Gold-coated superparamagnetic nanoparticles for single methyl discrimination in DNA aptamers

Au- and iron-based magnetic nanoparticles (NPs) are promising NPs for biomedical
applications due to their unique properties. The combination of a gold coating over a magnetic core
puts together the benefits from adding the magnetic properties to the robust chemistry provided
by the thiol functionalization of gold. Here, the use of Au-coated magnetic NPs for molecular
detection of a single methylation in DNA aptamer is described. Binding of -thrombin to two
aptamers conjugated to these NPs causes aggregation, a phenomenon that can be observed by UV,
DLS and MRI. These techniques discriminate a single methylation in one of the aptamers, preventing
aggregation due to the inability of -thrombin to recognize it. A parallel study with gold and
ferromagnetic NPs is detailed, concluding that the Au coating of FexOy NP does not affect their
performance and that they are suitable as complex biosensors. These results prove the high detection
potency of Au-coated SPIONs for biomedical applications especially for DNA repair detection.