Littérature scientifique sur le sujet « Nanorough substrate »

In this article, using the sol method successfully prepared the stabe alumina collosol, and the gel film plated on ceramic substrate. After heat treatment, with micro/nanorough double structure of alumina was constructed, and then alumina was processed by using stearic acid cyclohexane solution, reducing the surface energy. The obtained surface has good hydrophobic property. By using X-ray diffraction (XRD), scanning electron microscopy (SEM) and contact angle measurement instrument on ceramic surface was characterized microstructure and wettability of the thin film.

The cytocompatibility of titanium oxides (TiO2) and oxynitrides (N-TiO2, TiOxNy) thin films depends heavily on the surface topography. Considering that the initial relief of the substrate and the coating are summed up in the final topography of the surface, it can be expected that the same sputtering modes result in different surface topography if the substrate differs. Here, we investigated the problem by examining 16 groups of samples differing in surface topography; 8 of them were hand-abraded and 8 were machine-polished. Magnetron sputtering was performed in a reaction gas medium with various N2:O2 ratios and bias voltages. Abraded and polished uncoated samples served as controls. The surfaces were studied using atomic force microscopy (AFM). The cytocompatibility of coatings was evaluated in terms of cytotoxicity, adhesion, viability, and NO production. It has been shown that the cytocompatibility of thin films largely depends on the surface nanostructure. Both excessively low and excessively high density of peaks, high and low kurtosis of height distribution (Sku), and low rates of mean summit curvature (Ssc) have a negative effect. Optimal cytocompatibility was demonstrated by abraded surface with a TiOxNy thin film sputtered at N2:O2 = 1:1 and Ub = 0 V. The nanopeaks of this surface had a maximum height, a density of about 0.5 per 1 µm2, Sku from 4 to 5, and an Ssc greater than 0.6. We believe that the excessive sharpness of surface nanostructures formed during magnetron sputtering of TiO2 and N-TiO2 films, especially at a high density of these structures, prevents both adhesion of endothelial cells, and their further proliferation and functioning. This effect is apparently due to damage to the cell membrane. At low height, kurtosis, and peak density, the main factor affecting the cell/surface interface is inefficient cell adhesion.

The main focus of this work was to establish a correlation between surface topography and chemistry and surface colonization by lactic acid bacteria. For this reason, we chose gold substrates with different surface architectures (i.e., smooth and nanorough) that were characterized by atomic force microscopy (AFM), electron scanning microscopy (SEM), and X-ray diffractometry (XRD). Moreover, to enhance biocompatibility, we modified gold substrates with polymeric monolayers, namely cationic dextran derivatives with different molar masses. The presence of those layers was confirmed by AFM, infrared spectroscopy (IR), and X-ray photoelectron spectroscopy (XPS). In order to determine the adhesion abilities of non-modified and modified gold surfaces, we tested three lactic acid bacteria (LAB) strains (i.e., Lactobacillus rhamnosus GG, Lactobacillus acidophilus, and Lactobacillus plantarum 299v). We have shown that surface roughness influences the surface colonization of bacteria, and the most significant impact on the growth was observed for the Lactobacillus rhamnosus GG strain. What is more, covering the gold surface with a molecular polymeric film by using the layer-by-layer (LbL) method allows additional changes in the bacterial growth, independently on the used strain. The well-being of the bacteria cells on tested surfaces was confirmed by using selective staining and fluorescence microscopy. Finally, we have determined the bacterial metabolic activity by measuring the amount of produced lactic acid regarding the growth conditions. The obtained results proved that the adhesion of bacteria to the metallic surface depends on the chemistry and topography of the surface, as well as the specific bacteria strain.

