Synthesis and characterization of thiol-terminated poly(ethylene oxide) for chemisorption to gold surface

Thiol-terminated poly(ethylene oxide) (PEO) was synthesized using two different approaches: esterification of terminal hydroxyl groups with mercaptoacetic acid and amidation using N-hydroxysuccinimidyl PEO (NHS-PEO) and cysteine. The reaction of hydroxyl-terminated PEO with mercaptoacetic acid was carried out in boiling toluene. Different thiolated PEOs, including linear PEOs of varying molecular weights and end-group types, and star-type PEOs were synthesized. Nuclear magnetic resonance and infrared spectroscopy were used to characterize the products. The reaction kinetics were also briefly investigated. Gel permeation chromatography was used to investigate the relative amounts of the mono- and disubstituted products in the alpha,omega-dihydroxy PEOs. NHS-PEO was used both to attach terminal thiol groups via reaction with cysteine and to conjugate other amino acids (and potentially any amino-containing molecule) to PEO. Reactions using NHS-PEO were carried out at room temperature in water. The chemisorption of these thiolated PEOs to gold was expected to yield surfaces resistant to biofouling, in particular to unwanted protein adsorption. Chemisorption of amino acid-, peptide-, or protein-terminated PEOs in addition may yield surfaces having specific biological activity. Work on these aspects will be reported elsewhere. (C) 2003 Wiley Periodicals, Inc.