Surface characterization and platelet compatibility evaluation of the binary mixed self-assembled monolayers

Abstract

This report describes a technique that used mixed self-assembled monolayer (SAM) as a model surface to evaluate the effect of steric hindrance on the SAM packing quality and its platelet compatibility. Two series of binary mixed SAMs were formed by mixing the bulky terminated alkanethiol (HS(CH 2) 10PO 3H 2) with a smaller terminated one (HS(CH 2) 9CH 3 and HS(CH 2) 11OH) respectively. Surface characterization results showed the hydrophilicity on these two series of mixed SAMs changed with the solution mole fraction of PO 3H 2 terminated thiol, χ PO 3H 2,soln , and reached to a nearly constant value as χ PO 3H 2,soln was 0.6 for PO 3H 2 + CH 3 SAM and 0.4 for PO 3H 2 + OH SAM. This finding should be due to the gradual saturation of surface PO 3H 2 functionality on these mixed SAMs. The XPS analysis indicated the addition of the CH 3 and OH terminated thiol could reduce the steric hindrance effect of PO 3H 2 functionality on monolayer formation and, henceforth, improve the SAM packing quality. In vitro platelet adhesion assay revealed the platelet compatibility on the PO 3H 2 + OH SAMs was better than that on the PO 3H 2 + CH 3 and the pure PO 3H 2 ones. Moreover, the PO 3H 2 + OH SAM with a low χ PO 3H 2,soln value exhibited the least platelet activating property of these two mixed SAM systems. These findings suggested that material's surface wettability and surface charge density should act collectively in affecting its platelet compatibility.