By Paige Steiger, Chemistry
Advisor: Spencer Hendrickson
Abstract: Electrochemical aptamer-based (E-AB) sensors are powerful tools used in the detection of various analytes including proteins, cells, and small molecules. These aptamers are single-stranded DNA that bind to the target of interest with high affinity and selectivity, and upon doing so, undergo a three-dimensional conformation change. This change in conformation is critical for monitoring analyte concentrations, so the aptamer is modified at both the 3' and 5' end in order to add functional groups that aid in monitoring this process. The 5' end is modified with a short thiolated alkyl chain, which allows the aptamer to be tethered to surface of a gold electrode. At the 3' end, a redox active molecule, such as methylene blue or ferrocene, is added. This electron transfer kinetics of the redox label changes with the conformation of the aptamer, thus allowing the conformational change, and the target-binding interaction, to be monitored electrochemically. While commonly used redox labels like methylene blue and ferrocene work, they have some major pitfalls that often are overlooked. Dependence on pH, intercalation with DNA, susceptibility to nucleophilic attack, and negative standard potentials are all drawbacks that come with using methylene blue or ferrocene as the redox label. This work will focus on progress made in developing E-AB sensors with tunable platinum-based redox labels, including synthesis and characterization of the untethered redox probe.