues or mouse models in order to conduct experiments. For the monitoring of virulence factors in situ, a novel alternative method has been developed to mimic the environment of real tissues. For the purpose of developing tissue-mimicking models, mucin and mannose were used to modify the surface of gold electrodes. These components are known to contribute to the adhesion of pathogens to epithelial cells in mammals.

EVALUATION OF THE CURING KINETICS OF A POLYMER MATRIX COMPOSITE USING A SENSOR CONTAINING AN ELECTRICALLY CONDUCTIVE FILLER

In this work, the kinetics of the curing of fabric GFRP was carried out by measuring the parameters of its electrical conductivity. A compound of epoxy resin (ED-20), plasticizer (DBF) and hardener (PEPA) with the addition of finely milled graphite (FMG) was used as a matrix. To en-sure high-quality mixing of FMG in epoxy resin, a planetary mixer was used. Plain weave glass tape 0.2 mm thick with two woven wires was impregnated with a matrix compound. This tape was placed onto a beam 4 mm thick made of typical GFRP as an external electrically conductive functional sensor (FS). During curing at room temperature, periodic measurements of the electrical conductivity of the FS and the stiffness of the beam with FS in three-point bending were carried out. The amount of FMG into the matrix compound was below the percolation threshold; there-fore, electrical measurements of FS required alternating current. The dependence of the imped-ance on the current frequency (from 10 Hz to 1 MHz) was recorded. Comparison of the change in FS electrical impedance with the change in the beam stiffness during the curing showed their close correlation. The proposed method of measuring the FS impedance can be used to assess the degree of curing of the polymer matrix in critical large-sized composite products during the manufacturing process.

Real-Time Analysis of SARS-CoV-2-Induced Cytolysis Reveals Distinct Variant-Specific Replication Profiles.

The ability of each new SARS-CoV-2 variant to evade host humoral immunity is the focus of intense research. Each variant may also harbor unique replication capabilities relevant for disease and transmission. Here, we demonstrate a new approach to assessing viral replication kinetics using real-time cell analysis (RTCA). Virus-induced cell death is measured in real time as changes in electrical impedance through cell monolayers while images are acquired at defined intervals via an onboard microscope and camera. Using this system, we quantified replication kinetics of five clinically important viral variants: WA1/2020 (ancestral), Delta, and Omicron subvariants BA.1, BA.4, and BA.5. Multiple measures proved useful in variant replication comparisons, including the elapsed time to, and the slope at, the maximum rate of cell death. Important findings include significantly weaker replication kinetics of BA.1 by all measures, while BA.5 harbored replication kinetics at or near ancestral levels, suggesting evolution to regain replicative capacity, and both an altered profile of cell killing and enhanced fusogenicity of the Delta variant. Together, these data show that RTCA is a robust method to assess replicative capacity of any given SARS-CoV-2 variant rapidly and quantitatively, which may be useful in assessment of newly emerging variants.

Variación de la impedancia eléctrica a lo largo de cinco años postimplantación y relación con el umbral de confort máximo (MCL) en adultos portadores de implante coclear

IntroductionThe maximum comfort level (MCL), threshold level (THR) and electrical impedance change in the postoperative period of the cochlear implant for months until they stabilize. The objective of this article is to establish the variation during 5 post-surgical years of impedance, and its relationship with MCL in unilaterally implanted adults. MethodsRetrospective study over 5 years, with 78 adult patients implanted with MED-EL in a tertiary hospital from the year 2000 to 2015. The variation in impedance, MCL and the relationship between them were analyzed in basal (9-12), medial (5-8) and apical electrodes (1-4), performing an inferential ANOVA analysis of repeated measures with comparisons between consecutive times, corrected with Bonferroni criteria. Results33 men (42.3%) and 45 women (57.7%), with a mean age of 52.7 ± 14.6 years. “Stability” was considered the time of follow-up without statistically significant differences between one visit and the next. Changes in impedance in medial electrodes ceased to be statistically significant at 3 months, and in apicals at 6 months, with mean values of 5.84 and 6.43 kohms. MCL stabilized at 2 years in basal and apical electrodes, and at 3 years in medial, with mean values of 24.9, 22.7, and 25.6 qu. There was a correlation between MCL and impedance in medium electrodes up to 3 months and in apical ones up to one year. ConclusionsElectrical impedance drops significantly in medial and apical electrodes up to 3 and 6 months. MCL increases significantly up to two years. Impedance is related to MCL up to 6 months.

