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This work describes a sensitive voltammetric immunosensor for label‐free electroanalysis of the prostate specific antigen (PSA), the main biomarker of prostate cancer. A gold electrode was firstly modified with the optimum self‐assembled monolayer (SAM), 1,6‐hexanedithiol, followed by the subsequent adsorption of gold nanoparticles (AuNPs) and, then, the monoclonal antibody to recognize PSA was immobilized. The influence of the most significant experimental variables (SAM type and incubation time, AuNPs deposition, antibody concentration and bovine serum albumin immobilization) on the biosensor response was studied by microscopy and voltammetry techniques. The electroanalytical detection was based on the interaction between PSA antibody and PSA via square‐wave voltammetry using ferrocyanide/ferricyanide as electrochemical redox indicator. Using the proposed immunosensor, PSA was specifically detected within the linear range between 0.2 and 200 ng mL−1 with 0.01 ng mL−1 as limit of detection. The immunosensor allows accurate, reproducible and sensitive (22.7 % reduction mL ng−1) detection in a concentration range useful for clinical purposes. [ABSTRACT FROM AUTHOR]

Tracking unreported allergens in commercial foods can avoid acute allergic reactions. A 2-step electrochemical immunosensor was developed for the analysis of the peanut allergen Ara h 1 in a 1-h assay (<15 min hands-on time). Bare screen-printed carbon electrodes (SPCE) were used as transducers and monoclonal capture and detection antibodies were applied in a sandwich-type immunoassay. The short assay time was achieved by previously combining the target analyte and the detection antibody. Core/shell CdSe@ZnS Quantum Dots were used as electroactive label for the detection of the immunological interaction by differential pulse anodic stripping voltammetry. A linear range between 25 and 1000 ng·mL−1 (LOD = 3.5 ng·mL−1), an adequate precision of the method (Vx0 ≈ 6%), and a sensitivity of 23.0 nA·mL·ng−1·cm−2 were achieved. The immunosensor was able to detect Ara h 1 in a spiked allergen-free product down to 0.05% (m/m) of peanut. Commercial organic farming cookies and cereal and protein bars were tested to track and quantify Ara h 1. The results were validated by comparison with an ELISA kit. [ABSTRACT FROM AUTHOR]

Specific monitoring of cystatin C (CysC) levels in biological fluids is critical for diagnosis, treatment and mechanistic understanding of a spectrum of diseases, particularly chronic kidney disease (CKD). Despite evidences that CysC correlates with the high risk and/or progression of CKD, its use in clinical practice is still scarce. In this context, we report the development of a simple and sensitive immunosensor for the detection of CysC. The biosensor combines the technology of cost-effective screen-printed electrodes with the high specificity of a sandwich immunoassay. Optimized conditions showed that the sensor operates in a linear range between 10 and 100 ng mL−1, with a detection limit and a sensitivity of 6.0 ng mL−1 and 6.4 ± 0.3 μA ng mL−1 cm−2, respectively. Moreover, the sensor provided precise results (RSD ≤ 6.2%) and the quantification of CysC in CKD serum samples revealed to be in agreement with the values obtained by a particle-enhanced nephelometric immunoassay. In this light, the proposed immunosensor qualifies for clinical application, constituting a step forward in the development of fast, sensitive and cost-effective diagnostic tools that can improve the current medical care settings of CKD patients. Image 1 • An immunosensor for CysC, a chronic kidney disease biomarker, was developed. • Screen-printed carbon electrodes nanostructured with gold nanoparticles were used. • The sensor showed a linear concentration range with clinical utility. • The sensor was applied to CysC quantification in serum samples from CKD patients. [ABSTRACT FROM AUTHOR]

Cancer Antigen 15-3 (CA 15-3) and the extracellular domain of the human epidermal growth factor receptor 2 (HER2-ECD) are independent breast cancer biomarkers. The combination of their profiles (presence and concentration) could provide an important contribution to diagnostics and patient follow-up. Therefore, a disposable electrochemical immunosensor for the simultaneous detection of CA 15-3 and HER2-ECD was developed in this work. The immunosensor was constructed on a customized dual screen-printed carbon electrode. The carbon working electrodes' surfaces were first modified with in situ electrodeposited gold nanoparticles and then individually coated with either a monoclonal anti-human CA 15-3 or a monoclonal anti-human HER2-ECD antibody. After incubation with the biomarkers and monoclonal biotin-labelled detection antibodies, the antigen-antibody interactions were detected by linear sweep voltammetric analysis of enzymatically (alkaline phosphatase) generated metallic silver. The immunosensor’s limits of detection for the selected biomarkers were 5.0 U mL −1 for CA 15-3 and 2.9 ng mL −1 for HER2-ECD. These values could allow the use of the sensor in the non-invasive control of these biomarkers in breast cancer patients. [ABSTRACT FROM AUTHOR]

