Electrochemical Immunosensor Research Articles

Electrochemical Immunoassay for Capturing Capsular Polysaccharide of Burkholderia pseudomallei: Early Onsite Detection of Melioidosis.

This study presented the detection and quantification of capsular polysaccharide (CPS) as a biomarker for the diagnosis of melioidosis. After successfully screening four monoclonal antibodies (mAbs) previously determined to bind CPS molecules, the team developed a portable electrochemical immunosensor based on antibody-antigen interactions. The biosensor was able to detect CPS with a wide detection range from 0.1pg/mL to 1 μg/mL. The developed biosensor achieved high sensitivity for the detection of CPS spiked into both urine and serum. The developed assay platform was successfully programmed into a Windows app, and the sensor performance was evaluated with different spiked concentrations. The rapid electro-analytical device (READ) sensor showed great unprecedented sensitivity for the detection of CPS molecules in both serum and urine, and results were cross-validated with ELISA methods.

Biolayer-Interferometry-Guided Functionalization of Screen-Printed Graphene for Label-Free Electrochemical Virus Detection.

Additive manufacturing holds promise for rapid prototyping and low-cost production of biosensors for diverse pathogens. Among additive manufacturing methods, screen printing is particularly desirable for high-throughput production of sensing platforms. However, this technique needs to be combined with carefully formulated inks, rapid postprocessing, and selective functionalization to meet all requirements for high-performance biosensing applications. Here, we present screen-printed graphene electrodes that are processed with thermal annealing to achieve high surface area and electrical conductivity for sensitive biodetection via electrochemical impedance spectroscopy. As a proof-of-concept, this biosensing platform is utilized for electrochemical detection of SARS-CoV-2. To ensure reliable specificity in the presence of multiple variants, biolayer interferometry (BLI) is used as a label-free and dynamic screening method to identify optimal antibodies for concurrent affinity to the Spike S1 proteins of Delta, Omicron, and Wild Type SARS-CoV-2 variants while maintaining low affinity to competing pathogens such as Influenza H1N1. The BLI-identified antibodies are robustly bound to the graphene electrode surface via oxygen moieties that are introduced during the thermal annealing process. The resulting electrochemical immunosensors achieve superior metrics including rapid detection (55 s readout following 15 min of incubation), low limits of detection (approaching 500 ag/mL for the Omicron variant), and high selectivity toward multiple variants. Importantly, the sensors perform well on clinical saliva samples detecting as few as 103 copies/mL of SARS-CoV-2 Omicron, following CDC protocols. The combination of the screen-printed graphene sensing platform and effective antibody selection using BLI can be generalized to a wide range of point-of-care immunosensors.

A novel ratiometric electrochemical immunosensor for the detection of cancer antigen 125 based on three-dimensional carbon nanomaterial and MOFs

Accurate and sensitive detection of cancer antigen 125 (CA125) is important in early ovarian cancer diagnosis and monitoring. In the present work, a novel electrochemical ratiometric immunosensor for the determination of CA125 based on three-dimensional reduced graphene oxide/multi-walled carbon nanotube carboxylic acid- thionine (3DrGO/MWCNTs-Thi) and UIO-66-NH2/ferrocenecarboxylic acid (UiO-66-Fc) was constructed. 3DrGO/MWCNTs-Thi of immobilized primary antibody (Ab1) and UiO-66-Fc of labeled second antibody (Ab2) were used as capture probes and signaling probes for CA125, respectively. As the concentration of CA125 increases, the oxidation peak currents (IThi and IFc) generated by the two materials were changed in opposite directions, and therefore the ratio of the currents (IThi/IFc) was negatively correlated with the concentration of CA125. Thanks to the amplification of high loading of signaling molecules by the framework nanocomposites and the ratiometric strategy, the constructed electrochemical immunosensor exhibits outstanding accuracy, stability, and sensitivity. Under optimal conditions, the detection range spanned from 0.01 U mL−1 to 80 U mL−1, with a calculated limit of detection (LOD) of 0.0089 U mL−1. The immunosensor was successfully applied to real serum sample tests, indicating its potential for clinical detection applications.

