Figure 1. Array platforms. (A) Macroarrays use nucleic acid probes deposited on membrane filters. Samples are usually radioactively labeled and hybridized in parallel. Detection is performed either through autoradiography or phosphorimaging. (B) Microarrays are formated on glass or plastic. Fluorescently labeled control and experimental samples are hybridized to the array in a competitive manner. Detection is performed by means of a fluorescent scanner. (C) High-density oligonucleotide arrays use photolithographically synthesized probes on a silicon matrix. Due to the limited length and specificity of the probes, a mismatch pair is added to determine specific hybridization. (D) Microelectronic arrays are an emerging technology that uses an electric field generated by individually controllable electrodes to immobilize probes and to control target hybridization. Washing is accomplished by reversing the electric fields. (Reproduced with permission from Freeman et al., 2000)
