Nanotechnology and Dental Implants

The long-term clinical success of dental implants is related to their early osseointegration. This paper reviews the different steps of the interactions between biological fluids, cells, tissues, and surfaces of implants. Immediately following implantation, implants are in contact with proteins and platelets from blood. The differentiation of mesenchymal stem cells will then condition the peri-implant tissue healing. Direct bone-to-implant contact is desired for a biomechanical anchoring of implants to bone rather than fibrous tissue encapsulation. Surfaces properties such as chemistry and roughness play a determinant role in these biological interactions. Physicochemical features in the nanometer range may ultimately control the adsorption of proteins as well as the adhesion and differentiation of cells. Nanotechnologies are increasingly used for surface modifications of dental implants. Another approach to enhance osseointegration is the application of thin calcium phosphate (CaP) coatings. Bioactive CaP nanocrystals deposited on titanium implants are resorbable and stimulate bone apposition and healing. Future nanometer-controlled surfaces may ultimately direct the nature of peri-implant tissues and improve their clinical success rate

Click grafting of seaweed polysaccharides onto PVC surfaces using an ionic liquid as solvent and catalyst

International audienceSeaweed antibacterial polysaccharides were grafted onto poly(vinylchloride) (PVC) surfaces using an original click chemistry pathway. PVC isothiocyanate surfaces (PVC-NCS) were first prepared by nucleophilic substitution of the chloride groups by isothiocyanate groups in DMSO/water medium. Then, unmodified Ulvan, Fucan, Laminarin or Zosterin was directly grafted onto the PVC-NCS surface using 1-ethyl-3-methyl imidazolium phosphate, an ionic liquid, as solvent and catalyst. To attest the grafting effectiveness, the new PVC surfaces were well characterized by AFM, XPS and contact angle measurement

ELT instrumentation for seeing-limited and AO-corrected observations: A comparison

The next generation of large ground-based optical and infrared telescopes will provide new challenges for designers of astronomical instrumentation. The varied science cases for these extremely large telescopes (ELTs) require a large range of angular resolutions, from near diffraction-limited performance via correction of atmospheric turbulence using adaptive optics (AO), to seeing-limited observations. Moreover, the scientific output of the telescopes must also be optimized with the consideration that, with current technology, AO is relatively ineffective at visible wavelengths, and that atmospheric conditions will often preclude high-performance AO. This paper explores some of the issues that arise when designing ELT instrumentation that operates across a range of angular resolutions and wavelengths. We show that instruments designed for seeing-limited or seeing-enhanced observations have particular challenges in terms of size and mass, while diffraction-limited instruments are not as straightforward as might be imagined.Comment: 8 pages, to appear in the SPIE proceedings "ELTs: Which Wavelengths?", from the Lund Symposium on occasion of Arne Ardeberg's retiremen

Towards anode with low indium content as effective anode in organic solar cells

In2O3 thin films (100 nm thick) have been deposited by reactive evaporation of indium, in an oxygen partial atmosphere. Conductive (σ = 3.5×103 S/cm) and transparent films are obtained using the following experimental conditions: oxygen partial pressure = 1×10−1 Pa, substrate temperature = 300 ◦C and deposition rate = 0.02 nm/s. Layers of this In2O3 thick of 5 nm have been introduced in AZO/In2O3 and FTO/In2O3 multilayer anode structures. The performances of organic photovoltaic cells, based on the couple CuPc/C60, are studied using the anode as parameter. In addition to these bilayers, other structures have been used as anode: AZO, FTO, AZO/In2O3/MoO3, FTO/In2O3/MoO3 and FTO/MoO3. It is shown that the use of the In2O3 film in the bilayer structures improves significantly the cell performances. However the open circuit voltage is quite small while better efficiencies are achieved when MoO3 is present. These results are discussed in the light of surface roughness and surface work function of the different anodes

New Compounds Measured by Fluorescence Spectroscopy. Amino-Fluorene-Thiophene Derivatives to Be Proposed as Polarity Indicators.

