Antifouling Studies of Unsymmetrical Oligo(ethylene glycol) Spiroalkanedithiol Self-Assembled Monolayers

Pawilai Chinwangso,Lydia R St Hill,Maria D Marquez,T Randall Lee,Han Ju Lee,John W Craft,Hung-Vu Tran

doi:10.3390/micro1010012

Abstract

The antifouling properties of self-assembled monolayers (SAMs) on gold generated from custom-designed bidentate unsymmetrical spiroalkanedithiols containing both oligo(ethylene glycol) and hydrocarbon tailgroups (EG3C7-C7 and EG3C7-C18) were evaluated and compared to SAMs derived from analogous monodentate octadecanethiol (C18SH) and the tri(ethylene glycol)-terminated alkanethiol EG3C7SH. Complementary techniques, including in situ surface plasmon resonance spectroscopy (SPR), ex situ electrochemical quartz crystal microbalance (QCM) measurements, and ex situ ellipsometric thickness measurements, were employed to assess the protein resistance of the SAMs using proteins having a wide range of sizes, structures, and properties: protamine, lysozyme, bovine serum albumin (BSA), and fibrinogen. The studies found that SAMs generated from the bidentate adsorbates EG3C7-C7 and EG3C7-C18, which contain a 1:1 mixture of OEG and hydrocarbon tailgroups, exhibited a diminished capacity to resist protein adsorption compared to the EG3C7SH SAMs, which possess only OEG tailgroups. The data highlight the critical role of hydration of the OEG matrix for generating antifouling OEG-based surface coatings.

Highlights

Due to their ability to resist the adsorption of proteins and other macromolecules, coatings based on biocompatible poly(ethylene glycol) (PEG), known as poly(ethylene oxide) (PEO), have been used in many clinical and biological applications [1,2,3]
Since all the selected proteins are compatible with phosphate buffer solution (PBS), Phosphate buffer solution (PBS) was used as the solvent medium for the protein solution preparations
The non-specific adsorption of the selected proteins on the self-assembled monolayers (SAMs) surfaces were measured using surface plasmon resonance spectroscopy (SPR), quartz crystal microbalance (QCM), and ellipsometry

Summary

Introduction

Due to their ability to resist the adsorption of proteins and other macromolecules, coatings based on biocompatible poly(ethylene glycol) (PEG), known as poly(ethylene oxide) (PEO), have been used in many clinical and biological applications [1,2,3]. PEG-based polymeric coatings, are often difficult to characterize with accuracy and reliability due to their morphologically rough and non-uniform interfaces [9]. Surface coatings based on oligo(ethylene glycol) (OEG) moieties with two to six monomer units are markedly easier to characterize and have proven effective in resisting protein adsorption [10,11,12,13]. Andrade and co-workers proposed that when proteins approach high-molecular-weight PEG, there is a repulsive entropic effect, termed “steric

Methods

Results

Conclusion