Pseudo Reference Research Articles

Chemometric-assisted eMIP-modified screen-printed sensor for robust herbicide MCPA determination

The paper describes the development and application of a screen-printed electrode cell with a graphite-ink working electrode modified by a molecularly imprinted electropolymerized polypyrrole for the voltammetric determination of the herbicide 4‑chloro-2-methylphenoxyacetic acid (MCPA). The method exploits the direct measurement of the analyte by applying the differential pulse voltammetry (DPV) technique, taking advantage of the irreversible oxidation peak at about +1.0 V vs. Ag/AgCl pseudo reference electrode. The presence of the molecularly imprinted polypyrrole enhances the sensor's selectivity and sensitivity. A chemometric approach has been crucial for quantitative analysis because of the peak's broad and not well-defined shape. Firstly, a proper pretreatment of the voltammetric signals is identified, proving the most effective is the first-derivative function transformation of the signal. The Partial Least Square regression (PLS) is the tool applied for MCPA quantification. A preliminary PLS model has been developed and validated in dihydrogen phosphate solution at pH 5.5, aiming to optimize the data treatment approach. Then, the same approach is used to develop a PLS model analyzing tap water samples fortified with MCPA and other pesticides as possible interferents to simulate contaminated natural waters. The model correctly predicted the analyte concentration in the range of 2.5–75 μM, assuring the reliability and robustness of the sensor for the possible quantification of MCPA in wastewater samples.

High Areal Capacity Cycling of Three-Electrode Sodium/NBA/Sodium Cells

The cycling stability of Li and Na metal electrodes is influenced by the interface with the solid electrolyte. Study of the cycling behavior at areal capacities >>0.5 mAh/cm2 are uncommon, and plating and stripping behaviors remain relatively unknown for the individual electrode/electrolyte interfaces because of the difficulty of separating the individual interfaces in a two-electrode cell configuration. Because areal capacities of practical cells target >5 mAh/cm2, it is important to cycle at much higher areal capacities than typically studied. Here, we utilize a three-electrode symmetric cell of sodium metal with sodium beta alumina (NBA) electrolyte and cycled areal capacities ranging from 0.5 to 5 mAh cm-2 and achieved current densities >10 mA cm-2 at 1.0 mAh cm-2. We find that polarization increases most at the stripping electrode, and that during current density ramps the polarizations are greatly affected by the areal capacity, affecting the maximum current density that can be reached prior to either cell shorting or impedance rise that drives the voltage magnitude to well over 1 V. Additionally, we found resistance rise occurring at the Na/NBA interface during plate (reduction) as well as strip (oxidation) for the same electrode, potentially indicating voiding on plate at sufficiently high current densities and areal capacities (5 mAh cm-2, >2 mA cm-2). For two-electrode studies, the voltage evolution on the plating electrode we observe must be considered for the assumption that the plating electrode is a pseudo reference electrode. We also use our three-electrode cell configuration to study several other experimental conditions, including cycling to failure at a fixed current density and areal capacity, as well as a uni-directional current flow experiment to determine the maximum amount of plating / stripping that can be achieved in the absence of cycling. These findings will help direct future experiments and interpretation of data to quantify the limits and improve the engineering of Li and Na metal / solid electrolytes interfaces.Jolly, D. S.; Ning, Z.; Darnbrough, J. E.; Kasemchainan, J.; Hartley, G. O.; Adamson, P.; Armstrong, D. E. J.; Marrow, J.; Bruce, P. G. Sodium/Na Β″ Alumina Interface: Effect of Pressure on Voids. ACS Appl Mater Interfaces 2019, 12 (1), 678–685. https://doi.org/10.1021/ACSAMI.9B17786.Krauskopf, T.; Hartmann, H.; Zeier, W. G.; Janek, J. Toward a Fundamental Understanding of the Lithium Metal Anode in Solid-State Batteries - An Electrochemo-Mechanical Study on the Garnet-Type Solid Electrolyte Li 6.25 Al 0.25 La 3 Zr 2 O 12. ACS Appl Mater Interfaces 2019, 11 (15), 14463–14477. https://doi.org/10.1021/ACSAMI.9B02537/SUPPL_FILE/AM9B02537_SI_001.PDF.

