Abstract

In this work, ultrasensitive electrochemical doxorubicin impedance immunosensor was investigated based on immobilization of a specific monoclonal antibody on gold nanoparticles (GNPs) associated with a thiol base sol–gel (TBSol–Gel) modified gold electrode. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) were employed for characterization of the various layers that were formed at the electrode surface. The redox couples of 1.0 mmol L⁻¹, Fe(CN)₆^4−/3− species on the electrode surface was followed to study the layers formation and determination process, using electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). After optimization of analytical parameters, the relative charge transfer resistance (R_ct) increases linearly with doxorubicin concentration in the ranges of 0.1–1.0 and 2.5–50.0 pg mL⁻¹, with a detection limit of 0.09 pg mL^–1. A high association constant of 1.4×10¹¹ L mol^–1 was obtained for the affinity of doxorubicin toward the immobilized antibody on the electrode surface. The capability of the proposed immunosensor for the determination of doxorubicin in spiked human serum and urine samples was examined by standard addition method, and the results show that the immunosensor is a useful tool for the determination of doxorubicin in the biological samples.