Surface modification of gold electrode with gold nanoparticles and mixed self-assembled monolayers for enzyme biosensors

Abstract

This paper describes the development and evaluation of a generic method for the immobilization of enzymes onto a gold electrode and its application to amperometric biosensors. The surface of the gold electrode was modified with gold nano-particles (AuNP) and mixed self-assembled monolayers (SAMs) to form an enzyme biosensor matrix. Horseradish peroxidase (HRP) was immobilized on the modified surface to form a biosensor matrix on a gold electrode. After the deposition of gold nano-particles on a bare gold surface, the AuNP-deposited gold electrode and a bare electrode were compared for the surface area and electric current using AFM and cyclic voltammetry (CV). The AuNP strongly adhered to the surface of the gold electrode, had uniform distribution and was very stable. A mixed SAM, composed of two different monolayer molecules, dithiobis-N-succinimidyl propionate (DTSP) and inert tetradecane-1-thiol (TDT), was formed using reductive desorption technique and cyclic voltammetry was used to verify the formation of mixed deposition. First, 3-mercaptopropionic acid (MPA) and TDT were deposited with a specified deposition ratio between the two components. Then, MPA was desorbed by applying electric potential to the surface. Finally, DTSP was deposited where MPA was. The ratios of 20 : 80 and 50 : 50 between MPA and TDT were examined, and differences in the CV responses were discussed. HRP was immobilized on the mixed SAM surface. The investigated method is regarded as an effective way for stable enzyme attachment, while the presence of gold nanoparticles provides enhanced electrochemical activity; it needs very small amounts of samples and enzymes and the SAM matrix helps avoid enzyme leaking. It is interesting that the mixed SAM shows unique CV characteristics compared to the uni-molecular SAMs. The reaction kinetics of the SAM-immobilized enzyme is discussed with the CV results and is observed to obey the Michaelis-Menten equation.

Formation and modification of a binary self-assembled monolayer on a nano-structured gold electrode and its structural characterization by electrochemical impedance spectroscopy

“…Selective desorption is a method useful for preparation of an electrode with specific electrochemical properties such as electron transfer rate and capacitance. Because both the thickness and packing density of SAMs are associated with electrochemical properties of an electrode [18,19], the area of naked portion must be controlled or filled with another self-assembled molecules [20,21]. Poter and colleagues [4] found that SAMs adsorbed on gold and silver surfaces can be reductively desorbed and demonstrated that selective desorption is a useful tool for forming and characterizing binary SAMs [5,22,23].…”

“…Also there have been reports about formation of mono SAMs on the AuNP-modified electrodes [2,3], but very few demonstrated how the selective desorption was effected by the surface modification with gold nanoparticles. Park et al [21] demonstrated potential advantages of the combination of the AuNPmodified surface and a binary SAM synthesized using selective desorption in biosensor development. Similarly we first formed a binary SAM on a planar gold electrode and the AuNP-modified electrode, and then the binary SAM was further modified with selective desorption technique to make a TDT SAM with empty spots, i.e., defects.…”

A Novel Hybrid‐Structured Titanium Surface Promotes Adhesion of Human Dermal Fibroblasts and Osteogenesis of Human Mesenchymal Stem Cells while Reducing S. epidermidis Biofilm Accumulation

“…Four samples of each surface were imaged. The raw images were plane‐leveled to flatten the images through a numerical second‐order correction …”

Immobilization Techniques in the Fabrication of Nanomaterial-Based Electrochemical Biosensors: A Review

“…Mixed SAMs of long and short length are reported to show better electron transfer rates than singular component SAMs because of the increased flexibility of redox species distribution at the interface [35]. Park et al , investigated the use of a hetero-length binary SAM layout, utilizing gold nanoparticles and HRP [35]. The gold electrode surface was modified with mixed SAMs, onto which colloidal gold nanoparticles were immobilized.…”