An aging global population is accelerating the need for better, longer-lasting orthopaedic and dental implants. Additive manufacturing can provide patient-specific, titanium-alloy-based implants with tailored, three-dimensional, bone-like architecture. Studies using two-dimensional substrates have demonstrated that osteoblastic differentiation of bone marrow stromal cells (MSCs) is enhanced on surfaces possessing hierarchical macro/micro/nano-scale roughness that mimics the topography of osteoclast resorption pits on the bone surface. Conventional machined implants with these surfaces exhibit successful osseointegration, but the complex architectures produced by 3D printing make consistent nanoscale surface texturing difficult to achieve, and current line-of-sight methods used to roughen titanium alloy surfaces cannot reach all internal surfaces. Here, we demonstrate a new, non-line-of-sight, gas/solid-reaction-based process capable of generating well-controlled nanotopographies on all open (gas-exposed) surfaces of titanium alloy implants. Dense 3D-printed titanium-aluminum-vanadium (TiAl6V4) substrates were used to evaluate the evolution of surface nanostructure for development of this process. Substrates were either polished to be smooth (for easier evaluation of surface nanostructure evolution) or grit-blasted and acid-etched to present a microrough biomimetic topography. An ultrathin (90 ± 16 nm) conformal, titania-based surface layer was first formed by thermal oxidation (600 °C, 6 h, air). A calciothermic reduction (CaR) reaction (700 °C, 1 h) was then used to convert the surface titania (TiO2) into thin layers of calcia (CaO, 77 ± 16 nm) and titanium (Ti, 51 ± 20 nm). Selective dissolution of the CaO layer (3 M acetic acid, 40 min) then yielded a thin nanoporous/nanorough Ti-based surface layer. The changes in surface nanostructure/chemistry after each step were confirmed by scanning and transmission electron microscopies with energy-dispersive X-ray analysis, X-ray diffraction, selected area electron diffraction, atomic force microscopy, and mass change analyses. In vitro studies indicated that human MSCs on CaR-modified microrough surfaces exhibited increased protein expression associated with osteoblast differentiation and promoted osteogenesis compared to unmodified microrough surfaces (increases of 387% in osteopontin, 210% in osteocalcin, 282% in bone morphogenic protein 2, 150% in bone morphogenic protein 4, 265% in osteoprotegerin, and 191% in vascular endothelial growth factor). This work suggests that this CaR-based technique can provide biomimetic topography on all biologically facing surfaces of complex, porous, additively manufactured TiAl6V4 implants.

AbstractThree‐dimensional macroporous titanium–aluminum–vanadium (TiAl6V4) implants produced by additive manufacturing (AM) can be grit blasted (GB) to yield microtextured exterior surfaces, with additional micro/nano‐scale surface features provided by subsequent acid etching (AE). However, the line‐of‐sight nature of GB causes the topography of exterior GB + AE‐modified surfaces to differ from internal GB‐inaccessible surfaces. Previous in vitro studies using dense TiAl6V4 substrates indicated that a nonline‐of‐sight, calciothermic‐reaction (CaR)‐based process provided homogeneous osteogenic nanotextures on GB + AE surfaces, suggesting it could be used to achieve a homogeneous nanotopography on external and internal surfaces of macroporous AM constructs. Macroporous TiAl6V4 (3D) constructs were produced by direct laser melting and modified by GB + AE, with the CaR process then applied to 50% of constructs (3DCaR). The CaR process yielded nanoporous/nanorough internal surfaces throughout the macroporous constructs. Skeletally mature, male Sprague–Dawley rats were implanted with these constructs using a cranial on‐lay model. Prior to implantation, a Cu++‐free click hydrogel was applied to half of the constructs (3D + H, 3DCaR + H) to act as a challenge to osseointegration. Osseointegration was compared between the four implant groups (3D, 3DCaR, 3D + H, 3DCaR + H) at 4w. 3D + H implants exhibited lower bone volume (BV) and percent bone ingrowth (%BI) than the 3D implants. In contrast, osseointegrated 3DCaR + H implants had similar BV and %BI as the 3DCaR implants. Implant pull‐off forces correlated with these results. In vitro analyses indicated that human bone marrow stromal cells (MSCs) exhibited enhanced production of osteoblast differentiation markers and factors associated with osteogenesis when grown on CaR‐modified 3D substrates relative to control (TCPS) substrates. This work confirms that the CaR process provides osteogenic nanotextures on internal surfaces of macroporous 3D implants, and suggests that CaR‐modified surfaces can promote osseointegration in cases where osteogenesis is impaired.

