Electrochemical immunosensor for sensitive determination of transforming growth factor (TGF) - β1 in urine

The first amperometric immunosensor for the quantification of TGF-β1, a cytokine proposed as a biomarker for patients having or at risk for renal disease, is described in this work. The immunosensor design involves disposable devices using carboxylic acid-functionalized magnetic microparticles supported onto screen-printed carbon electrodes and covalent immobilization of the specific antibody for TGF-β1 using Mix&Go polymer. A sandwich-type immunoassay was performed using biotin-anti-TGF and conjugation with peroxidase-labeled streptavidin (poly-HRP-Strept) polymer. Amperometric measurements were carried out at −0.20 V by adding hydrogen peroxide solution onto the electrode surface in the presence of hydroquinone as the redox mediator. The calibration plot allowed a range of linearity extending between 15 and 3000 pg/mL TGF-β1 which is adequate for the determination of the cytokine in plasma and urine. The limit of detection, 10 pg/mL, is notably improved with respect to those obtained with ELISA kits. The usefulness of the immunosensor for the determination of low TGF-β1 concentrations in real samples was evaluated by analyzing spiked urine at different pg/mL concentration levels.