Application of an automated fluidic system using electrochemical bead-based immunoassay to detect the bacteriophage MS2 and ovalbumin

A fully-automated fluidic system for a bead-based immunoassay with electrochemical detection was developed. Assays for the bacteriophage MS2 and ovalbumin (OVA) were demonstrated using this system. Streptavidin-coated paramagnetic microbeads were used as a mobile solid phase. The immunoassay sandwich was made by attaching a biotinylated antibody to the streptavidin-coated beads, capturing antigen, and then exposing the antigen to an antibody conjugated with β-galactosidase. β-Galactosidase converts p-aminophenyl galactopyranoside (PAPG) to p-aminophenol (PAP), which is electrochemically oxidized to p-quinone imine (PQI). The behavior of paramagnetic microbeads in the fluidic system was investigated using beads with immobilized β-galactosidase at different concentrations of beads and flow rates for each procedure in the assay. Furthermore, the fully-automated MS2 and OVA assays were demonstrated using the fluidic system. The limits of detection for MS2 and OVA were 990 (1.6 × 10¹¹ particles mL^-1) and 470 ng mL^-1, respectively.