TRLS-03. IBRUTINIB DISRUPTS BLOOD-TUMOR BARRIER INTEGRITY TO ENHANCE CNS DRUG DELIVERY AND RODENT GLIOMA MODEL SURVIVAL

Abstract BACKGROUND In the setting of malignant glioma, cytotoxic drugs are often inhibited from accessing the tumor site due to the blood-brain-barrier (BBB). Identifying agents that transiently increase BBB permeability would advance glioma treatment. Ibrutinib, an FDA approved lymphoma treatment, has previously impaired aortic endothelial adhesion and in combination with cytotoxic therapy, increased rodent glioma model survival. In this study, we propose ibrutinib inhibits brain endothelial cell junctional expression to disrupt BBB integrity and increase chemotherapy delivery to malignant glioma cells. METHODS Using rat glioma cells, S635, we evaluated treatment effects with doxil (3mg/kg), ibrutinib (25mg/kg) and combination therapy. We measured effects with serial brain MRIs, doxil plasma and brain regional concentrations, along with 3kD dextran permeability. To evaluate the effects of ibrutinib on in vitro brain endothelial cells, we measured changes in cell-cell electrical impedance and rhodamine efflux, as a surrogate of Abcb1 transporter function, over time (0 to 8h) and at varied drug concentrations (1, 5, and 10µM ibrutinib). RESULTS Ibrutinib in combination with doxil, prolonged median survival in rodent glioma models (18 vs. 24days, p<0.05). MRI findings demonstrated a -14 or -53% vs -75% tumor volume change with doxil or ibrutinib alone vs. combination therapy, respectively (p<0.05). Comparing combination therapy vs. doxil alone, ibrutinib increased CNS concentrations of doxil in the tumor injected brain regions with statistical significance (56ng/mL vs. 74.6ng/mL, p<0.05). In in vitro studies, ibrutinib decreased brain endothelial cell-cell impedance maximally at 2 hours, in a dose dependently without affecting cell viability. Additionally, we observed ibrutinib dose dependently inhibit Abcb1 activity in both endothelial and glioma cells. CONCLUSION Our results suggest ibrutinib increases brain endothelial permeability by causing junctional disruption and inhibition of Abcb1, resulting in increased CNS drug entry and prolonged survival in glioma rat models.

The Evaluation of Activity of Selected Lactic Acid Bacteria for Bioconversion of Milk and Whey from Goat Milk to Release Biomolecules with Antibacterial Activity.

The aim of the study was to assess the antibacterial features of functional macromolecules released during the fermentation of goat milk and whey from goat milk by selected lactic acid bacteria strains that are components of kefir grain microflora. Two milk sources were used: goat milk and whey from goat milk. The lactic acid bacteria (LAB) and indicator microorganisms used were Lactobacillus plantarum PCM 1386, Lactobacillus fermentum PCM 491, Lactobacillus rhamnosus PCM 2677, Lactobacillus acidophilus PCM 2499, Escherichia coli PCM 2793, Salmonella enteritidis PCM 2548, Micrococcus luteus PCM 525, and Proteus mirabilis PCM 1361. The metabolic activity of LAB was described by the Gompertz model, and the parameters proposed for this experiment were the maximum rate of change of electrical impedance and potential biodegradability. Antibacterial activity was examined using the culture method in a liquid medium, determination of the reduction in indicator microorganisms, and optical density changes. Results show that the selective LAB produced certain active biomolecules with antibacterial activity from whey, a by-product that is sometimes troublesome for goat milk processors to manage. Lactobacillus acidophilus is a microorganism that is characterized by the highest metabolic activity in goat milk and whey from goat milk. It has the possibility to produce macromolecules with antibacterial activity.

Three Different Rapidly Prototyped Polymeric Substrates With Interdigitated Electrodes for Escherichia coli Sensing: A Comparative Study.

This work delves upon the development of different types of miniaturized and 3D printed devices having interdigitated electrodes (IDEs) for the detection of Escherichia coli (E. coli) bacteria. The IDEs were fabricated using different approaches including laser-induced graphene (LIG) on polyamide, direct laser writing on glass, and polymeric 3D printing technique, and their suitability for bacteria detection has been compared. The electrochemical impedance spectroscopy (EIS) technique was employed to detect the E. coli bacteria in the prepared miniaturized devices, and the sensory response was compared. EIS was performed in the frequency range between 1 Hz to 1 MHz to record the bacterial growth and activities as a function of change in electrical impedance, and detection performance of the different miniaturized devices with IDEs were compared. It was observed that the LIG-based IDE sensor provided better sensitivity compared to that of the other two approaches. The obtained results indicate that the magnitude of impedance changes by around 2.5 [Formula: see text] per doubling of E.coli cells. With fast and flexible fabrication process capabilities, such microdevices may be used as suitable IDE sensors for microscale pathogenic detection for biomedical and clinical analysis.

Electrical impedance spectroscopy for drug screening on ligand-gated ion channels.

