(12e) Measurement of Aptamer-Target Interactions for Sensor Applications

Molecular recognition between short synthetic oligonucleotide (DNA/RNA) sequences known as aptamers and their targets is increasingly being used for applications such as biodiagnostics and biosensors. As aptamers emerge as 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. We present studies on the interaction forces between specific aptamers and their targets measured using force spectroscopy via atomic force microscopy (AFM) and kinetic studies using a quartz crystal microbalance (QCM). These interactions of highly specific aptamers (RNA and DNA) with target proteins were investigated on a mixed self-assembled monolayer platforms of N-hydroxysuccinimide (NHS) and oligoethylene glycol (OEG)-terminated thiols on ultraflat gold surfaces with covalently immobilized proteins. By the optimization of attachment sites via lysine-NHS linkages on a protein-resistant layer of the OEG SAM, it is possible to fabricate molecular arrays of proteins for study in a controlled fashion. In particular, we present data on the specific interaction kinetics, 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 the development of sensor arrays and diagnostics.