Verification of Microphase-Separated Hypothesis of Blood Compatibility Utilizing Precisely Designed Polymer Surfaces

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The n-octadecyltrichlorosilane (OTS, CH_3(CH_2)_<17>SiCl_3), 18-nonadecenyltrichlorosilane (NTS, CH_2=CH(CH_2)_<17>SiCl_3), [2-(perfluorooctyl)ethyl]trichlorosilane (FOETS, CF_3(CF_2)_7CH_2CH_2SiCl_3) monolayers, and their mixed monolayers were used as model surfaces for the study of protein adsorption mechanism. Surface plasmon resonance (SPR) spectroscopy was applied to analyze the protein adsorption behavior onto the monolayer surfaces. The surfaces after exposure of these monolayers to bovine serum albumin (BSA) and γ-globulin(IgG) solutions were observed with atomic force microscope(AFM). AFM observation revealed that the charged protein either below or above pI was preferentially adsorbed onto the FOETS phase of the phase-separated (OTS/FOETS) mixed monolayer. in situ AFM observation of monolayer surfaces in BSA solution also revealed the preferential adsorption of BSA onto the hydrophobic FOETS surface. SPR clarified that the amount of adsorbed protein in the charged state was l … More ower than that in the neutral state. Adhesion force was not detected in the force-distance curve measurement between negatively-charged HOOC(CH_2)_9SH chemisorbed cantilever tip and the OTS phase in the presence of adsorbed BSA on FOETS phase of mixed monolayer. These results indicate that the preferential adsorption of protein onto the FOETS phase for the mixed monolayer systems at either below or above pI is due to (1) the minimization of interfacial free energy between the monolayer surface and the buffer solution, and (2) the electrostatic repulsion among protein molecules bearing charges.Multi-component micropatterned organosilane monolayers were successfully fabricated on Si substrate by stepwise vacuum ultraviolet-ray (VUV) photodecomposition and chemisorption process. The area-specific introduction of different organosilane molecules was confirmed by X-ray photoelectron spectroscopy (XPS). AFM and LFM observations revealed that the line-widths of micropatterned surface corresponded to those of photomask. Micropatterning of the functional groups influenced the magnitudes of surface free energy. Selective adsorption of protein was observed for this multicomponent surface. Less