An integrative pipeline for circular RNA quantitative trait locus discovery with application in human T cells.

Molecular quantitative trait locus (QTL) mapping has proven to be a powerful approach for prioritizing genetic regulatory variants and causal genes identified by Genome-wide association studies (GWAS). Recently, this success has been extended to circular RNA (circRNA), a potential group of RNAs that can serve as markers for the diagnosis, prognosis, or therapeutic targets of various human diseases. However, a well-developed computational pipeline for circRNA QTL (circQTL) discovery is still lacking. We introduce an integrative method for circQTL mapping and implement it as an automated pipeline based on Nextflow, named cscQTL. The proposed method has two main advantages. Firstly, cscQTL improves the specificity by systematically combining outputs of multiple circRNA calling algorithms to obtain highly confident circRNA annotations. Secondly, cscQTL improves the sensitivity by accurately quantifying circRNA expression with the help of pseudo references. Compared to the single method approach, cscQTL effectively identifies circQTLs with an increase of 20-100% circQTLs detected and recovered all circQTLs that are highly supported by the single method approach. We apply cscQTL to a dataset of human T cells and discover genetic variants that control the expression of 55 circRNAs. By colocalization tests, we further identify circBACH2 and circYY1AP1 as potential candidates for immune disease regulation. cscQTL is freely available at: https://github.com/datngu/cscQTL and https://doi.org/10.5281/zenodo.7851982. Supplementary data are available at Bioinformatics online.

Clinical heterogeneity of neuro-inflammatory PET profiles in early Alzheimer's disease.

The relationship between neuroinflammation and cognition remains uncertain in early Alzheimer's disease (AD). We performed a cross-sectional study to assess how neuroinflammation is related to cognition using TSPO PET imaging and a multi-domain neuropsychological assessment. A standard uptake value ratio (SUVR) analysis was performed to measure [18F]-DPA-714 binding using the cerebellar cortex or the whole brain as a (pseudo)reference region. Among 29 patients with early AD, the pattern of neuroinflammation was heterogeneous and exhibited no correlation with cognition at voxel-wise, regional or whole-brain level. The distribution of the SUVR values was independent of sex, APOE phenotype, early and late onset of symptoms and the presence of cerebral amyloid angiopathy. However, we were able to demonstrate a complex dissociation as some patients with similar PET pattern had opposed neuropsychological profiles while other patients with opposite PET profiles had similar neuropsychological presentation. Further studies are needed to explore how this heterogeneity impacts disease progression.

Decreased synaptic vesicle glycoprotein 2A binding in a rodent model of familial Alzheimer's disease detected by [18F]SDM-16.

Synapse loss is one of the hallmarks of Alzheimer's disease (AD) and is associated with cognitive decline. In this study, we tested [18F]SDM-16, a novel metabolically stable SV2A PET imaging probe, in the transgenic APPswe/PS1dE9 (APP/PS1) mouse model of AD and age-matched wild-type (WT) mice at 12 months of age. Based on previous preclinical PET imaging studies using [11C]UCB-J and [18F]SynVesT-1 in the same strain animals, we used the simplified reference tissue model (SRTM), with brain stem as the pseudo reference region to calculate distribution volume ratios (DVRs). To simplify and streamline the quantitative analysis, we compared the standardized uptake value ratios (SUVRs) from different imaging windows to DVRs and found that the averaged SUVRs from 60-90 min post-injection (p.i.) are most consistent with the DVRs. Thus, we used averaged SUVRs from 60-90 min for group comparisons and found statistically significant differences in the tracer uptake in different brain regions, e.g., hippocampus (p = 0.001), striatum (p = 0.002), thalamus (p = 0.003), and cingulate cortex (p = 0.0003). In conclusion, [18F]SDM-16 was used to detect decreased SV2A levels in the brain of APP/PS1 AD mouse model at one year old. Our data suggest that [18F]SDM-16 has similar statistical power in detecting the synapse loss in APP/PS1 mice as [11C]UCB-J and [18F]SynVesT-1, albeit later imaging window (60-90 min p.i.) is needed when SUVR is used as a surrogate for DVR for [18F]SDM-16 due to its slower brain kinetics.

