Impedance-based Detection Research Articles

Biosynthesized AgNP Modified Glassy Carbon Electrode as a Bacteria Sensor Based on Amperometry and Impedance-Based Detection

Biosynthesized AgNP Modified Glassy Carbon Electrode as a Bacteria Sensor Based on Amperometry and Impedance-Based Detection

Impedance-Based Detection of NO2 Using Ni-MOF-74: Influence of Competitive Gas Adsorption.

Chemically robust, low-power sensors are needed for the direct electrical detection of toxic gases. Metal-organic frameworks (MOFs) offer exceptional chemical and structural tunability to meet this challenge, though further understanding is needed regarding how coadsorbed gases influence or interfere with the electrical response. To probe the influence of competitive gases on trace NO2 detection in a simulated flue gas stream, a combined structure-property study integrating synchrotron powder diffraction and pair distribution function analyses was undertaken, to elucidate how structural changes associated with gas binding inside Ni-MOF-74 pores correlate with the electrical response from Ni-MOF-74-based sensors. Data were evaluated for 16 gas combinations of N2, NO2, SO2, CO2, and H2O at 50 °C. Fourier difference maps from a rigid-body Rietveld analysis showed that additional electron density localized around the Ni-MOF-74 lattice correlated with large decreases in Ni-MOF-74 film resistance of up to a factor of 6 × 103, observed only when NO2 was present. These changes in resistance were significantly amplified by the presence of competing gases, except for CO2. Without NO2, H2O rapidly (<120 s) produced small (1-3×) decreases in resistance, though this effect could be differentiated from the slower adsorption of NO2 by the evaluation of the MOF's capacitance. Furthermore, samples exposed to H2O displayed a significant shift in lattice parameters toward a larger lattice and more diffuse charge density in the MOF pore. Evaluating the Ni-MOF-74 impedance in real time, NO2 adsorption was associated with two electrically distinct processes, the faster of which was inhibited by competitive adsorption of CO2. Together, this work points to the unique interaction of NO2 and other specific gases (e.g., H2O, SO2) with the MOF's surface, leading to orders of magnitude decrease in MOF resistance and enhanced NO2 detection. Understanding and leveraging these coadsorbed gases will further improve the gas detection properties of MOF materials.

A Passive Wireless Acceleration Sensing System Based on Patch Antenna and FMCW Radar

Traditional acceleration sensors use cables to transport data and batteries to supply power, which may increase failure risk, deployment inconvenience and maintenance difficulty. This paper proposes a passive and wireless acceleration sensing system, namely a newly designed patch-antenna-based sensing node interrogated by frequency-modulated continuouswave (FMCW) radar. The acceleration is correlated with the location of a cantilever beam, whose oscillation alter the additional capacitance of the patch antenna and consequently the resonant frequencies. The testing range can be adjusted by change the material and dimensions of the cantilever beam, which is designed up to 1 110m/s2 with a sampling rate of 500Hz to meet the requirements of different conditions. The working mechanism of the sensing system is analyzed theoretically and then verified by the simulation in COMSOL Multiphysics. Then an experiment is carried out to evaluate the performance of the sensing system. Both the resonant frequency and remaining power can be utilized to extract the acceleration response, and results show a good fit with the actual response (i.e., an average error of 4.5%). Empowered by FMCW Radar, the passive accelerometer may have great potential in identifying structure strain mode, impedance-based detection of bolt loosening, automation in construction, etc.

Wireless dielectrophoresis trapping and remote impedance sensing via resonant wireless power transfer

Nearly all biosensing platforms can be described using two fundamental steps—collection and detection. Target analytes must be delivered to a sensing element, which can then relay the transduced signal. For point-of-care technologies, where operation is to be kept simple, typically the collection step is passive diffusion driven—which can be slow or limiting under low concentrations. This work demonstrates an integration of both active collection and detection by using resonant wireless power transfer coupled to a nanogap capacitor. Nanoparticles suspended in deionized water are actively trapped using wireless dielectrophoresis and positioned within the most sensitive fringe field regions for wireless impedance-based detection. Trapping of 40 nm particles and larger is demonstrated using a 3.5 VRMS, 1 MHz radiofrequency signal delivered over a distance greater than 8 cm from the nanogap capacitor. Wireless trapping and release of 1 µm polystyrene beads is simultaneously detected in real-time over a distance of 2.5 cm from the nanogap capacitor. Herein, geometric scaling strategies coupled with optimal circuit design is presented to motivate combined collection and detection biosensing platforms amenable to wireless and/or smartphone operation.