Regardless the controversies surrounding genetically modified organisms (GMO), their cultivation is constantly increasing and in according to the EU legislation, labeling is mandatory for products containing EU-authorized-GMO higher than 0.9%. Thereby, new analytical strategies for rapid and effective detection of GMO on foodstuffs are required. In this work, an electrochemical immunosensor for effective determination of Cry1Ab protein from MON810 transgenic maize (EU-authorized-GMO) is described. The immunosensor was developed onto indium tin oxide (ITO) electrodes modified by 3-aminopropyltrimethoxysilane (APTES) monolayer to covalently immobilize Anti-Cry1Ab polyclonal antibodies. The protein interaction with the polyclonal antibody (PAb) recognition platform was directly monitored and measured by cyclic voltammetry and electrochemical impedance spectroscopy using commercially Cry1Ab protein. After the analytical features optimization a linear response from 1 to 10 ng mL −1 , a limit of detection (LOD) of 0.37 ng mL −1 and a limit of quantification (LOQ) of 1.23 ng mL −1 – which provided accurate results (RSD < 7.5%) – were achieved. The immunosensor allowed a simple and fast detection of Cry1Ab protein extracted from maize seeds with different GM maize mass percentages (0%, 0.5%, 1%, 2.5% and 5%). To crosscheck the detection of Cry1Ab protein, an enzyme-linked immunosorbent assay (ELISA) was used. The results indicate that the immunosensor is suitable for the transgenic protein Cry1Ab detection in GM maize representing a successfully tool to verify the compliance of the EU regulations. [ABSTRACT FROM AUTHOR]

Human epidermal growth factor receptor 2 (HER2) is a breast cancer biomarker that plays a major role in promoting breast cancer cell proliferation and malignant growth. The extracellular domain (ECD) of HER2 can be shed into the blood stream and its concentration is measurable in the serum fraction of blood. In this work an electrochemical immunosensor for the analysis of HER2 ECD in human serum samples was developed. To achieve this goal a screen-printed carbon electrode, modified with gold nanoparticles, was used as transducer surface. A sandwich immunoassay, using two monoclonal antibodies, was employed and the detection of the antibody-antigen interaction was performed through the analysis of an enzymatic reaction product by linear sweep voltammetry. Using the optimized experimental conditions the calibration curve (ip vs. log[HER2 ECD]) was established between 15 and 100 ng/mL and a limit of detection (LOD) of 4.4 ng/mL was achieved. These results indicate that the developed immunosensor could be a promising tool in breast cancer diagnostics, patient follow-up and monitoring of metastatic breast cancer since it allows quantification in a useful concentration range and has an LOD below the established cut-off value (15 ng/mL). [ABSTRACT FROM AUTHOR]

This work reports the development of an electrochemical immunosensor for rapid, specific and decentralized detection of the invasion-associated protein p60 secreted by Listeria monocytogenes , a life-threatening foodborne pathogen. A disposable screen-printed electrode was used as transducer surface and monoclonal and polyclonal antibodies that specifically recognize Listeria monocytogenes p60 protein and Listeria spp. p60 proteins, respectively, were used as the sandwich immuno-pair. The reaction was detected with the aid of an additional secondary antibody conjugated with the enzyme reporter (alkaline phosphatase) and using 3-indoxyl phosphate/silver ions as the mixture substrate. The analytical signal was acquired through the voltammetric stripping of the enzymatically deposited silver, which was directly correlated to p60 concentration in the sample. In optimized conditions, a limit of detection and quantification of 1.5 ng mL−1 and 5.1 ng mL−1 were achieved, respectively, in a useful time (<3 h). As proof-of-concept, the proposed immunosensor was successfully applied to spiked milk samples, demonstrating to be a suitable device for further use in real sample detection of Listeria monocytogenes in food products. Image 1 • Listeria monocytogenes is a life-threatening foodborne pathogen. • Invasion-associated protein p60 is a virulence factor secreted by Listeria spp.. • A disposable electrochemical immunosensor for Listeria monocytogenes p60 determination was developed. • The immunosensor achieved a limit of detection of 1.5 ng mL−1 in a useful time (<3 h). • The immunosensing approach accurately detected Listeria monocytogenes p60 in spiked milk samples. [ABSTRACT FROM AUTHOR]

Early detection of cancer increases the possibility for an adequate and successful treatment of the disease. Therefore, in this work, a disposable electrochemical immunosensor for the front-line detection of the ExtraCellular Domain of the Human Epidermal growth factor Receptor 2 (HER2-ECD), a breast cancer biomarker, in a simple and efficient manner is presented. Bare screen-printed carbon electrodes were selected as the transducer onto which a sandwich immunoassay was developed. The affinity process was detected through the use of an electroactive label, core/shell CdSe@ZnS Quantum Dots, by differential pulse anodic stripping voltammetry in a total time assay of 2 h, with an actual hands-on time of less than 30 min. The proposed immunosensor responded linearly to HER2-ECD concentration within a wide range (10–150 ng/mL), showing acceptable precision and a limit of detection (2.1 ng/mL, corresponding to a detected amount (sample volume = 40 μL) of 1.18 fmol) which is about 7 times lower than the established cut-off value (15 ng/mL). The usefulness of the developed methodology was tested through the analysis of spiked human serum samples. The reliability of the presented biosensor for the selective screening of HER2-ECD was confirmed by analysing another breast cancer biomarker (CA15-3) and several human serum proteins. Image 1 • Detection of cancer biomarkers in biological fluids is useful for early diagnosis. • An electrochemical immunosensor was developed for HER2-ECD. • Quantum dots were used as detection label. • The assay was selective towards the target biomarker. • The assay was successfully tested in the analysis of human serum. [ABSTRACT FROM AUTHOR]