Ligand-gated ion channels (LGICs) are involved in many pathophysiological processes and represent a relevant, although challenging, target for drug discovery. The gold standards for studying the ligand-induced ion channel currents and their modulations by drugs are manual patch clamp or two-electrode voltage clamp (TEVC) electrophysiology, but the throughput is low. Higher throughput has been achieved with automated patch clamp instruments, but these have immense acquisition and significant operating costs. In a proof-of-concept study, we developed a reliable, easy to use and multiplexable microfluidic setup to screen the action of drugs at LGICs heterologously expressed in X. laevis oocytes by measuring the electrical impedance changes across the plasma membrane induced by ligand pulses. We validated our setup by simultaneous TEVC electrophysiology and tested the effects of the reference drugs suramin, TNP-ATP, PPADS or diazepam on oocytes expressing P2X2 or GABAAreceptors, respectively. The drugs modulate ATP-induced and GABA-induced currents of P2X2 and GABAA receptors, respectively. The results obtained with TEVC are similar in terms of drug efficacy to those obtained with simultaneously recorded membrane impedances, which are determined by electrical impedance changes. Thus, the study shows the reliability of our setup as a faster (higher throughput) and more cost-effective method for drug screening compared to conventional electrophysiological techniques. After multiplexing of the system, the setup may facilitate commercial and academic drug screening of ligand gated ion channels that are receiving less attention due to limitations in current assays. [Funded under the Excellence Strategy of the Federal Government and the Länder - OPSF671]

P20 Novel phenotypic, impedance-based fast antibiotic susceptibility test (AST) can distinguish between MRSA and MSSA in 2 h

Abstract Background Antimicrobial resistance (AMR) is a global problem and is forecast that by 2050 it will cause 10 million deaths a year. Current antimicrobial susceptibility tests (ASTs) used clinically, can take 24–48 h or longer to report results, requiring that initial treatment uses broad spectrum antibiotics. The novel impedance-based fast AST (iFAST) method can report results within 2 h of exposure to an antibiotic. The impedance cytometer measures changes in the electrical charge flow between electrodes when bacterial cells flow individually through a microfluidic channel by an AC current of multiple frequencies. This is interpreted as a read-out of electrical radius (a surrogate measure of cell volume) and opacity (a measure of the resistance properties of the bacterial membranes). Exposure to antibiotics can change the electrical characteristics of the bacterial cell in size and opacity compared with the control sample. The number of exposed cells within a contour defined by a control sample, is used to assess how the cells following exposure. Objectives To demonstrate concordance of this novel rapid method with the current gold standard AST, as performed in a diagnostic laboratory. To distinguish between MRSA and MSSA isolates. Cefoxitin was used as a surrogate for methicillin in laboratory testing as outlined in EUCAST guidelines. Sequentially collected bacterial isolates were used in the clinical microbiology laboratory of University Hospital Southampton from May–July 2022. Methods 60 blinded concurrent clinical isolates of S. aureus were taken from the clinical workflow and tested on the iFAST. S. aureus isolates were streaked onto blood plates and incubated at 37°C for 2 h. The bacteria were diluted into 3 mL of saline solution. The concentration of the bacteria was adjusted to 5 × 105 cfu/mL, in line with EUCAST guidelines, exposed to the beta lactam antibiotic cefoxitin for 2 h at the EUCAST breakpoint concentration of 8 mg/L. Following exposure, the samples were diluted 1:20 in saline solution and measured on the iFAST. Cefoxitin-exposed cells were compared with a control sample, which has not been challenged with antibiotic. The iFAST results were compared with gold standard disk diffusion assay results, generated in the clinical lab as part of normal clinical service. Results The iFAST results showed 100% concordance with disk diffusion susceptibility testing for cefoxitin carried out in parallel by the clinical laboratory. The data showed different electrical impedance changes for both resistant and susceptible isolates. Susceptible strains showed a decrease in electrical radius, suggesting that the cells are smaller and a significant reduction in overall cell count was observed. Resistant strains showed a distinctive increase in electrical radius, suggesting that the cells are larger in size when exposed to cefoxitin. However, this and other factors that may contribute to an increase in electrical radius are currently being investigated. An electrical MIC carried out for selected strains, was used to confirm that the transition from one response to the other corresponded to the MIC measured by microbroth dilution. An analysis of the data with hospital laboratory staff, suggested that the iFAST can provide an MRSA confirmation to clinicians 16 h before the current AST's, which could benefit patient management and treatment. Conclusions The iFAST can rapidly differentiate between MRSA and MSSA isolates in concordance with current susceptibility testing in the clinical setting. The results help to show how the iFAST could reduce the time taken to provide critical and accurate antibiotic treatment to patients.

