Screen‐printed Gold Electrodes Functionalized with Grafted p‐Aminobenzoic Acid for the Construction of Electrochemical Immunosensors. Determination of TGF‐β1 Cytokine in Human Plasma

Abstract

AbstractScreen‐printed gold electrodes were modified with grafted p‐aminobezoic acid to provide scaffolds with high loading of surface confined carboxyl groups that can be used to construct electrochemical immunosensors. As a specific application, an immunosensor for the determination of the cytokine transforming growth factor beta 1 (TGF‐β1) is reported. The capture antibody (anti‐TGF) was covalently immobilized on the surface of the prepared disposable scaffold and a sandwich‐type immunoassay was implemented with biotinylated detector antibody (Biotin‐anti‐TGF) and streptavidin labeled with alkaline phosphatase (AP‐Strept). The transduction event was monitored by differential pulse voltammetry after addition of 1‐naphthyl phosphate (1‐NPP) as the enzyme substrate. The different variables affecting the preparation and the analytical behavior of the AP‐Strept‐Biotin‐anti‐TGF‐TGF‐β1‐anti‐TGF‐SPAuE immunosensor were optimized, and the functionalized gold electrodes and the prepared immunosensor were characterized using several techniques. A linear range extending between 0.05 and 3.0 ng/mL TGF‐β1, adequate for the determination of the cytokine in human plasma, and a LOD of 10 pg/mL, better than that claimed for commercial ELISA kits, were achieved. The immunosensor exhibits also a great selectivity against other proteins and an excellent storage ability. The usefulness of the immunosensor was demonstrated by analyzing human plasma spiked with TGF‐β1.