Electrochemical Enzyme-linked Immunosorbent Assay Research Articles

Dielectrophoretic capture and electrochemical enzyme-linked immunosorbent assay of single melanoma cells at an array of interlocked spiral bipolar electrodes.

Analysis of single cancer cells is critical to obtain accurate patient diagnosis and prognosis. In this work, we report the selective dielectrophoretic capture and electrochemical analysis of single melanoma cells at an array of interlocked spiral bipolar electrodes (iBPEs). Following dielectrophoretic capture, individual melanoma cells are hydrodynamically transferred into picoliter-scale chambers for subsequent analysis. The interlocked spiral end of the iBPE (the sensing pole) is utilized to read out an electrochemical enzyme-linked immunosorbent assay (eELISA), which quantifies the expression of a cell surface antigen, melanoma cell adhesion marker (MCAM). The opposite pole of each BPE is located in a fluidically isolated compartment containing reagents for electrogenerated chemiluminescence (ECL), such that luminescence reports iBPE current. In a preliminary device design, the ECL intensity was insufficient to detect MCAM expression on single cells. To achieve single-cell analysis, we decreased the gap size between the interlocked spirals tenfold (5.0 μm to 0.5 μm), thereby creating a more sensitive biosensor by enhanced redox cycling of the product of eELISA. This work is significant because it allows for the selective isolation and sensitive analysis of individual melanoma cells in a device amenable to point-of-care (POC) application by combining dielectrophoresis (DEP) with interdigitated bipolar electrodes (IDBPEs).

Application of enzyme-linked immunosorbent assay in cancer detection

The enzyme-linked immunosorbent assay (ELISA) has emerged as an indispensable method in the realm of cancer detection., serving as a significant factor in the timely identification, prediction, and surveillance of many forms of cancer. ELISA as a highly sensitive immunological assay, utilizes the binding affinity between antibodies and antigens to detect and quantify cancer-associated biomolecules, such as tumor markers, oncogenic proteins, and specific antibodies. The recently adopted methodology facilitates the identification of cancer-associated biomarkers in various types of samples, such as plasma, urine, and tissue extracts. In the context of cancer diagnosis, ELISA aids in the early detection of malignancies by detecting cancer-specific biomarkers at low concentrations, allowing for timely intervention and improved patient outcomes. This research provides a concise overview of the multifaceted applications of ELISA in the field of oncology, especially in electrochemical ELISA and gold nanoparticle–based ELISA. It discusses the diverse biomarkers employed, and elucidates its significance in cancer research and clinical practice.

Improving design features and air bubble manipulation techniques for a single-step sandwich electrochemical ELISA incorporating commercial electrodes into capillary-flow driven immunoassay devices.

Integrating electrochemistry into capillary-flow driven immunoassay devices provides unique opportunities for quantitative point-of-care testing. Although custom electrodes can be inexpensive and are tunable, they require skilled fabrication. Here, we report the incorporation of a commercial electrode into a capillary-flow driven immunoassay (iceCaDI) device for a single end-user step sandwich electrochemical enzyme-linked immunosorbent assay (ELISA). The iceCaDI device is a pump-free portable microfluidic device with an integrated commercial screen-printed electrode and flow driven by capillary action. The iceCaDI device is composed of alternating polyester transparency film and double-sided adhesive film layers that are patterned with a laser cutter. This platform was designed to address known limitations of laminated device fabrication methods and operation. First, we developed a foldable laminated device fabrication using hinges for easy assembly and precise alignment. Second, reagent dispersing was achieved by incorporating a 1 mm wide arrow-shaped notch in the middle of the channel that trapped an air bubble and formed a baffle that facilitated reagent spreading to cover the detection area. Third, small vent holes were added to the top layer of the channels to prevent air bubbles from blocking flow. Finally, we fabricated a CRP immunosensor with a detection range of 0.625 to 10.0 μg mL-1 as a proof-of-concept to demonstrate an automatically driven sandwich electrochemical ELISA using the iceCaDI device. Three concentrations of CRP were successfully measured under flow conditions within 8 min. Our proposed device is a promising approach and a step forward in the development of point-of-care (POC) devices for techniques that traditionally require multiple user steps.

Electrochemical Cellulase-Linked ELASA for Rapid Liquid Biopsy Testing of Serum HER-2/neu.