Determination of the cervical cancer biomarker SCCA using CMK-3@UiO-66@AuNPs composite-modified glassy carbon electrodes

In order to detect the cervical cancer biomarker squamous cell carcinoma antigen (SCCA) in human serum, an electrochemical immunosensor was constructed. Zirconium 1,4-dicarboxybenzene MOF (UiO-66), with a high specific surface area, was coupled with gold nanoparticles (AuNPs), creating the UiO-66@AuNPs nanomaterial. This coupling increased the sensitivity of the electrochemical immunosensor by providing many biological binding sites for antibodies to bind to Au-S bonds. Then, mesoporous carbon (CMK-3) was added to the UiO-66@AuNPs nanomaterial to obtain a CMK-3@UiO-66@AuNPs nanocomposite. This further increased the electron transfer proficiency of the material and enhanced the electrochemical signal. Finally, the sensitive detection of squamous cell carcinoma antigen (SCCA) was made possible by unique immunological responses between antigens and antibodies. Transmission electron microscopy (TEM) analysis of CMK-3@UiO-66@AuNPs revealed embedded surfaces and voids; cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) confirmed the successful assembly of the electrochemical immunosensor. The developed electrochemical immunosensor demonstrated good linearity (R12 = 0.999) from 0.01 pg/mL – 10,000 pg/mL, which is the concentration range of SCCA in human serum. The limit of detection was 0.0034 pg/mL (at an S/N ratio of 3). The immunosensor exhibited excellent precision, stability and selectivity, with a high rate of recovery (98.26–101.8 %). The experimental validation studies demonstrated that the electrochemical immunosensor was effective for the detection of SCCA in human serum, offering a novel method for the early diagnosis and dynamic surveillance of cervical cancer.

A universal three-dimensional hydrogel electrode for electrochemical detection of SARS-CoV-2 nucleocapsid protein and hydrogen peroxide

Coronavirus disease 2019 (COVID-19) is a highly contagious illness caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), resulting in a global health crisis. The primary diagnostic method for COVID-19 is quantitative reverse transcription PCR, which is time-consuming and requires expensive instrumentation. Here, we developed an electrochemical biosensor for detecting SARS-CoV-2 biomarkers using a 3D porous polyacrylamide/polyaniline hydrogel (PPG) electrode prepared by UV photopolymerization and in situ polymerization. The electrochemical immunosensor for detecting SARS-CoV-2 N protein via the immune sandwich principle demonstrated a lower detection limit of 42 pg/mL and comparable specificity to commercial enzyme-linked immunosorbent assay, which was additionally validated in pseudoviruses. The electrochemical sensor for hydrogen peroxide showed a low detection limit of 0.5 μM and excellent selectivity, which was further confirmed in cancer cells under oxidative stress. The biomarkers of SARS-CoV-2 were successfully detected due to the signal amplification capability provided by 3D porous electrodes and the high sensitivity of the antigen-antibody specific binding. This study introduces a novel three-dimensional electrode with great potential for the early detection of SARS-CoV-2.

A nanoDiamond/gold nanoparticle-based electrochemical immunosensor for the detection of HER 2 cancer biomarker

We report a highly sensitive electrochemical immunosensor based on a nanohybrid platform for the detection of the breast cancer biomarker human epidermal growth factor receptor 2 (HER 2). NanoDiamond (nanoD) and gold nanoparticles (AuNPs) immobilised by drop coating and electrodeposition methods, respectively, were employed to fabricate an immunosensor for HER 2 detections on a glassy carbon electrode (GCE). Voltammetry and electrochemical impedance spectroscopy (EIS) techniques were used to characterise each step of the modification process of the immunosensor. In addition, transmission electron microscopy (TEM), X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM) techniques were used to characterise the materials used to fabricate the modified electrode. Under optimal conditions of temperature, time, and pH (35 °C, 50 min, and pH 7.2), different concentrations were investigated within a wide range of 1 pg mL−1 to 50 ng mL−1 using differential pulse voltammetry (DPV). With a low detection limit of 0.29 pg mL−1 from the DPV analysis, the immunosensor showed very good sensitivity and had a high specificity for HER 2. Additionally, the immunosensor demonstrated good applicability in the analysis of HER 2 in human serum samples, demonstrating a potential for use in the early identification of breast cancer.

