Screen-printed Electrode Array Research Articles

Organ-on-a-Chip Platform with an Integrated Screen-Printed Electrode Array for Real-Time Monitoring Trans-Epithelial Barrier and Bubble Formation.

Cellular tight junctions play a key role in establishing a barrier between different compartments of the body by regulating the selective passage of different solutes across epithelial and endothelial tissues. Over the past decade, significant efforts have been conducted to develop more clinically relevant "organ-on-a-chip" models with integrated trans-epithelial electrical resistance (TEER) monitoring systems to help better understand the fundamental underpinnings of epithelial tissue physiology upon exposure to different substances. However, most of these platforms require the use of high-cost and time-consuming photolithography processes, which limits their scalability and practical implementation in clinical research. To address this need, we have developed a low-cost microfluidic platform with an integrated electrode array that allows continuous real-time monitoring of TEER and the risk of bubble formation in the microfluidic system by using scalable manufacturing technologies such as screen printing and laser processing. The integrated printed electrode array exhibited excellent stability (with less than ∼0.02 Ω change in resistance) even after long-term exposure to a complex culture medium. As a proof of concept, the fully integrated platform was tested with HMT3522 S1 epithelial cells to evaluate the tight barrier junction formation through TEER measurement and validated with standard immunostaining procedures for Zonula occludens-1 protein. This platform could be regarded as a stepping stone for the fabrication of disposable and low-cost organ and tissue-on-a-chip models with integrated sensors to facilitate studying the dynamic response of epithelial tissues to different substances in more physiologically relevant conditions.

A Flexible Iontronic Capacitive Sensing Array for Hand Gesture Recognition Using Deep Convolutional Neural Networks.

Hand gesture recognition, one of the most popular research topics in human-machine interaction, is extensively used in visual and augmented reality, sign language translation, prosthesis control, and so on. To improve the flexibility and interactivity of wearable gesture sensing interfaces, flexible electronic systems for gesture recognition have been widely studied. However, these systems are limited in terms of wearability, stability, scalability, and robustness. Herein, we report a flexible wearable hand gesture recognition system that is based on an iontronic capacitive pressure sensing array and deep convolutional neural networks. The entire capacitive array is integrated into a flexible silicone wristband and can be comfortably and conveniently wrapped around the wrist. The pressure sensing array, which is composed of an iontronic film sandwiched between two flexible screen-printed electrode arrays, exhibits a high sensitivity (775.8 kPa-1), fast response time (65 ms), and high durability (over 6000 cycles). Image processing techniques and deep convolutional neural networks are applied for sensor signal feature extraction and hand gesture recognition. Several contexts such as intertrial test (average accuracy of 99.9%), intersession rewearing (average accuracy of 93.2%), electrode shift (average accuracy of 83.2%), and different arm positions during measurement (average accuracy of 93.1%) are evaluated.

(Digital Presentation) Rapid and Oxygen-Insensitive Electrochemical Immunoassay for Detection and Staging of Prostate Cancer

Prostate cancer (PCa) is the most common cancer among men diagnosed worldwide. The conventional non-invasive test for detection and staging of prostate cancer include prostate specific antigen (PSA) test which often can give false positives and is unable to distinguish between aggressive and indolent stages of PCa. This results in doing unnecessary invasive tests like digital rectal examination (DRE), biopsy etc., which only gives further anxiety to patients. Here we describe a rapid and oxygen-insensitive microfluidic immunoassay for on-line capture and precise detection of potential prostate cancer protein biomarkers. Measurement of a panel of biomarkers will help in not only diagnosing the PCa precisely but may also help in staging the cancer.The microfluidic system includes protein capture from serum using a sandwich ELISA arrangement and signal-transducing poly-horseradish peroxidase (poly-HRP) enzyme labels on an 8-electrode screen-printed carbon array. A major challenge in using these screen-printed electrode arrays is the estimation of the electrochemical surface area (ECSA) of electrodes because the current signal is proportional to ECSA and variability in the electrode surface areas generate variability in the corresponding currents. We show that normalization of electrode responses having different surface areas can be achieved using in-situ experimental methods and that the normalization methods can improve the precision of the immunoassay. Another challenge in electrochemical immunoassay systems is the interference of oxygen using the mediator hydroquinone1. A range of osmium polypyridyl complexes were studied to find the best mediator that is not affected by oxygen.Using an optimized mediator and a simple method to estimate carbon electrode surface area, immunoassays can be designed with improved detection characteristics.(1) Dhanapala, L.; Jones, A. L.; Czarnecki, P.; Rusling, J. F. Sub-Zeptomole Detection of Biomarker Proteins Using a Microfluidic Immunoarray with Nanostructured Sensors. Anal. Chem. 2020, 92 (12), 8021–8025. ttps://doi.org/10.1021/acs.analchem.0c01507.

