APTAFRAME · DNA-origami frame platform for co-evolution ligand selection

Affinity reagents such as antibodies and aptamers are of paramount importance as tools in biotechnology and the treatment of a wide range of diseases. However, despite their scientific and economAffinity reagents such as antibodies and aptamers are of paramount importance as tools in biotechnology and the treatment of a wide range of diseases. However, despite their scientific and economic impact it remains challenging to systematically generate high-affinity ligands to cover all epitopes of a given target. Here I propose a strategy to provide spatial control over ligand discovery process leveraging the power of in vitro evolution in conjunction with the spatial addressability of DNA nanotechnology methods. Together they form a new discovery platform for the systematic and parallel generation of ligands, specifically aptamers and single-chain Fv antibody fragments (scFv), to provide coverage of epitopes at predefined targets. The proposed strategy exploits cooperative binding (avidity), by co-evolution of the affinity reagents, in the context of a defined molecular three-dimensional framework provided by DNA origami structures. This further expedites structure determination of ligand-target complexes by cryo-electron microscopy (cryo-EM). The combination of rational framework design, in vitro evolution and structural feedback provided by cryo-EM reconstructions will provide a toolbox for the systematic generation of ligands to all accessible epitopes. Our approach also provides a tool for electron microscopy reconstruction of smaller (< 100kDa) biomolecules and their molecular interactions by enhancing contrast and providing context. Once established, this approach will provide a transformational technology platform that enables the parallel interrogation of multidimensional, spatially resolved libraries, yielding cooperative ligands for highly specific target recognition, with direct applications in biosensor development, proteome analysis, diagnostics and therapy.