MULTIPLEX ASSAY SERVICES

Overview of two common multiplex formats

The planar format includes platforms such as Boster’s Q–Plex™ array whereby high-affinity capture ligands are immobilised discretely on a solid phase, 2D support, usually in a microtiter plate format. The immobilised ligands are subsequently exposed to treatment with the sample and probing with detection antibodies labelled with a reporter system. The suspension format includes platforms such as Luminex™, whereby high-affinity capture ligands are immobilized discretely on fluorescently activated plastic microbeads and mixed with the sample in liquid phase. Subsequent addition of detection antibodies labelled with a reporter dye enables high-resolution analysis of specific fluorescent signal via flow cytometric methods.

Microplate Q-Plex™ Platform Principle

The Q-Plex™ multiplex assays utilize a sandwich enzyme immunoassay technique for the measurement of multiple targets. These assays use two different antibodies specific for their respective targets. Analyte specific antibodies are immobilized in specific locations on the array. Samples or calibrators are pipetted into wells, and after washing away any unbound protein, a mixture containing biotinylated analyte specific antibodies is added, completing the sandwich for each specific arrayed analyte. After washing away unbound biotinylated antibody, streptavidin-horseradish peroxidase (SHRP) is added, washed, and the amount of SHRP remaining on each location of the array is proportional to the amount of the target initially captured. The amount of conjugated enzyme on each location of the array is measured with the addition of a chemiluminescent substrate using a Q-Plex plate reader.

Q-plex benefits:

• Customizable
  
• Premade popular panels available
• Faster turnaround
• Lower cost on average

Microbead-based Assay Platform Principle

Microbead-based assays such as the Luminex xMAP technology, utilize the same sandwich ELISA principle as above to multiplex up to 100 different assays within a single sample. This technique involves distinctly colored bead sets, antibody pairs to specific analytes and reporter dyes. One antibody to a specific analyte is attached to a set of beads with the same color, and the second antibody to the analyte is attached to a fluorescent reporter dye label. The use of different colored beads enables the simultaneous multiplex detection of many other analytes in the same sample. A dual detection flow cytometer or Luminex machine is used to sort out the different assays by bead colors in one channel and determine the analyte concentration by measuring the reporter dye fluorescence in another channel.

The advantage of using this platform is that it gives you the ability for large scale screening of many analytes against your sample at one time. However one disadvantage of larger panels may be the loss of resolution for lower expressing markers

Microbead-Based Assay benefits:

• Customizable for large scale screening
  
• Premade popular panels available
• Faster turnaround