Printed Stretchable Liquid Metal Electrode Arrays for In Vivo Neural Recording.

The adoption of neural interfacing into neurological diagnosis is severely hampered by the complex, costly, and error-prone manufacturing methods, requiring new fabrication processes and materials for flexible neural interfacing. Here a strategy for fabricating highly stretchable neural electrode arrays based on screen printing of liquid metal conductors onto polydimethylsiloxane substrates is presented. The screen-printed electrode arrays show a resolution of 50µm, which is ideally applicable to neural interfaces. The integration of liquid metal-polymer conductor enables the neural electrode arrays to retain stable electrical properties and compliant mechanical performance under a significant (≈108%) strain. Taking advantage of its high biocompatibility, liquid metal electrode arrays exhibit excellent performance for neurite growth and long-term implantation. The stretchable electrode arrays can spontaneously conformally come in touch with the brain surface, and high-throughput electrocorticogram signals are recorded. Based on stretchable electrode arrays, real-time monitoring of epileptiform activities can be provided at different states of seizure. The method reported here offers a new fabrication strategy to manufacture stretchable neural electrodes, with additional potential utility in diagnostic brain-machine interfaces.

Bioimpedance method for monitoring venous ulcers: Clinical proof-of-concept study

Evaluation of wound status is typically based on means which require the removal of dressings. These procedures are often also subjective and prone to inter-observer bias. To overcome aforementioned issues a bioimpedance measurement-based method and measurement system has been developed to evaluate the state of wound healing. The measurement system incorporated a purpose-built bioimpedance device, a measurement software and a screen-printed electrode array. The feasibility and the performance of the system and method were assessed in an open non-randomized follow-up study of seven venous ulcers. Healing of ulcers was monitored until the complete re-epithelialization was achieved. The duration of follow-up was from 19 to 106 days (mean 55.8 ± 25.2 days). A variable designated as the Wound Status Index (WSI), derived from the bioimpedance data, was used for describing the state of wound healing. The wound surface area was measured using acetate tracing for the reference. A strong correlation was found between the WSI and the acetate tracing data, r(93) = - 0.84, p < 0.001. The results indicate that the bioimpedance measurement-based method is a promising quantitative tool for the evaluation of the status of venous ulcers.

Electrochemical Microphysiometry Detects Cellular Glutamate Uptake

Glutamate is the principal excitatory amino acid in the vertebrate nervous system and is responsible for learning and memory. Understanding of these complex biological processes can be gained through experimentally accessible systems of glutamate detection. In this work, the microclinical analyzer (μCA) was used with a sensitive and stable glutamate sensor and model neuronal cells for quantitative glutamate detection under physiological relevant shear. Glutamate was detected by immobilized glutamate oxidase on a screen-printed electrode array. The sensor's linear range spanned glutamate's physiological to pathophysiological concentration range, and the biologically relevant sub-second to month temporal range. After 11 hours of use, the sensor retained 91 ± 1% of its signal, and it was able to be stored for a month without a significant decrease. When model neuronal cells were integrated into the μCA bioreactor and exposed to glutamate, they initially took up 210 ± 100 μmoles of glutamate, which increased to 390 ± 50 μmoles during their second exposure. These data suggest that the neurotransmitter uptake systems were functional and may be upregulated. The dynamic and durable μCA platform offers an experimentally accessible system of glutamate detection that can be used to monitor glutamate metabolism and signaling.

