Impedimetric Label-Free Immunosensor on Disposable Modified Screen-Printed Electrodes for Ochratoxin A

Abstract

An impedimetric label-free immunosensor on disposable screen-printed carbon electrodes (SPCE) for quantitative determination of Ochratoxin A (OTA) has been developed. After modification of the SPCE surface with gold nanoparticles (AuNPs), the anti-OTA was immobilized on the working electrode through a cysteamine layer. After each coating step, the modified surfaces were characterized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The capacitance was chosen as the best parameter that describes the reproducible change in electrical properties of the electrode surface at different OTA concentrations and it was used to investigate the analytical parameters of the developed immunosensor. Under optimized conditions, the immunosensor showed a linear relationship between 0.3 and 20 ng/mL with a low detection limit of 0.25 ng/mL, making it suitable to control OTA content in many common food products. Lastly, the immunosensor was used to measure OTA in red wine samples and the results were compared with those registered with a competitive ELISA kit. The immunosensor was sensitive to OTA lower than 2 μg/kg, which represents the lower acceptable limit of OTA established by European legislation for common food products.

Fabrication of SrTiO3 Layer on Pt Electrode for Label-Free Capacitive Biosensors

“…Therefore, as expected, the experimental complex plane impedance spectra for the bare Pt electrode and SrTiO 3 perovskite layer modified Pt electrode, obtained under non-faradaic conditions, exhibited an almost linear and close-to-vertical spectra ( Figure 2 ), which indicates a purely capacitive response of the electrode properties [ 16 , 17 ]. In particular, when the SrTiO 3 perovskite layer has been deposed, an increase of the curve slope was observed.…”

The selection of highly specific and selective aptamers using modified SELEX and their use in process analytical techniques for Lucentis bioproduction

“…In our case, the most intense ssDNA aptamer band was obtained at a primer ratio of 20 : 1 (reverse : forward) in lane 6 with the lowest yield of dsDNA; hence, for the regeneration of ssDNA aptamers in the SELEX process, this primer ratio was used. Further, using this primer ratio, the number of PCR cycles used for asymmetric PCR was also optimized, testing 10,15,20,25,30,35, and 40 PCR cycles. A gel image is shown in Fig.…”

“…Lucentis could displace the solvated ions and water outwards from the electrode surface, thus increasing the thickness (d) of the double layer and decreasing the dielectric permittivity (3), thereby resulting in a decrease in the doublelayer capacitance (C dl ), as shown in eqn (1), and an increase in the capacitive component (ÀIm(Z)/ohm). 25,26 Similarly, interactions between Lucentis and the aptamer on the electrode would further increase the thickness and decrease the dielectric permittivity of the double layer. This phenomenon would enhance with an increase in the concentration of aptamer-Lucentis complex present, resulting in a proportional increase in the capacitive component (ÀIm(Z)/ohm), as shown in Fig.…”

Sensitive Detection of Escherichia coli O157:H7 in Food Products by Impedimetric Immunosensors

“…The voltammograms of Au electrodes display well defined anodic and cathodic peaks due to the reversible interconversion of the redox probe K 3 [Fe(CN) 6 ]/K 4 [Fe(CN) 6 ]. After the Au electrodes were covered with short-chain thiols of MBA (immobilization Schemes a and b— Figure 2 a,b) and cysteamine (immobilization Schemes c, d and e— Figure 2 c–e), the response current decreases due to the MBA and cysteamine layers, which hinder the redox probe on the electrode surface [ 10 , 18 ].…”