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Abstract

A simple surface chemical bi-functionalization procedure, involving micro contact printing of silane molecules is presented. The printing process has been optimized for obtaining high quality layers of good homogeneity. The produced chemical templates are used in order to spatially localize the adsorption of different entities diluted in liquid solution. By combining optical and Atomic Force microscopy we confirm the selective adsorption of gold nanoparticles, dendrimers and bacteria.

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Abstract

It is well-established that, during microcontact printing (CP) using poly(dimethylsiloxane) (PDMS)-based stamps, some unexpected siloxane fragments can be transferred from the stamp to the surface of the sample. This so-called contamination effect coexists with the delivery of the molecules constituting the ink and by this way influences the printing process. The real impact of this contamination for the CP technique is still partially unknown. In this work, we investigate the kinetics of this contamination process through the surface characterization of both the sample and the stamp after imprinting. The way both the curing conditions of the PDMS material and the contact time influence the degree of contamination of the surface is investigated on silicon and glass substrates. We propose a cleaning process of the stamp during several hours which eliminates any trace of contamination during printing. We show that hydrophobicity recovery of PDMS surfaces after hydrophilic treatment using oxygen plasma is considerably slowed down when the PDMS material is cleaned using our procedure. Finally, by comparing cleaned and uncleaned PDMS stamps, we show the influence of contamination on the quality of CP using fluorescent DNA molecules as an ink. Surprisingly, we observe that the amount of DNA molecules transferred during CP is higher for the uncleaned stamp, highlighting the positive impact of the presence of low molecular weight siloxane fragments on the CP process. This result is attributed to the better adsorption of oligonucleotides on the stamp surface in presence of these contaminating molecules.

Abstract

A simple chemical procedure for fixing streptavidin molecules on the periphery of commercial Au nanoparticles stabilized by citrate groups is presented. Using a flocculation test, we determine the adequate quantity of streptavidin molecules necessary for coating Au nanoparticles with approximately one monolayer of streptavidin. Our results indicate that on average, one molecule of streptavidin occupies an area of 40 nm2 on the surface of the Au nanoparticles, which is the good order of magnitude with respect to the size of this biomolecule. The optical properties of these nanoparticles were found to be sensitive to the biofunctionalization process. We have observed that the changes in photoluminescence spectra could be used to monitor the coverage ratio of the nanoparticles with streptavidin.

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Abstract

Combining patterning methods with the ability of biomolecules to arrange themselves in organized molecular structures is a very interesting approach for building complex 3D architectures. Along this route, that combines nano-patterning with bottom-up assembly, we have used micro-contact printing (¼CP) for fabricating self assembled supported phospholipids membranes that can mimic cell membranes and their compartments due to the ability of the technique to shape domains at the micron scale. Micro-domains of lipidic membranes were obtained, though the selective fusion of liposomes on SiO2 surfaces printed with bovins serum albumine patterns. We found that BSA pattern obtained by ¼CP prevents the fusion of liposomes. This result was confirmed by atomic force microscopy, fluorescence imaging and FRAP experiments.

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