Biosensor design using an electroactive label-based aptamer to detect bisphenol A in serum samples

A new and simple procedure was applied to detect bisphenol A (BPA) based on a BPA aptamer and its complementary strand (Comp. Str.). An electrode was modified with a mixture of carboxylated multiwalled carbon nanotubes and chitosan. The Comp. Str. was immobilized on a modified-glassy carbon electrode (GCE) surface via covalent binding. After the incubation of the aptamer with the electrode surface, it could interact with the Comp. Str. In the presence of BPA, its aptamer will interact with the analyte, resulting in some changes in the configuration and leading to separation from the electrode surface. Due to the attached ferrocene (Fc) group on the 50 head of the aptamer, the redox current of Fc has reduced. This aptasensor can sense the level of BPA in the linear range of 0.2-2 nM, with a limit of detection of 0.38 nM and a sensitivity of 24.51 lA/μM. The proposed aptasensor showed great reliability and selectivity. The acceptable selectivity is due to the specificity of BPA binding to its aptamer. The serum sample was used as a real sample; the aptasensor was able to effectively recover the spiked BPA amounts. It can on-site monitor the BPA in serum samples with acceptable recoveries.