Electrochemical detection of 0.6% genetically modified maize MON810 in real flour samples

We demonstrate an approach for the electrochemical detection of genetically modified maize in real maize flour samples by means of square-wave voltammetry (SWV). After labeling the asymmetric PCR-amplified targets with osmium tetroxide bipyridine [OsO4(bipy)], they were hybridized with immobilized oligonucleotide probes on gold electrodes. We could detect the maize genes ivrp and SSIIb in near isogenic maize. The transgene cryIa/b and the MON810 specific fragment were detected in all transgenic maize samples, down to a content of 0.6% of MON810 in mixed samples. While it was possible to detect all sequences in the samples containing 100% near isogenic or respectively transgenic maize after a hybridization time of less than 10 min, a hybridization time of 30 min was necessary for the detection of the genetic modifications in samples containing only 0.9 to 0.6% of transgenic maize. No significant detection of the transgene cryIa/b or MON810 was possible when only 0.5% of transgenic maize was present in the sample, most likely due to insufficient amplification of the template DNA.

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► Asymmetric PCR (one primer in excess) to produce single-stranded DNA for electrochemical labeling.
► Labeling of PCR-amplified ssDNA with Osmium tetroxide bipyridine.
► Detection of 0.6% of MON 810 besides the wildtype.
► Coupling of asymmetric PCR with voltammetric hybridization detection.
► Rapid analysis of genetically modified plants at the trace level is an urgent topic in crop and food sectors.