Atmospheric pressure plasma spraying of silane-based coatings targeting whey protein fouling and bacterial adhesion management

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Biomimetic nanostructured surfaces for antifouling in dairy processing

In dairy pasteurization equipment, fouling is an ongoing problem. Indeed, when heated, milk and its derivatives generate mineral and proteinaceous deposits on stainless steel walls. This heat-induced fouling impairs the process through the addition of an increasing thermal resistance to the system. Deposits are also a threat to food safety as they provide micro-organisms with good settlement opportunities. As a consequence, fouling mitigating strategies are needed. Biomimetic surfaces in particular, inspired from the surface morphology of lotus leaf could be considered for their self-cleaning abilities. Its dual-scale roughness (i.e. a micro roughness supporpsed by nanoscale roughness) allows for the composite Cassie-Baxter wetting state due to air remaining trapped between the liquid and the solid surface. As a result, those surfaces possess very high contact angles (typically higher than 150o) and very low contact angle hysteresis (typically less than 10°). However, a major limitation of this type of surface is the difficulty to maintain a stable Cassie-Baxter state over time: depending on the experimental conditions (pressure, vibration, evaporation, surface defect) the liquid penetrates sooner or later into the structures degrading their anti-biofouling properties. To overcome this limitation, it has been proposed to impregnate the textured surface by a liquid of low surface tension (usually an inert oil not miscible with water). This led to SLIPS surfaces (Slippery Liquid-Infused Porous Surfaces). Even if these surfaces present low contact angle, their hysteresis is also almost null whatever the experimental conditions leading to antifouling properties [1].   This work aims at designing Cassie-Baxter and SLIPS surfaces and test them in dairy processing conditions to assess their antifouling properties. To this end, 316L stainless steel surfaces were texturized via femtosecond laser irradiation to generate dual-scale (cauliflower-like) structures [2]. Some of the fabricated surfaces underwent further modifications: (i) silanization with perfluorodecyltrichloro-silane or (ii) silanization followed by impregnation with a fluorinated oil to create Slippery Liquid Infused Porous Surfaces (SLIPS) [3]. All surfaces were tested for their fouling properties in a pilot pasteurization equipement (UMET-PIHM, Institut National de la Recherche Agronomique, Villeneuve d'Ascq) [4] allowing to mimick industrial conditions of the pasteurization process. Thorough characterizations were performed on the surfaces before and after fouling, to (i) establish clearly their surface properties (wettability, surface energy, roughness) and (ii) to investigate the impact of the different surface properties on heat-induced dairy fouling compared to a native stainless steel as reference. A wide range of analytical tools such as Goniometry, cross-section Electron Probe Micro-Analysis X-ray mappings, and Scanning Electron Microscopy were implemented to this end. Outstanding results were obtained regarding antifouling properties of dual-scaled roughness surfaces in dairy processing conditions, with a reduction of fouling by more than 90% in weight. References [1] T.-S. Wong, S. H. Kang, S. K. Y. Tang, E. Smythe, B. D. Hatton, A. Grinthal, and J. Aizenberg, ?Bioinspired self-repairing slippery surfaces with pressure-stable omniphobicity,? Nature, vol. 477, pp. 443?447, 2011. [2] A.-M. Kietzig, S. G. Hatzikiriakos, and P. Englezos, ?Patterned Superhydrophobic Metallic Surfaces,? Langmuir, vol. 25, no. 8, pp. 4821?4827, 2009. [3] A. K. Epstein, T.-S. Wong, R. A. Belisle, E. M. Boggs, and J. Aizenberg, ?Liquid-infused structured surfaces with exceptional anti-biofouling performance,? PNAS, vol. 109, no. 33, pp. 13182?13187, 2012. [4] M. Jimenez, G. Delaplace, N. Nuns, S. Bellayer, D. Deresmes, G. Ronse, G. Alogaili, M. Collinet-Fressancourt, and M. Traisnel, ?Toward the understanding of the interfacial dairy fouling deposition and growth mechanisms at a stainless steel surface: A multiscale approach,? J. Colloid an interface Sci., vol. 404, pp. 192?200, 2013

Wettability Switching Techniques on Superhydrophobic Surfaces

The wetting properties of superhydrophobic surfaces have generated worldwide research interest. A water drop on these surfaces forms a nearly perfect spherical pearl. Superhydrophobic materials hold considerable promise for potential applications ranging from self cleaning surfaces, completely water impermeable textiles to low cost energy displacement of liquids in lab-on-chip devices. However, the dynamic modification of the liquid droplets behavior and in particular of their wetting properties on these surfaces is still a challenging issue. In this review, after a brief overview on superhydrophobic states definition, the techniques leading to the modification of wettability behavior on superhydrophobic surfaces under specific conditions: optical, magnetic, mechanical, chemical, thermal are discussed. Finally, a focus on electrowetting is made from historical phenomenon pointed out some decades ago on classical planar hydrophobic surfaces to recent breakthrough obtained on superhydrophobic surfaces

