Flow Injection Renewable Surface Immunoassay: A New Approach to Immunoanalysis with Fluorescence Detection

This paper introduces a new methodology of carrying out heterogeneous immunoassays automatically, using a flow injection technique on a renewable surface. Flow injection renewable surface immunoassay (FIRSI) relies on the use of a minute amount of beads to form a reactive surface, which is interrogated by fluorescence spectrometry. Following the assay, on-line regeneration normally used in flow based immunoassays is avoided by fluidically removing the spent reactive surface and replacing it with a new layer of beads. This allows the monitoring of antibody-antigen binding at its early stages, dramatically increases the sampling frequency of a serial assay, and eliminates the problems associated with a decrease in surface reactivity caused by repetitive use. A model system utilizing anti-mouse IgG1-coated beads and mouse IgG1 protein is used to characterize the method with respect to reproducibility, flow rate, contact time, and amount of beads.