The solvatochromic effect is high in conjugate compounds and easy to observe by the colour change emitted when the solutions are exposed to UV light. It was found in a series of aminofluorene thiophene derivatives, previously synthesized, that irradiating at different wavelengths, the same pattern is obtained, i.e. a dual behaviour in the solvatochromism of the studied compounds. For each one, a bathochromic and hypsochromic effect exists, in polar and nonpolar solvents, respectively. Wavelength vs. polarity index plots clearly showed the abovementioned dual behaviour as well as the improved linearity in its plots. Amidst the wavelengths at which each compound is excited in each solvent, 280 nm was selected as the fixed wavelength for the measurements; (E)-9,9-diethyl-N-hexyl-N-phenyl-7-(2-(thiofen-2-yl)vinyl)-9H-fluoren-2-amine (M6-6) exhibits better linearity as compared to the other studied compounds, being the best to be proposed as polarity sensor or indicator

Interaction of Rep and DnaB on DNA

Genome duplication requires not only unwinding of the template but also the displacement of proteins bound to the template, a function performed by replicative helicases located at the fork. However, accessory helicases are also needed since the replicative helicase stalls occasionally at nucleoprotein complexes. In Escherichia coli, the primary and accessory helicases DnaB and Rep translocate along the lagging and leading strand templates, respectively, interact physically and also display cooperativity in the unwinding of model forked DNA substrates. We demonstrate here that this cooperativity is displayed only by Rep and not by other tested helicases. ssDNA must be exposed on the leading strand template to elicit this cooperativity, indicating that forks blocked at protein–DNA complexes contain ssDNA ahead of the leading strand polymerase. However, stable Rep–DnaB complexes can form on linear as well as branched DNA, indicating that Rep has the capacity to interact with ssDNA on either the leading or the lagging strand template at forks. Inhibition of Rep binding to the lagging strand template by competition with SSB might therefore be critical in targeting accessory helicases to the leading strand template, indicating an important role for replisome architecture in promoting accessory helicase function at blocked replisomes

Imagerie et spectroscopies en champ proche optique (de la nano-sonde à la caractérisation des matériaux)

Les propriétés singulières des ondes évanescentes ont permis le développement de la microscopie en champ proche optique, mais également l émergence de capteurs moléculaires basée sur l excitation de plasmons de surface. Ce travail de thèse est consacré au développement de nano-sondes à base de fibres optiques destinées à ces deux applications. Après un état de l art des différents procédés de la littérature, ce travail aborde une nouvelle approche pour créer des nano-sondes optiques. La gravure chimique, pour créer une pointe à l extrémité d une fibre conique, est premièrement optimisée. Les étapes suivantes sont réalisées dans un dispositif plasma original, basé sur une décharge en régime de cathode creuse cylindrique. Pour finaliser la fabrication des sondes, les pointes métallisées sont ouvertes in situ avec une micro-étincelle obtenue via une décharge couronne en configuration pointe-plan. Notre microscope est ensuite détaillé et une étude paramétrique est menée afin d optimiser la formation des images, les capacités de résolution du sont discutées. A titre d exemple, le microscope est ensuite appliqué à la science des nano-matériaux, et quelles pistes d investigation de nano-structures sont explorées, ainsi que le potentiel de spectroscopie Raman en champ proche. La spectroscopie résonante des plasmons de surface est aussi abordée. Les sondes spécialement modifiées sont ici destinées à la détection moléculaire en milieu aqueux. Les capteurs ainsi élaborés sont testés dans des microvolumes de solution, et leur capacité d exaltation du signal Raman est présentéeEvanescent wave uncommon properties allow for the development of scanning near-field optical microscopy (SNOM) and for creating highly sensitive sensors by surface plasmon excitation. This works deals with developments and investigations to produce near-field optical fiber probes for these both applications. After a review of the actual processes, this work reports a new approach for probes manufacturing. The wet-etching process, to create the tip at the apex of a tapered fiber, has been improved. Next process steps, cleaning and coating, are performed in an original arrangement of plasma device, based on a modified hollow cathode discharge. The last step of probe fabrication is the tips opening by a micro-spark between the biased tip and another plane electrode working as a corona-like discharge in point-to-plane configuration. The home-made SNOM is detailed and the probe sensitivity is discussed with respect to different parameters, in order to achieve the highest spatial resolution. Imaging capabilities with nano-materials and the first SNOM-Raman spectra recorded in our laboratory are shown, emphasizing a sub micrometric spectral resolution. The microscale tip sensors based on the plasmon resonance are reported; the probe s manufacturing process is modified for this spectroscopic approach. The miniaturized sensor allows molecule detection in aqueous environment. The Raman scattering enhancement trough these micro-sensors demonstrates the important role played by the localized plasmon resonanceNANTES-BU Sciences (441092104) / SudocSudocFranceF