Non-invasive liquid biopsy assays for blood-circulating biomarkers of cancer allow both its early diagnosis and treatment monitoring. Here, we assessed serum levels of protein HER-2/neu, overexpressed in a number of aggressive cancers, by the cellulase-linked sandwich bioassay on magnetic beads. Instead of traditional antibodies we used inexpensive reporter and capture aptamer sequences, transforming the enzyme-linked immuno-sorbent assay (ELISA) into an enzyme-linked aptamer-sorbent assay (ELASA). The reporter aptamer was conjugated to cellulase, whose digestion of nitrocellulose film electrodes resulted in the electrochemical signal change. ELASA, optimized relative aptamer lengths (dimer vs monomer and trimer), and assay steps allowed 0.1 fM detection of HER-2/neu in the 10% human serum in 1.3 h. Urokinase plasminogen activator and thrombin as well as human serum albumin did not interfere, and liquid biopsy analysis of serum HER-2/neu was similarly robust but 4 times faster and 300 times cheaper than both electrochemical and optical ELISA. Simplicity and low cost of cellulase-linked ELASA makes it a perspective diagnostic tool for fast and accurate liquid biopsy detection of HER-2/neu and of other proteins for which aptamers are available.

Array of Interdigitated Bipolar Electrodes for the Selective Capture and Analysis of Melanoma Cells

In this work, we develop an array of biosensors for the selective dielectrophoretic capture and electrochemical detection of single to few melanoma cells. Each biosensor in the array consists of a gold thin film interdigitated bipolar electrode (IDBPE) patterned on a glass substrate. Microwells are patterned over the interdigitated end of each IDBPE to restrict the number of cells captured and to retain cells on the electrodes for subsequent analysis. An overlying microfluidic channel controls delivery of the cell sample to the microwells. Cells are attracted to the interdigitated electrode by a positive dielectrophoretic force, thereby pulling them into the microwells, where they remain trapped during the next step – introduction of reagents for electrochemical enzyme-linked immunosorbent assay (eELISA). The dimensions of the wells, solution flow rate, and AC voltage applied all support the retention of the cells on the electrodes once they are captured.A bipolar electrode (BPE) is a conductor, which in the presence of an externally applied electric field, facilitates electrically coupled faradaic reactions at its opposing ends. In the context of analysis, a sensing reaction at one pole of the BPE is coupled to a reporting reaction, which produces a visual signal at the opposite pole. Because of their wireless operation, arrays of tens to thousands of BPEs can be operated in parallel with a single power supply – an advantageous feature for parallel analysis of few or single cells. However, traditional BPEs with electrogenerated chemiluminescence (ECL) as the reporting reaction do not provide sufficient sensitivity for biologically relevant detection limits, and therefore, require a means of signal amplification for such applications. To address this issue, we previously developed IDBPEs, which facilitate redox cycling by interdigitation of the sensing pole of each BPE of an array with a shared driving electrode, thereby yielding more intense ECL at the reporting pole.1 In the present study, the interdigitated end of the IDBPE is utilized for eELISA to quantify the expression of a cell surface antigen, melanoma cell adhesion marker (MCAM). Cells are labelled with biotinylated anti-human MCAM and alkaline phosphatase (ALP) conjugated streptavidin. Once cells are captured, the redox inactive substrate, para-aminophenyl phosphate (PAPP), is flowed through the microchannels and ALP catalyzes its conversion to the redox active species para-aminophenol (PAP). The amplified current obtained at each IDBPE by the redox cycling of PAP and its oxidized form, quinone imine (QI), is reported by an ECL reaction on its opposing pole. The ECL signal obtained at each IDBPE is correlated to the expression level of MCAM on the melanoma cells isolated in the corresponding well. This work is significant because it allows for the sensitive detection of melanoma cells in a device amenable to point-of-care application by combining selective enrichment of malignant cells by dielectrophoresis with the amplification and facile arraying afforded by IDBPEs. Borchers, J.S., Campbell, C.R., Van Scoy, S.B., Clark, M.J. and Anand, R.K. (2021), Redox Cycling at an Array of Interdigitated Bipolar Electrodes for Enhanced Sensitivity in Biosensing. ChemElectroChem. https://doi.org/10.1002/celc.202100523

Rolling circle amplified DNAzyme followed with covalent organic frameworks: Cascade signal amplification of electrochemical ELISA for alfatoxin M1 sensing