Selection of Automated Platelet Counting Methods Based on Mean Platelet Volume (MPV).

Impedance-based detection and optic detection with fluorescence are common platelet counting methods used by modern hematology analyzers. There are few studies to compare the accuracy of platelet counts using these methods in case of increased MPV. Sixty patients with immune-related thrombocytopenia (IRTP) and 60 healthy controls were included. Platelet counts were obtained by BC-6900 analyzer using impedance detection (PLT-I) and optic detection with fluorescence (PLT-O). Flow cytometry was used as the reference (FCM-ref). The platelet counts in patients using PLT-I were significantly lower than those using PLT-O or FCM-ref by an average of 13.3%. The platelet counts by PLT-O compared to FCM-ref were not statistically significant. MPV inversely affected the platelet counts. When MPV was < 13 fL, platelet counts by all three methods were not statistically different. When MPV was ≥ 13 fL, platelet counts by PLT-I were significantly lower (-15.8%) than those by PLT-O or FCM-ref. Furthermore, when MPV was ≥ 15 fL, platelet counts using PLT-I were further decreased (-23.6%) compared to the counts obtained by PLT-O or FCM-ref. The platelet counts by PLT-O in patients with IRTP is as accurate as by FCM-ref. When MPV is < 13 fL, platelet counts by all three methods are comparable. However, when MPV is ≥ 13 fL, platelet counts by PLT-I can erroneously decrease by as many as 23.6%. Therefore, in case of IRTP, or any cases when MPV ≥ 13 fL, platelet counts obtained by PLT-I method should be carefully checked by other methods, such as PLT-O to ensure a more accurate platelet count.

Adaptive fast charging control using impedance-based detection of lithium deposition

The recently introduced impedance-based detection method for the retrospective identification of lithium deposition is used in a long-term ageing study. Six lithium-ion cells are fast charged for 250 cycles with two different strategies, (i) constant-current constant-voltage and (ii) detection-based, adaptive charging control in which the current of the following step is controlled by the detection result of the previous step. The adaptive charging control leads intentionally to critical charging currents with minor lithium deposition effects for the majority of cases. Nevertheless, only marginal capacity fade can be observed after the whole long-term experiment, proving that the detection method reacts sensitively and reliably on minor lithium deposition. On the other hand, the adaptive charge control leads to significantly higher currents, thus reduced charging durations. Hence, the method qualifies for both adaptive fast charging control and for the identification of charging rate limits. A differential voltage analysis is performed before and after the long-term study, identifying the loss of lithium inventory, as well as the loss of anode active material as dominant degradation modes. Additionally, a sensitivity analysis with varying detection time and measurement accuracy is carried out to identify minimum measurement requirements and to increase the method’s time- and cost-efficiency.

Integrating biofouling sensing with fouling mitigation in a two-electrode electrically conductive membrane filtration system

Biofouling detection enables the adoption of effective cleaning strategies for biofouling prevention. This work investigates the use of electrical impedance spectroscopy (EIS) to monitor the biofilm development and the use of electric fields to mitigate biofouling on the surface of gold-coated membranes. The multi-bacterial suspension was injected into a two-electrode crossflow filtration system where the permeate flux and impedance spectra were recorded to monitor the biofilm growth. Permeate flux declined over time while the impedance at low frequency regions (<10 Hz) rapidly decreased with fouling at the early stages of fouling, and then gradually decreased as biofilm matured. The normalized diffusion-related impedance (Rd), an EIS-derived parameter, was extracted to determine the sensitivity of EIS detection. We observed that impedance-based detection was more sensitive to changes as compared to the decline of permeate flux during the early stage of biofouling. With early detection of fouling, fouling mitigation strategies could be applied more effectively. Further, under the same conditions as fouling detection, either applying an intermittent cathodic potential (−1.5 V) or cross-flow flushing delayed the biofilm growth on the electrically conductive membranes (ECMs). EIS sensitivity was repeatably recovered across four cycles of mechanical fouling removal. Hence ECMs were demonstrated to play a dual function: EIS-enabled detection of biofouling evolution and surface biofouling mitigation.

