DNA biosensors for the detection of arbuscular mycorrhizae at plant roots as well as phytopathogenic viruses and bacteria based on (A) a microtiterplate assay or (B) the SPR platform:
(A) Oligos based on arbuscular mycorrhizae or viral/bacterial DNA sequences were labelled with digoxigenin (DIG) at the 5´-end and biotin at the 3´-end to bind to a streptavidin coated microtiterplate. Since the two primer ends contain complementary DNA sequences the arbuscular mycorrhizae or viral/bacterial DNA sequences form a loop. If the sample contains arbuscular mycorrhizae or viral/bacterial DNA the loop structure breaks open and the DIG lebelled 5´-end of the oligo is able to interact with the antidigoxigenin antibody conjugated to alkaline phosphatase (AP). The hybridisation can be detected biochemically via a phosphatase reaction.