DNA aptamers have been utilized in different detection schemes, resulting in sensing platforms with great sensitivity and selectivity. Typically, the binding of the aptamer to the target is proposed to occur through a conformational change that is engineered to result in a signal that can be measured and quantified. Gold nanoparticle aptasensors (Apt-AuNPs) are particularly attractive due to their ease of preparation and their versatility to detect different types of analytes from small molecules to whole cells. Apt-AuNPs are designed by adsorbing an aptamer on the AuNPs surface which stabilizes the nanoparticles. Analyte binding by the aptamer disrupts the aptamer-AuNPs interactions and therefore affects the AuNPs’ plasmonic response. Despite their popularity, no solid evidence of the aptamer conformational changes that is proposed to occur on the surface of the Apt-AuNPs has been experimentally demonstrated. In this work, we used a combination of techniques, including nuclear magnetic resonance, UV-vis and fluorescence spectroscopy, and dynamic light scattering to monitor the molecular changes the aptamer experiences through the sensing mechanism and their effect on particle stability and overall assay response. Our results show that a dramatic change in conformation of the aptamer upon analyte binding is not necessary to obtain a plasmonic response, and that the final assay response depends critically on the thermodynamics involved in the interactions between the aptamer/AuNPs surface and the aptamer/target.

Effects of analyte-induced DNA aptamer conformational changes in aptasensors response

255th National Meeting (2018)

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