Voltammetric immunoassay for α-fetoprotein by using a gold nanoparticle/dendrimer conjugate and a ferrocene derived ionic liquid.

An immunosensor is described for the voltammetric determination of α-fetoprotein. It is making use of an AuNP-dendrimer conjugate and an ionic liquid. A gold electrode was first modified with chitosan. Then, the AuNP-dendrimer conjugate was covalently immobilized on the electrode. Following this, an ionic liquid was placed on the electrode via formation of a covalent bond between the amino groups of PAMAM and the aldehyde groups of an ionic liquid containing ferrocene. Thus, the redox probe ferrocene becomes immobilized on the electrode surface. PAMAM increases the amount of ferrocene immobilized on the electrode due to its globular shape and rich amino groups. The use of AuNPs improves the conductivity of the electrode. The modified electrode was applied to the determination of α-fetoprotein in human serum and has a linear response that covers the 0.05 to 30 ng mL-1 α-fetoprotein concentration range, with a detection limit of 0.02 ng mL-1. This assay is stable, selective and reproducible. It is perceived to provide a powerful tool for the early detection of cancer markers. Graphical abstract Schematic of a voltammetric immunoassay for α-fetoprotein based on a gold nanoparticle/dendrimer conjugate and ionic liquids anchored with both aldehyde and ferrocene. Chit: chitosan; GA: glutaraldehyde ; PAMAM: G4 polyamidoaminic dendrimers; AuNP: Au nanoparticle; Fc: ferrocene; IL: ionic liquid. PB: phosphate buffer solution.