Search Results (37)

Celiac disease (CD), a human leukocyte antigen-associated disorder, is caused by gluten sensitivity and is characterized by mucosal alterations in the small intestine. Currently, its diagnosis involves the determination of serological markers. The traditional method for clinically determining these markers is the enzyme-linked immunosorbent assay. However, immunosensors offer sensitivity and facilitate the development of miniaturized and portable analytical systems. This work focuses on developing an amperometric immunosensor for the quantification of IgA antibodies against tissue transglutaminase (IgA anti-TGA) in human serum samples, providing information on a critical biomarker for CD diagnosis. The electrochemical device was designed on a polyimide substrate using a novel solid ink of wax and carbon nanofibers (CNFs). The working electrode microzone was defined by incorporating aminofunctionalized TiO₂ nanoparticles (TiO₂NPs). The interactions and morphology of CNFs/wax and TiO₂NPs/CNFs/wax electrodes were assessed through different characterization techniques. Furthermore, the device was electrochemically characterized, demonstrating that the incorporation of CNFs into the wax matrix significantly enhanced its conductivity and increased the active surface area of the electrode, while TiO₂NPs contributed to the immunoreaction area. The developed device exhibited remarkable sensitivity, selectivity, and reproducibility. These results indicate that the fabricated device is a robust and reliable tool for the precise serological diagnosis of CD. Full article

The development of biosensors for determining the most diverse biomolecules is a constant focus of many research groups. There is a latent need to propose sensors that combine portability, simple measurements, and good analytical performance. Here, we propose an electrochemical immunosensor that is fully portable and energy-independent for diagnosing antibodies against SARS-CoV-2 (the virus that causes COVID-19). Initially, disposable screen-printed carbon electrodes (SPEs) were covered by gold microblobs (AuMBs), which were synthesized amperometrically from Au³⁺ ions. Then, the SPE-AuMBs were coated with cysteamine, which allowed the N-hydroxysuccinimide-activated SARS-CoV-2 antigen (spike protein) to be immobilized. The antigen-activated electrode was used to detect COVID-19 antibodies from current measurements obtained by differential pulse voltammetry. The AuMBs synthesis time was optimized, and the presence of gold structures improved the electrochemical responses of the SPE. It was possible to quantitatively determine antibodies in the concentration range of 0.25 to 10 µg mL⁻¹. This range includes concentrations found in biological fluids from patients at any stage of the disease. An analysis took approximately the same time as traditional rapid nasal tests (20 min) and costed less, considering all the steps necessary to prepare a disposable antigen-functionalized SPE. Full article

Neuron-specific enolase (NSE) has gained extensive attention as a reliable target for detecting small cell carcinoma of lungs. In this paper, an electrochemical immunoassay method based on molybdenum disulfide (MoS₂) is proposed to detect NSE sensitively. By an in-situ growth method, MoS₂ and Au nanoclusters (Au NCs) were composited to form a MoS₂@Au nanozyme, and then the secondary antibodies were modified. Primary antibodies were immobilized on amino-reduced graphene oxides to capture NSE. The flower-like MoS₂ nanozyme provided abundant sites to load Au NCs and catalyze the decomposition of H₂O₂, which were beneficial to amplify an amperometric response as well as build up sensitivity. Under optimum conditions, the detection range of this strategy was 0.1 pg·mL⁻¹–10 ng·mL⁻¹ and the limit of detection was 0.05 pg·mL⁻¹. This sensing strategy achieved the prospect of sensitively detecting NSE. Moreover, the prepared electrochemical immunosensor provides a theoretical basis and technical support for the detection of other disease markers. Full article

