(467e) Single Molecule Aptamer-Target Interactions for Sensor Applications

Highly specific interactions between oligonucleotides and proteins are ubiquitous in nature. Short synthetic oligonucleotide (DNA/RNA) sequences known as aptamers are increasingly being used for applications such as biodiagnostics and biosensors to directly exploit their exquisite molecular recognition abilities. As aptamers emerge as extremely valuable tools in the development of therapies and diagnostic devices, understanding the modes of interaction of aptamers and their targets is of vital importance in the rational design of such devices. Force spectroscopy using an atomic force microscope (AFM) is a valuable tool for studying such interactions and molecular biorecognition at a single molecule level. Here we present studies of the interactions of highly specific aptamers (RNA and DNA) with target proteins on a mixed self-assembled monolayer (SAM) platform. In this study, mixed SAMs consisting of N-hydroxysuccinimide (NHS) and oligoethylene glycol (OEG)-terminated thiols on ultraflat gold surfaces were used to covalently immobilize proteins. By the optimization of attachment sites via lysine-NHS linkages on a protein-resistant layer of the OEG SAM, it is possible to isolate single proteins for study in a controlled fashion. In particular, we present data on the specific interaction profiles, rupture forces and environmental determinants for the binding of specific aptamers with the clinically relevant biomarker vascular endothelial growth factor (VEGF). It is envisioned that this technology will enable insight into the fundamental biophysical interactions between aptamers and their target proteins for various sensor applications.