title: Protein-repellent silicon nitride surfaces: UV-induced formation of oligoethylene oxide monolayers.
abstract: The grafting of polymers and oligomers of ethylene oxide onto surfaces is widely used to prevent nonspecific adsorption of biological material on sensors and membrane surfaces. In this report, we show for the first time the robust covalent attachment of short oligoethylene oxide-terminated alkenes (CH(3)O(CH(2)CH(2)O)(3)(CH(2))(11)-(CH═CH(2)) [EO(3)] and CH(3)O(CH(2)CH(2)O)(6)(CH(2))(11)-(CH═CH(2)) [EO(6)]) from the reaction of alkenes onto silicon-rich silicon nitride surfaces at room temperature using UV light. Reflectometry is used to monitor in situ the nonspecific adsorption of bovine serum albumin (BSA) and fibrinogen (FIB) onto oligoethylene oxide coated silicon-rich silicon nitride surfaces (EO(n)-Si(x)N(4), x > 3) in comparison with plasma-oxidized silicon-rich silicon nitride surfaces (SiO(y)-Si(x)N(4)) and hexadecane-coated Si(x)N(4) surfaces (C(16)-Si(x)N(4)). A significant reduction in protein adsorption on EO(n)-Si(x)N(4) surfaces was achieved, adsorption onto EO(3)-Si(x)N(4) and EO(6)-Si(x)N(4) were 0.22 mg m(-2) and 0.08 mg m(-2), respectively. The performance of the obtained EO(3) and EO(6) layers is comparable to those of similar, highly protein-repellent monolayers formed on gold and silver surfaces. EO(6)-Si(x)N(4) surfaces prevented significantly the adsorption of BSA (0.08 mg m(-2)). Atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), X-ray reflectivity and static water contact angle measurements were employed to characterize the modified surfaces. In addition, the stability of EO(6)-Si(x)N(4) surfaces in phosphate-buffered saline solution (PBS) and alkaline condition (pH 10) was studied. Prolonged exposure of the surfaces to PBS solution for 1 week or alkaline condition for 2 h resulted in only minor degradation of the ethylene oxide moieties and no oxidation of the Si(x)N(4) substrates was observed. Highly stable antifouling coatings on Si(x)N(4) surfaces significantly broaden the application potential of silicon nitride-coated microdevices, and in particular of microfabricated filtration membranes.
authors.affiliation: Laboratory of Organic Chemistry, Wageningen University, Dreijenplein 8, 6703 HB Wageningen, The Netherlands.
authors.forename: Michel
authors.initials: M
authors.lastname: Rosso
authors.forename: Ai T
authors.initials: AT
authors.lastname: Nguyen
authors.forename: Ed
authors.initials: E
authors.lastname: de Jong
authors.forename: Jacob
authors.initials: J
authors.lastname: Baggerman
authors.forename: Jos M J
authors.initials: JM
authors.lastname: Paulusse
authors.forename: Marcel
authors.initials: M
authors.lastname: Giesbers
authors.forename: Remko G
authors.initials: RG
authors.lastname: Fokkink
authors.forename: Willem
authors.initials: W
authors.lastname: Norde
authors.forename: Karin
authors.initials: K
authors.lastname: Schroën
authors.forename: Cees J M
authors.initials: CJ
authors.lastname: van Rijn
authors.forename: Han
authors.initials: H
authors.lastname: Zuilhof
mesh_terms: D000327:Adsorption; D001672:Biocompatible Materials / Q000138:chemical synthesis*; D005027:Ethylene Oxide / Q000138:chemical synthesis* / Q000528:radiation effects; D005340:Fibrinogen / Q000737:chemistry*; D008422:Materials Testing; D011485:Protein Binding; D012710:Serum Albumin, Bovine / Q000737:chemistry*; D017655:Silicon Compounds / Q000737:chemistry* / Q000528:radiation effects; D014466:Ultraviolet Rays
chemical_list: D001672:Biocompatible Materials; D017655:Silicon Compounds; D012710:Serum Albumin, Bovine; D005340:Fibrinogen; D005027:Ethylene Oxide; C032734:silicon nitride