Binding of biotin to gold surfaces functionalized by self-assembled monolayers of cystamine and cysteamine: Combined FT-IRRAS and XPS characterization

As part of our project of developing a new IR-based immunosensor, we invest igated the functionalization of gold substrates with thin organic films con taining biotin ligands, A two-step procedure was developed consisting of th e chemisorption of short amine-terminated organosulfur compounds, followed by their reaction at the solid liquid interface with an activated ester der ivative of biotin. Covalent binding of biotin to these attachment layers wa s assessed by Fourier transform infrared reflection-absorption spectroscopy (FT-IRRAS) and X-ray photoelectron spectroscopy (XPS), The interaction of activated biotin with alcohol- and carboxylic acid-terminated monolayers wa s also investigated, and, as expected, no binding occurred, Moreover, mixed layers of short alcohol- and amine-terminated thiolates were successfully constructed at the gold surfaces and were shown to be the most efficient fo r the covalent binding of biotin thanks to the blocking effect of the thioa lcohol, which prevented direct adsorption of biotin to the gold surface. (C ) 2001 Academic Press.