Patterns of DNA-Labeled and scFv-Antibody-Carrying Lipid Vesicles Directed by Material-Specific Immobilization of DNA and Supported Lipid Bilayer Formation on an Au/SiO2 Template

Much effort is currently concentrated on research devoted to biofunctional patterned surfaces, which constitute the fundament for the development of microarrays for high-throughput gene and protein analyses. DNA microarrays have proved very successful and the concept is in the process of being applied to protein arrays. However, in contrast to DNA fragments, proteins are easily denatured in contact with solid supports, and robotic printing of proteins onto chemically reactive glass slides will not necessarily be applicable as a generic protocol for the preparation of protein arrays. Supported phosphatidyl- choline lipid bilayers have emerged as interesting candidate substrates for protein chips,since they efficiently reduce non- specific protein adsorption and, at the same time, allow different strategies for protein immobilization with biospecific interactions;for example:biotin-streptavidin, Ni ²⁺- mediated binding of histidine-tagged proteins to nitrilotriacetic acid (NTA)- lipids, or covalent coupling reactions such as those between maleimides and thiols. Furthermore, progress in patterning of lipid bilayers and/or vesicles with varying lipid composition has been achieved by using dispensing,micro contact printing, gradients in microfluidic flow devices, and/or immobilization of biotin-functionalized vesicles to streptavidin-patterned surfaces. In the present work, we combine the concept of micropatterns of supported lipid bilayers with the concept introduced by Niemeyer, who advocates the use of immobilized complementary DNA (cDNA) strands to direct spatial distribution of DNA-labeled proteins. Previously, DNA-modified vesicles have been used for signal enhancement of DNA hybridization reactions. Here, we present the first case of DNA-directed immobilization of intact vesicles to patterned surfaces (arrays),where the vesicles have the in-built potential to act as protein carriers (for transmembrane or water-soluble proteins). The strategy was proven by detecting antigens by using histidine-tagged single-chain antibody fragments (scFv) coupled to Ni²⁺-NTA- and DNA-modified lipid vesicles, and a simple array was demonstrated by using DNA-directed immobilization of intact vesicles to two different cDNA-functionalized spots. The surface modification was experimentally verified with the quartz crystal microbalance with dissipation monitoring (QCM-D) technique and fluorescence microscopy.