Electrochemical synthesis of Fe2O3 on graphene matrix for indicator-free impedimetric aptasensing

Herein, an electrochemical platform was employed for the detection of protein. Fe2O3 was electrochemically deposited on graphene modified glassy carbon electrode surface. Electrodeposition conditions, such as temperature, and time, were optimized for controlling morphologies and electrochemical activities of Fe2O3. Negatively charged lysozyme-binding aptamer (LBA) was immobilized on positively charged Fe2O3 (isoelectric point ∼7.0) via electrostatic interaction. Electrochemical impedance spectroscopy was adopted for indicator-free detection of lysozyme. The LBA on the outermost layer would catch lysozyme in solution by physical affinity, which induced the increase of impedimetric signals. In this strategy, a wide detection range (0.5 ng mL−1–5 μg mL−1) and low detection limit (0.16 ng mL−1) for model target lysozyme was obtained. The results showed that indicator-free impedimetric aptasensing strategy had good sensitivity and selectivity.