Label-free Detection of Prostate Specific Antigen at a Screen-printed Immunosensor Modified with a Nanostructured Gold Layer

The development of a disposable immunosensor based on a hybrid gold–carbon screen-printed electrode array is described. The electrodeposition of gold is shown to lead to a field of nanocrystals that facilitates antibody immobilization and enhances electron transfer. A label-free analysis protocol based on ferrocyanide has been developed for the detection of Prostate Specific Antigen in the fg mL−1 range.

Detection of biomarkers for inflammatory diseases by an electrochemical immunoassay: The case of neopterin

An electrochemical immunoassay for neopterin was developed using recently produced specific antibodies immobilized to protein A-coated magnetic beads in combination with differential pulse voltammetry and screen-printed array of electrodes. Neopterin–alkaline phosphatase conjugate was used as label in a competitive assay format. Multiplexed analysis of neopterin was demonstrated by replacing the traditional ELISA with electrochemical detection and the traditional plastic wells with screen-printed array of electrodes. The optimized electrochemical method, based on polyclonal antibodies, reached a limit of detection of 0.008ng/mL with an average RSD %=10. Serum samples collected from patients with sepsis, healthy volunteers and other patients without a confirmed clinical diagnosis were also analyzed. The obtained results, compared with those of a commercial ELISA kit, had a significant correlation, showing the possibility to distinguish among the serum samples from ill or healthy subjects.

Disposable Electrochemical Aptasensor Array by Using in Situ DNA Hybridization Inducing Silver Nanoparticles Aggregate for Signal Amplification

Nanomaterials as tracing tags have been widely used in biosensors with high sensitivity and selectivity. In this work, a signal amplification electrochemical aptamer sensing strategy for the detection of protein was designed by combining the hybridization-inducing aggregate of DNA-functionalized silver nanoparticles (AgNPs) and differential pulse stripping voltammetry (DPSV) detection. The multiprobes containing hybridization DNA and aptamers were anchored onto the silver nanoparticles. The protein assay was prepared through the immobilization of capture aptamer that specifically recognizes platelet-derived growth factor (PDGF-BB) on gold nanoparticles modified screen-printed electrode (SPE) array. After a sandwich-type reaction, two kinds of DNA-modified AgNPs were simultaneously added on the electrode surface for specifically recognizing PDGF-BB and forming the AgNPs aggregate caused by in situ hybridization of DNA. Compared to the signal-labeled tag, the tracing aggregate tags showed a strong electroactivity for signal amplification through stripping detection of silver after preoxidation. By using the hybridization-inducing aggregate as electrochemical readouts, the sensor showed wide linear range and low detection limit. The hybridization-inducing AgNPs aggregate were further used as tracing tags in multiplied proteins assays for PDGF-BB and thrombin by using the SPE array chip as sensing platform. The cross-talk between different aptamer-modified electrodes on the same array was avoided because of the advantage of labeled AgNPs. The array detection was also applied in the logic gate operation. The proposed method described here is ideal for multianalytes determination in clinical diagnostics with good analytical performance.

Label-free voltammetric detection of MicroRNAs at multi-channel screen printed array of electrodes comparison to graphite sensors

The multi-channel screen-printed array of electrodes (MUX-SPE16) was used in our study for the first time for electrochemical monitoring of nucleic acid hybridization related to different miRNA sequences (miRNA-16, miRNA-15a and miRNA-660, i.e, the biomarkers for Alzheimer disease). The MUX-SPE16 was also used for the first time herein for the label-free electrochemical detection of nucleic acid hybridization combined magnetic beads (MB) assay in comparison to the disposable pencil graphite electrode (PGE). Under the principle of the magnetic beads assay, the biotinylated inosine substituted DNA probe was firstly immobilized onto streptavidin coated MB, and then, the hybridization process between probe and its complementary miRNA sequence was performed at MB surface. The voltammetric transduction was performed using differential pulse voltammetry (DPV) technique in combination with the single-use graphite sensor technologies; PGE and MUX-SPE16 for miRNA detection by measuring the guanine oxidation signal without using any external indicator. The features of single-use sensor technologies, PGE and MUX-SPE16, were discussed concerning to their reproducibility, detection limit, and selectivity compared to the results in the earlier studies presenting the electrochemical miRNA detection related to different miRNA sequences.