Test‐Time Optimization for Video Depth Estimation Using Pseudo Reference Depth

AbstractIn this paper, we propose a learning‐based test‐time optimization approach for reconstructing geometrically consistent depth maps from a monocular video. Specifically, we optimize an existing single image depth estimation network on the test example at hand. We do so by introducing pseudo reference depth maps which are computed based on the observation that the optical flow displacement for an image pair should be consistent with the displacement obtained by depth‐reprojection. Additionally, we discard inaccurate pseudo reference depth maps using a simple median strategy and propose a way to compute a confidence map for the reference depth. We use our pseudo reference depth and the confidence map to formulate a loss function for performing the test‐time optimization in an efficient and effective manner. We compare our approach against the state‐of‐the‐art methods on various scenes both visually and numerically. Our approach is on average 2.5× faster than the state of the art and produces depth maps with higher quality.

Microelectronic fibers for multiplexed sweat sensing.

Wearable bioelectronics are gaining extraordinary attention due to their capabilities to achieve continuous monitoring of human health status. However, mainstream manufacturing technologies, including photolithography and printing technology, limit current wearable bioelectronics on 2D planar structures with little surface area in contact with the body. It thus limits the amount of physiological information that current wearable bioelectronics could obtain. Furthermore, they need to be firmlyattached to the body, affecting the wearing comfort. In this study, we leveraged the versatile thermal drawing process and developed a flexible microelectronic fiber with bioanalytical functions that could be woven into textiles as a new form of wearable bioelectronics. Within a single strand of fiber, we successfully integrated all-in-one multiplexed electrochemical sensing capabilities, with the sweat as the primary object. Adopting the laser micromachining technique, we developed biosensing functions on the longitudinal surface of the fiber with two sensing electrodes for Na+ and uric acid (UA), respectively, together with a pseudo reference electrode (p-RE). We carefully characterized the all-in-one multiplexed sensing performance of the fiber and demonstrated its successful application in sweat sensing based on its textile forms. The results show significant potential for application in wearable textiles for monitoring key health signals of humans.

Electrochemical biosensor for quantitative determination of fentanyl based on immobilized cytochrome c on multi-walled carbon nanotubes modified screen-printed carbon electrodes.

Fentanyl is a powerful synthetic opioid used to treat severe pain. New administration routes toward its illegal consumption for recreational purposes pose a growing threat to public health, either due to misuse or abuse of this substance. As a result, the rapid qualitative and quantitative determination of fentanyl in biofluids is of great interest. A novel enzymatic biosensor based on adsorptive-stripping cyclic voltammetry is proposed as a cost-effective, reliable, and efficient device for fentanyl determination in urine samples. Disposable screen-printed carbon electrodes modified with multi-walled carbon nanotubes and cytochrome c were used to develop the testing platform. The electrochemical behavior of fentanyl exhibited a well-defined anodic wave around 0.66Vvs. pseudo reference electrode. The experimental conditions were optimized to obtain the best analytical response, and linear regression analysis of increasing concentration standards was applied to estimate the performance parameters. The results suggest a simple method with a wide linearity range, high sensitivity, low limits of detection (0.086μg/mL) and quantification, and satisfactory precision (2.9%RSD). The feasibility and applicability of the voltammetric approach were assessed by fentanyl-spiked urine samples by standard additions calibration curves in two levels of enrichment with an accuracy of 92% and 100%.

In Vivo Chemogenetic Biocompatibility of Mercury as a Specific Hypercalcemia Actuator in Snail's Spinal Cord Cell Manipulation: An Extracellular Field Potential Biosensor.