Highly Reusable Electrochemical Immunosensor for Ultrasensitive Protein Detection

AbstractThe detection and quantification of protein biomarkers in bodily fluids is important for many clinical applications, including disease diagnosis and health monitoring. Current techniques for ultrasensitive protein detection, such as enzyme‐linked immunosorbent assay (ELISA) and electrochemical sensing, involve long incubation times (1.5–3 h) and rely on single‐use sensing electrodes which can be costly and generate excessive waste. This work demonstrates a reusable electrochemical immunosensor employing magnetic nanoparticles (MNPs) and dually labeled gold nanoparticles (AuNPs) for ultrasensitive measurements of protein biomarkers. As proof of concept, this platform is used to detect C‐X‐C motif chemokine ligand 9 (CXCL9), a biomarker associated with kidney transplant rejection, immune nephritis from checkpoint inhibitor therapy, and drug‐associated acute interstitial nephritis, in human urine. The sensor successfully detects CXCL9 at concentrations as low as 27 pg mL−1 within ≈1 h. This immunosensor was also adapted onto a handheld smartphone‐based diagnostic device and used for measurements of CXCL9, which exhibited a lower limit of detection of 65 pg mL−1. Lastly, this work demonstrates that the sensing electrodes can be reused for at least 100 measurements with a negligible loss in analytical performance, reducing the costs and waste associated with electrochemical sensing.

Noninvasive and Continuous Monitoring of On-Chip Stem Cell Osteogenesis Using a Reusable Electrochemical Immunobiosensor.

Noninvasive monitoring of biofabricated tissues during the biomanufacturing process is needed to obtain reproducible, healthy, and functional tissues. Measuring the levels of biomarkers secreted from tissues is a promising strategy to understand the status of tissues during biofabrication. Continuous and real-time information from cultivated tissues enables users to achieve scalable manufacturing. Label-free biosensors are promising candidates for detecting cell secretomes since they can be noninvasive and do not require labor-intensive processes such as cell lysing. Moreover, most conventional monitoring techniques are single-use, conducted at the end of the fabrication process, and, challengingly, are not permissive to in-line and continual detection. To address these challenges, we developed a noninvasive and continual monitoring platform to evaluate the status of cells during the biofabrication process, with a particular focus on monitoring the transient processes that stem cells go through during in vitro differentiation over extended periods. We designed and evaluated a reusable electrochemical immunosensor with the capacity for detecting trace amounts of secreted osteogenic markers, such as osteopontin (OPN). The sensor has a low limit of detection (LOD), high sensitivity, and outstanding selectivity in complex biological media. We used this OPN immunosensor to continuously monitor on-chip osteogenesis of human mesenchymal stem cells (hMSCs) cultured 2D and 3D hydrogel constructs inside a microfluidic bioreactor for more than a month and were able to observe changing levels of OPN secretion during culture. The proposed platform can potentially be adopted for monitoring a variety of biological applications and further developed into a fully automated system for applications in advanced cellular biomanufacturing.

Hydrangea-like TiO2/Bi2MoO6 porous nanoflowers triggering highly sensitive electrochemical immunosensing to tumor marker.

