Electrochemical Aptamer-Based (E-AB) Sensors stand as promising biochemical tools for the highly sensitive and selective detection of a wide range of target species in a variety of complex media. The EA-B sensor platform comprises of a thiol-modified aptamer sequence attached to a gold electrode surface, passivated with a layer of 6-Mercapto-1-Hexanol. The sensor uses the conformational change upon target binding to bring the redox label (Methylene Blue) closer to the electrode surface facilitating a change in electron transfer and thus changing the observed current response for a signal on/off response. This study investigates the kinetics of target and sensor binding to determine the binding affinity of the resulting complex to represent the strength of the binding between aptamer and its target. Intermittent Pulse Amperometry (IPA) coupled with a flow-cell injection system allowed for high temporal resolution analysis of sixty-second injection runs with a five second injection of target to reach equilibrium through the association state of aptamer to target before a reinjection of buffer to dissociate target from sensor. The rates of association and dissociation were then determined to yield binding affinity of the sensor/target complex. Association rates at low concentrations gave proportionately linear data for the change in concentration of target analyte, however the trend fell off at higher concentrations due to mass transfer limitation of the pseudo-second order rate reaction of bringing target to the sensing surface. This was supported by a trial of variable flowrate at saturating concentration of target in which flowrate influenced association rate. To solve this mass transfer limitation a complimentary oligonucleotide strand was added onto the redox-labelled aptamer, hypothesizing that the rate of association would become slower and therefore more easily and accurately studied as the aptamer must first unbind from its compliment strand before binding to its target. Data from this set of experiments showed that this method is capable of slowing the experimental association rates, however more precise data from further trials needs to be collected before the binding kinetics can be said to be accurately represented.

Interrogation of small molecules to surface-bound aptamer binding kinetics with electrochemical, aptamer-based sensors using intermittent pulse amperometry

Where thousands of chemistry professionals meet to share ideas and advance scientific and technical knowledge. Spring 2023 abstracts, posters, and presentations will launch at the end of March.

ACS Spring 2023

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.