Design of a redox-active surface for ultrasensitive redox capacitive aptasensing of aflatoxin M1 in milk

Herein, we report the design of a novel label-free aptasensor based on ferrocene and silicon nanoparticles (SiNPs) for ultrasensitive detection of aflatoxin M1 (AFM1) in milk. Given that silicon nanomaterials stand out by their high capacitive power, we used them to develop a novel capacitive transduction system based on electrochemical capacitance spectroscopy (ECS). This strategy relies on the changes of the redox capacitance signal owed to the surface-tethered ferrocene film, by performing electrochemical impedance spectroscopy (EIS) measurements without using an external redox probe. The redox capacitance variation was found to correlate well with the increasing concentrations of AFM1 in the linear range from 10 to 500 fmol⋅L-1 with a sensitivity of 0.46 μF*fM-1*cm − 2. Furthermore, the aptasensor allowed to reach very low limits of detection and quantification equal to 4.53 fM and 14.95 fM, respectively. The platform revealed a high selectivity toward the target analyte, and it was applied to quantify very low concentrations of AFM1 in commercial pasteurized milk. Finally, the results of real sample analysis were successfully gauged against those obtained using commercially available enzyme-linked immunoassay (ELISA) kits. [Display omitted] •Development of a highly sensitive aptasensor for aflatoxin M1 detection in milk using a novel electrochemical capacitance spectroscopy approach.•This work highlights the first feasibility study of redox capacitance transduction (ECS) using screen-printed carbon electrodes (SPCE).•Detection of very low amounts of target (femtomolar range) with minimal interferences in real matrix.