Microspheres, also known as latex beads, polystyrene beads, and microbeads are a proven solid-phase format for development of assays used in both research and clinical diagnostics.

Key advantages to bead format assays are:

• Ease of manufacture
• Faster assays; near–fluid-phase binding kinetics
• Increased sensitivity; increased surface allows more antigen, antibody, or DNA to be included in the assay

Easily automated assay formats

Compatibility with enzymatic, agglutination, and fluorescence detection systems

A key advantage of bead assays is multiplexing or the ability to detect multiple analytes simultaneously in the same sample. Multiplexing is achieved through the use of beads of different sizes, colors, or fluorescence intensities. Each different bead type can be used to provide a separate assay.

Rolling circle amplification technology (RCAT) can be applied to agglutination, enzymatic, and fluorescence detection systems covering all of the detection methods commonly used with beads. In each of these formats, RCAT offers significantly improved sensitivity.

Flow cytometers are rapidly becoming the detection system of choice for bead assays using fluorescent antibodies or fluorescent DNA probes.

RCAT is well suited to flow cytometry assay formats because the amplification product remains tethered to the target molecules captured by the bead and does not interfere with the intrinsic fluorescence of the bead.

Advantages of RCAT for beads:

• Increased sensitivity
• Use of less antigen, antibody, or DNA probe
• Compatibility with flow cytometers
• Compatibility with Luminex bead assay systems