A sensitive, selective and high-throughput electrochemical enzyme-linked immunosorbent assay (EC-ELISA) platform was constructed for determination of alfatoxin M1 (AFM1). Rolling circle amplified (RCA) DNAzyme coupled with covalent organic frameworks (COFs) modified electrode was used as signal amplification strategies. The immunoreaction was performed on a microplate via specific recognition of AFM1 by primer-AuNPs-aptamer and anti-AFM1 antibody. The primer triggered RCA reaction produced a long single-stranded DNA, which can fold into a peroxidase-mimicking DNAzyme with the presence of hemin and K+. In the presence of H2O2, DNAzyme catalyzed the oxidation of 2-aminophenol and the oxidation product 3-aminophenylhydrazine was enriched as a signal molecule on the TpBD modified electrode with a significant current response. Under optimized conditions, the sensor exhibited high selectivity and sensitivity towards AFM1 with a detection limit of 0.15 ng/mL. In addition, the AFM1 can also be quantified by the naked eye. This EC-ELISA platform was successfully applied for the determination of AFM1 in milk samples with recoveries from 93.37% to 104.01%.

Microfluidic electrochemical immunosensor for the trace analysis of cocaine in water and body fluids.

Quick but accurate testing and on-the-spot monitoring of cocaine in oral fluids and urine continues to be an important toxicological issue. In terms of drug testing, a number of devices have been introduced into the market in recent decades, notably for workplace inspection or roadside testing. However, these systems do not always fulfill the requirements in terms of reliability, especially when low cut-off levels are required. With respect to surface water, the presence of anthropogenic small organic molecules such as prescription and over-the-counter pharmaceuticals as well as illicit drugs like cannabinoids, heroin, or cocaine, has become a challenge for scientists to develop new analytical tools for screening and on-site analysis because many of them serve as markers for anthropogenic input and consumer behavior. Here, a modular approach for the detection of cocaine is presented, integrating an electrochemical enzyme-linked immunosorbent assay (ELISA) performed on antibody-grafted magnetic beads in a hybrid microfluidic sensor utilizing flexible tubing, static chip and screen-printed electrode (SPE) elements for incubation, recognition, and cyclic voltammetry measurements. A linear response of the sensor vs. the logarithm of cocaine concentration was obtained with a limit of detection of 0.15ng/L. Within an overall assay time of 25minutes, concentrations down to 1ng/L could be reliably determined in water, oral fluids, and urine, the system possessing a dynamic working range up to 1mg/L.

A simple electrochemical immunosensor platform for detection of Apolipoprotein A1 (Apo-A1) as a bladder cancer biomarker in urine

Bladder cancer is one of the tumors associated with the highest mortality rate. It is clinically characterized by high recurrent rates and poor prognosis once tumors invade the lamina propia. Nevertheless, current diagnostic techniques such as cystoscopy and cytology are invasive, time-consuming, and expensive. To address these challenges, we developed an electrochemical enzyme-linked immunosorbent assay (eELISA) platform on indium tin oxide (ITO) glass strips to quantify Apolipoprotein-A1 (Apo-A1) proteins in urine reported as an early bladder cancer biomarker with high sensitivity and specificity. We thoroughly studied the kinetics of ALP enzyme on the surface of ITO electrode so that we determined the minimum incubation time (2 min) and temperature (25 °C) for electrochemical measurement. Combined with chronocoulometry (CC) method under optimized conditions, our developed ITO-based eELISA platform can sensitively detect the existence of Apo-A1 as low as 1 pM in both PBS and urine with the dynamic range of concentrations (1 pM–100 nM) in a small one-drop assay system. Also, the simply prepared detection platform was successfully applied to urine condition. By using the developed platform, urine samples of bladder patients were clearly distinguished from normal controls. Our developed eELISA platform offers a simple and sensitive immunoassay approach for point-of-care (POC) diagnostic system.

Recent Advances in Enhancement Strategies for Electrochemical ELISA-Based Immunoassays for Cancer Biomarker Detection.

Electrochemical enzyme-linked immunosorbent assay (ELISA)-based immunoassays for cancer biomarker detection have recently attracted much interest owing to their higher sensitivity, amplification of signal, ease of handling, potential for automation and combination with miniaturized analytical systems, low cost and comparative simplicity for mass production. Their developments have considerably improved the sensitivity required for detection of low concentrations of cancer biomarkers present in bodily fluids in the early stages of the disease. Recently, various attempts have been made in their development and several methods and processes have been described for their development, amplification strategies and testing. The present review mainly focuses on the development of ELISA-based electrochemical immunosensors that may be utilized for cancer diagnosis, prognosis and therapy monitoring. Various fabrication methods and signal enhancement strategies utilized during the last few years for the development of ELISA-based electrochemical immunosensors are described.