Label-free and multiplexed electrochemical detection of PCR fragments on screen-printed electrode arrays. Application to spoligotyping of Mycobacterium tuberculosis

Label-free and multiplexed electrochemical detection of PCR fragments on screen-printed electrode arrays. Application to spoligotyping of Mycobacterium tuberculosis

Multi channel screen printed array of electrodes for enzyme-linked voltammetric detection of MicroRNAs

In the present work, a sensitive and selective enzyme-linked electrochemical sensor technology using magnetic beads assay was demonstrated for voltammetric detection of microRNAs (miRNAs) as the first time herein by using the multi-channel screen-printed array of electrodes (MUX-SPE16s). The streptavidin coated magnetic beads were used as a solid phase to immobilize biotinylated DNA capture probe, and then the complementary target RNA sequence (miRNA-15a) was recognized with the capture DNA probe. After attachment of the streptavidin–alkaline phosphatase enzyme (SALP) to biotinylated hybrid, the electroactive product α-naphthol was measured +0.188V by linear sweep voltammetry (LSV) technique in combination with a single-use pencil graphite electrode (PGE) compared to MUX-SPE16. The oxidation signal of α-naphthol indicates the hybridization occurred between DNA probe and its RNA target in the sample. The selectivity of our assay was tested in the presence of non-complementary miRNA sequence, a very good discrimination was achieved compared to the results obtained with the full match hybridization of probe with miRNA-15a target. The detection limit of miRNA-15a target sequence was also calculated as 0.992μg/mL (98.60pmole in 1mL sample) at PGE, and 0.114μg/mL (34.20fmole in 3μL sample) with MUX-SPE16 system.

Electrochemical Bioassay for The Detection of Tnf-α Using Magnetic Beads and Disposable Screen-Printed Array of Electrodes

In this study we have developed an electrochemical bioassay for the analysis of TNF-α, coupling magnetic beads with disposable electrochemical platforms. TNF-α is a pro inflammatory cytokine that participates in the regulation of immune defense against various pathogens and the recovery from injury. It plays a central role in the development of many inflammatory diseases. The bioassay was based on a sandwich format using alkaline phosphatase as an enzymatic label and an eight-sensor screen-printed array as an electrochemical transducer. The modified magnetic beads were captured by a magnet on the surface of each graphite working electrode of the array and the electrochemical detection was thus achieved through the addition of the alkaline phosphatase substrate (1-naphthylphosphate); 1-naphthol produced during the enzymatic reaction was detected using differential pulse voltammetry. The parameters influencing the different steps of the assay were optimized in order to reach the best sensitivity and specificity. The proposed strategy offers great promise for analysis of clinical diagnostics, considering also that arrays allow the simultaneous analysis of different samples.

A novel screen-printed electrode array for rapid high-throughput detection

A novel multi-channel electrode array sensing device was fabricated by screen-printing techniques using 96-well plate as the template. To confirm its practical value, we developed a one-step preparation of multi-walled carbon nanotubes (MWCNTs) doped electrode array by an ink containing MWCNTs, which was applied to the simultaneous detection of a variety of biological samples and environmental pollutants. Results demonstrated that the designed sensing device could carry out the multiple measurements of different analytes at the same time, while MWCNTs enhanced the electrocatalytic activity of electrodes toward electroactive molecules. The required amount of each sample was only ∼200 μL. Moreover, the excellent differential pulse voltammetric (DPV) response toward dopamine, hydroquinone and catechol was obtained and the detection limits was determined to be 0.337, 0.289 and 0.369 μM, respectively. Comparing it with the traditional screen-printed electrode (SPE), this sensing device possesses the advantages of high-throughput, fast electron transfer rate for electrodes, short-time analysis and low sample consumption.

