Label-free and sensitive determination of toxic Cd(II) in environmental waters using a Fe3O4-PEI-Au based electrochemical aptasensor

A novel electrochemical strategy was presented using gold nanoparticles decorated on polyethyleneimine-modified iron oxide nanoparticles (Fe3O4-PEI-Au) as a nanocomposite modifier for sensitive and selective detection of Cd(II). The aptasensor was fabricated by immobilizing a thiol-terminated Cd(II) aptamer onto a screen-printed carbon electrode modified with the Fe3O4-PEI-Au nanocomposite. This nanocomposite provided high surface area for enhanced aptamer loading, excellent biocompatibility, and good conductivity to promote the signal amplification at the sensing interface. Differential pulse voltammetry was used for quantitative measurement of Cd(II), demonstrating a dynamic linear detection range from 0.04 nM to 25 nM. The limit of detection was found to be 0.01 nM, which is lower than the safe limit in drinking water defined by the U.S. Environmental Protection Agency. The label-free aptasensor showed high selectivity, reproducibility, stability and reliability for real-time Cd(II) monitoring in environmental water samples. This work successfully demonstrates the development of a novel electrochemical aptasensor utilizing a Fe3O4-PEI-Au nanocomposite modifier for sensitive and selective detection of trace levels of Cd(II) in water resources.