Hybridization performance of DNA/mercaptohexanol mixed monolayers on electrodeposited nanoAu and rough Au surfaces

Abstract

Abstract In this article we investigated the hybridization performance of thiol-modified probe DNA/mercaptohexanol (MCH) mixed self-assembled monolayers (SAMs) on nanoAu and rough Au surfaces with target DNA in 1 M electrolytical solution. The nanoAu surfaces were prepared by electrodeposition in 2 mM HAuCl4 and 0.1 M Na2SO4 aqueous solution based on different deposition time (0.33 min, 2 min, 5 min, 10 min and 20 min), deposition potential (− 0.4 V, − 0.8 V, − 1.2 V) and deposition methods (direct electrodeposition or firstly self-assembly of 1-dodecanethiol, then electrodeposition). Scanning electron microscopy (SEM) observed that size and density of gold nanoparticles formed were related to electrodeposition conditions. The rough Au surfaces were prepared by roughly hand-polishing and the gold roughness factors (Rf) were from 1 to 3. Chronocoulometry (CC) experiments showed that DNA hybridization density (HD) arrived at the biggest for 16.3 × 10− 12 mol cm− 2 when electrodeposition was performed at − 1.2 V for 10 min and the concentration ratio of probe DNA and MCH (CDNA/CMCH) for mixed assembly was 1:1. DNA hybridization performance of probe DNA/MCH mixed SAMs on some nanoAu surfaces was much better than that on rough Au or planar Au surfaces and the biggest HD for DNA optimal hybridization increased by 85% and 51% respectively. For rough Au, DNA hybridization performance was almost independent of Rf. Based on our previous reported simple DNA hybridization model, the size fitting coefficient (dc/dt) for DNA optimal hybridization on nanoAu was calculated to be 0.71, smaller than that on rough Au (0.99) or planar Au (0.93). It meant that surface coverage of probe DNA in probe DNA/MCH mixed SAMs should be much bigger on nanoAu than that on rough Au or planar Au surface for DNA optimal hybridization. These results indicated that Au surface configuration played the important role on DNA hybridization. The intermolecular repulsion and steric hindrance for DNA hybridization might be reduced on nanoAu than those on rough Au or planar Au, which possibly led to the improvement of DNA hybridization performance. The conclusions provided the important reference for constructing electrochemical DNA sensor with the optimal performance.