(11c) Surface Immobilization of DNA Aptamers for Biosensing and Protein Interaction Analysis

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. To utilize aptamers as molecular recognition agents in biosensors and biodiagnostics, it is important to develop strategies for reliable immobilization of aptamers so that they retain their biophysical characteristics and binding abilities. Here we present quartz crystal microbalance (QCM) measurements and atomic force microscope (AFM)-based force spectroscopy studies to evaluate aptasensors. Gold surfaces were modified with mixed self assembled monolayers (SAMs) of aptamer and oligoethylene glycol (OEG) thiols (HS-C11-(EG)nOH) to impart resistance to nonspecific protein adsorption. By affinity analysis, we show that short OEG thiols have less impact on aptamer accessibility than longer chain thiols. Immunoglobulin E and vascular endothelial growth factor (VEGF) are presented as target proteins in these experiments. Binding forces obtained by these strategies are similar, demonstrating that the biophysical properties of the aptamer on the sensors are independent from the immobilization strategy. The results present mixed SAMs with aptamers and co-adsorbents as a versatile strategy for aptamer sensor platforms including ultrasensitive biosensor design. It is envisioned that this technology will enable insight into the fundamental biophysical interactions between aptamers and their target proteins for the development of sensitive sensor arrays and diagnostics.