Using technology developed at the Argonne National Laboratory, Motorola Life Sciences (Northbrook, IL) has developed a novel "gel pad array" technology and has begun early production rounds of these arrays. Within each "gel pad," or gel matrix, several different kinds of reaction technologies can be embedded, including oligonucleotides. Although the oligonucleotides attached to the gel pads (themselves 100 1m in width) might not seem to have the same access to the free-floating complementary DNA strands in a biological sample as they might have on a glass slide, in practice they appear to have similar specificity and sensitivity of hybridization. The use of oligonucleotides is preferable to full length cDNA as reproducibility and cost are kept lower and the probes can be suitably normalized for GC content. As is the case for other oligonucleotide technologies, care must be taken in selecting an oligonucleotide sequence so that it does not cross-hybridize with other genes.
As the gel pads allow oligonucleotides lengths of greater than the 251m used in Affymetrix microarrays, in theory they can provide higher specificity. Also, although the feature size is relatively large compared to oligonucleotide arrays made by Affymetrix, current gel pad technologies can be arrayed up to 10,000 probes on a single glass slide. As for other platforms, higher densities are promised.
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