Bender MedSystems bead-based assays follow the same principle as a sandwich immunoassay.

• Fluorescent polystyrol beads are coupled with antibodies specific to the analytes to be detected.
• A mix of coupled beads is incubated with the samples to be tested.
• Analytes in the sample bind to the antibodies coupled to the beads.
• A biotin conjugated antibody mix is added, which binds to the analytes bound to the capture antibodies. Streptavidin-Phycoerythrin (PE) is added which binds to the biotin conjugates.
• Beads are differentiated by their sizes and distinct spectral signature by flow cytometry. FlowCytomix Pro 2.1 Software enables calculation of analyte concentration in the tested samples.

• Two sets of beads with different sizes (4 μm & 5 μm) are used in the FlowCytomix assay.
• Each of the two sizes consists of bead populations which are differentiated by varying intensities of an internally fluorescent dye.
• The dye can be excited with an Argon, He-Ne, or even UV laser, and emits in the far red (690 nm) which is detected in the FL-3/FL-4 channel.
• The combination of the two different bead sizes and different internal dye intensities makes it possible to distinguish up to 20 bead sets in one fluorescent channel.
• Streptavidin-PE, which binds to the biotin conjugate, emits at 578 nm and is detected in the FL-2 channel and allows the quantification of the analyte.