Surface Characterization and In-vitro Blood Compatibility Study of the Mixed Self-assembled Monolayers

Abstract

Self assembled monolayer (SAM) of the longchain alkanethiols (HS(CH2)nX, n=10) with variant terminal functionalities adsorbed on Au substrate can serve as a welloriented surface with a broad range of chemical configuration for studying the blood-material interactions. The mixed SAM can be produced by adsorption from mixtures of two alkanethiols with different types of terminal groups and the complicated microstructures of this surface can be explored and tailored to mimic the physiological microenvironment associated with variant biological entities. In this study, two different mixed SAMs by mixing labsynthesized sulfonic acid terminated alkanethiol, which carried heparin-like chemical structure, with the methyl terminated alkanethiol or hydroxyl terminated one were prepared. Surface characterization results showed that the contact angle was gradually decreased with the increase the solution mole fraction of -SO3H thiol (÷SO3H,soln) on -SO3H/-CH3 mixed SAMs. On -SO3H/-OH mixed SAMs the surfaces were hydrophilic. The surface composition of the -SO3H thiol (÷SO3H,surf) was analyzed by X-tray photoelectron spectroscopy (XPS) and the adsorption behavior of two mixed SAMs was all presented as "-SO3H poor". The surface charge was evaluated by streaming potential and the charge of these mixed SAMs was all negative in PBS (pH 7.4). In vitro platelet adhesion assay indicated that the amount of adhered platelets was similar on both mixed SAMs, except on the pure -OH SAM. The adhered platelets on -SO3H/-CH3 mixed SAMs were more activated than on - SO3H/-OH mixed SAMs. This finding suggested that the surface wettability and surface charge could affect the material's platelet compatibility synergistically.