Impedimetric Sensor of ss-HSDNA/Reduced Graphene Oxide Aerogel Electrode toward Aflatoxin B1 Detection: Effects of Redox Mediator Charges and Hydrodynamic Diffusion.

Here, an impedimetric biosensor for determination and quantification of an aflatoxin B1 (AFB1) level using a reduced graphene oxide aerogel labeled with a single strand DNA (ss-HSDNA/rGOae) modified on a rotating disk electrode (RDE) is presented. Owing to the large biomolecule biding on the electrode, an electron transfer is interrupted and not easily accessible to a target molecule. To address this issue, we aim to study two effects; one considers electro-redox mediators and the other considers the hydrodynamic effect. By observing a cyclic voltammetric response from the ss-HSDNA/rGOae electrode in three different charges of the redox mediators (i.e., neutral FcCH2OH, cationic Ru(NH3)63+, and anionic Fe(CN)64-) in a phosphate buffer solution (PBS) containing AFB1, the magnitude of anodic current at 50 mV s-1 is 825, 615, and 550 mA cm-1, respectively, which is significant dominated by the charge of the redox probe. The effect of hydrodynamic diffusion of the ss-HSDNA/rGOae rotating disk electrode (RDE) toward AFB1 detection using FcCH2OH as the redox mediator was recorded by applying a range of rotating speed from 500 to 4000 rpm. Increasing rotating speed reduces the charge transfer resistance resulting in the lower detectable level for AFB1 quantification. In the case of 4000 rpm, the AFB1 can be detected with a limit of detection of 0.04 ng/mL and a linear range of 1 × 10-10 to 7 × 10-8g/mL.