The in vivo chemogenetic property of mercuric ions (Hg2+) was investigated as a specific hypercalcemia actuator in snail's spinal cord cell manipulation by extracellular field potential biosensing analysis. For this purpose, a three-microelectrode system with working, counter, and pseudo reference electrodes was blindly implanted into the snail's spinal cord to electrically stimulate (triggering) the action potential with a staircase electrical voltage at a very low frequency level, along with measurement of the electrical current, as a detection system. Under optimum conditions, using the one-factor-at-a-time method, a wide linear range between 1.0 × 10-14 and 1.0 × 10-1 mol L-1 with correlation coefficients (R2) >0.98 and a response time (t90) of maximum 10.0 s were approximated. Percentages of relative standard deviation were estimated to be 3.08 (reproducibility, n = 50) and 7.31 (repeatability, n = 15). The detection limit was estimated to be sub 2.1 × 10-16 mol L-1 based on the Xb- + 3Sb definition. The reliability of this phenomenon was evidenced by the estimation of recovery percentages (between 95 and 107%) during spiking Hg2+ standard solutions. The probable mechanism behind this process could be attributed to the following: (i) the neuronal ephaptic coupling during electrical synchronization by a specific brain-triggered wave as a neuronal motor toolkit and (ii) chemical synchronization using a Hg2+ hypercalcemia actuator (biosensor). Linear correlation has been evidenced during interactions between Hg2+ and a calcium ionic channel's protein with a gram molecular weight of 66.2 ± 0.3 KCU. This process, therefore, caused an opening of the Ca2+ channel gates and majorly released the Ca2+ (hypercalcemia) that was detected as the main source of the measured electrical current. At this condition, ultratrace levels of Hg2+ ions not only were considered as nontoxic reagents but also had chemically regulating effects as ephaptic synchronizers to the neuron cells. This report may pave the way for using mercury ions at an ultratrace level for clinical controlling purposes during neuronal spinal cord cell manipulation.

Homemade Silver/Silver chloride ink with low curing temperature for screen-printed electrodes

Here we report the synthesis of Ag/AgCl ink with low curing temperature for application in electrochemical sensors. The ink characterization was carried out by atomic force microscopy, scanning electron microscopy with energy dispersive spectroscopy, X-ray diffraction, thermogravimetry analysis, DC electrical resistivity, and cyclic voltammetry. Furthermore, the ink was used in a pseudo reference electrode of a screen-printed device, which was then applied for carbendazim quantification as proof of concept. The electrochemical sensor presented linear response in the range of carbendazim concentrations from 0.25 to 1.48 µmol L−1 and limit of detection of 0.10 µmol L−1, suggesting the potential of the as-developed ink for designing miniaturized electrochemical sensing devices.

Pseudo-Reference Counter-Based FLL for 6 Gb/s Reference-Less CDR in 65-nm CMOS

A 6 Gbps frequency-locked loop (FLL) for reference-less clock recovery loop has been designed. Based on the analyzed noise characteristic of the pseudo reference clock and the effect on the FLL output, we propose design strategies to decide the speed of the pseudo clock and the loop bandwidth for low phase noise. A non-linear digital sub loop enables the FLL to converge to the optimal noise bandwidth with a fast lock time. The proto-type reference-less clock recovery loop has been fabricated in 65 nm CMOS process and the FLL occupies 0.131 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> chip area. The FLL consumes 12.5 mW from 1 V supply and the measured output jitter is 4.13 ps,rms at 6 GHz.

No-Reference Image Quality Assessment by Hallucinating Pristine Features.

In this paper, we propose a no-reference (NR) image quality assessment (IQA) method via feature level pseudo-reference (PR) hallucination. The proposed quality assessment framework is rooted in the view that the perceptually meaningful features could be well exploited to characterize the visual quality, and the natural image statistical behaviors are exploited in an effort to deliver the accurate predictions. Herein, the PR features from the distorted images are learned by a mutual learning scheme with the pristine reference as the supervision, and the discriminative characteristics of PR features are further ensured with the triplet constraints. Given a distorted image for quality inference, the feature level disentanglement is performed with an invertible neural layer for final quality prediction, leading to the PR and the corresponding distortion features for comparison. The effectiveness of our proposed method is demonstrated on four popular IQA databases, and superior performance on cross-database evaluation also reveals the high generalization capability of our method. The implementation of our method is publicly available on https://github.com/Baoliang93/FPR.

