| xMAP® is commonly called as “Bead Array | | | | assay, tags are attached to allele specific primers |
| Technology”. It is a novel concept developed to | | | | which are extended in the presence of biotinylated |
| eliminate the limitations of planar microarrays during | | | | dNTPs. Tagged ASPE products are then detected by |
| array preparation. Planar microarrays employs glass | | | | hybridization to antitag sequences attached to |
| slides as solid substrate which makes it technically | | | | microspheres. A two laser flow cytometer is |
| challenging and laborious. With the advent of this new | | | | employed for quantification and separation of the |
| high throughput platform, there is a gradual shift from | | | | beads from the hybridized targets. In direct |
| the microarray format of glass slides to the | | | | hybridization assays, the presence of the probe on |
| efficacious bead format. Being more flexible in array | | | | the bead is detected by one laser which reads the |
| preparation the bead format is easy to use, cost | | | | unique internal color of the bead whereas the |
| effective and offers faster hybridization solution | | | | fluorescent signal emitted by the reporter dye on the |
| kinetics along with statistical superiority as compared | | | | labeled target DNA is detected by the second laser. |
| to the conventional technique. In other assay | | | | For ASPE assays, the bead having antitag is detected |
| chemistries utilizing a solid phase, the reaction kinetics | | | | by one laser and fluorescence emitted by tagged |
| can be adversely affected by immobilization of a | | | | ASPE product is detected by the second laser. |
| reactant on a solid surface. The effects are less | | | | Thus different microsphere sets can be combined |
| severe for a microsphere in suspension than for a | | | | within an assay enabling multiplexing of up to 100 |
| flat array as the diffusion rate of the immobilized | | | | samples in a single reaction. This greatly reduces the |
| capture probe can be slower and the effective | | | | amount of the test sample utilized.xMAP® is highly |
| concentration is reduced as compared to free DNA in | | | | desirable for bio-pharmaceutical studies which involves |
| solution In broader terms the integration of three | | | | drug discovery researches and diagnostic applications. |
| prominent technologies: PCR, microarray and | | | | It is capable of providing high content data that |
| fluorimeter into a small bead makes xMAP® both | | | | enables high throughput nucleic acid detection. Its a |
| sensitive and specific.xMAP® or the suspension | | | | promising technology that will suffice the present as |
| array technology involves the use of polystyrene | | | | well as the future requirements of the molecular |
| microspheres or beads. These beads contains a | | | | research laboratory in the areas of SNP genotyping, |
| unique mixture of internal fluorescent dyes or | | | | gene expression profiling, HLA DNA typing and |
| spectral addresses. In direct hybridization assays, | | | | microbial detection. |
| DNA probes are attached to these beads. The | | | | This novel technology is now supported in-silico. |
| probes bind to the target DNA molecule that are in | | | | PREMIER Biosoft has included support for designing |
| turn labeled with distinct fluorescent dyes (reporter | | | | oligos for multiplex analysis on suspension array |
| dye). To carry on the analysis of different probes | | | | systems in one of their tools called PrimerPlex. The |
| simultaneously, bead sets coupled to the probes are | | | | tool is supported on both Windows and Mac. It |
| thoroughly mixed in a microtiter plate of 100 wells. | | | | designs specific capture probes for direct |
| In solution based microsphere capture assay format, | | | | hybridization assays and primer pairs for Allele Specific |
| microspheres are attached to a short stretch of | | | | PCR Extension (ASPE) assays. These assays are |
| unique sequence called as FlexMAP antitag which | | | | widely used for high throughput SNP applications such |
| captures the complementary tags attached to the | | | | as genotyping, pathogen detection, strain typing, and |
| custom oligos. In allele specific primer extension | | | | haplotyping. |