DNA microarray

The DNA chip technology uses techniques from the semiconductor industry, to identify known genes on a fingernail-sized plastic or glass slides, the microarray, and to measure their activity.

In the developed since the late 1980s by Stephen PA Fodor process patient samples can be identified from various tissues over 100,000 known genes in to be examined. The individual fields of the microarray are coated with single-stranded DNA fragments. Microarrays are used to determine relative changes in gene expression. They can also be used for genotyping. By adding the fields with a red and green fluorescence dye test samples bind them in complementary base sequence of the DNA in the chip. The position, intensity and wavelength of the resulting mixed color to be detected with a high resolution laser camera, and provide information about the difference in the expression of the genes between the two samples, for example, in various organ regions.

In 1994, the company with the Affymetrix " GeneChip HIV " the first commercially available DNA chip on the market. Today there are a wide range of application specific arrays for genomic DNA, plasmids, PCR products, and long oligonucleotides.

Surface chemistry of the chips

Often one uses Aldehydslides in which the surface of the chips, aldehyde groups are attached, via a formation of an imine bond to an amino-modified oligonucleotides ( covalent bond ).

• Epoxy-modified slides: amino-modified oligos bind to the epoxy group to form an amine.
• Streptavidin -modified Slides: biotin - modified oligos bind to the protein. ( The tetramer streptavidin has four binding sites that can bind a biotin each )
• NHS Slides: These slides are coated with NHS - ester groups. An amino-modified oligo to an amide forms. (NHS = N- hydroxysuccinimide )
• Aminoslides: unmodified oligo binds to an indeterminate position during the irradiation with light in the UV range ( indefinite reaction).

Manufacturer

• Miltenyi Biotec, business MACSmolecular.
• Agilent Life Sciences, originally prepared set the scanner in collaboration with Affymetrix.
• Applied Biosystems, which have brought a system on the market that can detect gene expression, due to the chemiluminescence technology.
• CombiMatrix, the life science company Acacia Research Holding.
• Eppendorf Biochip Systems, which developed the Silverquant detection system for the colorimetric detection of signals.
• Febit biomed, a company that has the world's first Random Access Analyzer Genomic developed ( the Geniom ).
• GE Healthcare (a division of GE), formed from the merger of GE Medical and Amersham Life Sciences, 2004.
• Illuminating, a company which operates on the basis of the bead technology.
• NimbleGen, life science company, since 2007, subsidiary of Roche Diagnostics. Provider for high-density microarrays with long oligo probes, reagents and scanner system MS 200 array synthesis based on the Maskless Array Synthesis ( MAS) technology.
• PolyAn, a company that develops and produces 3D slides functionalized polymer or glass as carrier material and fluorescently coded beads for molecular diagnostics.
• Schott Nexterion Microarray Solutions The product group Nexterion Microarray Solutions, a portion of the Schott Jena glass GmbH, develops, manufactures and sells coated and uncoated glass substrates for DNA and protein analysis.