Modélisation, réalisation et caractérisation d'un capteur plasmonique à fibre optique (effets de la rugosité, des réactions de surface et de la cinétique dans un système microfluidique)

Actuellement une forte demande existe pour des dispositifs de détection chimique et biochimique en temps réel, miniatures, automatisés, bon marchés, et tout particulièrement pour l étude des interactions biomoléculaires. Les capteurs à fibre optique basés sur la résonance plasmon de surface (FO-SPR) peuvent répondre à cette attente sous réserve que leur fiabilité soit améliorée. En effet, pour rendre ces capteurs performants et compétitifs, il est nécessaire d améliorer leur sensibilité et leur limite de détection. L objectif de notre travail a consisté à optimiser la performance du capteur à fibre optique basé sur la résonance plasmon de surface. Pour atteindre cet objectif, nous avons réalisé et étudié d une part des fibres capteurs réalisées au laboratoire, et d autre part, nous avons développé un modèle numérique qui nous a permis de déterminer les valeurs optimales des paramètres géométriques et physiques ajustables du capteur. Ainsi, des caractérisations de la surface métallique ont été réalisées afin d en déterminer la rugosité et les permittivités diélectriques complexes puis d en étudier l influence sur la réponse du capteur FO-SPR. Finalement, le capteur a été utilisé dans une cellule microfluidique ce qui nous a permis de suivre en temps réel l évolution de la réponse SPR en fonction de la cinétique des réactions de surface. L implémentation de notre modèle numérique avec des paramètres cinétiques issus des mesures expérimentales met en évidence la capacité du capteur SPR à fibre optique à répondre aux attentes dans le domaine de la détection biochimique.In the last decade, the surface plasmon resonance (SPR) has become a very sensitive technique for real-time detection in many application areas: chemistry, environmental studies, biological systems, etc. Considering the optic-fiber concept and the important needs for analyzing biomolecular reactions through automated and miniaturized components, optical fiber sensors based on the SPR technique are becoming the first choice in the field of sensing of different chemical and biochemical applications. However, such sensor does not provide yet reasonably high value of performance for an efficient detection fulfilling those needs. Therefore, an improvement of the values of performance parameters, like sensitivity and detection limit, is required. In the present work, the effect of key design factors on the response of the sensor is studied. To be done, we first manufactured optic-fiber sensor for conducting experiments and evaluating sensor s responses in particular. We also developed a tool to perform numerical response curves in conjunction with the experimental results to set up sensor s suitable framework. Furthermore, experimental characterizations of the deposited metallic layer have been investigated to evaluate the effect of the roughness and other parameters (dielectric constant, thickness...) of the metallic layer on sensor s responses. By comparing the experimental results with the simulated curves, a study is carried out in order to validate our numerical tool. On the other hand, the valid tool is then used to define the optimal geometry of a reliable sensor using numerical parametric simulation. Finally, microfluidic system associated with optic-fiber sensor based on SPR is accomplished for monitoring in real-time the variation of sensor s responses at each kinetic reaction occurring at the surface. Thereby, the introduction of kinetic parameters produced by experimental measurement into our numerical model enables us to demonstrate the potential of optic-fiber sensor based on SPR for biological analysis purposes.NANTES-BU Sciences (441092104) / SudocSudocFranceF