Au cours des dernières décennies, l'utilisation des produits phytosanitaires communément appelés pesticides a augmenté. Ces substances sont devenues de plus en plus présentes dans notre environnement, s’'accumulant ainsi dans les sols, l'air et les eaux. Ces produits, même en très faible concentration, représentent un danger pour la santé humaine, végétale et animale. Pour toutes ces raisons il est important d'encadrer l'utilisation des produits phytosanitaires en interdisant l'utilisation de certaines de ces substances et en mettant en place des réglementations pour fixer les Limites Maximales de Résidus (LMR). Il est aussi nécessaire de développer de nouvelles méthodes de détection et d’identification de polluants à l'état de trace car les techniques conventionnelles nécessitent de gros équipements de laboratoire qui ne sont pas compatibles avec des analyses sur site.Dans le cadre de nos travaux, nous utilisons la Diffusion Raman Exaltée de Surface (DRES) pour détecter et identifier des molécules à l’'état de trace. Nous avons étudié et analysé les performances de trois substrats DRES commerciaux (Hamamatsu, SERSitive et Ocean Insight) pour la détection et l'identification d'une molécule modèle à des concentrations de l'ordre de 10-6 M et 10-8 M. Nous avons comparé les réponses Raman à partir des cartographies enregistrées sur leurs surfaces à deux longueurs d’onde incidentes. Nous avons également développé et optimisé des supports métalliques nanorugueux capables de détecter et identifier des molécules avec une limite de détection à 10-9 M. Nous présenterons le protocole expérimental utilisé pour fabriquer ces substrats nanorugueux en or. Ensuite, nous avons étudié les propriétés topographiques des surfaces pour mieux comprendre les propriétés d'exaltation des substrats. Ces derniers sont analysés par microscopie électronique à balayage et par microscopie à force atomique (AFM). Les réponses optiques des supports nanorugueux sont étudiées en champ proche par photoémission d’électrons (PEEM) et en champ lointain par spectrométrie Raman une fois ces supports mis en contact avec des solutions contenant des molécules à très faibles concentrations. Nous avons comparé la réponse spectrale, les distributions d'intensité, et la stabilité sous faisceau laser, des substrats nanorugueux en or et le substrat le plus efficace parmi les trois substrats DRES commerciaux en analysant les spectres Raman à une concentration de 10-8 M.La stabilité de la réponse Raman des substrats DRES commerciaux et du substrat nanorugueux optimisé a été étudiée dans le temps, pendant une durée de plusieurs mois. Avec le temps, l'efficacité des substrats diminue et il n'est alors plus possible de détecter la présence des molécules. Nous avons développé une méthode qui permet d'améliorer les performances Raman de ces substrats vieillis. Les performances de ces substrats améliorés ont été étudiées en analysant les distributions d'intensité Raman à partir d'imagerie contenant plusieurs centaines de spectres. Nous avons utilisé les substrats nanorugueux en or pour détecter les molécules présentes dans un mélange binaire de molécules modèles à une concentration de 10-8 M. Nous avons analysé les cartographies Raman en utilisant des outils chimiométriques, à savoir l’'Analyses en Composantes Principales (ACP), et la Multivariate Curve Resolution (MCR)
In recent decades, the use of phytosanitary products commonly called pesticides has increased. These substances have become increasingly present in our environment, accumulating in soil, air and water. Even at very low concentration these products represent a danger to human, plant and animal health. For all these reasons it is important to regulate the use of phytosanitary products by prohibiting the use of certain of these substances and by strengthening regulations to set Maximum Residue Limits (MRLs) as low as possible. It is also necessary to develop new methods for detecting and identifying trace pollutants because conventional techniques require large laboratory capabilities which are not compatible with on-site analyses.In my PhD. work, we have used Surface Enhanced Raman Scattering (SERS) to detect and identify trace molecules. We studied and analyzed the performance of three commercial DRES substrates (Hamamatsu, SERSitive and Ocean Insight) for the detection and identification of a model molecule at concentrations of the order of 10-6 M and 10-8 M. We compared the Raman responses from the Raman maps recorded on their surfaces at two incident wavelengths. We have also developed and optimized efficient nanorough metallic substrates to detect and identify molecules with a detection limit of 10-9 M. We will present the experimental protocol used to fabricate our nanorough gold substrates. The topographical properties of the surfaces were studied by scanning electron microscopy (SEM) and atomic force microscopy (AFM) to better understand the reason of SERS properties of the substrates. The optical responses of our nanorough substrates were studied in the near field by electron photoemission (PEEM) and in the far field by Raman spectrometry after putting them in contact with solutions containing molecules at very low concentrations. We compared the spectral response, intensity distributions, and stability under laser beam, of gold nanorough substrates and the most efficient substrate among the three commercial DRES substrates by analyzing the Raman spectra at a concentration of 10-8 M.The stability of the Raman response of the commercial SERS substrates and our optimized nanorough substrates was studied over time, for a period of several months. The effectiveness of the substrates decreases over time and it is no longer possible to detect the presence of the molecules after several months. In my PhD work we have tested a method that makes it possible to improve the Raman performance of these aged substrates. The performance of these improved substrates was studied by analyzing Raman intensity distributions from imaging containing several hundred spectra. Finally, we used the gold nanorough substrates to detect molecules present in a binary mixture of model molecules at a concentration of 10-8 M. We analyzed the Raman maps using chemometric tools, namely Component Analysis. Principal (ACP), and Multivariate Curve Resolution (MCR)