Electric-field assisted immobilization and hybridization of DNA oligomers on thin-filmmicrochips

Abstract

Single, square voltage pulses in the microsecond timescale result in selective5′-end covalent bonding (immobilization) of thiolated single-stranded (ss)DNA probes to a modified silicon dioxide flat surface and in specifichybridization of ssDNA targets to the immobilized probe. Immobilization andhybridization rates using microsecond voltage pulses at or below 1 V are at least108 times faster than in the passive control reactions performed without electric field(E), and can be achieved with at least three differently functionalized thin-film surfaces onplastic or glass substrates. The systematic study of the effect of DNA probe and targetconcentrations, of DNA probe and target length, and the application of asymmetric pulses onE-assistedDNA immobilization and hybridization showed that: (1) the rapidly rising edge of the pulse is most criticalto the E-assisted processes, but the duration of the pulse is also important;(2) E-assisted immobilization and hybridization can be performed with micrometre-sizedpixels, proving the potential for use on microelectronic length scales, andthe applied voltage can be scaled down together with the electrode spacingto as low as 25 mV; and (3) longer DNA chains reduce the yield in theE-assisted immobilization and hybridization because the density ofphysisorbed single-stranded DNA is reduced. The results show that theE-induced reactions can be used as a general method in DNA microarrays to produce high-density DNAchips (E-immobilization) and speed the microarray-based analysis(E-hybridization).