Development of disposable low density screen-printed electrode arrays for simultaneous electrochemical measurements of the hybridisation reaction

Abstract This paper deals with the development of different formats of screen-printed array of electrodes. The arrays consist of a silver pseudo-reference electrode surrounded by four or eight radially distributed working electrodes. Two different commercially available inks were used to fabricate the working electrode (WE) surfaces: a carbon-based ink and a gold-based ink. Due to their low curing temperature, the inks were screen-printed onto an inert plastic substrate. The electrochemical characterisation of these arrays is shown; reproducibility of the arrays as well as the batch-to-batch reproducibility were also assessed. As model case, the four WE array was used as platform to develop an electrochemical genosensor. Analytical parameters such as linearity range, reproducibility and detection limit of the genosensor were evaluated. Preliminary results on real samples were also reported.

Electroaddressed immobilization of recombinant HIV-1 P24 capsid protein onto screen-printed arrays for serological testing

A serological chemiluminescent biochip was designed based on screen-printed electrode arrays composed of nine 1-mm 2 electrodes. Arrays were shown to be produced with good batch-to-batch reproducibility (standard deviations of 4.4 and 12.0% for ferricyanide oxidation potential and current, respectively) and very good reproducibility within a particular array (2.0 and 7.5% standard deviations for the same controls). Electrode arrays were used to electroaddress various bioconjugate structures comprising a recombinant HIV-1 P24 capsid protein (RH24K) in polypyrrole film. Entrapment of RH24K preimmobilized onto maleic anhydride- alt-methyl vinyl ether copolymer was shown to be the more efficient immobilization procedure. This addressed sensing layer enabled the detection of anti-P24 antibodies at a concentration of 3.5 ng/ml through peroxidase-labeled anti-human immunoglobulin G reaction. The biochip was used to perform an HIV-1 serological test in human sera. HIV-1 seropositive and seronegative sera were easily discriminated using serum dilutions greater than 1/10,000.

Amperometric screen-printed biosensor arrays with co-immobilised oxidoreductases and cholinesterases

Amperometric screen-printed biosensor arrays for detection of pesticides (organophosphates and carbamates) and phenols have been developed. Cholinesterases (AChE and BChE), tyrosinase (TYR), peroxidases (SBP, soybean and HRP, horseradish) and cellobiose dehydrogenase (CDH) were combined on the same array consisting of one Ag/AgCl reference electrode surrounded by eight radially distributed working electrodes of either carbon or platinum. Mainly cross-linking with glutaraldehyde was employed for enzyme immobilisation. The substrates for the enzymes were acetylthiocholine for cholinesterases (ChEs), cellobiose for CDH and hydrogen peroxide for peroxidases. Hydrogen peroxide was generated in the presence of glucose by co-immobilised glucose oxidase (GOx). All measurements were performed in an electrochemical steady state system specially constructed for eight channel screen-printed electrode arrays. The achieved relative standard deviation values calculated for different enzyme substrates (10 measurements) were typically below 7% and one assay was completed within less than 10 min. The detection limits for pesticides and phenols were in the nanomolar and micromolar ranges, respectively. The developed biosensor array was evaluated on wastewater samples. To simplify interpretation of results, the measured data were treated with multivariate analysis–principal component analysis (PCA).

Screen-printed ultramicroelectrode arrays for on-site stripping measurements of trace metals

The properties and advantages of mercury-coated screen-printed electrode arrays for on-site stripping analysis of trace metals are described. These disposable composite electrodes are fabricated by a combination of thick-film printing and laser machining technologies, and offer a stripping performance comparable with that of traditional stripping electrodes. Scanning electron microscopy illustrates the attractive microdisk and interelectrode dimensions, which offer a non-linear diffusional flux during long stripping experiments. The stripping performance is not compromised by placing non-deaerated/quiescent sample drops on the strip, as desired for field monitoring of trace metals. Various experimental variables have been optimized to yield low detection limits (e.g. 0.1 μg/l lead for 4 min deposition) and good precision (e.g. relative standard deviation of 4.7% for ten repetitive measurements). The applicability to assays of drinking water and wine is illustrated.