Fonctionnalisation de supports chromatographiques par des ligands pseudobiospécifiques pour l'élimination extracorporelle de biomolécules pathogènes du sang

Dans cette étude nous nous sommes intéressés à la mise au point de procédés d'élimination extracorporelle pour une adsorption sélective d'autoanticorps chez des patients atteints de maladies autoimmunes. Dans un premier temps, un module de membranes fibres creuses thiophilique (2S) permettant l'élimination d'environ 1.5g/m2 d'immunoglobuline G à partir du plasma humain a été mis au point. Les problèmes de dilution et d'ajout de sel antichaotropique rencontrés nous ont conduit à rechercher des ligands pour l'adsorption spécifique des IgG à partir directement du plasma. Pour cela une approche de chimie combinatoire limitée a été utilisée. Des composés mercaptohétérocyc1iques ont été couplés sur des membranes pré-activées par le divinylsulfone (DVS). Les groupements pyridine, imidazole et purine ont montré une capacité à adsorber spécifiquement les IgG sous conditions sel-indépendante et à pH physiologique. Néanmoins, il ressort que le mercaptométhylimidazole semble être une base intéressante pour la mise au point de futurs ligands de pseudobioaffinité pour la purification des IgG. Une approche originale a été d'essayer de mettre au point un modèle plan afin d'étudier les interactions protéines-ligands. Le Pluronic@ F1O8 s'est vite avéré un candidat potentiel pour limiter les interactions non spécifiques rencontrées lors de la fonctionnalisation de surfaces en silicium. Après avoir réalisé la chimie de synthèse du Pluronic F1O8-histidine et après avoir trouvé la surface adéquate pour son adsorption, nous n'avons pas pu détecter de différence entre les surfaces recouvertes avec le F1O8 et celles recouvertes avec le F1O8-Histidine pour l'adsorption d'IgG.COMPIEGNE-BU (601592101) / SudocSudocFranceF

Diamond Nanowires: A Novel Platform for Electrochemistry and Matrix-Free Mass Spectrometry

Over the last decades, carbon-based nanostructures have generated a huge interest from both fundamental and technological viewpoints owing to their physicochemical characteristics, markedly different from their corresponding bulk states. Among these nanostructured materials, carbon nanotubes (CNTs), and more recently graphene and its derivatives, hold a central position. The large amount of work devoted to these materials is driven not only by their unique mechanical and electrical properties, but also by the advances made in synthetic methods to produce these materials in large quantities with reasonably controllable morphologies. While much less studied than CNTs and graphene, diamond nanowires, the diamond analogue of CNTs, hold promise for several important applications. Diamond nanowires display several advantages such as chemical inertness, high mechanical strength, high thermal and electrical conductivity, together with proven biocompatibility and existence of various strategies to functionalize their surface. The unique physicochemical properties of diamond nanowires have generated wide interest for their use as fillers in nanocomposites, as light detectors and emitters, as substrates for nanoelectronic devices, as tips for scanning probe microscopy as well as for sensing applications. In the past few years, studies on boron-doped diamond nanowires (BDD NWs) focused on increasing their electrochemical active surface area to achieve higher sensitivity and selectivity compared to planar diamond interfaces. The first part of the present review article will cover the promising applications of BDD NWS for label-free sensing. Then, the potential use of diamond nanowires as inorganic substrates for matrix-free laser desorption/ionization mass spectrometry, a powerful label-free approach for quantification and identification of small compounds, will be discussed

Stability of gold/silica thin film interface: Electrochemical and surface plasmon resonance studies

International audienceThis article reports chemical stability studies of a gold film electrode coated with thin silicon oxide (SiOx) layers using electrochemical, surface plasmon resonance (SPR) and atomic force microscopy (AFM) techniques. Silica films with different thicknesses (d = 6.4, 9.7, 14.5, and 18.5 nm) were deposited using a plasma-enhanced chemical vapor deposition technique (PECVD). For SiOx films with d ≥ 18.5 nm, the electrochemical behavior is characteristic of a highly efficient barrier for a redox probe. SiOx films with thicknesses between 9.5 and 14.5 nm were found to be less efficient barriers for electron transfer. The Au/SiOx interface with 6.4 nm of SiOx, however, showed an enhanced steady-state current compared to that of the other films. The stability of this interface in solutions of different pH was investigated. Whereas a strongly basic solution led to a continuous dissolution of the SiOx interface, acidic treatment produced a more reticulated SiOx film and improved electrochemical behavior. The electrochemical results were corroborated by SPR measurements in real time and AFM studies

Sliding Droplets on Superomniphobic Zinc Oxide Nanostructures

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