‘Green’ immunochromatographic electrochemical biosensor for mercury(II)

Abstract

We describe an immunochromatographic electrochemical biosensor (IEB) for highly specific and sensitive determination of Hg(II) ions. The IEB is based on the use of a new monoclonal antibody (McAb) against Hg(II) ions that affects the recognition of an antigen. The McAb is placed on the surface of gold nanoparticles (AuNPs) and can recognize the antigen only in the absence of Hg(II) ions. This detection scheme was used to design an immunochromatographic test strip using dually labeled AuNPs along with electrochemical detection. Signal amplification was accomplished by a competitive reaction and the use of horseradish peroxidase. Following immunochromatography, the test zone was cut out and transferred into a reaction cell loaded with a substrate solution containing ortho-phenylenediamine and H2O2. After 10-min incubation with horseradish peroxidase, square wave voltammetry was performed with a screen-printed electrode. Under optimal conditions and a working voltage of −0.57 V, the IEB displays a linear response in the 0.1 to 200 ng.mL−1 Hg(II) concentration range and a 30 pg.mL−1 limit of detection. It was applied to the determination of Hg(II) in (spiked) waters and milk where its sensitivity by far surpassed the maximum allowed contamination levels. This sensitive IEB therefore possesses substantial advantages over other assays. In addition, the detection scheme may be extended to other metal ions for which appropriate antibodies are available.