Protein Sensing with Aptamer Immobilized on an Antifouling Binary Self-Assembled Monolayer

A binary self-assembled monolayer (SAM) of 11-mercaptoundecanoic acid (MUA) and 3,6-dioxa-8-mercaptooctan-1-ol (DMOL) was formed on a gold electrode as a base for protein aptamer immobilization. The aptamer, specific to hemoglobin, was bound to MUA. A DMOL SAM was used to prevent nonspecific protein adsorption. Electrochemical impedance spectroscopy was performed to determine the electrochemical characteristics of a unary SAM of MUA and a binary SAM consisting of MUA and DMOL. The DMOL SAM prevented adsorption of nonspecific proteins (e.g., thrombin). For the binary SAM, 20:80, 50:50, and 80:20 mol % MUA and DMOL were used. The antifouling effect against nonspecific proteins was enhanced as the ratio of DMOL increased, but the signal intensity (impedance change) decreased. The binary SAM with 50:50 mol % MUA and DMOL showed repelling of nonspecific adsorption of thrombin (70.5% decrease in the impedance change), and it still generated a sufficient signal for target molecules. Additional tests with pure pr...