Rapid and sensitive detection of carcinoembryonic antigen (CEA) is of great significance for cancer patients. Here, molybdenum (Mo) was doped into bismuth oxide (Bi2O3) by one-pot hydrothermal method forming porous tremella Bi2MoO6 nanocomposites with a larger specific surface area than the spherical structure. Then, a new kind of hydrangea-like TiO2/Bi2MoO6 porous nanoflowers (NFs) was prepared by doping titanium into Bi2MoO6, where titanium dioxide (TiO2) grew in situ on the surface of Bi2MoO6 nanoparticles (NPs). The hydrangea-like structure provides larger specific surface area, higher electron transfer ability and biocompatibility as well as more active sites conducive to the attachment of anti-carcinoembryonic antigen (anti-CEA) to TiO2/Bi2MoO6 NFs. A novel label-free electrochemical immunosensor was then constructed for the quantitative detection of CEA using TiO2/Bi2MoO6 NFs as sensing platform, showing a good linear relationship with CEA in the concentration range 1.0pg/mL ~ 1.0mg/mL and a detection limit of 0.125pg/mL (S/N = 3). The results achieved with the designed immunosensor are comparable with many existing immunosensors used for the detection of CEA in real samples.

Green-Synthesized Amino Carbons for Impedimetric Biosensing of E. coli O157:H7.

This study describes the synthesis of amino-functionalized carbon nanoparticles derived from biopolymer chitosan using green synthesis and its application toward ultrasensitive electrochemical immunosensor of highly virulent Escherichia coli O157:H7 (E. coli O157:H7). The inherent advantage of high surface-to-volume ratio and enhanced rate transfer kinetics of nanoparticles is leveraged to push the limit of detection (LOD), without compromising on the selectivity. The prepared carbon nanoparticles were systematically characterized by employing CO2-thermal programmed desorption (CO2-TPD), Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), ultraviolet-visible (UV-visible), and transmission electron microscopy (TEM). The estimated limit of detection of 0.74 CFU/mL and a sensitivity of 5.7 ((ΔRct/Rct)/(CFU/mL))/cm2 in the electrochemical impedance spectroscopy (EIS) affirm the utility of the sensor. The proposed biosensor displayed remarkable selectivity against interfering species, making it well suited for real-time applications. Moreover, the chitosan-derived semiconducting amino-functionalized carbon shows excellent sensitivity in a comparative analysis compared to highly conducting amine-functionalized carbon synthesized via chemical modification, demonstrating its vast potential as an E. coli sensor.

Diazo-functionalised immunoelectrochemical sensor for the detection of ochratoxin a in foods

Ochratoxin A (OTA) is a toxic fungal metabolite that is commonly found in cereals and animal feed. It is economically damaging and potentially hazardous to human health. Herein, we propose an electrochemical immunosensor for the rapid detection of OTA using anti-OTA antibodies and diazonium-functionalized, screen-printed electrodes. We attached 4-aminobenzoic acid to an electrode surface, activated the carboxyl groups on the surface with carbodiimide, and attached an antibody to the diazo layer. Subsequently, we used bovine serum protein as a blocker to prevent non-specific antigens from binding to the antibody. We evaluated the performance of the sensor by cyclic voltammetry, electrochemical impedance spectroscopy, and differential pulse voltammetry. The sensor is highly specific and sensitive, has good linear responses in the range 20–200 ng/mL, a limit of detection of 0.5 ng/mL, and good recoveries of 90.5%–100.9% in spiked samples. It can be stored at 4 °C for approximately 2 weeks, and is highly stable, with a current response variation of no more than 4.6%.

