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 -SO(3)H 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 -SO(3)H 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 -SO(3)H terminal group is situated in the outermost layer of the monolayer, as previous alkanethiol SAM structure models proposed. The platelet reactivity of the -SO(3)H SAM was higher than that of -OH SAM but less than the -CH(3) terminated one in vitro, whereas similar platelet reactivity was noticed between the -SO(3)H and -COOH SAMs. The higher platelet reactivity found on the -SO(3)H 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.