Surface modification strategies for gold electrode backfilling and sensing

Abstract

Biosensors are a vital technological advancement adapted for many applications to measure analytes in biological or chemical settings1. Biosensors are known for having high sensitivity and specificity while being cost effective2. A challenge when designing these sensors is their susceptibility to interfering species which lead to inconclusive results or false positives3. To reduce the impact from interfering species in a sample, blocking agents are added to the surface of the sensor4. A blocking agent is a compound that coats the surface of an electrode to inhibit non-specific binding4. The purpose of this project is to compare the blocking strength of four alkanethiol analogs. The blocking agents analysed in this paper include 6-mercapto-1-hexanol (MCH), 3-mercapto-1-propanol (MCP), 11-mercapto-1-undecanol (MCU), and 1,6-hexanedithiol (HDT). Screen-printed gold electrodes and gold disk electrodes are used during experiments. 6-mercapto-1-hexanol and 3-mercapto-1-propanol demonstrated the greatest blocking ability while 11-mercapto-1-undecanol, and 1,6-hexanedithiol produced poor results. 3-mercapto-1-propanol exhibited unusual results after attachment leading to an in-depth investigation into the behaviour of this molecule within the sensor environment. The next project goal was to design and begin the optimization process of a chemical platform for use in immunosensor design. 3-mercaptopropanoic acid (MPA) would act as a carboxylic acid source for attachment of 1-Ethyl-3-(3-dimethylaminopropyl)-carbodiimide (EDC) and N-hydroxysuccinimide (NHS) to the gold surface. We briefly investigated a dual attachment of MPA and MCP approach to lay the foundation for EDC/NHS attachment as well as introduce a blocking agent at the same time. Due to challenges in analysis, this approach will be revisited in future work. The focus of the second part is optimizing the attachment of MPA to the gold surface in preparation for EDC/NHS attachment. Through optimization experiments, it is concluded that for the best attachment of MPA to a gold surface, 15 l of the molecule should be drop cast on a gold screen-printed electrode and incubated for 24 hours at 26℃ while the concentration used can vary. Based on the results from testing of preferred EDC/NHS incubation temperature, it can be concluded that cool temperatures (4℃) are preferred. These tests verified that MPA successfully attached to the gold surface.