Ultrasensitive Label-Free Electrochemical Immunosensor for Carbohydrate Antigen-125 (CA125) Employing Cu(II)-Polyethyleneimine (PEI)/Silica Nanoparticle@Overoxidized Polypyrrole (OPPy)/Multi-Walled Carbon Nanotubes (MWNTs) Hybrid Nanomaterial

Novel electroactive nanotags of Cu(II) functionalized polyethylenimine (PEI)/SiO2 nanoparticles (abbreviated as Cu2+/PEI/SiO2 NPs) were conveniently synthesized using a strong coordination reaction between Cu(II) and the multi-amino groups of PEI. These electroactive nanotags were easily coated on the overoxidized polypyrrole (OPPy) modified Nafion/multi-walled carbon nanotubes (abbreviated as Nafion/MWNTs) electrode surface through Cu-N bonds and strong electrostatic interactions. The Cu2+/PEI/SiO2 NPs@OPPy/MWNTs hybrid nanomaterial was formed without the addition of extra membrane-forming substances. The experimental results demonstrate that the OPPy/MWNTs composite membrane coupled with electrocatalytic Cu(Tris)4 2+ complexes in tris(hydroxymethyl)aminomethane (Tris)-HCl buffer medium amplified the electrochemical signals of nanotags based on the mutual synergistic effects. As an application, a label-free electrochemical immunosensor for epithelial ovarian cancer biomarker-carbohydrate antigen-125 (CA125) was constructed by covalently immobilizing CA125 antibody onto the hybrid nanomaterial modified electrode. With the increasing concentrations of CA125 antigen, different decreases in the electrochemical signals of the nanotags were observed due to the formation of antigen-antibody immune complexes. The electrochemical immunosensor showed a linear relationship from 0.001 to 500 U·mL−1 for CA125 with a detection limit of 3.4 × 10−4 U·mL−1. In addition, the proposed immunosensor was applied to the determination of CA125 in human serum with satisfactory results.

Polydopamine Modified Carbon Nitride and PAMAM Assembled Electrochemical Immunosensor for Detection of Indole‐3‐Acetic Acid

AbstractIndole‐3‐acetic acid (IAA) assumes a pivotal role as a phytohormone of utmost importance, intricately orchestrating the nuanced processes associated with the growth and developmental trajectories of botanical organisms. In this study, we have designed and fabricated a label‐free electrochemical impedance immunosensor for the precise detection of IAA. The detection strategy predominantly relied upon polydopamine modified carbon nitride (C3N4) nanosheets (PCN) and polyamidoamine (PAMAM) dendrimer. Through the modification with PCN and PAMAM, the electrode has increased the active area and enhanced the immobilization capacity of antibodies for IAA. The immunosensor‘s ability to capture IAA was significantly improved by enhancing the immunoreaction between the antibody and antigen. This enhancement led to an increased response in the electrochemical behavior of the Fe(CN)63−/4− redox probe. The impedance immunosensor developed exhibits remarkable sensitivity, exceptional selectivity, and consistent performance in the detection of IAA. This assay method, with the potential to replace antibodies, could offer an alternative approach for detecting various phytohormones.

Sandwich-type electrochemical immunosensing of CA125 by using nanoribbon-like Ti3C2Tx MXenes and toluidine blue/UIO-66-NH2.

CA125 (carbohydrate antigen 125) is an important biomarker of ovarian cancer, so developing effective method for its detection is of great significance. In the present work, a novel sandwich-like electrochemical immunosensor (STEM) of CA125 was constructed by preparing nanoribbon-like Ti3C2Tx MXenes (Ti3C2TxNR) to immobilize primary antibody (PAb) of CA125 and UIO-66-NH2 MOFs structure to immobilize second antibody (SAb) and electroactive toluidine blue (Tb) probe. In this designed STEM assay, the as-prepared Ti3C2TxNR nanohybrid offers the advantages in large surface area and conductivity as carrier, and UIO-66-NH2 provided an ideal platform to accommodate SAb and a large number of Tb molecules as signal amplifier. In the presence of CA125, the peak currents of Tb from the formed STEM structure increase with the increase of CA125 level. After optimizing the related control conditions, a wide linear range (0.2-150.0 U mL-1) and a very low detection limit (0.05 U mL-1) of CA125 were achieved. It's thus expected the developed STEM strategy has important applications for the detection of CA125.