Feasibility Study of Early Pressure Ulcer Detection Using Electrical Impedance Tomography

Pressure ulcers are chronic skin wounds with a particularly high morbidity and a relatively low recovery rate. At present, there is still a lack of a portable and visual real-time monitoring system for early pressure ulcers. Electrical impedance tomography (EIT) is a kind of functional imaging technique that can diagnose the healthy condition in the measured tissues by visualizing the distribution of bioelectrical impedance parameters. According to the principle of electrical characteristic of pressure ulcers, i.e., changes in physiological and pathological information of tissues caused by pressure lead to changes in electrical impedance of tissues, a non-invasive imaging system of pressure ulcers based on EIT with novel flexible electrode array is proposed. Two kinds of 3D finite element simulation models are constructed to discuss the measurement effects of the flexible array on simulated pressure ulcers at different locations, depths, and with different sizes. The effects of different imaging algorithms on imaging results are also compared and analyzed. Physical phantom model experiments and preliminary experiments on human skin are conducted. Both simulations and physical experiments indicate that EIT technique is excepted to realize a safer, portable, low-cost and visual real-time monitoring system for early pressure ulcers.

Experimental Investigation on the Compressive Stress-Sensing Ability of Steel Fiber-Reinforced Cement-Based Composites under Varying Temperature Conditions

This study investigates the piezoresistive (self-sensing) properties of short stainless-steel fiber-reinforced mortar under varying temperature conditions. Different reinforced mortars were produced by varying fiber and aggregate content. First, Electrical Impedance Spectroscopy (EIS) measurements were used to characterize the electrical properties of the mortar specimens. EIS measurements were performed at temperatures of 24 °C, 35 °C, and 50 °C. Second, to investigate the self-sensing capacity of the different composites, the fractional changes of electrical impedance at 1 kHz were monitored under two conditions: temperature variation alone (cooling down from 35 °C or 50 °C to room temperature), and temperature variation combined with cyclic compressive loading (up to 5 MPa). The results of the former were used to compensate for the effect of temperature variations in the latter. Both temperature and mechanical loading produced meaningful variations in the electrical impedance and piezoresistivity of the investigated composites. Conclusions are drawn with respect to the stress and temperature sensitivity of the composites. The real and imaginary parts of the electrical impedance of the mortar produced with the highest fiber volume fraction (0.01%) and higher aggregate content (volume fraction of 60%) were distinctly sensitive to temperature and stress, which suggests the possibility of using the same composite as a stress and temperature sensor.

Electromechanical impedance-based embeddable smart composite for condition-state monitoring

In the present study, an alternating current (AC) based electro-mechanical impedance (EMI) technique was employed to evaluate the performance of smart cementitious composite-based impedance sensor (SCC- i S) over a frequency range, and then was employed as embeddable sensor for monitoring and assessing the health of concrete structure. For this purpose, a method for developing SCC-iS by reinforcing the carboxylic group (COOH-) multi-walled carbon nanotube (COOH-MWCNT) in the cementitious composite matrix is described. The optimal CNT concentration in SCC- i S was obtained based on the AC impedance measurement technique over a specified frequency range. After finding the optimal CNT concentration in SCC- i S, their piezoresistive behaviour (in terms of change in electrical impedance or electrical conductance) was examined using an electro-mechanical impedance measurement approach under uniaxial compressive loading. Finally, the developed sensor is employed as an embedded sensor for damage monitoring of structures under flexural loading. The acquired electrical impedance- and conductance- responses from the SCC- i S were utilized to evaluate the occurrence and progression of damage in real-time. The damage metric and the shift in frequency band were used to quantify the level of damage in the structures. From the experimental study, 0.50 wt% CNT concentration is found to be optimum for developing the efficient SCC- i S. Under the uniaxial compressive loading, the electrical variation in impedance (EVZ) and electrical variation in conductance (EVC) in SCC- i S exhibit excellent correlation with compressive strain and are capable of detecting the damage. The acquired signals from embedded SCC- i S show the effectiveness and sensitivity (in both qualitative and quantitative terms) for damage monitoring of structures; even they are capable of tracing the early-stage damage initiation in concrete structures. The electrical conductance spectra within a specified frequency range show a leftward shift, indicating the degradation in stiffness of concrete structure. Overall, the developed SCC- i S is the first of its kind and is found to be very effective and durable for real-time monitoring of structures, especially in the aggressive environment. • Development of smart nanoengineered composite using functionalized CNT. • Embedded sensors for capturing the electro-mechanical impedance (EMI) signature. • Sensor characterization and evaluation of piezoresistive behavior in frequency bands. • Demonstration for damage monitoring of structures under flexural loading. • Damage metric and shift in frequency band for accurate damage quantification.