The working principle of a genosensor is based on the mechanism of ion‐channel mimetic sensors. The analytical signals generated upon hybridization processes were recorded by a redox active marker [Fe(CN)6]3−/4− present in the sample solution using voltammetric techniques. The developed genosensor was suitable for determination of 20‐mer complementary oligonucleotide sequence, and also of the PCR products containing the complementary 20‐mer sequence in various positions, with detection limits in the 10 pM range. The noncomplementary 20‐mer oligonucleotide sequence as well as the PCR product without complementary region generated very weak response. The good discrimination of the position of the complementary part in the PCR products was observed.
The duo-genosensor consisting of two different oligonucleotide probes immobilized covalently on the surface of one gold electrode via Au-S bond formation was used for simultaneous determination of two different oligonucleotide targets. One of the probes, decorated on its 5'-end with ferrocene (SH-ssDNA-Fc), is complementary to the cDNA representing a sequence encoding part of H5 hemagglutinin from H5N1 virus. The second probe, decorated on its 5'-end with methylene blue (SH-ssDNA-MB), is complementary to cDNA representing the fragment of N1 neuraminidase from the same virus. The presence of both probes on the surface of gold electrodes was confirmed with Osteryoung square-wave voltammetry (OSWV). The changes in redox activity of both redox active complexes before and after the hybridization process were used as analytical signal. The peak at +400 ± 2 mV was observed in the presence of 40 nM ssDNA used as a target for SH-ssDNA-Fc probe. This peak increased with the increase of concentration of target ssDNA. It indicates the "signal on" mode of analytical signal generation. The peak at -250 ± 4 mV, characteristic for SH-ssDNA-MB probe, was decreasing with the increase of the concentration of the complementary ssDNA target starting from 8 to 100 nM. This indicates the generation of electrochemical signal according to the "signal off" mode. The proposed duo-genosensor is capable of simultaneous, specific, and good sensitivity probing for the sequences derived from genes encoding two main markers of the influenza virus, hemagglutinin and neuraminidase.
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