Electrochemical immunosensor for the determination of 8-isoprostane aging biomarker using carbon nanohorns-modified disposable electrodes

The first electrochemical immunosensor for the determination of 8-isoprostane (8-iso prostaglandin F2 alpha, ISO), one of the most reliable biomarkers of lipid peroxidation in the human body and of aging related to Alzheimer's disease or atherosclerosis is reported in this article. Disposable screen-printed carbon electrodes modified with carboxylated carbon nanohorns (CNHs) were employed as scaffolds for covalent immobilization of a specific anti-ISO antibody). A competitive immunoassay involving ISO and HRP-labeled antigen was designed and the determination of ISO was carried out by amperometry at -200 mV using the H2O2/hydroquinone (HQ) system. Under the optimized conditions, the immunosensor provides a linear response for ISO (r(2) = 0.998) extending up to 700 pg/mL, which is suitable for the determination of the target compound in human serum. The analytical performance of the immunosensor improves that claimed for ELISA kits in terms of linearity of the calibration plot, precision, with RSD values lower than 1%, and assay time (1 h 30 min), and exhibits a low limit of detection, 12 pg/mL, a long storage stability (30 days), and an excellent selectivity against other proteins that may be found in human serum. The analytical utility of the developed immunosensor was demonstrated by determining ISO in two types of human serum samples: lyophilized spiked serum, and real human serum from healthy male and female individuals with good results. (C) 2017 Elsevier B.V. All rights reserved.