Detection of tumor marker CA72-4 with an electrochemical immunosensor based on MnO2 nanosheets and HNM-AuPtPd nanocomposites.

To accurately detect tumor marker carbohydrate antigen 72-4 (CA72-4) of serum samples is of great significance for the early diagnosis of malignant tumors. In the present study, MnO2/hollow nanobox metal-organic framework (HNM)-AuPtPd nanocomposites were prepared via multi-step synthesis and superposition method and a series of characterizations were carried out. A highly sensitive immunosensor Ab/MnO2/HNM-AuPtPd/GCE based on the composite nanomaterial was further prepared and used to detect the tumor marker CA72-4. The constructed immunosensor achieved signal amplification by increasing the electrocatalytic activity to H2O2 by means of the synergistic effect of MnO2 ultra-thin nanosheets (MnO2 UNs) and HNM-AuPtPd. At the same time, the electrochemical properties of the immunosensor were analyzed using cyclic voltammetry, electrochemical impedance, amperometry (with the test voltage of -0.4 V), and differential pulse voltammetry. The experimental results showed that the MnO2/HNM-AuPtPd nanocomposites were successfully prepared, and the immunosensor Ab/MnO2/HNM-AuPtPd/GCE demonstrated an excellent electrochemical performance. The electrochemical immunosensor had the highest detection sensitivity under the optimal experimental conditions, such as incubation pH of 7.0, incubation time of 60 min, with the addition of 15 μL of H2O2, and in the concentration range 0.001-500 U/mL. It had a low detection limit of 1.78×10-5 U/mL (S/N = 3). Moreover, the serum sample recovery were in the range from 99.38 to 100.52%. This study provides a new method and experimental basis for the detection of tumor markers in clinical practice.

Clinical validation of SARS-CoV-2 electrochemical immunosensor based on the spike-ACE2 complex

Clinical validation of SARS-CoV-2 electrochemical immunosensor based on the spike-ACE2 complex

Immunosensing of carbohydrate antigen 19–9 based on covalent organic framework loaded Prussian blue as signal amplification platform

Immunosensing of carbohydrate antigen 19–9 (CA 19–9) by using covalent organic framework (COF) loaded Prussian blue (PB) as signal amplification platform was developed. Firstly, two-dimensional (2D) vinyl-rich COFTAGH-Dva (TAGH, triaminoguanidine hydrochloride; Dva, 1,4-benzenedicarboxaldehyd) was prepared to load PB, and further the Ab2 was assembled through the “click” reaction between –SH of Ab2 and vinyl of COFTAGH-Dva to construct the beacon complex of PB/COFTAGH-Dva/Ab2. Another 2D COFTp-BD (Tp, 2,4,6-trihydroxybenzene-1,3,5-tricarbaldehyde; BD, benzidine) rich in –NH- groups was combined with AuNPs to form AuNPs/COFTp-BD by in-situ reduction method, and then Ab1 was assembled through Au-S bond. In the process of electrochemical immunosensing, AuNPs/COFTp-BD was first assembled on glassy carbon electrode (GCE) to form AuNPs/COFTp-BD/GCE, which then adsorbed Ab1 by Au-S bond, and specifically and quantitatively captured CA 19–9 and the beacon complex of PB/COFTAGH-Dva/Ab2. With the increase of antigen CA 19–9, the redox peak signal of Fe2+/Fe3+ derived from PB in the beacon complex of PB/COFTAGH-Dva/Ab2 gradually increased. The linear range of the electrochemical immunosensor was 0.01–150 U/mL (U/mL represents the concentration of CA 19–9, which is the number of units of CA 19–9 per 1 mL volume) and the detection limit was 0.003 U/mL. This work provides a reference for constructing high-performance electrochemical immunosensor probes by using good biocompatibility and electroactive materials loaded on non electroactive COFs.

