Morpholino probe detection of DNA (amperometric)

[Jon Moulton]

Gao Z, Boon PT. A DNA biosensor based on a morpholino oligomer coated indium-tin oxide electrode and a cationic redox polymer. Analyst. 2009; [Epub ahead of print]
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My notes:

A system was developed for detection of DNA sequences complementary to Morpholino probes. The Morpholinos were attached to an electrode surface. The electrode was exposed to a solution which might contain a complementary DNA analyte. Next the electrode was exposed to a solution containing a cationic polymer able to undergo redox reactions. If the DNA hybridized to the Morpholino, the cationic redox polymer would stick to the DNA by electrostatic attraction. In the presence of ascorbic acid, the electrical properties of the coated electrode were assayed and could detect whether as little as 1 pM of complementary DNA analyte was present in the analyte solution.

This system exploits the uncharged nature and good specificity of the Morpholino oligo. If the complementary DNA is not present in the analyte solution, the Morpholino remains unhybridized and without immobilized anionic DNA, the cationic redox polymer won’t stick. Without the redox polymer present, the amperometric measurements find no redox current.