In this work, two human epidermal growth factor receptors, HER-1 and HER-2, were selected as biomarkers to enable the detection of breast cancer. Therefore, two biosensors were developed using gold sensor chips coupled with amperometric detection of the enzyme label horse radish peroxidase (HRP). The biosensors/immunosensors relied on indirect sandwich enzyme-linked immunosorbent assays with monoclonal antibodies (Ab) against HER-1 and HER-2 attached to the sensors to capture the biomarkers. Detection polyclonal antibodies followed by secondary anti-rabbit (for HER-1) and anti-goat (for HER-2) IgG antibody-HRP were then applied for signal generation. In buffer, the developed sensors showed limits of detections (LOD) of 1.06 ng mL⁻¹ and 0.95 ng mL⁻¹ and limits of quantification (LOQ) of 2.1 ng mL⁻¹ and 1.5 ng mL⁻¹ for HER-1 and HER-2, respectively. In 100% (undiluted) serum, LODs of 1.2 ng mL⁻¹ and 1.47 ng mL⁻¹ and LOQs of 1.5 ng mL⁻¹ and 2.1 ng mL⁻¹ were obtained for HER-1 and HER-2, respectively. Such limits of detections are within the serum clinical range for the two biomarkers. Furthermore, gold nanoparticles (AuNP) labelled with secondary anti-rabbit and anti-goat IgG antibody-HRP were then used to enhance the assay signal and increase the sensitivity. In buffers, LODs of 30 pg mL⁻¹ were seen for both sensors and LOQs of 98 pg mL⁻¹ and 35 pg mL⁻¹ were recorded for HER-1 and HER-2, respectively. For HER-2 the AuNPs biosensor was also tested in 100% serum obtaining a LOD of 50 pg mL⁻¹ and a LOQ of 80 pg mL⁻¹. The HER-2 AuNP electrochemical immunosensor showed high specificity with very low cross-reactivity to HER-1. These findings demonstrate that the two developed sensors can enable early detection as well as monitoring of disease progression with a beneficial impact on patient survival and clinical outcomes. Full article

Myeloperoxidase (MPO) has been demonstrated to be a biomarker of neutrophilic inflammation in various diseases. Rapid detection and quantitative analysis of MPO are of great significance for human health. Herein, an MPO protein flexible amperometric immunosensor based on a colloidal quantum dot (CQD)-modified electrode was demonstrated. The remarkable surface activity of CQDs allows them to bind directly and stably to the surface of proteins and to convert antigen–antibody specific binding reactions into significant currents. The flexible amperometric immunosensor provides quantitative analysis of MPO protein with an ultra-low limit of detection (LOD) (31.6 fg mL⁻¹), as well as good reproducibility and stability. The detection method is expected to be applied in clinical examination, POCT (bedside test), community physical examination, home self-examination and other practical scenarios. Full article

Electrochemical immunosensors have attracted immense attention due to the ease of mass electrode production and the high compatibility of the miniature electric reader, which is beneficial for developing point-of-care diagnostic devices. Electrochemical immunosensors can be divided into label-free and label-based sensing strategies equipped with potentiometric, amperometric, voltammetric, or impedimetric detectors. Emerging nanomaterials are frequently used on electrochemical immunosensors as a highly rough and conductive interface of the electrodes or on nanocarriers of immobilizing capture antibodies, electroactive mediators, or catalyzers. Adopting nanomaterials can increase immunosensor characteristics with lower detection limits and better sensitivity. Recent research has shown innovative immobilization procedures of nanomaterials which meet the requirements of different electrochemical immunosensors. This review discusses the past five years of advances in nanomaterials (metal nanoparticles, metal nanostructures, carbon nanotubes, and graphene) integrated into the electrochemical immunosensor. Furthermore, the new tendency and endeavors of nanomaterial-based electrochemical immunosensors are discussed. Full article

An amperometric immunosensor was developed for the analysis of the major egg-white allergen ovotransferrin (Gal d 3) in commercial food products because the (accidental) intake, skin contact with, and/or inhalation of eggs can lead to severe disorders in allergic individuals. Employing a sandwich-type immunosensing strategy, screen-printed carbon electrodes (SPCE) were biomodified with anti-Gal d 3 (capture) antibodies, and the allergen’s detection was achieved with anti-Gal d 3 antibodies labelled with horseradish peroxidase (HRP). The 3,3′,5,5′-tetramethylbenzidine (TMB)/H₂O₂ reaction with HRP was used to obtain the electrochemical (amperometric) signal. An attractive assay time of 30 min and a remarkable analytical performance was achieved. The quantification range was established between 55 and 1000 ng·mL⁻¹, with a limit of detection of 16 ng·mL⁻¹. The developed method demonstrated good precision (V_x0 = 5.5%) and provided precise results (CV < 6%). The sensor also detected extremely low amounts (down to 0.010%) of egg. The analysis of seven raw and/or cooked egg and egg-white samples indicated that food processing influences the amount of allergen. Furthermore, to assure the compliance of product labelling with EU legislation, 25 commercial food ingredients/products were analysed. The accuracy of the results was confirmed through an ELISA assay. The stability of the ready-to-use sensing surface for 20 days allows a reduction of the reagents’ volumes and cost. Full article

