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We propose a new strategy using a sandwich approach for the detection of two HF biomarkers: tumor necrosis factor-α (TNF-α) and interleukin-10 (IL-10). For this purpose, magnetic nanoparticles (MNPs) (MNPs@aminodextran) were biofunctionalized with monoclonal antibodies (mAbs) using bis (sulfosuccinimidyl) suberate (BS3) as a cross-linker for the pre-concentration of two biomarkers (TNF-α and IL-10). In addition, our ISFETs were biofunctionalized with polyclonal antibodies (pAbs) (TNF-α and IL-10). The biorecognition between pAbs immobilized on the ISFET and the pre-concentrate antigen (Ag) on MNPs was monitored using electrochemical impedance spectroscopy (EIS). Our developed ImmunoFET showed a low detection limit (0.03 pg/mL) toward our target analyte when compared to previously published electrochemical immunosensors. It showed a higher sensitivity than for other HF biomarkers. Finally, the standard addition method was used to determine the unknown concentration in artificial saliva. The results matched with the expected values well. [ABSTRACT FROM AUTHOR]

We propose a salivary Interleukin‐10 detection strategy as part of an easily integrable Lab‐on‐Chip and Point‐of‐Care IMFET for multi‐detection Heart Failure (HF) biomarkers. Our developed IMFET showed good linearity between increasing IL‐10 concentration and the charge transfer resistance in both standard solutions and real saliva samples with a LOD of 0.02 pg mL−1. Moreover, the cross‐selectivity study showed that the developed IMFET was highly selective towards IL‐10 against other HF biomarkers. The precision of our IMFET was also evaluated, and the difference between the determined IL‐10 concentration using the standard addition method and its expected one is<20 %. [ABSTRACT FROM AUTHOR]

As an antibody-free sensing membrane for the detection of the antibiotic tetracycline (TC), a liquid PVC membrane doped with the ion-pair tetracycline/θ-shaped anion [3,3′-Co(1,2-C2B9H11)2]− ([o-COSAN]−) was formulated and deposited on a SWCNT modified gold microelectrode. The chosen transduction technique was electrochemical impedance spectroscopy (EIS). The PVC membrane was composed of: the tetracycline/[o-COSAN]− ion-pair, a plasticizer. A detection limit of 0.3 pg/L was obtained with this membrane, using bis(2-ethylhexyl) sebacate as a plasticizer. The sensitivity of detection of tetracycline was five times higher than that of oxytetracycline and of terramycin, and 22 times higher than that of demeclocycline. A shelf-life of the prepared sensor was more than six months and was used for detection in spiked honey samples. These results open the way to having continuous monitoring sensors with a high detection capacity, are easy to clean, avoid the use of antibodies, and produce a direct measurement. [ABSTRACT FROM AUTHOR]

Impedance spectroscopy is an electrochemical technique widely used for the electrical characterization of the behavior of biomaterials in all kinds of biosensors. Field‐effect devices, and in particular ion‐sensitive field‐effect transistors (ISFETs), have been extensively studied as transducers for biosensing. They however have not been much analyzed with impedance spectroscopy, because they typically generate non‐Faradaic capacitance measurements, since there is no charge transfer through the insulating gate in contact with the liquid solution. We have recently experimentally shown that Faradaic‐like impedance spectroscopy spectra can be obtained with ISFET devices, allowing high‐sensitivity measurements for different pH and biomarker concentrations. In this paper, we report that both Faradaic‐like and non‐Faradaic impedance behavior can be well understood by a DC and small‐signal AC model of the ISFET working in different conditions. Faradaic‐like impedance measurements are described by the operation of the ISFET in subthreshold conditions. A Nyquist plot semicircle is obtained, corresponding to the transimpedance 1/gm of the ISFET in parallel to the gate capacitances. We show that this behavior is independent of the presence of membrane material on the gate surface. In these conditions, the change in the semicircle diameter for different pH or biomarker concentrations can be understood by the change of 1/gm corresponding to a threshold voltage shift of the transistor. This description is illustrated with our recent results for pH measurements and the detection of tumor necrosis factor‐α with functionalized devices in standard solutions in the concentration range of 1–20 pg/ml. The use of the impedance spectroscopy technique takes advantage of the exponential behavior of the gm(VGS) curves in the subthreshold (weak inversion) operation of the ISFET. This results in a large signal amplification, where a small change in the threshold voltage results in a large change in the impedance spectrum, thus achieving an increased precision in the measurement of the device response to changes in the analyte concentration. [ABSTRACT FROM AUTHOR]