PNA microprobe for label-free detection of expanded trinucleotide repeats.

We present a PNA microprobe sensing platform to detect trinucleotide repeat mutation by electrochemical impedance spectroscopy. The microprobe platform discriminated Huntington's disease-associated CAG repeats in cell-derived total RNA with S/N 1 : 3. This sensitive, label-free, and PCR-free detection strategy may be employed in the future to develop biosensing platforms for the detection of a plethora of repeat expansion disorders.

Electrochemical impedimetric analysis of different dimensional (0D–2D) carbon nanomaterials for effective biosensing of L-tyrosine

Electrochemical biosensors employing nano-transduction surfaces are considered highly sensitive to the morphology of nanomaterials. Various interfacial parameters namely charge transfer resistance, double layer capacitance, heterogeneous electron transfer rate and diffusion limited processes, depend strongly on the nanostructure geometry which eventually affects the biosensor performance. The present work deals with a comparative study of electrochemical impedance-based detection of L-tyrosine (or simply tyrosine) by employing carbon nanostructures (graphene quantum dots, single walled carbon nanotubes (CNTs) and graphene) along with tyrosinase as the bio-receptor. Specifically, the role of carbon nanostructures (i.e. 0D, 1D and 2D) on charge transfer resistance is investigated by applying time-varying electric field at the nano-bioelectrode followed by calculating the heterogeneous electron transfer rate, double layer capacitor current and their effects on limits of detection and sensitivities towards tyrosine recognition. A theoretical model based on Randel’s equivalent circuit is proposed to account for the redox kinetics at various carbon nanostructure/enzyme hybrid surfaces. It was observed that, the 1D morphology (single walled CNTs) exhibited lowest charge transfer resistance ∼2.62 kΩ (lowest detection limit of 0.61 nM) and highest electron transfer rate ∼0.35 μm s−1 (highest sensitivity 0.37 kΩ nM−1 mm−2). Our results suggest that a suitable morphology of carbon nanostructure would be essential for efficient and sensitive detection of tyrosine.

Rapid Sars-Cov-2 Virus Detection Using Modular Transistor-Based Biosensor Platform with Disposable Test Strips

