Adsorption of a PEO–PPO–PEO triblock copolymer on metal oxide surfaces with a view to reducing protein adsorption and further biofouling

Biomolecule adsorption is the first stage of biofouling. The aim of this work was to reduce the adsorption of proteins on stainless steel (SS) and titanium surfaces by modifying them with a poly(ethylene oxide) (PEO)–poly(propylene oxide) (PPO)–PEO triblock copolymer. Anchoring of the central PPO block of the copolymer is known to be favoured by hydrophobic interaction with the substratum. Therefore, the surfaces of metal oxides were first modified by self-assembly of octadecylphosphonic acid. PEO–PPO–PEO preadsorbed on the hydrophobized surfaces of titanium or SS was shown to prevent the adsorption of bovine serum albumin (BSA), fibrinogen and cytochrome C, as monitored by quartz crystal microbalance (QCM). Moreover, X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry were used to characterize the surfaces of the SS and titanium after competitive adsorption of PEO–PPO–PEO and BSA. The results show that the adsorption of BSA is well prevented on hydrophobized surfaces, in contrast to the surfaces of native metal oxides

Understanding and controlling type I collagen adsorption and assembly at interfaces, and application to cell engineering

tCollagen is a large anisotropic and self-assembling extracellular matrix protein. Understanding and con-trolling its adsorption and assembly at interfaces is expected to increase our general knowledge of proteinadsorption as well as to open the way to the development of biointerfaces of interest for biomaterials sci-ence and tissue engineering. The work related to type I collagen adsorption performed in our laboratoryover the past twenty years is reviewed. Substrate chemical nature and adsorption conditions (collagenconcentration, adsorption duration) were shown to affect collagen adsorbed amount and supramolecularorganization. Collagen assemblies were formed starting from the interface, and assembly was favored byhydrophobic substrates and high adsorbed amount. Substrates were designed to better control collagenadsorption and assembly. The spatial control of adsorption was ensured by chemically heterogeneoussubstrates, which also affected collagen assembly when domains with a dimension smaller than thelength of the collagen molecule (i.e. 300 nm) were prepared. Mixed polymer brushes were used to achievea temporal control of adsorption: adsorption and desorption were reversibly triggered by changes of pHand ionic strength. Layer-by-layer assembly of collagen in a nanoporous template was used to elabo-rate collagen-based nanotubes, which were further deposited on ITO glass substrates by electrophoreticdeposition. Finally, the evaluation of cell behavior on the created biointerfaces showed that the controlof collagen organization can be successfully used to alter cell behavior

Introduction à la physico-chimie des surfaces.

Cet ouvrage pluridisciplinaire est le fruit d’un travail collectif synthétisant les présentations effectuées par différents spécialistes des domaines concernés lors de l’école CNRS « BIODEMAT », qui a eu lieu en octobre 2014 à la Rochelle sous l’égide du CEFRACOR. Il est conçu pour des lecteurs de différentes spécialités scientifiques (chimie, biologie, physique…) et s’intéresse à différents problèmes industriels (eau, assainissement, maintenance des ouvrages…). Les matériaux, qu’ils soient métalliques, cimentaires, polymériques, composites, vieillissent en fonction de leur environnement de service. Ainsi, lorsque des microorganismes sont présents, ces derniers peuvent induire une biodétérioration. Cependant, les microorganismes peuvent également contribuer à la protection des structures, à condition de maîtriser et d’exploiter leurs immenses possibilités. Cet ouvrage se décompose en cinq thèmes relatifs à la biocolonisation puis à la biodétérioration des matériaux et enfin à leurs améliorations possibles pour obtenir une meilleure performance vis-à-vis de la biodétérioration : – physico-chimie des surfaces, – les biofilms : des acteurs de la biodétérioration, – biocorrosion des matériaux métalliques, – biodétérioration des matériaux non métalliques, – conception et modification des matériaux. L’affiliation des auteurs des différents chapitres, dont la liste est donnée en fin d’ouvrage, permet d’illustrer la nécessaire synergie entre la recherche académique et sa transposition au niveau industriel. Ceci démontre bien l’interaction indispensable entre les différents acteurs de ce domaine complexe, pour analyser, comprendre et répondre aux enjeux scientifiques liés à la biodétérioration

Orientation of adsorbed antibodies: in situ monitoring by QCM and random sequential adsorption modeling.

