Enhanced Performance of an Affinity Biosensor Interface Based on Mixed Self-Assembled Monolayers of Thiols on Gold

Abstract

An affinity biosensor interface of a biosensor is the interface between the sample and the transducer surface and is therefore of the utmost importance for the general performance of a biosensor. For immunosensor applications the affinity biosensor interface consists of antibodies, which are preferably covalently attached to the transducer surface. In this paper the properties and the enhanced performance of an affinity biosensor interface based on mixed self-assembled monolayers (SAMs) on gold are discussed. Mixed SAMs consist of two different functionalities, which allow attachment of bioreceptor molecules and avoid nonspecific adsorption. In this work, mixed SAMs of thiols with carboxylic and hydroxyl or poly-(ethylene glycol) groups are characterized with contact angle measurements, cyclic voltammetry, and grazing-angle Fourier transform infrared spectroscopy. It is found that the various mixed SAMs exhibit acceptable coverage and structural properties. Most importantly, surface plasmon resonance measurements clearly show the enhanced performance of these mixed SAMs with regard to sensitivity, stability, and selectivity compared to commercially available affinity biosensor interfaces. This superiority is experimentally demonstrated by evaluating the amount of immobilized antibodies, the recognition of antigens by the immobilized antibody, and the nonspecific adsorption of IgG molecules on the antibody-coated surfaces.

Immunosensor interface based on physical and chemical immunoglobulin G adsorption onto mixed self-assembled monolayers

“…In the development of affinity biosensors, the fabrication of the interface plays a crucial role, since it determines the specificity, the reproducibility, and the stability of the entire sensor [1,2]. The nonspecific adsorption together with a proper bioreceptor orientation/distribution on the surface is an important factor that must be controlled in order to get the best biosensor performance.…”

Monitoring human serum albumin cell cultures using surface plasmon resonance (SPR) spectroscopy

“…The sensor surface of the system, a 50 nm × 12 mm × 3 mm gold layer, is illuminated by three selectable LEDs, each covering an area of (9 × 0.8) mm 2 (Henseleit et al, 2011;Mertig et al, 2009). A CCD camera with a spatial resolution of 1280 rows (spots) and an angledependent intensity distribution of 960 columns records the reflected light (Mertig et al, 2009).…”

“…100 nm, depending on pH and ionic strength) between the biomolecules and gold surface that is almost 50 times thicker than the SAM formed in the li SPR system. This leads to signal masking due to evanescent waves decaying as a function of the distance from the gold surface (Frederix et al, 2003). Furthermore, the three-dimensional structure increases steric hindrance during the diffusion of the proteins inside the matrix.…”

“…Henseleit et al: Monitoring human serum albumin cell cultures flected light (Henseleit et al, 2011). When molecules bind to (or dissociate from) the surface, the refractive index and thus the angle at which the energy transfer occurs changes immediately.…”

“…However, they are costly, large and thus not ideal for point-of-care applications. In marked contrast, the li SPR instrument is a benchtop spectrometer, which affords high sensitivity and up to 180 sensing spots (Henseleit et al, 2011). We assessed the utility of SPR spectroscopy generally, and both the wellestablished Biacore platform and the li SPR system specifically, for immunologically measuring HSA concentrations of in vitro hepatocyte cultures.…”