There is tremendous interest in development of systems for fast and high throughput testing technology for transmissive diseases and emergency medicine, especially after the outbreak of SARS-CoV-2 virus (COVID-19). To date (Apr 23rd, 2021), the number of infected populations worldwide has reached above 145 millions with more than 3 millions fatalities from the pandemic. Electrochemical sensing could potentially meet the demand of rapid yet low-cost detection and diagnosis for decentralized and widespread use. Recent advances in electrochemical sensing for COVID-19 include analog signal detection using graphene based field effect transistors (FET) [1], electrochemical impedance-based detection [2], as well as sensing of the N-gene of SARS-CoV-2 using antisense oligonucleotides [3]. In this work, we present a modular and low-cost platform Si-MOSFET based biosensor system utilizing disposable cartilages for sensing of SARS-CoV-2 spiked peptide and inactivated virus.Figure 1 shows the overall schematics of the sensing system, which consists of a Si enhancement mode MOSFET (Texas Instruments SN74S124N) based circuit board and biofunctionalized test strips. The sensing test strips, Figure 2, are connected between the VGG and the gate electrode. A voltage-controlled oscillator (VCO), shown in Fig 3, converted the output drain waveform into a digital reading. The starting materials for the sensing cartridges are multi-electrode graphite-based sensor strips with a single electrode plated with Au for sensing. Figure 4 shows the surface morphology of the electroplated surface. The Au-plated surface was then functionalized, subsequently, with thioglycolic acid (TGA), N, N’-dicyclohexylcarbodi-imide and N-hydroxysuccinimide, to form chemical bonding between Au surface and the desired antibody. Diluted antibody was then incubated on the Au electrode surface to finalize the biofunctionalization.Figure 5 shows a schematic of the synchronous drain (VDD) and gate (VGG) waveform, as well as the resultant dynamic drain current (ID/Isen) and voltage (VD/Vsen) caused by the electric field induced deformation of the antigen/antibody complex [4]. Figure 6 shows the dynamic drain waveform of the NMOS transistor at different tested spike peptide concentrations. Figure 7 shows the voltage extracted at 750μs of the drain waveform, which is designated as the analog signal reported in this work. Two types of antibodies, SARS-CoV-Spike ECD monoclonal antibody and polyclonal spike antibody, were tested in this study. The built-in digital readout allows direct readout of the relative virus concentration. Both antibodies show sensitivity in range of 10-15 to 10-5 g/mL with digital signal sensitivity of 53/dec for monoclonal antibody and 56/dec for polyclonal antibody. Figure 8 shows the digital outputs for human inactivated virus (ATCC VR-1986HK) under test. The sensor strips with electrodes presented in Figure 2 can reach detection limits down to 100 PFU/mL with digital sensitivity of 150/dec for monoclonal antibody and 454/dec for polyclonal antibody. By slightly modifying the sensor tip configuration, the sensitivity for inactivated virus detection can be lowered to 5 PFU/mL. For the same range of peptide/virus concentration tested, a larger change in drain voltage/digital reading represents a high sensitivity to doped solution due to the different epitopes these antibodies interact with. The fast response time and low detection of limit exemplified by this technique provides an opportunity for inexpensive semiconductor-based sensor systems in such applications. This approach is versatile and can be functionalized with different antibodies for different viruses and the cartridges printed with multiple functional areas to test for multiple variants.[1] G. Seo et al., ACS Nano, vol. 14, p. 5135 (2020)[2] M. Z. Rashed et al., Biosens. Bioelectron., vol. 171, p. 112709 (2021)[3] M. Alafeef, et al, ACS Nano, vol. 14, pp. 17028–17045 (2020)[4] S. Shan et al., IEEE Trans. Biomed. Circuits Syst. vol 14, 1362 (2020) Figure 1

Parallelized Impedance-Based Platform for Continuous Dose-Response Characterization of Antischistosomal Drugs.

Schistosomiasis is an acute and chronic disease caused by tropical parasitic worms of the genus Schistosoma, which parasitizes annually over 200 million people worldwide. Screening of antischistosomal compounds is hampered by the low throughput and potential subjectivity of the visual evaluation of the parasite phenotypes, which affects the current drug assays. Here, an impedance-based platform, capable of assessing the viability of Schistosoma mansoni schistosomula exposed to drugs, is presented. This automated and parallelized platform enables unbiased and continuous measurements of dose-response relationships for more than 48 h. The platform performance is established by exposure of schistosomula to three test compounds, praziquantel, oxethazaine, and mefloquine, which are known to affect the larvae phenotypes. The system is thereafter used to investigate the response of schistosomula to methiothepine, an antipsychotic compound, which causes complex drug-induced effects. Continuous monitoring of the parasites reveals transient behavioral phenotypes and allows for extracting temporal characteristics of dose-response curves, which are essential for selecting drugs that feature high activity and fast kinetics of action. These measurements demonstrate that impedance-based detection provides a wealth of information for the in vitro characterization of candidate antischistosomals and, represents a promising tool for the identification of new lead compounds.

Impedance Based Automatic Detection of Ventilations During Mechanical Cardiopulmonary Resuscitation.

Monitoring ventilation rate is key to improve the quality of cardiopulmonary resuscitation (CPR) and increase the probability of survival in the event of an out-of-hospital cardiac arrest (OHCA). Ventilations produce discernible fluctuations in the thoracic impedance signal recorded by defibrillators. Impedance-based detection of ventilations during CPR is challenging due to chest compression artifacts. This study presents a method for an accurate detection of ventilations when chest compressions are delivered using a piston-driven mechanical device. Data from 223 OHCA patients were analyzed and 399 analysis segments totaling 3101 minutes of mechanical CPR were extracted. A total of 18327 ventilations were annotated using concurrent capnogram recordings. An adaptive least mean squares filter was used to remove compression artifacts. Potential ventilations were detected using a greedy peak detector, and the ventilation waveform was characterized using 8 waveform features. These features were used in a logistic regression classifier to discriminate true ventilations from false positives produced by the greedy peak detector. The classifier was trained and tested using patient wise 10-fold cross validation (CV), and 100 random CV partitions were created to statistically characterize the performance metrics. The peak detector presented a sensitivity (Se) of 99.30%, but a positive predictive value (PPV) of 54.43%. The best classifier configuration used 6 features and improved the mean (sd) Se and PPV of the detector to 93.20% (0.06) and 94.43% (0.04), respectively. When used to measure per minute ventilation rates for feedback to the rescuer, the mean (sd) absolute error in ventilation rate was 0.61 (1.64) min-1. The first impedance-based method to accurately detect ventilations and give feedback on ventilation rate during mechanical CPR has been demonstrated.

