Label-free genetic and proteomic marker detection within a single flowcell assay

No one technique for multiplexing 100+ label-free measurements in a single well or flowcell has yet gained wide acceptance, probably because the added complexity introduced by the multiplexing element is seen to outweigh any possible cost advantage, or the multiplexing scheme itself is not flexible enough to accommodate the desired combinations of immobilization conditions and target/analyte molecules. Here, we demonstrate a simple yet highly versatile technology which uses microparticles, each bearing both an identifier code and an optical grating, to permit the inclusion of diverse molecules such as protein A, IgG and DNA, on chemically diverse –OH, –NH2 and –COOH-terminated surfaces, within a single flowcell assay. Binding of avidin is used to reveal the presence of the immobilized biotinylated species, and to compare directly the binding of similar molecules on dissimilar surfaces, and vice-versa. Though we report the results of a 26-plex assay here, the technique itself has scope for increased throughput up to the level of hundreds of molecular species.