Automated Washing Of Multiplex Bead Based Assays For The Luminex MAGPIX® Reader System

By Paul Held Ph.D., Laboratory Manager, Applications Dept., BioTek Instruments, Inc.

Luminex xMAP® technology provides the means to measure multiple analytes simultaneously from the same sample. Originally designed around polystyrene MicroPlex® beads which required vacuum aspiration for washing, the latest generation of MagPlex® beads use embedded ferrite particles to allow for the use of magnets to immobilize the microspheres during the wash steps. Both beads can be read using a flow cytometry based reader that interprets the bead type as well as quantitate the analyte. Recently, a new paradigm of xMAP reader has been developed by Luminex which does not utilize flow cytometry principles for detection. The MAGPIX® reader system has been developed by Luminex exclusively for use with MagPlex® microspheres. With both reader technologies, distinct internally color-coded magnetic microspheres coated with a specific antibody, capture and quantitate different analytes. Using traditional Luminex flow cytometry technology, microspheres were channeled to pass rapidly and individually through a laser beam which excites the internal dyes identifying the bead and analyte, while a second laser excites the reporter molecule, quantifying the analyte. The MAGPIX® reader used in this study employs CCD fluorescent imaging to identify and quantitate the analyte. Both technologies require the same assay process prior to multiplex analyte determination by the reader. While we have established that the wash steps for MagPlex beads can be automated using an appropriately configured microplate washer using the LX100 reader, little data exists using the MAGPIX reader in conjunction with automated wash systems. Here we compare the results obtained with the MAGPIX reader to that of the LX100 using the BioTek ELx50 Automated Microplate Strip Washer to automate the wash steps of a EMD Millipore Cancer Biomarker 22-plex multiplex assay.