Probing Antigen-Antibody Interactions on Electrode Supports by the Biocatalyzed Precipitation of an Insoluble Product

Abstract

The ampli®ed sensing of an antibody by an antigen monolayer-functionalized transducer by using a biocatalyzed precipitation of an insoluble product on the transducer is addressed. Faradaic impedance spectroscopy, cyclic voltammetry and microgravimetric, quartz crystal microbalance analyses are used to probe the precipitation of the insoluble product on the transducer. A dinitrophenyl, DNP, antigen monolayer is assembled on a Au-electrode, or a Au-quartz crystal, as a sensing interface for the dinitrophenyl-antibody, DNP-Ab. An anti-Fc-antibody-HRP conjugate is used as a biocatalytic probe for the formation of the antigen/DNP-Ab complex on the transducer. Biocatalyzed oxidation of 4-chloronaphthol by H 2 O 2 in the presence of the anti-Fc-antibody-HRP conjugate yields an insoluble product on the transducer. Formation of the insoluble ®lm on the electrode results in the increase of interfacial electron-transfer resistances detected by impedance spectroscopy or cyclic voltammetry. The precipitate formation also results in the mass increase of the modi®ed Au-quartz crystal detected as a frequency change of the piezoelectric transducer. The DNP-Ab is easily sensed at a sensitivity that corresponds to 0.5 ng mL 71 (3610 712 M).

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