Binary Thiolate DNA/Ferrocenyl Self-Assembled Monolayers on Gold: A Versatile Platform for Probing Biosensing Interfaces.

The properties of DNA self-assembled monolayers (SAMs) have strong influences on the interfacial DNA-analyte binding behavior, which further affect the performance of biosensors built upon. In this work, we prepared binary thiolate DNA/6-ferrocenyl-1-hexanethiol (FcC6SH) SAMs on gold (DNA/FcC6S-Au) for convenient electrochemical characterization and subsequent data analysis. Our cyclic voltammetric (CV) studies confirmed that the redox responses of surface-tethered Fc and electrostatically bound [Ru(NH3)6]3+ are capable of providing quantitative information regarding the DNA film properties, including the surface density, structural heterogeneity, and molecular orientation under different preparation and measurement conditions. With the binary thiolate DNA/FcC6S-Au SAM prepared in the conventional post-assembly exchange protocol as a trial system, we are demonstrating the capability of introducing redox-active thiols as passivating and labeling reagents for preparing many other DNA-based biosensing interfaces via varied assembly steps and under different measurement conditions.