Other Microarray Technologies

A number of new microarray technologies are emerging. It is not possible to describe all of them in this monograph. The best way to keep up with the development in this area is to visit the websites listed in Section 10.1. Here, two specific examples are briefly described.

MAGIChip™ Technology. MAGIChip™, an acronym for microarrays of gel-immobilized compounds on a chip, utilize glass substrates on which an array of polyacrylamide gel pads are produced (Zlatanova and Mirzabekov, 2001). The size of these pads can range from 10 mm x 10 mm x 5 mm to 100 mm x 100 mm x 20 mm. The overall scheme of the MAGIChip™ technology is presented in Figure 10.4. The array of the polyacrylamide gel pads is created by photopolymerization of the acrylamide monomer, spread over the glass substrate and exposed to UV light through a patterned mask. The unpoly-merized acrylamide monomer (in the dark region) is then washed away. Each individual gel pad then acts as a separate test tube for localizing DNA probes, because the surrounding hydrophobic glass surface prevents exchange of sample solution among the pads. The acrylamide has also been copolymerized with oligonucleotides to combine the polymerization step with the step of probe immobilization (Vasiliskov et al., 1999).

The Flow-Thru Chip™. This technology provides a three-dimensional biochip platform, with the benefit of enhancing the surface area and thus increasing the capture rate (Steel et al., 2000). This concept of a 3D Flow-Thru Chip™ is illustrated in Figure 10.5. This technology utilizes a uniformly porous substrate. Three types of porous substrates have been utilized: glass capillary arrays, electrochemically etched porous silicon, and metal oxide filters. The probe molecules are immobilized on the walls of the pores (microchannels) of the substrate. A spot in the array may contain several discrete microchannels in which a single probe may be immobilized. This technology is still in an early stage of development.

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