A lateral flow channel immunoassay combining a particle binding zone geometry with nanoparticle labelling amplification

A lateral flow channel immunoassay is described which combines two strategies for signal enhancement. A packed silicagel microparticle matrix, covalently labelled with capture antibodies, was incorporated into a microchannel, providing a detection surface to sample volume ratio at least 20 times the standard wall modified microfluidic channel format. Strong signal amplification was achieved with non-direct fluorescence labelling. Fluorescein diacetate nanoparticles, synthesized by a simple top-down method, increase the number of fluorophores per antibody binding event, compared with a classical molecular fluorescein label. The fluorescent signal generation mechanism, triggered by the addition of a solution of NaOH:DMSO, was optimised to produce highly fluorescent uranin. The packed channel immunoassay showed a linear relationship between fluorescence intensity and antibody concentration for detection of 0.4–1.67 nM in a model system of rabbit polyclonal antibodies (RbIgG) and goat anti-rabbit polyclonal antibodies (Gt-α RbIgG), potentially enabling this format to achieve semi-quantitative or quantitative measurement of multiple target analytes, where packed silica zones modified with different capture antibodies are incorporated into the same microchannel system.