Dielectrophoresis assisted impedance spectroscopy for detection of gold-conjugated amplified DNA samples

Molecular diagnostics have always been at the forefront of disease identification and control. Various approaches exist for carrying out molecular diagnostics through identification of genes or proteins and are largely deployed in the laboratories for testing; although there exist a wide possibility of refinement in these existing processes. In this respect, impedance-based detection methods have emerged as one of the most deployable methods primarily due to their robust and easy nature of measurement and easy integrability with microelectronic systems. Impedance assisted technique is very commonly used for detection of DNA and DNA amplification through PCR process although it does not really make a very specific identification system parallel to some other optical techniques; like TaqMan PCR, qPCR or Molecular beacon assisted detection of DNA sequences. In the current article, we have developed a novel strategy through nanoparticle labeling and dielectrophoretic manipulation which enhances the specificity of the identification of tagged-amplified DNA samples coming out of a PCR process. Impedance characteristics with respect to a various number of PCR cycles with a product consisting of nanoparticle-labeled DNA samples are measured with respect to increasing concentration. A significant differentiation is observed between the non-labeled non-specifically amplified DNA and the labeled specifically amplified sequence through varied impedance signals. The impedance characterization is performed at the instance where the analyte is mostly near the electrodes and this is accomplished through dielectrophoresis scheme. The different dielectrophoretic capture frequencies have been observed for non-labeled and labeled DNA products. This sensor has achieved a limit of detection of the range of 25–30 DNA copies. The eventual goal here is to integrate this strategy with microchip PCR to evolve a paradigm shift in the PCR microchip technology.

Real-Time Impedance-Based Detection of LFA-1-Stimulated T-Cell Transwell Chemotaxis.

The ability of activated T-lymphocytes to transmigrate toward certain chemokine is one of their characteristic functional properties. Here, we provide step-wise details about an in vitro technique to quantify the kinetics of chemotactic behavior of LFA-1-stimulated T-lymphocytes. The method described herein utilizes a noninvasive electrical impedance-based detection system to monitor T-cell chemotaxis in real-time.

Impedance-Based Detection of Bacteria.

Pathogenic bacteria have always posed one of the most serious threats to public health, and continue to be especially dangerous with the rise in antibiotic resistance. The prevalence of these infectious agents necessitates rapid, point-of-care sensors for their detection, identification, and monitoring. Electrochemical sensors are promising for the low-cost monitoring of bacterial growth and the detection of specific microbial species due to the consistency and ease-of-use of impedance measurements. Though the commercialization of these sensors is currently limited, they offer significant promise for detecting pathogens from real-world environments.

Discovery of Novel Small-Molecule Inducers of Heme Oxygenase-1 That Protect Human iPSC-Derived Cardiomyocytes from Oxidative Stress.