As a steroid hormone, cortisol has a close relationship with the stress response, and therefore, can be used as a biomarker for early detection of stress. An electrochemical immunosensor is one of the most widely used methods to detect cortisol, with antibodies as its bioreceptor. Apart from conventional laboratory-based methods, the trend for cortisol detection has seemed to be exploiting antibodies and aptamers. Both can provide satisfactory performance with high selectivity and sensitivity, but they still face issues with their short shelf life. Molecularly imprinted polymers (MIPs) have been widely used to detect macro- and micro-molecules by forming artificial antibodies as bioreceptors. MIPs are an alternative to natural antibodies, which despite demonstrating high selectivity and a low degree of cross-reactivity, often also show a high sensitivity to the environment, leading to their denaturation. MIPs can be prepared with convenient and relatively affordable fabrication processes. They also have high durability in ambient conditions, a long shelf life, and the ability to detect cortisol molecules at a concentration as low as 2 ag/mL. By collecting data from the past five years, this review summarizes the antibody and aptamer-based amperometric sensors as well as the latest developments exploiting MIPs rather than antibodies. Lastly, factors that can improve MIPs performance and are expected to be developed in the future are also explained. Full article

A facile and highly sensitive determination of prostate-specific antigen (PSA) is of great significance for the early diagnosis, monitoring and prognosis of prostate cancer. In this work, a disposable and label-free electrochemical immunosensing platform was demonstrated based on chitosan–graphene-modified indium tin oxide (ITO) electrode, which enables sensitive amperometric determination of PSA. Chitosan (CS) modified reduced graphene oxide (rGO) nanocomposite (CS–rGO) was easily synthesized by the chemical reduction of graphene oxide (GO) using CS as a dispersant and biofunctionalizing agent. When CS–rGO was modified on the patterned ITO, CS offered high biocompatibility and reactive groups for the immobilization of recognition antibodies and rGO acted as a transduction element and enhancer to improve the electronic conductivity and stability of the CS–rGO composite film. The affinity-based biosensing interface was constructed by covalent immobilization of a specific polyclonal anti-PSA antibody (Ab) on the amino-enriched electrode surface via a facile glutaraldehyde (GA) cross-linking method, which was followed by the use of bovine serum albumin to block the non-specific sites. The immunosensor allowed the detection of PSA in a wide range from 1 to 5 ng mL⁻¹ with a low limit of detection of 0.8 pg mL⁻¹. This sensor also exhibited high selectivity, reproducibility, and good storage stability. The application of the prepared immunosensor was successfully validated by measuring PSA in spiked human serum samples. Full article

Biosensors used for medical diagnosis work by analyzing physiological fluids. Antibodies have been frequently used as molecular recognition molecules for the specific binding of target analytes from complex biological solutions. Electrochemistry has been introduced for the measurement of quantitative signals from transducer-bound analytes for many reasons, including good sensitivity. Recently, numerous electrochemical immunosensors have been developed and various strategies have been proposed to detect biomarkers. In this paper, the recent progress in electrochemical immunosensors is reviewed. In particular, we focused on the immobilization methods using antibodies for voltammetric, amperometric, impedimetric, and electrochemiluminescent immunosensors. Full article

A magnetic beads (MB)-involved amperometric immunosensor for the determination of ST2, a member of the IL1 receptor family, is reported in this work. The method utilizes a sandwich immunoassay and disposable screen-printed carbon electrodes (SPCEs). Magnetic immunoconjugates built on the surface of carboxylic acid-microsized magnetic particles (HOOC-MBs) were used to selectively capture ST2. A biotinylated secondary antibody further conjugated with a streptavidin peroxidase conjugate (Strep-HRP) was used to accomplish the sandwiching of the target protein. The immune platform exhibits great selectivity and a low limit of detection (39.6 pg mL⁻¹) for ST2, allowing the determination of soluble ST2 (sST2) in plasma samples from healthy individuals and patients diagnosed with pancreatic ductal adenocarcinoma (PDAC) in only 45 min once the immunoconjugates have been prepared. The good correlation of the obtained results with those provided by an ELISA kit performed using the same immunoreagents demonstrates the potential of the developed strategy for early diagnosis and/or prognosis of the fatal PDAC disease. Full article

