by Keyword: SAMs

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Santander-Nelli, M., Silva, C. P., Espinoza-Vergara, J., Silva, J. F., Olguín, C. F., Cortés-Arriagada, D., Zagal, J. H., Mendizabal, F., Díez-Pérez, I., Pavez, J., (2017). Tailoring electroactive surfaces by non-template molecular assembly. Towards electrooxidation of L-cysteine Electrochimica Acta 254, 201-213

We have prepared a nanoelectrode ensemble containing vertically aligned single walled carbon nanotubes (SWCNTs) using a non-template molecular self-assembling strategy. We used a bottom-up construction approach to assemble amino functionalized SWCNTs (af-SWCNTs) in a well-defined architecture. These af-SWCNTs were linked and vertically aligned to pre-formed self-assembled monolayers of 4-MBA. A Cobalt(II) tetracarboxyphthalocyanine (Co(COOH)4Pc) complex was covalently bonded to external portion of af-SWCNTs to complete the final nanoelectrode ensemble. X-ray photoelectron spectroscopy (XPS) and Atomic Force Microcopy (AFM) confirmed the effectiveness of the assembling steps on the gold surface starting from the Au/MBA SAMs. The system Au/4-MBA/af-SWCNTs shows an interface with large ordered array, which exhibits a high activity for the electrooxidation of L-cysteine (L-cys). Theoretical calculations suggest that the incorporation of the af-SWCNTs increased the activity of the assembly to electronic transfer and it was observed that the electrooxidation reaction is energetically favorable.

Keywords: Bottom-up construction, DFT, Modified electrode, Molecular assembly, SAMs, Single walled carbon nanotube

Miranda Coelho, Nuno, Gonzalez-Garcia, Cristina, Salmeron-Sanchez, Manuel, Altankov, George, (2011). Arrangement of type IV collagen on NH(2) and COOH functionalized surfaces Biotechnology and Bioengineering 108, (12), 3009-3018

Apart from the paradigm that cell-biomaterials interaction depends on the adsorption of soluble adhesive proteins we anticipate that upon distinct conditions also other, less soluble ECM proteins such as collagens, associate with the biomaterials interface with consequences for cellular response that might be of significant bioengineering interest. Using atomic force microscopy (AFM) we seek to follow the nanoscale behavior of adsorbed type IV collagen (Col IV)-a unique multifunctional matrix protein involved in the organization of basement membranes (BMs) including vascular ones. We have previously shown that substratum wettability significantly affects Col IV adsorption pattern, and in turn alters endothelial cells interaction. Here we introduce two new model surfaces based on self-assembled monolayers (SAMs), a positively charged - NH(2), and negatively charged -COOH surface, to learn more about their particular effect on Col IV behavior. AFM studies revealed distinct pattern of Col IV assembly onto the two SAMs resembling different aspects of network-like structure or aggregates (suggesting altered protein conformation). Moreover, the amount of adsorbed FITC-labeled Col IV was quantified and showed about twice more protein on NH(2) substrata. Human umbilical vein endothelial cells attached less efficiently to Col IV adsorbed on negatively charged COOH surface judged by altered cell spreading, focal adhesions formation, and actin cytoskeleton development. Immunofluorescence studies also revealed better Col IV recognition by both alpha(1) and alpha(2) integrins on positively charged NH(2) substrata resulting in higher phosphorylated focal adhesion kinase recruitment in the focal adhesion complexes. On COOH surface, no integrin clustering was observed. Taken altogether these results, point to the possibility that combined NH(2) and Col IV functionalization may support endothelization of cardiovascular implants.

Keywords: Collagen type IV, SAMs, AFM, Surface-induced protein assembly, Endothelial cells, Vascular grafts

Sanmarti, M., Iavicoli, P., Pajot-Augy, E., Gomila, G., Samitier, J., (2010). Human olfactory receptors immobilization on a mixed self assembled monolayer for the development of a bioelectronic nose Procedia Engineering (EUROSENSOR XXIV CONFERENCE) 24th Eurosensor Conference (ed. Jakoby, B., Vellekoop, M.J.), Elsevier Science (Linz, Austria) 5, 786-789

The present work focuses on the development of an immunosensing surface to build a portable olfactory system for the detection of complex mixture of odorants. Homogeneous cell derived vesicles expressing the olfactory receptors were produced and immobilized with efficiency onto a gold substrate through an optimized surface functionalization method.

Keywords: Bioelectronic noses, Biosensors, Nanoproteoliposomes, Nanosomes, Olfactory receptors, SAMs