Luminex xMAP Technology
Luminex xMAP technology enables the profiling of up to 100 different analytes in a single multiplex reaction. Luminex Corp. has developed a standard set of 100 polystyrene microspheres, each imbedded with specific ratios of two different fluorecent dyes. The ratio of the two dyes gives each bead type a unique specific identification of that bead in a mixture of other beads. (Fig. 1) It is possible to design multiplexed protein profiling assays for the xMAP technology platform. Several hundred assay kits are already available.
In the typical xMAP cytokine assay, specific bead types are each assigned to a different cytokine and coupled to primary antibodies directed against unique cytokine molecules. The bead mixtures are incubated with serum or cell culture supernatants in filter plates. The beads are then washed and incubated successively with biotinylated antibodies against each cytokine and with streptavadin-phycoerythrin.
Mixtures of beads are injected in to the Luminex LX100 instrument, a modified flow-cytometer, wherein the type and levels of each analyte can be determined by laser-induced fluorescence. (Fig. 2)
Figure 1: Impregnation of polystyrene beads with specific concentrations of two different red-emitting fluorophores allows the specific identification of 100 different bead types.
Figure 2: Dual lasers in the LX100 instrument excite the identification flurophores within each bead as well as the phycoerythrin fluorescent detection protein on the bead surface.