Zika virus (ZIKV) is a mosquito-borne infection, predominant in tropical and subtropical regions causing international concern due to the ZIKV disease having been associated with congenital disabilities, especially microcephaly and other congenital abnormalities in the fetus and newborns. Development of strategies that minimize the devastating impact by monitoring and preventing ZIKV transmission through sexual intercourse, especially in pregnant women, since no vaccine is yet available for the prevention or treatment, is critically important. ZIKV infection is generally asymptomatic and cross-reactivity with dengue virus (DENV) is a global concern. An innovative screen-printed electrode (SPE) was developed for amperometric detection of the non-structural protein (NS2B) of ZIKV by exploring the intrinsic redox catalytic activity of Prussian blue (PB), incorporated into a carbon nanotube–polypyrrole composite. Thus, this immunosensor has the advantage of electrochemical detection without adding any redox-probe solution (probe-less detection), allowing a point-of-care diagnosis. It was responsive to serum samples of only ZIKV positive patients and non-responsive to negative ZIKV patients, even if the sample was DENV positive, indicating a possible differential diagnosis between them by NS2B. All samples used here were confirmed by CDC protocols, and immunosensor responses were also checked in the supernatant of C6/36 and in Vero cell cultures infected with ZIKV. Full article

Facile detection methods for mycotoxins with high sensitivity are of great significance to prevent potential harm to humans. Herein, a label-free amperometric immunosensor based on a 3-D interconnected carbon nanofibers (CNFs) network coupled with well-dispersed Au nanoparticles (AuNPs) is proposed for the quantitative determination of aflatoxin B₁ (AFB₁) in wheat samples. In comparison to common carbon nanotubes (CNTs), the CNFs network derived from bacterial cellulose biomass possesses a unique hierarchically porous structure for fast electrolyte diffusion and a larger electrochemical active area, which increases the peak current of differential pulse voltammetry curves for an immunosensor. Combined with AuNPs that are incorporated into CNFs by using linear polyethyleneimine (PEI) as a soft template, the developed Au@PEI@CNFs-based immunosensor showed a good linear response to AFB₁ concentrations in a wide range from 0.05 to 25 ng mL⁻¹. The limit of detection was 0.027 ng mL⁻¹ (S/N = 3), more than three-fold lower than that of an Au@PEI@CNTs-based sensor. The reproducibility, storage stability and selectivity of the immunosensor were proved to be satisfactory. The developed immunosensor with appropriate sensitivity and reliable accuracy can be used for the analysis of wheat samples. Full article

Veterinary drugs could contaminate animal-derived food products for human consumption. Some antibiotic residues (e.g., chloramphenicol (CAP), nitrofuran metabolites) are banned in foodstuffs of animal origin (e.g., milk, honey, etc.) in the European Union because of toxicological risks for the consumer. Screening methods applied for food safety monitoring should be sensitive, specific, cheap, quick, and portable for field testing (e.g., self-control). Electrochemical biosensors make it possible to develop a promising and economically interesting approach. An innovative and cheap electrochemical method based on disposable screen-printed carbon electrodes (SPCE), coupled to magnetic beads (MB), that allows the simultaneous detection of three families of antibiotics in milk was published by a Spanish academic team. When the biosensor method was applied to detect CAP residues in honey, two major issues were identified: firstly, the very low levels of residues to reach (i.e., regulatory limits below 1 µg/kg), and secondly, the complexity of the honey matrix; there is not a single honey matrix. Honey composition and color vary considerably depending on the botanical origin. Moreover, some honey ingredients can interfere with the electrochemical detection, especially substances with antioxidant activities (e.g., polyphenols). Therefore, in parallel with the optimization of the electrochemical method, the reduction of matrix effects was a big challenge. Full article

The method of Salmonella detection recommended is cultural, but it is laborious, presents a high consumption of material, and requires about five days for presumptive results. Immunosensor is an alternative tool that has shown promising and rapid results, although many devices have their performance evaluated only under buffering conditions and few achieve the validation stage. The objective was to perform a pre-collaborative validation of an electrochemical immunosensor assembled on screen-printed electrodes for the detection of Salmonella sp. in milk. The antibodies were immobilized by cysteamine self-assembled monolayer. The sandwich-type amperometric immunosensor was evaluated for contaminated raw and whole UHT milk and compared to performance with a gold standard reference method (BAM) according to AOAC recommendations for a single laboratory. A binary response (positive/negative) of the immunosensor was used based on a cut off established from current electric obtained for the absence of the pathogen. There was no significant difference for the results of the biosensor and the reference method, in the absence and the levels from 10¹ to 10³ CFU mL⁻¹ of Salmonella Typhimurium for the two types of milk. This result indicates the efficiency of the biosensor in detecting the pathogen into a complex matrix. Full article