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

Putrescine differently influences the effect of salt stress on polyamine metabolism and ethylene synthesis in rice cultivars differing in salt resistance

Effects of salt stress on polyamine metabolism and ethylene production were examined in two rice (Oryza sativa L.) cultivars [I Kong Pao (IKP), salt sensitive; and Pokkali, salt resistant] grown for 5 d and 12 d in nutrient solution in the presence or absence of putrescine (1 mM) and 0, 50, and 100 mM NaCl. The salt-sensitive (IKP) and salt-resistant (Pokkali) cultivars differ not only in their mean levels of putrescine, but also in the physiological functions assumed by this molecule in stressed tissues. Salt stress increased the proportion of conjugated putrescine in salt-resistant Pokkali and decreased it in the salt-sensitive IKP, suggesting a possible protective function in response to NaCl. Activities of the enzymes ornithine decarboxylase (ODC; EC 4.1.1.17) and arginine decarboxylase (ADC; EC 4.1.1.19) involved in putrescine synthesis were higher in salt-resistant Pokkali than in salt-sensitive IKP. Both enzymes were involved in the response to salt stress. Salt stress also increased diamine oxidase (DAO; 1.4.3.6) and polyamine oxidase (PAO EC 1.5.3.11) activities in the roots of salt-resistant Pokkali and in the shoots of salt-sensitive IKP. Gene expression followed by reverse transcription-PCR suggested that putrescine could have a post-translational impact on genes coding for ADC (ADCa) and ODC (ODCa and ODCb) but could induce a transcriptional activation of genes coding for PAO (PAOb) mainly in the shoot of salt-stressed plants. The salt-resistant cultivar Pokkali produced higher amounts of ethylene than the salt-sensitive cultivar IKP, and exogenous putrescine increased ethylene synthesis in both cultivars, suggesting no direct antagonism between polyamine and ethylene pathways in rice

Effects of serum proteins on corrosion behavior of ISO 5832–9 alloy modified by titania coatings

Stainless steel ISO 5832–9 type is often used to perform implants which operate in protein-containing physiological environments. The interaction between proteins and surface of the implant may affect its corrosive properties. The aim of this work was to study the effect of selected serum proteins (albumin and γ-globulins) on the corrosion of ISO 5832–9 alloy (trade name M30NW) which surface was modified by titania coatings. These coatings were obtained by sol– gel method and heated at temperatures of 400 and 800 °C. To evaluate the effect of the proteins, the corrosion tests were performed with and without the addition of proteins with concentration of 1 g L−1 to the physiological saline solution (0.9 % NaCl, pH 7.4) at 37 °C. The tests were carried out within 7 days. The following electrochemical methods were used: open circuit potential, linear polarization resistance, and electrochemical impedance spectroscopy. In addition, surface analysis by optical microscopy and X-ray photoelectron spectroscopy (XPS) method was done at the end of weekly corrosion tests. The results of corrosion tests showed that M30NW alloy both uncoated and modified with titania coatings exhibits a very good corrosion resistance during weekly exposition to corrosion medium. The best corrosion resistance in 0.9 % NaCl solution is shown by alloy samples modified by titania coating annealed at 400 °C. The serumproteins have no significant effect onto corrosion of investigated biomedical steel. The XPS results confirmed the presence of proteins on the alloy surface after 7 days of immersion in proteincontaining solutions.The investigations were supported by the National Science Centre project No. N N507 501339. The authors gratefully acknowledge Dr. Janusz Sobczak and Dr. hab. Wojciech Lisowski from Institute of Physical Chemistry of PAS for XPS surface analyses

Morphology and Nanomechanics of Sensory Neurons Growth Cones following Peripheral Nerve Injury

A prior peripheral nerve injury in vivo, promotes a rapid elongated mode of sensory neurons neurite regrowth in vitro. This in vitro model of conditioned axotomy allows analysis of the cellular and molecular mechanisms leading to an improved neurite re-growth. Our differential interference contrast microscopy and immunocytochemistry results show that conditioned axotomy, induced by sciatic nerve injury, did not increase somatic size of adult lumbar sensory neurons from mice dorsal root ganglia sensory neurons but promoted the appearance of larger neurites and growth cones. Using atomic force microscopy on live neurons, we investigated whether membrane mechanical properties of growth cones of axotomized neurons were modified following sciatic nerve injury. Our data revealed that neurons having a regenerative growth were characterized by softer growth cones, compared to control neurons. The increase of the growth cone membrane elasticity suggests a modification in the ratio and the inner framework of the main structural proteins

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

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

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

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