Pro / The Hydrophobic Regulation Preparation And Application Of Self-assembled Monolayers

Self-assembled monolayer films show a lot of interesting properties in chemistry, physics, optics and electronic transport. In addition, they have stable tructure and simple facture. Self-assembled monolayer films have potential application in biomaterials, sensors, nano electro-mechanical systems, separation materials and so on. In this study, we constructed self-assembled monolayer film on glass surface and silica surface, investigated the blood compatibility and protein separation ability of the modified surface.The main contents are listed as follows:1. We modified a glass surface by step grafting with phosphorylcholine groups. First step, glass surface was hydroxylized, the hydroxyl groups of glass surface were grafted with 1, 6-diisocyanatohexane. Second step, 2-hydroxy-2-ethylphosphorylcholine was grafted onto the attached isocyanate groups. Dynamic contact angle (DCA) measurement and X-ray photoelectron spectroscopy (XPS) analysis confirmed that the two step modification process was successful.2. We modified a glass surface by step grafting with both phosphorylcholine and stearyl groups to adjust the hydrophilicity and hydrophobicity. After the glass surface was hydroxylized, some amount of octadecyldimethylchlorosilane was chemically adsorbed onto the surface to impart the required hydrophobicity, In the next step, the remaining hydroxyl groups were grafted with 1 , 6-diisocyanatohexane. Finally, 2-hydroxy-2-ethylphosphorylcholine was grafted onto the attached isocyanate groups to increase the hydrophilicity. Dynamic contact angle (DCA) measurement and X-ray photoelectron spectroscopy (XPS) analysis confirmed that the step-by-step modification process was successful. By altering the grafted densities of the groups, the hydrophilicity and hydrophobicity of the surface was adjusted successfully as shown clearly in the DCA loops. The results of Platelet adhesion test showed that the adhered platelets on the surface modified with stearyl groups showed large sizes, which suggested the aggregation and agglomeration of the platelets. This result indicated the activation of the platelets by the hydrophobic surface. On the other hand, for the same surface further grafted with phosphorylcholine groups, the adhered platelets remained the original size of platelet (2-4μm), suggesting no aggregation or agglomeration of the platelets. These results indicated that the poor biocompatibility of a hydrophobic surface can be improved by introducing Phospholipid moieties onto the surface. Protein adsorption test showed that the amounts of albumin and fibrinogen adsorption on the surface modified with both stearyl and phosphorylcholine groups were 0.21 and 0.71μg/cm~2, respectively, which was 70% and 50% reduction compared with the surface modified with only the stearyl groups. Platelet adhesion and protein adsorption results suggested that a considerable enhancement of blood compatibility could be achieved on phosphorylcholine modified surfaces.3. A monolayer film with tunable hydrophilicity and hydrophobicity on silica's surface was constructed successfully by a 4-step modification method. Step one: some amount of octadecyldimethylchlorosilane was chemically adsorbed onto the hydroxyl groups of silica surface; Step two: the remaining hydroxyl groups of silica's surface were grafted with (3-aminopropyl)triethoxysilane; Step three: the suface modified after step two was grafted with 1, 6-diisocyanatohexane; Step four: 2-hydroxy-2-ethylphosphorylcholine was grafted onto the attached isocyanate groups. By this method, three surfaces with different hydrophilicity and hydrophobicity were prepared. Protein separation ability of the surface modified silica was primarily investigated.