ABSTRACT
The development of DNA sensors attracts recent research efforts directed to gene analysis, the detection of genetic disorders, tissue matching, forensic applications, and the detection of viral infections [1-3]. Optical detection of DNA was accomplished by the application of fluorescence-labeled oligonucleotides [4] and the use of surface plasmon resonance spectroscopy (SPR) [5]. Recent optical detection of DNA was accomplished by the use of Au-nanoparticles as photonic probes [6, 7]. Electronic transduction of oligonucleotide-DNA recognition events, and specifically the quantitative assay of DNA, are major challenges in DNA-based bioelectronics [8]. Electrochemical DNA sensors based on the amperometric or voltammetric transduction of the formation of doublestranded (ds) oligonucleotide-DNA complexes were reported by following the direct electrical response of the ds-assembly [9], the examination of the effect of the dsassembly on the voltammetric wave of conductive polymers [10], and the electrical response of transition metal complexes [11] or dyes [12] that are intercalated or electrostatically attracted to the double-stranded assembly. Microgravimetric quartzcrystal-microbalance (QCM) analyses were also applied to sense the formation of dsoligonucleotide-DNA complexes on surfaces [13]. Two fundamental problems that need to be addressed while developing electronic DNA sensors relate to the sensitivity and specificity of the devices. PCR provides a means for the amplification of the DNA content, but the method is limited to quantitative and parallel high throughput analyses of DNA [14]. Thus, the development of novel amplification means for the quantitative DNA sensing events is essential. Furthermore, the specificity of the DNA recognition is important, and the feasibility of discriminating mutants from the normal base-sequence, with the optimal capability to distinguish single-base mismatches or mutations, is a challenging goal.