A LOW-COST PAPER-BASED MICROFLUIDIC IMPEDIMETRIC DEVICEC FOR THE DETECTION OF WATER HARDNESS

A microfluidic paper-based impedimetric device was developed as a water hardness sensor. This device is capable of performing the analysis with a sample volume of few microliters with no prior treatments. A phenol-formaldehyde graphene electrode modified with ethylenediaminetetraacetate was used as the working electrode. Ag pseudo reference and carbon electrodes were used to fabricate the device. Current simultaneous metal ion detection sensors are based on complex and expensive electrode setups. The proposed inexpensive, quick and portable device is capable of detecting Ca2+ and Mg2+ simultaneously. Electrode double layer-based charge transfer resistance and the maximum negative imaginary impedance produced a linear correlation with each metal ion concentration. The calculated limits of detection for Ca2+ and Mg2+ were 0.31 and 0.24 ppm, respectively. A set of samples containing Ca2+ and Mg2+ with a hardness of 2 ppm (as calcium carbonate) were used to test the device. The proposed tool is suitable as a semi-quantitative device for the determination of hardness in water.

A LOW-COST PAPER-BASED MICROFLUIDIC IMPEDIMETRIC DEVICEC FOR THE DETECTION OF WATER HARDNESS

A microfluidic paper-based impedimetric device was developed as a water hardness sensor. This device is capable of performing the analysis with a sample volume of few microliters with no prior treatments. A phenol-formaldehyde graphene electrode modified with ethylenediaminetetraacetate was used as the working electrode. Ag pseudo reference and carbon electrodes were used to fabricate the device. Current simultaneous metal ion detection sensors are based on complex and expensive electrode setups. The proposed inexpensive, quick and portable device is capable of detecting Ca2+ and Mg2+ simultaneously. Electrode double layer-based charge transfer resistance and the maximum negative imaginary impedance produced a linear correlation with each metal ion concentration. The calculated limits of detection for Ca2+ and Mg2+ were 0.31 and 0.24 ppm, respectively. A set of samples containing Ca2+ and Mg2+ with a hardness of 2 ppm (as calcium carbonate) were used to test the device. The proposed tool is suitable as a semi-quantitative device for the determination of hardness in water.

Integration of Ultra-Low Volume Pneumatic Microfluidics with a Three-Dimensional Electrode Network for On-Chip Biochemical Sensing.

This paper reports a novel miniaturized pseudo reference electrode (RE) design for biasing Ion Sensitive Field Effect Transistors (ISFETs). It eliminates the need for post-CMOS processing and can scale up in numbers with the CMOS scaling. The presented design employs silane-mediated transfer of patterned gold electrode lines onto PDMS microfluidics such that the gold conformally coats the inside of microfluidic channel. Access to this electrode network is made possible by using “through-PDMS-vias” (TPV), which consist of high metal-coated SU-8 pillars manufactured by a novel process that employs a patterned positive resist layer as SU-8 adhesion depressor. When integrated with pneumatic valves, TPV and pseudo-RE network were able to bias 1.5 nanoliters (nL) of isolated electrolyte volumes. We present a detailed characterization of our pseudo-RE design demonstrating ISFET operation and its DC characterization. The stability of pseudo-RE is investigated by measuring open circuit potential (OCP) against a commercial Ag/AgCl reference electrode.

Chemical and Biological Sensor Capsules for Real-Time Measurement of Cell Properties in Bioreactors

