Stainless steel modified with an aminosilane layer and gold nanoparticles as a novel disposable substrate for impedimetric immunosensors

In this work, stainless steel (SS) was used as a substrate to fabricate an inexpensive and disposable impedimetric immunosensor. SS surface was modified with a stable thin layer of 3-aminopropyltriethoxysilane (APTES), and followed by electrodeposition of gold nanoparticles (GNPs). The morphology and size of the electrodeposited GNPs were studied using scanning electron microscopy (SEM) and atomic force microscopy (AFM). The interfacial properties of the SS electrode after each modification step were characterized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) in a solution containing [Fe(CN)6]3−/4− as a redox probe. The results indicated that APTES layer was successfully formed on the electrode surface and GNPs enhanced the conductivity and sensitivity of the electrode. The applicability of the proposed assembled electrode in electrochemical immunosensors was followed by immobilizing doxorubicin-specific monoclonal antibodies onto the GNP-modified electrode to determine doxorubicin concentration using the EIS technique. The relative charge transfer resistance was found to increase linearly with doxorubicin concentration in two ranges from 2.5 to 30.0 and 30.0 to 100.0 pg mL−1. The detection limit of the immunosensor was 1.7 pg mL−1 (3sb/m) doxorubicin. The satisfactory results were obtained from determination of doxorubicin concentrations in spiked human serum samples. The recoveries were in the range of 88.0-122.2%. These results indicate that modified SS electrodes are promising sensing elements to construct economical electrochemical immunosensors for routine quantitative analyses.