Synthesis, Surface Characterization and In Vitro Blood Compatibility Studies of the Self-assembled Monolayers (SAMs) Containing Lipid-like Phosphorylethanolamine Terminal Group

Creating a surface with structure mimicking the phospholipid configuration, the most abundant component of the cell membrane, has been considered as one of the important methods to improve the blood compatibility of artificial surfaces. In this study, self-assembled monolayers (SAMs) formed by alkanethiol with phospholipid terminal group, 11-mercaptoundecanephosphorylethanolamine (PE), were explored as the potential surface modification technique to vary the blood contacting characteristics of metallic biomaterials. The surface characteristics and blood contacting properties of the SAMs formed from different solvents and concentrations are evaluated in this study. It was noted that the SAMs with phosphorylethanolamine terminal functionality is more hydrophilic, especially the ones formed using PBS as the solvent, than those with methyl terminate and the non-modified pure gold. ESCA analyses have suggested these phosphorylethanolamine terminated SAMs are less- ordered, likely due to the steric hindrance as well as the charging effects caused by this terminal end. This less-ordered configuration might explain the surface hydrophilicity of phosphorylethanolamine terminated SAMs was not as high as expected from its chemical structure. In addition, the ESCA analyses have shown that unbound thiols were noted within the SAMs, resulted from the steric hindrance caused by these bulky phospholipid-like terminal ends. Blood-contacting property evaluation has shown that parts of the SAMs surfaces exhibited platelet activation and aggregation while others didn't as compared to those prepared from the alkanethiol with methyl terminal end. Further study is undergoing to explore this unique blood contacting phenomena.