Oxidative injury to cardiomyocytes plays a critical role in cardiac pathogenesis following myocardial infarction. Transplantation of stem cell-derived cardiomyocytes has recently progressed as a novel treatment to repair damaged cardiac tissue but its efficacy has been limited by poor survival of transplanted cells owing to oxidative stress in the post-transplantation environment. Identification of small molecules that activate cardioprotective pathways to prevent oxidative damage and increase survival of stem cells post-transplantation is therefore of great interest for improving the efficacy of stem cell therapies. This report describes a chemical biology phenotypic screening approach to identify and validate small molecules that protect human-induced pluripotent stem cell cardiomyocytes (hiPSC-CMs) from oxidative stress. A luminescence-based high-throughput assay for cell viability was used to screen a diverse collection of 48,640 small molecules for protection of hiPSC-CMs from peroxide-induced cell death. Cardioprotective activity of "hit" compounds was confirmed using impedance-based detection of cardiomyocyte monolayer integrity and contractile function. Structure-activity relationship studies led to the identification of a potent class of compounds with 4-(pyridine-2-yl)thiazole scaffold. Examination of gene expression in hiPSC-CMs revealed that the hit compound, designated cardioprotectant 312 (CP-312), induces robust upregulation of heme oxygenase-1, a marker of the antioxidant response network that has been strongly correlated with protection of cardiomyocytes from oxidative stress. CP-312 therefore represents a novel chemical scaffold identified by phenotypic high-throughput screening using hiPSC-CMs that activates the antioxidant defense response and may lead to improved pharmacological cardioprotective therapies.

Impedance-based detection of Schistosoma mansoni larvae viability for drug screening.

Human schistosomiasis is a neglected tropical disease caused by trematodes, affecting almost 250 million people worldwide. For the past 30 years, treatment has relied on the large-scale administration of praziquantel. However, concerns regarding the appearance of drug-resistance parasites require efforts in identifying novel classes of suitable drugs against schistosomiasis. The current drug screening system is manual, slow and subjective. We present here a microfluidic platform capable of detecting changes in viability of Schistosoma mansoni larvae (Newly Transformed Schistosomula, NTS). This platform could serve as a pre-screening tool for the identification of drug candidates. It is composed of a pair of coplanar electrodes integrated in a microfluidic channel for the detection and quantification of NTS motility. Comparison of viability detection by using our platform with the standard visual evaluation shows that our method is able to reliably detect viable and non-viable NTS at high sensitivity, also in case of low-motility parasites, while enabling a 10 fold decrease in sample consumption.

A New Rate of Change of Impedance-based Islanding Detection Scheme in Presence of Distributed Generation

—Integration of distributed generation with utility network demands satisfactory operation of an islanding detection scheme, as it can otherwise lead to such problems such enhancement in non-detection zone, out-of-phase reclosing, personnel safety, and degradation of power quality. This article presents a new islanding detection scheme based on the rate of change of impedance (dz/dt) of each phase. To calculate dz/dt, phasor computation is carried out using a half-cycle modified discrete Fourier transform algorithm. Test data are generated using the PSCAD/EMTDC software package (HVDC Research Center, Inc., Manitoba). Various islanding conditions have been simulated by disconnecting the main circuit breaker with different values of active and reactive power mismatch. At the same time, different non-islanding conditions have also been simulated through switching (ON/OFF) of load, energization/de-energization of medium transmission lines, short-circuit on an adjacent feeder, and switching (ON/OFF) of the transformer and capacitor bank in the network. The simulation results indicate that the proposed scheme is capable of providing effective discrimination between islanding and non-islanding conditions. The proposed scheme is able to detect islanding conditions within a half-cycle from event inception.

Cu impedance-based detection of superparamagnetic nanoparticles

A novel method for superparamagnetic nanoparticle detection using copper impedance as the sensing property is presented. The increase of impedance produced by the proximity of the nanoparticles in the copper is comparable to that of classical magnetoimpeditive materials. A physical interpretation of the detection in terms of the induction of eddy currents in the copper element by the oscillating magnetic moments of the particles is proposed. Experimental research has been done to support this hypothesis, namely, analyses of the influence of the driving current frequency and amplitude, and of the geometry and size of the sensing conductor. The ability of copper to quantify the number of nanoparticles was successfully verified, evidencing the great potential of this new method.

Impedance-based detection of extracellular DNA in wounds

Wound infection status is a relevant diagnostic parameter to enhance wound treatment towards better healing rate. Impedance evaluation is a powerful tool to measure the inflammatory response like the released DNA of neutrophils. In our research we investigated the dielectric behaviour of neutrophils settled on electrodes in vitro. The cells have been stimulated to react in the same way as in a wound infection. The result is a significant impedance deviation of about 50% with comparable amount of cells like in an infected wound. Microscopic fluorescence verifications acknowledge these findings.