Interface functional architecture using mixed thiol monolayers: Effect of the composition and spatial organization on the immobilization of low-molecular-weight ligands

Abstract

A simple procedure is examined for forming a selective sensor coating using mixed self-assembling thiol monolayers functionalized by molecules of the sulfanilamide antibiotic, sulfamethoxazol (SMX). A model is proposed for the interface processes, which accounts for the complex dependence of the adsorption capacity of the coatings obtained on the surface density of the reactive groups and the low adsorption capacity at high reaction site concentrations. The model was supported by competitive inhibition analysis.The past few decades have seen extensive research in the formation and characterization of thin films of molecular elements of living systems, including the formation of a new generation of biosensors and analytical methods using such biosensors. Various concepts for the formation of interface structures providing selective interaction with a given analyte that inhibits adsorption of another macromolecules have been proposed and, in many cases, studied in detail [1]. This work has permitted a significant expansion of our understanding of interactions of functionalized surfaces and, thus, the development of approaches for the creation of optimal spatially-organized structures with a given chemical or biochemical functionality [2]. The constant goal of these studies has been the development of procedures, permitting us either to enhance or suppress a specific adsorption process. Such control is possible only when we have a clear understanding of the mechanisms of interaction of the macromolecular receptor and immobilization ligand.Heterogeneous chemical and biochemical reactions are usually seen from the viewpoint of three major approaches: molecular functionality of the macromolecular receptor (analyte) and an immobilized analog of the selective ligand, spatial organization of the immobilized ligand on the surface, and diffusion limitations, accounting for the specific nature of access of the macromolecular analyte to the surface. In many cases, this permits us to delineate the predominant process and describe it analytically [3]. Thus, for example, the use of mixed thiol monolayers (MTM) with an active group for immobilization of a selective ligand (the sulfanilamide antibiotic, sulfamethoxazol (SMX)) and a chemically-inert terminal group of the base matrix permits us to create functional surfaces for sensitive biosensor elements for surface plasmon resonance (SPR) and the further application of such surfaces, especially for classical competitive analysis [4]. At low and medium immobilized ligand densities, this process is due to the static nature of surface site distribution. On the other hand, the reasons for the significant 0040-5760/08/4403-0165

Metallic-Nanoparticle-Based Sensing: Utilization of Mixed-Ligand Monolayers

“…39 While there have been numerous works focused on understanding and predicting mixed-ligand monolayer conformations through simulations, 53,63,69,79,149 these are very rarely focused on sensing. 150 Fundamental research is further restricted by what may be the largest obstacle currently facing all mixed-ligand particle applications: the difficulty of the monolayer characterization. In order to examine this issue, the main methods used for the characterization of the mixed-ligand monolayer by all the works cited in this Review were surveyed.…”

In vivo characterization of protein uptake by yeast cell envelope: single cell AFM imaging and μ-tip-enhanced Raman scattering study

“…This suggests that the existence of "dark areas" in the region of the peaks may be related not so much to real variations of the surface composition as to the features of the surface prole. 82 So, we can assume that the outer cell wall is constructed from the same material for both cell types and the observed "mountains" are the result of the formation of subsurface clusters etc. To verify this observation, force spectroscopy measurements have been performed which indicate the mechanical properties 83,84 Single-cell Raman spectroscopy: measurement conditions A suitable approach to analyze or ngerprint the chemical composition of the cell is the use of vibrational spectroscopy.…”

Gold surface cleaning by etching polishing: Optimization of polycrystalline film topography and surface functionality for biosensing

“…Currently, the main biosensing approaches involve the integration of nano-sized building blocks such as functionalized nanoparticles, biological macromolecules or conjugates of nanoparticles with bio-recognition sites with surface-based physical transducers. This strategy requires careful control of the interfacial architecture, as illustrated by sensors relying on functionalized gold surfaces: a thin gold film supports a self-assembled monolayers (SAM) of thiols which itself acts as an intermediate layer for the coupling of a wide range of functional biomolecules [6][7][8]. While flexible and powerful, this strategy fails for rough gold substrates; studies have established a correlation between the substrate roughness and the density of defects in SAMs as well as the stability of the monolayer systems itself [9,10].…”

“…Gold-based biosensors are widely used for Surface Plasmon Resonance (SPR) measurements which are particularly sensitive to surface imperfections in the gold. This is due to scattering of the captured light and a complex interplay between signal measured and the functionalizing elements of the sensor [1,5,7,13]. Surface roughness leads to broadening of the resonance spectra and increases the background noise [14][15][16]].…”