Antibodies (IgGs) are widely used for diagnostic assays, for which they are in certain cases immobilized by adsorption on hydrophobic substrates. Antigen recognition efficiency will depend on the orientation of the adsorbed IgG molecules. The aim of the present study was to investigate the binding-ability of a range of IgG isotypes from rat and mouse, all directed against the same antigen, using quartz crystal microbalance. The results allow identifying some isotypes which adsorb in higher amount and which provide a better bound antigen to adsorbed IgG ratio. This ratio was found to remain rather constant with the adsorbed IgG amount. Random sequential adsorption (RSA) modeling was used to simulate IgG adsorption. In the chosen modeling conditions, it is shown that even if adsorption in flat orientation is more favorable, a high proportion of IgG molecules adsorb in end-on orientation when surface coverage increases, owing to the low surface area spaces left between IgG molecules already adsorbed in flat orientation. The apparent discrepancy between experimental data collected by QCM and the output of RSA modeling may be attributed to variations in the water content of the adsorbed layer, to steric hindrance and multivalency effects upon antigen binding, or to the role of albumin molecules used to prevent non specific adsorption of the antigen

Nano-organized collagen layers obtained by adsorption on phase-separated polymer thin films.

The organization of adsorbed type I collagen layers was examined on a series of polystyrene (PS)/poly(methyl methacrylate) (PMMA) heterogeneous surfaces obtained by phase separation in thin films. These thin films were prepared by spin coating from solutions in either dioxane or toluene of PS and PMMA in different proportions. Their morphology was unraveled combining the information coming from X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and water contact angle measurements. Substrates with PMMA inclusions in a PS matrix and, conversely, substrates with PS inclusions in a PMMA matrix were prepared, the inclusions being either under the form of pits or islands, with diameters in the submicrometer range. The organization of collagen layers obtained by adsorption on these surfaces was then investigated. On pure PMMA, the layer was quite smooth with assemblies of a few collagen molecules, while bigger assemblies were found on pure PS. On the heterogeneous surfaces, it appeared clearly that the diameter and length of collagen assemblies was modulated by the size and surface coverage of the PS domains. If the PS domains, either surrounding or surrounded by the PMMA phase, were above 600 nm wide, a heterogeneous distribution of collagen was found, in agreement with observations made on pure polymers. Otherwise, fibrils could be formed, that were longer compared to those observed on pure polymers. Additionally, the surface nitrogen content determined by XPS, which is linked to the protein adsorbed amount, increased roughly linearly with the PS surface fraction, whatever the size of PS domains, suggesting that adsorbed collagen amount on heterogeneous PS/PMMA surfaces is a combination of that observed on the pure polymers. This work thus shows that PS/PMMA surface heterogeneities can govern collagen organization. This opens the way to a better control of collagen supramolecular organization at interfaces, which could in turn allow cell–material interactions to be tailored

Modulable nanometer-scale surface architecture using spin-coating on an adsorbed collagen layer

A strategy was developed to create a modulable polymer surface architecture (topography, chemical composition) at the nanometer scale. Therefore, collagen was first adsorbed on a poly(methyl methacrylate) (PMMA) substrate and dried at high or low rate to produce continuous or discontinuous layers, respectively. Solutions of PMMA in chlorobenzene were then spin-coated on top of these collagen layers. The obtained surfaces were investigated using atomic force microscopy and X-ray photoelectron spectroscopy. Spin-coating with pure chlorobenzene on the continuous collagen layer produced pits in the PMMA substrate through the collagen layer; spin-coating with PMMA solutions of increasing concentrations progressively led to the formation of a surface covered by particles made of PMMA and collagen, resulting from a combination of dissolution of PMMA from the substrate and deposition of PMMA from the solution. Spin-coating with pure chlorobenzene on the discontinuous collagen layer led to dissolution of PMMA and to its redeposition on the collagen pattern, which served as a template. This provided a surface entirely composed of PMMA, with cavities in the range of 0.1-1 mum diameter and 50-250 nm depth. In this case, the surface relief was independent of the PMMA concentration of the spin-coated solution, the substrate PMMA dissolution and redeposition being the dominant processes

Patterned collagen layers on polystyrene: direct probing using AFM in the adhesion mapping mode

Patterned collagen layers, showing a net-like structure with nanometer-scale dimensions, were obtained by collagen adsorption onto polystyrene (PS) followed by drying at low rate. These obtained surfaces were characterized and compared, on the one hand, to the PS substratum and, on the other hand, to uniform collagen layers obtained by adsorption onto PS and drying at high rate. In a first approach, atomic force microscope (AFM) images, X-ray photoelectron spectroscopy data and wetting measurements were compared. The results indicated that PS was present at the extreme surface in the holes of the collagen net. A second approach, allowing a direct and spatially-resolved probing of the surface chemistry, was based on the adhesion mapping mode of the AFM. The net-like structure observed on the AFM topographic images was also found in the adhesion map obtained in water: no or very low adhesion was found on collagen threads as observed on a uniform collagen layer; a higher adhesion was recorded in the holes of the net as observed on pure PS. This shows, in a direct manner, that the patterned surface is chemically heterogeneous, with PS domains present at the outermost surface in the holes of the collagen pattern, and that this is preserved under water. (C) 2003 Elsevier B.V. All rights reserved