First label-free impedimetric aptasensor based on Au NPs/TiO2 NPs for the determination of leptin

In this work, the first aptamer-based electrochemical impedance spectroscopy method was developed to determine leptin. This aptasensor is based on the titanium-dioxide nanoparticles and gold nanoparticles modified screen-printed electrode for determination of leptin in human serum and human plasma samples. Firstly, a screen-printed electrode was coated with titanium-dioxide nanoparticles, and then this surface was modified with gold nanoparticles by electrodeposition. The aptasensor was fabricated by immobilizing a thiol tethered DNA aptamer onto the modified electrode surface. The electrodes preparation for measurements constitutes the fabrication process completed by incubating the different concentrations of leptin solution into aptamer modified electrode. After the final step comprises of leptin aptasensor, impedance measurements were carried out. Electrochemical methods of cyclic voltammetry and electrochemical impedance spectroscopy, along with scanning electron microscopy, were employed for electrochemical and morphological characterization of the fabricated aptasensor. The determination of leptin was performed by using the impedance response with increasing concentrations of leptin. The aptasensor exhibited a high electrocatalytic performance towards the impedimetric detection of leptin with two linear ranges (1.0-100.0 pg mL(-1) and 100.0-1000.0 pg mL(-1)). Also, a limit of detection was found equal to 0.312 pg mL(-1). The fabricated aptasensor showed excellent sensitivity and stability, which approved that the developed impedimetric aptasensor is a novel and promising platform determination of leptin. Moreover, the fabricated aptasensor was applied to determine leptin in human serum and plasma samples, and the recovery values were in the range of 96.40-107.79%.