Microstructured bioreactive surfaces: covalent immobilization of proteins on Au(111)/silicon via aminoreactive alkanethiolate self-assembled monolayers

Micrometer-scale patterns of a defined surface chemistry and structure were produced on both ultraflat Au(1 1 1) and on gold-coated monocrystalline si licon surfaces by a method combining microcontact printing, wet chemical et ching and the replacement of etch-resist self-assembled monolayers (SAMs) b y functionalized or reactive SAMs. Key steps in this methodology were chara cterized by X-ray photoelectron spectroscopy (XPS), ellipsometry and contac t angle measurements. The covalent immobilization of (functional) biologica l systems on these surfaces was tested using an N-hydroxysuccinimide ester omega-functionalized disulphide (DSU), which covalently binds primary amine s without the need for further activation steps. Atomic force microscope im ages of native collagen V single molecules immobilized on these patterned s urfaces revealed bath high spatial resolution and strong attachment to the monolayer/gold surface. Microcontact printing of DSU is shown to be feasibl e on specially prepared, ultraflat Au(1 1 1) surfaces providing a valuable tool for scanning probe experiments with biomolecules. The retention of enz ymatic activity upon immobilization of protein was demonstrated for the cas e of horseradish peroxidase. The described approach can thus be used to con fine biological activity to predetermined sites on microstructured gold/sil icon devices - an important capability in biomedical and biomolecular resea rch. (C) 1999 Kluwer Academic Publishers.