Multivalent foldamer-based affinity assay for selective recognition of Aβ oligomers

•A sandwich-type immunoassay is developed to detect β-amyloid.•The assay utilizes foldamer helices as recognition elements.•The assay is selective to β-amyloid oligomers against monomeric forms.•β-amyloid oligomers can be detected at pM levels.

Mimicking the molecular recognition functionality of antibodies is a great challenge. Foldamers are attractive candidates because of their relatively small size and designable interaction surface. This paper describes a sandwich type enzyme-linked immunoassay with a tetravalent β-peptide foldamer helix array as capture element and enzyme labeled tracer antibodies. The assay was found to be selective to β-amyloid oligomeric species with surface features transiently present in ongoing aggregation. In optimized conditions, with special emphasis on the foldamer immobilization, a detection limit of 5 pM was achieved with a linear range of 10-500 pM. These results suggest that protein mimetic foldamers can be useful tools in biosensors and affinity assays.

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