Synthesis, surface characterization, and platelet reactivity evaluation for the self-assembled monolayer of alkanethiol with sulfonic acid functionality

Owing to the capability of fabricating a well-defined chemical structure on the surface, self-assembled alkanethiols with a variety of terminal functionalities were prepared on the gold substrate for investigating the interactions between the biological environment and synthetic surface. In this study, we report the synthesis of the sulfonic acid terminated long- chain alkanethiol, 10-mercaptodecane-sulfonic acid, for direct preparation of a self-assembled monolayer (SAM) with -SO₃H functionality. Nuclear magnetic resonance (NMR) and elemental analysis studies indicated that a high purity of sulfonic acid terminated alkanethiol was obtained. Surface characterization results showed that the -SO₃H terminated SAM is hydrophilic and has a slightly higher hysteresis value, possibly because of the slower chain mobility of the bound sulfonic acid alkanethiol. Electron spectroscopy for chemical analysis (ESCA) analysis demonstrated that the SO₃H terminal group is situated in the outermost layer of the monolayer, as previous alkanethiol SAM structure models proposed. The platelet reactivity of the - SO₃H SAM was higher than that of -OH SAM but less than the -CH₃ terminated one in vitro, whereas similar platelet reactivity was noticed between the - SO₃H and -COOH SAMs. The higher platelet reactivity found on the -SO₃H SAM could be caused by the higher surface functional group density inherent in the SAM structure and/or the composition and conformation state of the adsorbed protein layer.(C) 2000 John Wiley and Sons, Inc.