Advancing CEA quantification: Designing a sensitive electrochemical immunosenor using MWCNT/Ni(OH)2 nanocomposite

An ultra-sensitive immunosensor was designed for the accurate determination of Carcinoembryonic Antigen (CEA). To enhance the performance of immunosensor, an MWCNT/Ni(OH)2 nanocomposite was utilized as the electrochemical interface and modifier of the electrode surface. The simple preparation procedures for MWCNT/Ni(OH)2 composite were provided. Its characteristics and properties were investigated by HRTEM, FESEM, XRD, and FTIR techniques. Leveraging the unique electrochemical characteristics shown by the MWCNT/Ni(OH)2 nanocomposite and its correlation with CEA, high accuracy in CEA detection was achieved. Experimental findings provide evidence that the proposed immunosensor has the ability to detect CEA in laboratory samples. This research contributes towards achieving precise and rapid CEA detection in cancer diagnosis and prognosis. Across a wide concentration range of CEA, the designed immunosensor demonstrated a linear response from 0.0001 ng/mL to 2 ng/mL, and its limit of detection (LOD) was just 0.076 pg/mL. To evaluate the practical applicability of the electrochemical immunosensor, blood serum samples were examined, revealing the immunosensor's remarkable specificity and longevity. Its high accuracy and stability make it a valuable tool in clinical settings and biomedical research, paving the way for improved cancer management and patient outcomes.

S Development of an electrochemical immunosensor using gold nanoparticles (AuNPs) for the detection of Apolipoprotein A1 (ApoA1) in chicken blood plasma

The research aims to develop an electrochemical immunosensing assay using gold nanoparticles (AuNPs) on screen printed carbon electrode (SPCE) for the specific detection of Apolipoprotein A1 (ApoA1) proteins in chicken blood plasma (CBP). The biotin anti-ApoAI antibody was first immobilized on magnetic beads (MBs), while antibody ApoA1 was then conjugated with AuNPs. After a series of sandwich-type immunoreaction complexes was performed on the screen-printed carbon electrode, AuNPs were quantified by subjecting the immunocomplex to a peroxidation process of high potential at 1.2 V for 330 s and immediately reduced and scanned by differential pulse voltammetry (DPASV). This study obtained a linear relationship between reduction peak current signals and ApoA1 concentration from 0 to 100% (correlation coefficient of 0.996 with a detection limit of 5% of chicken blood plasma (CBP). The efficacy of our immunosensor is predicated on the seamless integration of antibodies with MBs to the target analyte, which provide ample surface area, biocompatibility, and user-friendliness. This breakthrough improves preliminary food fraud detection's sensitivity, reliability, and usability. It could improve diagnostic food safety, leading to a worldwide health breakthrough.

Label-free simultaneous detection of quinolone antibiotic residues using an origami paper–based electrochemical immunosensor

Label-free electrochemical sensors have gained popularity as point-of-care devices because they do not require complicated labeling procedures. However, they have difficulties detecting multiple analytes simultaneously. In this study, we developed a novel label-free electrochemical immunosensor on an origami paper–based analytical device (oPAD) for the simultaneous detection of quinolone antibiotics, in which norfloxacin (Nor) and enrofloxacin (Enr) were used as a model. The oPAD was designed with two antibody zones, each zone contains different antibodies. The oPAD has two thionine- and ferrocenecarboxylic acid-coated reagent zones, as redox species, which will generate the response current signals for the detection of quinolone antibiotics. The simultaneous current responses of thionine and ferrocenecarboxylic acid decreased proportionately when exposed to Nor and Enr concentrations, respectively. Under optimal conditions, this device provided linear range at concentrations of 0.01–10 µg/mL for the detection of Nor and Enr and limit of detection was calculated as 2.02 and 1.70 ng/mL, respectively. Moreover, this device demonstrates performance comparable to standard methods for the simultaneous detection of Nor and Enr in milk, honey, and fish. Therefore, label-free electrochemical immunosensors provide a highly potent, inexpensive, and portable method for detecting multiple quinolone antibiotics simultaneously on a single device.