Introduction Real-time bioprocess monitoring and control is needed for the scalable production and deployment of cancer cell therapies at reasonable cost. For example, CAR-T cell therapy shows promise as an effective treatment for cancer with high (83%) remission rates.1 However, the cost of these treatments is too expensive for their mass adoption.2 One reason for the steep price is the difficulty scaling production while ensuring delivery of an efficacious therapy to the patient. One factor preventing scalability is the lack of effective process analytical technology. As a potential solution to this issue, we have developed a fully integrated, wireless, 3D-printed sensor capsule to be used for multiplexed sensing of critical quality attributes (CQAs), namely pH, glucose, and lactate concentrations within cell bioreactors. CQAs are used not only as metrics for cell viability, but also as determinants of a cell’s ability to deliver efficacious treatment. Unlike current process monitoring technology, capsule sensors are buoyant and can be propelled using impellers within the bioreactor. This allows for measurements uniformly inside the bioreactor. To our knowledge, this is the first time that 3D-printed, wireless sensor capsules have been developed for use in cell bioreactors for cancer cell therapy. Methods The capsule consists of electrochemical sensors, and read-out and wireless transmission electronics integrated into a capsule made of a biocompatible polymer (Figure 1). The different sensors for glucose, lactate, and pH along with an Ag on-chip reference electrodes were fabricated using standard lithographic techniques on silicon substrates. The reference electrode consisted of a thin film of Ag deposited by e-beam evaporation that was later coated with polyvinyl butyral (PVB) to improve stability.3 Glucose and lactate sensing was achieved amperometrically using enzymes, glucose oxidase or lactase oxidase respectively, immobilized on a Pt working electrode biased to 0.7 V. pH sensing was achieved by depositing a pH-sensitive oxide on a gold electrode. A pH-sensitive Al2O3 or HfO2 layer was deposited through atomic layer deposition.Figure 1 shows the capsule and sensor design. The capsule packaging was 3D printed using a Stratasys Connex 350 and was designed to be fully insulated from solution except for an opening on the top revealing the various sensors. The sensor chip is installed within the cap of the capsule which can be screwed off, but with wired connection to the electronics housed in the body of the capsule. This allows for simple replacement of the multiplexed sensor chip while retaining the capsule electronics, rechargeable battery, and packaging for reuse. Results and Conclusions Before testing within the capsule, the sensors were tested using microfluidics. Figure 2 shows the performance of the Ag/PVB on-chip pseudo reference electrode (pseudo-RE). The pseudo-RE shows a stable potential in different pH buffer solutions and shows similar sensitivity results for pH sensing when compared to a commercial reference electrode. By having a stable microfabricated pseudoRE, the sensing components will not be a limiting factor for miniaturization of the capsule. Figure 3 shows the response of the pH, lactate, and glucose sensors at different concentrations. The pH sensor shows high sensitivity (~53 mV/pH) over the range of pH 3 to 7. Glucose and lactate sensing was tested in 1X PBS. The glucose sensor shows a linear response to glucose concentrations from 0 to 25 mM validating the use of the sensor within cell culture media.4 The glucose sensor shows the same linear range when tested in human mesenchymal stem cell culture. In this case, the glucose concentration was first tested using a commercial sensor and then diluted to targeted glucose concentrations by dilution with PBS. The lactate sensor shows sensitivity in the concentration range of 1 to 5 mM with saturation occurring around ~6 mM. The capsule’s wireless sensing capability was validated using pH sensing in a beaker. The pH sensing results in Figure 4 were obtained wirelessly from the capsule and were nearly identical to the results measured using our microfluidic system and conventional parameter analyzer.This work has successfully demonstrated wireless sensing using a 3D-printed sensor capsule and functionality of electrochemical sensors for multiple CQAs for cell growth in bioreactors. These sensor capsules can enable scalability of the cell manufacturing process while ensuring delivery of an efficacious treatment. Future work will focus on capsule sensor validation in cell growth media and eventually monitoring of cell growth in bioreactors.

Simple and rapid electrochemical detection of 1-benzylpiperazine on carbon screen-printed electrode

