The rapidly growing knowledge base in drug discovery and protein research has placed increased pressure on researchers to quickly gain a greater understanding of protein-protein interactions, cell signaling pathways, and markers of metabolic processes. This information is difficult or impractical to obtain using manual ELISAs or Western blots, which are limited to detecting proteins one at a time, isolated from other proteins that share the same pathway. In contrast, bead-based multiplex immunoassays, such as those using the Luminex xMAP platform, provide quantitative, high throughput protein detection, measuring up to 500 analytes per sample well.¹ Most recently, the development of magnetic beads for Luminex-based immunoassays has improved the precision of these quantitative assays while simultaneously enhancing convenience and automation capability.
click to enlarge
Figure: Magnetic bead mouse cytokine kit used with the BioTek Instruments Elx405RM plate washer vs. non-magnetic bead mouse cytokine kit used with vacuum filtration/filter plate. TNFα was measured in 35 mouse serum samples. |
|
Improved multiplex immunodetection
Magnetization of immunoassay beads improves the precision of protein quantitation by making the bead washing step more reproducible.² Arrays of bead-based immunoassays require washing to remove impurities and nonspecifically bound proteins. Magnetic beads are immobilized to the bottom of the assay plate using an automated magnetic microplate washer, enabling thorough removal of buffers and avoiding clogging of individual wells that may occur with filter plates and vacuum manifolds. As a result, multiplex protein quantitation using magnetic beads exhibits lower coefficients of variation than traditional beads.
Because magnetic microplate washing does not require regulation of vacuum pressure, blotting of the underside of the filter plate, or clearance of clogged wells, there is less need for hands-on intervention from the user, increasing throughput.
Increasing availability of existing multiplex assay kits in magnetic format
The MILLIPLEX MAG kits allow users of Luminex technology to switch to a magnetic format. The kits are compatible with traditional vacuum manifolds and filter plates as well as magnetic microplate washers. Quantitative measurements of proteins using a magnetic bead assay kit compared to the corresponding non-magnetic bead assay kit show equivalent performance (Figure), enabling easy correlation between studies conducted in the two different bead formats.³
Areas of research that are already being addressed by magnetic bead-based multiplex assay kits include cytokine/chemokines, metabolic disease, and gut-hormone biomarker studies. As researchers embrace magnetic bead-based multiplexing and life science suppliers develop dedicated instrumentation and automation capabilities, the applications will continue to expand.
About the Author
Cindy Fry integrates product development and marketing for MILLIPLEX MAG magnetic bead-based multiplex immunoassay reagents and kits at Millipore.
References
1. http://www.luminexcorp.com/01_xMAPTechnology, Accessed February 10, 2010.
2. Greene J. Automating Magnetic Bead Multiplexing Assays. Gen Eng News. 2009; 29(13).
3. Millipore. MILLIPLEX MAG platform, Technical Publication PF2923EN00 2009: p. 2.
This article was published in Drug Discovery & Development magazine: Vol. 13, No. 1, January/February, 2010, p. 22.
