High Resolution Electrochemical In Situ Printing

This work demonstrates a new method for making oligonucleotide microarrays by synthesis in situ. The method uses conventional DNA synthesis chemistry with an electrochemical deblocking step. Acid is delivered to specific regions on a glass slide, thus allowing nucleotide addition only at chosen sites. Deblocking is complete in a few seconds, when competing side-product reactions are minimal. Features generated in this study are 40 microns wide, with sharply defined edges. The acid used for synthesis is produced by electrochemical oxidation of a reversible redox couple at microelectrodes. Under suitable conditions, the active species is confined to micron-sized features and diffusion does not obscure the surface pattern produced. Experimental results, theoretical analysis, and digital simulation identify a chemical annihilation process critical to ensuring high feature resolution. The microelectrodes used for synthesis are designed to sustain high currents, chemical attack, and mechanical wear so that many hundreds of syntheses can be performed with the same microelectrode set. Software, custom electronics, and a sealed piston and cylinder fluidics chamber allow synthesis automation. The electrochemical and mechanical system is robust and may be adapted to a range of other biomolecule syntheses.