1-Benzylpiperazine (BZP) is an illegal synthetic drug commonly used in combination with alcoholic beverages for recreational purposes due to its amphetamine-like stimulant and hallucinogenic effects. In this work, we described a simple, portable and low-cost electrochemical method for BZP determination in beverage (vodka, whisky and white wine) and seized street samples. The electrochemical behavior of BZP was investigated by differential pulse voltammetry (DPV) and cyclic voltammetry (CV) using a screen-printed carbon electrode (SPCE), where a single irreversible oxidation processes was presented at around +0.7 V (vs. Ag pseudo reference). An electrochemical mechanism for BZP oxidation at SPCE was proposed. The quantification of BZP in beverage samples was optimized by the DPV technique in 0.12 mol L−1 Britton Robison buffer solution (pH = 5.0) using a drop-casting method of small sample volume (~100 μL) on SPCE. The proposed method showed a good linear range for BZP determination from 1 to 75 μmol L−1 with a low limit of detection (0.3 μmol L−1) and recovery values between 90 and 102%. Additionally, interference studies for other synthetic drugs from piperazine class and for other drugs commonly found in combination with BZP, such as 3,4-methylenedioxymethamphetamine (ecstasy), caffeine and synthetic cathinones, were performed. The analytical performance of the SPCE for detection of BZP in beverage and seized samples presents great potential for a simple and rapid screening method in forensic analysis.

PHAIR: a biosensor for pH measurement in air\u2013liquid interface cell culture

In many biological systems, pH can be used as a parameter to understand and study cell dynamics. However, measuring pH in live cell culture is limited by the sensor ion specificity, proximity to the cell surface, and scalability. Commercially available pH sensors are difficult to integrate into a small-scale cell culture system due to their size and are not cost-effective for disposable use. We made PHAIR—a new pH sensor that uses a micro-wire format to measure pH in vitro human airway cell culture. Tungsten micro-wires were used as the working electrodes, and silver micro-wires with a silver/silver chloride coating were used as a pseudo reference electrode. pH sensitivity, in a wide and narrow range, and stability of these sensors were tested in common standard buffer solutions as well as in culture media of human airway epithelial cells grown at the air–liquid interface in a 24 well cell culture plate. When measuring the pH of cells grown under basal and challenge conditions using PHAIR, cell viability and cytokine responses were not affected. Our results confirm that micro-wire-based sensors have the capacity for miniaturization and detection of diverse ions while maintaining sensitivity. This suggests the broad application of PHAIR in various biological experimental settings.

Multiwalled Carbon Nanotube (MWCNT) Based Electrochemical Paper-Based Analytical Device (ePAD) for the Determination of Catechol in Wastewater

A novel platform for the phenolics in wastewater based on an electrochemical multiwalled carbon nanotube paper-based analytical device (MWCNT-ePAD) has been developed. Phenolics such as catechol are widely used in industrial processes. Catechol has a strong aroma and is a possible human carcinogen. Therefore, this work focused on the determination of catechol in wastewater. The ePAD was fabricated on chromatography paper. Graphite ink was used as the working electrode and counter electrode, while Ag/AgCl ink was employed as a pseudo reference electrode. The sensitivity of the MWCNT-ePAD biosensor toward phenolics was improved using a multiwall carbon nanotube modified working electrode. The determination of phenolics as the enzyme-catalyzed reaction product using laccase was performed by chronoamperometry. The MWCNT-ePAD biosensor was used for the determination of catechol from 0.8 to 3.0 mg/L with a detection limit of 0.25 mg/L. The reproducibility of the MWCNT-ePAD biosensor was less than 4.95%, and the lifetime of the device was more than 30 days. Additionally, the developed biosensor was applied to determine catechol in wastewater with consistent results compared to a Folin-Ciocalteu assay. The MWCNT-ePAD biosensor was rapid (15 s), cost-effective (0.7 $), and required low reagent consumption (15 µL) with accurate phenolic determination in wastewater by the combination of a paper-based device, an electrochemical biosensor, and a nanomaterial technology.

Improved Height Estimation Using Extended Kalman Filter on UWB‐Barometer 3D Indoor Positioning System

Indoor 3D positioning system requires precise information from all three dimensions in space, but measurements in the vertical direction are usually interfered by sensors properties, unexpected obstructions, and other factors. Thus, accuracy and robustness are not guaranteed. Aiming at this problem, we propose a novel sensor fusion algorithm to improve the height estimation for a UWB‐barometer integrated positioning system by introducing a pseudo reference update mechanism and the extended Kalman filter (EKF). The proposed fusion approach effectively helps with sensing noise reduction and outlier restraint. The results from numerical experiment investigations demonstrate that the accuracy and robustness of the proposed method achieved better improvement in height determination.