Electrochemical immunosensor for tumor necrosis factor-alpha detection in undiluted serum.

An immunosensor for the sensitive detection and estimation of tumor necrosis factor-alpha (TNF-α) in undiluted serum has been developed via an electrochemical enzyme-linked immunosorbent assay (ELISA) process. Electrochemical sensing was performed using a TNF-α specific monoclonal antibody modified self-assembled monolayer of dithiobis(succinimidyl propionate) on a comb-shaped gold electrode microarray. After anti-TNF-α antibody binding, unreacted active groups of DTSP were blocked using ethanol amine (EA) and nonspecific binding was prevented using phosphate buffer based starting block T20 (SB). Sensitive and disposable SB-EA-anti-TNF-α/DTSP/Au electrodes were exposed to solutions with different TNF-α concentrations for 20min in undiluted serum. Conversion of 4-aminophenyl phosphate to 4-aminophenol and its electrochemical oxidation was utilized for indirect estimation of TNF-α. Results for SB-anti-TNF-α/DTSP/Au electrodes indicate that the sensors can be used for the sensitive estimation of TNF-α in undiluted serum in the range 500pg/ml to 100ng/ml with a detection limit of 60pg/ml and sensitivity of 0.46 (ng/ml)-1. Negligible interference from serum and other biomarker proteins was observed. The described electrochemical ELISA is much faster than conventional ELISA and can be applied for sensing of a range of analytes in real patient samples.

The reliability of electrochemical enzyme-linked immunosorbent assay for detection of dentin sialophosphoprotein in gingival crevicular fluid

To investigate the reliability of electrochemical enzyme-linked immunosorbent assay(ELISA)for the detection of dentin sialophosphoprotein(DSPP)in gingival crevicular fluid(GCF)of orthodontic patients. GCF were collected from the orthodontic patients, and then the amount of DSPP in GCF were detected by electrochemical ELISA and spectroscopic ELISA respectively. The difference between the results of two methods were analyzed. In electrochemical ELISA, the second order derivative linear sweep voltammetric peak current was linear with DSPP concentration in the range from 0.25-800.00 ng/L. It was found that the detection limit of the electrochemical method(0.25 ng/L)was much lower than that of the spectroscopic method. The paired-samples rank sum test showed no significant difference between the DSPP concentrations in human GCF samples measured by spectroscopic ELISA procedure and those measured by electrochemical ELISA procedure(P=0.063). Electrochemical ELISA is a viable way of detecting DSPP in GCF with higher sensitivity than spectroscopic ELISA.

A nanocoaxial-based electrochemical sensor for the detection of cholera toxin.

Sensitive, real-time detection of biomarkers is of critical importance for rapid and accurate diagnosis of disease for point of care (POC) technologies. Current methods do not allow for POC applications due to several limitations, including sophisticated instrumentation, high reagent consumption, limited multiplexing capability, and cost. Here, we report a nanocoaxial-based electrochemical sensor for the detection of bacterial toxins using an electrochemical enzyme-linked immunosorbent assay (ELISA) and differential pulse voltammetry (DPV) or square wave voltametry (SWV). The device architecture is composed of vertically-oriented, nanoscale coaxial electrodes in array format (~10(6) coaxes per square millimeter). The coax cores and outer shields serve as integrated working and counter electrodes, respectively, exhibiting a nanoscale separation gap corresponding to ~100 nm. Proof-of-concept was demonstrated for the detection of cholera toxin (CT). The linear dynamic range of detection was 10 ng/ml-1 µg/ml, and the limit of detection (LOD) was found to be 2 ng/ml. This level of sensitivity is comparable to the standard optical ELISA used widely in clinical applications, which exhibited a linear dynamic range of 10 ng/ml-1 µg/ml and a LOD of 1 ng/ml. In addition to matching the detection profile of the standard ELISA, the nanocoaxial array provides a simple electrochemical readout and a miniaturized platform with multiplexing capabilities for the simultaneous detection of multiple biomarkers, giving the nanocoax a desirable advantage over the standard method towards POC applications.

