Photolithographic Synthesis of High-Density DNA and RNA Arrays on Flexible, Transparent, and Easily Sub-Divided Plastic Substrates.

The photolithographic fabrication of highdensity DNA and RNA arrays on flexible and transparent plastic substrates is reported. The substrates are thin sheets of poly(ethylene terephthalate) (PET) coated with cross-linked polymer multilayers that present hydroxyl groups suitable for conventional phosphoramidite-based nucleic acid synthesis. We demonstrate that by modifying array synthesis procedures to accommodate the physical and chemical properties of these materials, it is possible to synthesize plastic-backed oligonudeotide arrays with feature sizes as small as 14 um x 14 tan and feature densities in excess of 125 000/cm2, similar to specifications attainable using rigid substrates such as glass or glassy carbon. These plastic-backed arrays are tolerant to a wide range of hybridization temperatures, and improved synthetic procedures are described that enable the fabrication of arrays with sequences up to 50 nucleotides in length. These arrays hybridize with S/N ratios comparable to those fabricated on otherwise identical arrays prepared on glass or glassy carbon. This platform supports the enzymatic synthesis of RNA arrays and proof-ofconcept experiments are presented showing that the arrays can be readily subdivided into smaller arrays (or "rnillichips") using common laboratory-scale laser cutting tools. These results expand the utility of oligonudeotide arrays fabricated on plastic substrates and open the door to new applications for these important bioanalytical tools.