Evaluation of Different Monolayer Chemistries on Carbon Electrodes for the Fabrication of Electrochemical, Aptamer-Based Sensors

Abstract

Electrochemical, DNA-based sensors represent a powerful tool to selectively detect and quantify molecular targets in highly complex media such as whole blood in living animals. These sensors consist of a biointerface containing redox reporter-modified DNA molecules attached to the surface of (typically) gold electrodes via sulfur-gold bonds. They also employ short chain alkanethiols for the purpose of passivating the electrode surface, thus preventing undesired electrochemical reactions and achieving antifouling characteristics to, for example, prevent non-specific protein binding. Despite the huge success and promising applications of electrochemical, DNA-based sensors and the development of this platform for over 15 years, the DNA sensing architecture has been almost exclusively limited to the use of thiol-based monolayers on gold electrodes. This limits the performance of such sensors by the surface stability of alkanethiols, which are labile, and excludes the use of electrode materials other than gold, considerably reducing potential fields of application for DNA-based sensors. Motivated to expand the diversity of monolayer chemistries and electrode materials that can be used to fabricate DNA-based sensors, our group is currently exploring different approaches to chemically functionalize the surface of carbon-based electrodes. In this work, I will discuss the different chemical approaches we are pursuing in this regard and their performance in terms of monolayer packing, extent of surface passivation, and long-term stability in physiological buffers and biological fluids. I will also discuss how these chemistries compare with benchmark thiol-on-gold monolayers.