Folding analytical devices for electrochemical ELISA in hydrophobic R(H) paper.

This work describes a device for electrochemical enzyme-linked immunosorbent assay (ELISA) designed for low-resource settings and diagnostics at the point of care. The device is fabricated entirely in hydrophobic paper, produced by silanization of paper with decyl trichlorosilane, and comprises two zones separated by a central crease: an embossed microwell, on the surface of which the antigen or antibody immobilization and recognition events occur, and a detection zone where the electrodes are printed. The two zones are brought in contact by folding the device along this central crease; the analytical signal is recorded from the folded configuration. Two proof-of-concept applications, an electrochemical direct ELISA for the detection of rabbit IgG as a model antigen in buffer and an electrochemical sandwich ELISA for the detection of malarial histidine-rich protein from Plasmodium falciparum (Pf HRP2) in spiked human serum, show the versatility of this device. The limit of detection of the electrochemical sandwich ELISA for the quantification of Pf HRP2 in spiked human serum was 4 ng mL(-1) (10(2) pmol L(-1)), a value within the range of clinically relevant concentrations.

Electrochemical enzyme-linked immunosorbent assay (ELISA) for α-fetoprotein based on glucose detection with multienzyme-nanoparticle amplification.

Since glucose biosensors are one of the most popular and widely used point-of-care testing devices, a novel electrochemical enzyme-linked immunosorbent assay (ELISA) for protein biomarkers has been developed based on a glucose detection strategy. In this study, α-fetoprotein (AFP) was used as the target protein. An electrochemical ELISA system was constructed using anti-AFP antibodies immobilized on microwell plates as the capture antibody (Ab1) and multi-label bioconjugates as signal tracer. The bioconjugates were synthesized by attaching glucoamylase and the secondary anti-AFP antibodies (Ab2) to gold nanoparticles (AuNPs). After formation of the sandwich complex, the Ab2-glucoamylase-AuNPs conjugates converted starch into glucose in the presence of AFP. The concentration of AFP can be calculated based on the linear relation between AFP and glucose, the concentration of which can be detected by the glucose biosensor. When the AFP concentration ranged from 0.05 to 100 ng/mL, a linear calibration plot (i (µA) = 13.62033 − 2.86252 logCAFP (ng/mL), r = 0.99886) with a detection limit of 0.02 ng/mL was obtained under optimal conditions. The electrochemical ELISA developed in this work shows acceptable stability and reproducibility, and the assay for AFP spiked in human serum also shows good recovery (97.0%–104%). This new method could be applied for detecting any protein biomarker with the corresponding antibodies.

A Chemically Synthesized Capture Agent Enables the Selective, Sensitive, and Robust Electrochemical Detection of Anthrax Protective Antigen

We report on a robust and sensitive approach for detecting protective antigen (PA) exotoxin from Bacillus anthracis in complex media. A peptide-based capture agent against PA was developed by improving a bacteria display-developed peptide into a highly selective biligand through in situ click screening against a large, chemically synthesized peptide library. This biligand was coupled with an electrochemical enzyme-linked immunosorbent assay utilizing nanostructured gold electrodes. The resultant assay yielded a limit of detection of PA of 170 pg/mL (2.1 pM) in buffer, with minimal sensitivity reduction in 1% serum. The powdered capture agent could be stably stored for several days at 65 °C, and the full electrochemical biosensor showed no loss of performance after extended storage at 40 °C. The engineered stability and specificity of this assay should be extendable to other cases in which biomolecular detection in demanding environments is required.

Development of a Membrane-based Microwave-mediated Electrochemical ELISA Method for TNF-α Detection in Patients with Periodontitis

The tumor necrosis factor-α (TNF-α) is implicated in periodontal disease, and there was an attempt to quantitate it by a membrane-based microwave-mediated electrochemical enzyme-linked immunosorbent assay (MMeELISA) using p-aminophenyl phosphate (pAPP) with an over-all time of 1.5 h. A differential pulse voltammetric signal increased linearly with an increase in the amount of TNF-α with a detection limit of 0.48 pg mL(-1). This bio-sensing platform revealed a significant difference in the TNF-α level between GCF samples from periodontal patients and healthy volunteers.

Electrochemical Enzyme-Linked Immunosorbent Assay Featuring Proximal Reagent Generation: Detection of Human Immunodeficiency Virus Antibodies in Clinical Samples

We describe a simple electrochemical immunoassay for human immunodeficiency virus (HIV) antibody detection that localizes capture and detection reagents in close proximity to a microelectrode. Antigenic peptides from HIV-1 gp41 or HIV-2 gp36 were covalently attached to a SU-8 substrate that also presented a template for the deposition of three-dimensional microelectrodes. The detection of HIV antibodies was achieved with an electrochemical immunoassay where an alkaline phosphatase conjugated secondary antibody reacts with p-aminophenyl phosphate (pAPP) to produce a redox-active product, p-aminophenol. The current derived from the oxidation of the reporter group increased linearly over a wide antibody concentration range (0.001-1 μg mL(-1)), with a detection limit of 1 ng mL(-1) (6.7 pM) for both HIV-1 and HIV-2. This level of sensitivity is clinically relevant, and the feasibility of this approach for clinical sample testing was also evaluated with HIV clinical patient samples, with excellent performance observed compared against a commercially available gold standard. This approach was used to develop the first electrochemical enzyme-linked immunosorbent assay (ELISA) to detect HIV in clinical samples, and excellent performance relative to a gold standard test was achieved.

A Novel Electrochemical Immunosensor Based on DNA/Fe<sub>3</sub>O<sub>4</sub> (Core) /ZrO<sub>2</sub>（Shell）one Dimension Magnetic Probes for Carcino-Embryonic Antigen

A novel and sensitive electrochemical enzyme-linked immunosorbent assay (ELISA) system of Hydroquinones (HQ)- peroxide hydantoin (CP) -horseradish-peroxidase (HRP) by using magnetic DNA linked core-shell Fe3O4@ZrO2（ZMPs）nanoparticles as labels and signal amplification was established. In the presence of carcinoembryonic antigen (CEA) analyte, the sandwich-type immunocomplex could be formed between HRP labeled CEA second antibody（CEA Ab2） modified DNA-ZMPs probes (DNA / (ZMPs-HRP-CEA Ab2) n) and nano-gold CEA modified glassy carbon electrode (GCE | CEA Ab1) as an immune electrode.The concentration of CEA was determined based on the current signal, which was generated in the reaction between HQ and CP catalyzed by HRP on the sandwich-type immunocomplex. ZMPs nanoparticles as label material can not only perform the rapid separation and purification of signal antibody on magnetic field, but also immensely enhance the labeled capacity of HRP-anti-CEA which can amplify the catalytic current signal. Furthermore, the electrode modification process was not required. The method provided a linear response range between 0.01 and 200 ng·mL-1with a detection limit of 4 pg·mL-1.Moreover, the proposed electrochemical ELISA method exhibited good precision, high sensitivity and acceptable reproducibility, and could be further developed for clinical detections of CEA and other biomarkers.

Synergistic effects of micro/nano modifications on electrodes for microfluidic electrochemical ELISA

Microfluidic electrochemical sensing has been considered to be highly efficient. However, we showed, by using numerical simulations in this study, that a planar electrode formed on the bottom of a microchannel is exposed to only a small fraction of analytes in amperometric detection. We also showed that three-dimensional (3D) micropillar electrodes significantly improve the detection current. The practical performance was evaluated using 3D micropillar electrodes fabricated by photolithography. The output current increased as the diameters of the micropillars decreased, as predicted by the simulations. It is noteworthy that the current enhancements obtained with the 3D electrodes were larger than those expected from an increase in the surface area. Further increase in current was achieved by electrical deposition of nanoporous gold-black onto the surface of the 3D electrode: when a 3D electrode with micropillars 30 μm in diameter was used, the output current was approximately 20 times that obtained with a 2D electrode without modification. The applicability of the micropillar electrodes was demonstrated in electrochemical enzyme-linked immunosorbent assay (ELISA) of bone metabolic marker proteins. Although an increase in the surface area of the electrode leads to more noise in general, there is no significant difference in the signal-to-noise ratio between the modified 3D electrode and the 2D electrode without modification in the ELISA experiments. This nanoporous micropillar electrode could potentially be a useful component for the development of on-site diagnosis systems.

Gold-black micropillar electrodes for microfluidic ELISA of bone metabolic markers

Modification with gold black considerably increased the detection current of protruding micropillar electrodes in microfluidic electrochemical enzyme-linked immunosorbent assay (ELISA).