Inhibition de l'adhérence de Porphyromonas gingivalis sur la surface de titane greffé de poly(styrène sulfonate de sodium)

1 - ArticleRésumé Les infections péri-implantaires représentent l'une des causes majeures d'échec de l'ostéo-intégration des implants dentaires en titane. Ces infections sont induites par des bactéries de la flore buccale comme Porphyromonas gingivalis, dont l'adhérence sur l'implant dépend des propriétés physico-chimiques et topographiques de surface de celui-ci. À titre d'exemple, nous avons montré que la modification chimique de surfaces implantaires en titane par greffage d'un polymère " bioactif " tel que le poly(styrène sulfonate de sodium) permet de diminuer sensiblement (> 40 %) l'adhérence de Staphyloccocus aureus. L'objectif de cette étude est d'évaluer l'adhérence de Porphyromonas gingivalis sur des surfaces de titane greffées de poly(styrène sulfonate de sodium) afin d'obtenir des surfaces implantaires dotées de propriétés inhibitrices de l'adhérence de bactéries pathogènes de la flore buccale. Le greffage du poly(styrène sulfonate de sodium) sur le titane est réalisé en deux étapes : oxydation chimique du titane pour créer des espèces actives, puis greffage du poly(styrène sulfonate de sodium) par voie radicalaire. La caractérisation chimique des surfaces est réalisée par spectroscopie infrarouge à transformée de Fourier. L'adhérence bactérienne a été étudiée sur les surfaces de titane greffées et non greffées (titane contrôle), préadsorbées ou non de protéines plasmatiques. L'adsorption protéique et le comptage des bactéries sont suivis par marquage des protéines et des bactéries à la fluorescéine puis quantification par analyse d'images. Les résultats montrent que l'adsorption protéique est plus importante (~3 fois) et l'adhérence de P. gingivalis est fortement inhibée (~73 %) sur les surfaces greffées de poly(styrène sulfonate de sodium) par comparaison au titane témoin non greffé. De plus, l'inhibition de l'adhérence bactérienne observée sur les surfaces greffées et préadsorbées de protéines du plasma est comparable à celle observée sur les surfaces préadsorbées de fibronectine. En conclusion, les résultats obtenus montrent que la modification de la surface du titane par greffage poly(styrène sulfonate de sodium) conduit à une inhibition significative de l'adhérence de P. gingivalis et que cette activité inhibitrice de l'adhérence bactérienne implique l'adsorption protéique. Ces surfaces de titane greffées présentent un intérêt évident en application clinique dentaire pour le revêtement des implants. Dental implant-associated infections as peri-implantitis represent one of the major causes of osteointegration failures of oral implants. Adhesion of Porphyromonas gingivalis, one of the bacterial strains mainly involved in such infections, is tightly dependent on the topographical and/or physico-chemical properties of the implant surfaces. As a matter of fact, we showed that the grafting of one bioactive polymer such as poly(sodium styrene sulfonate) onto titanium implant surfaces allowed a sensitive decrease of Staphylococcus aureus adhesion (> 40%). The aim of the study consists in evaluating the adhesion of P. gingivalis onto titanium surfaces grafted with poly(sodium stryrene sulfonate) in order to elaborate implants exhibiting appropriate inhibiting properties towards the adhesion of periodontal pathogens. The grafting of poly(sodium stryrene sulfonate) onto titanium surfaces is carried out in two steps: chemical oxydation of titanium to initiate radical species then grafting of poly(sodium stryrene sulfonate) by radical polymerization. Chemical characterization of the surfaces is achieved by Fourier transformed infrared spectroscopy (FTIR). Bacterial adhesion was studied on grafted and non grafted (control) titanium surfaces, preadsorbed or not by plasmatic proteins. Protein adsorption as well as bacteria adhesion is followed by fluorescence spectroscopy by using proteins or bacteria previously labelled with fluorescence probes; the quantification of adsorption and bacteria adhesion are performed by image analysis. Results showed that protein adsorption is more important (~3 times) and that P. gingivalis adhesion is strongly inhibited (~73%) onto poly(sodium styrene sulfonate) grafted surfaces when compared to titanium control. Moreover, the inhibition of bacterial adhesion on grafted surfaces preadsorbed with plasma proteins is comparable to that observed on grafted surfaces preadsorbed with fibronectin. In conclusion, the obtained results evidenced that the grafting of titanium surface by poly(sodium styrene sulfonate) led to significant inhibition of P. gingivalis adhesion and that this inhibitory activity involved adsorbed proteins. Poly(sodium styrene sulfonate) grafted titanium surfaces present a high interest for the elaboration of oral implants in various clinical dental applications

New antitumor agent: In vitro activity on breast carcinoma cells

1 - ArticlePrevious work showed that established interactions between water-soluble polymers and cell membrane receptors can lead to modulate cell proliferation and differentiation in vitro. These polymers can be considered as bioactive. The aim of this work was to establish the consequences of the interactions between human breast cancer cells MCF7 and polymers of various chemical compositions regarding cell adhesion and proliferation onto tissue culture plate. Water soluble copolymers were synthesized by radical polymerization and are composed of methacrylic acid and sodium styrene sulphonate units. The modulation of the MCF7, biological-induced by these polymers of various compositions, was evaluated. The influence of the polymers chemical composition on the kinetics of cell proliferation, as well as cell morphology and spreading, were studied. A polymer concentration-dependent inhibition effect was observed. One hundred microgram per liter polymers solutions induced strong inhibition of cell proliferation, as well as a change of the MCF7 cells morphology, which can be related to an inhibition of cell spreading. The polymers/MCF7 cells interactions are modulated by the chemical composition of the copolymers and then the respective rate in sulphonate and carboxylate groups distributed along the macromolecular chain

Inhibition of Staphylococcus epidermidis adhesion on titanium surface with bioactive water-soluble copolymers bearing sulfonate, phosphate or carboxylate functions

1 - ArticleImplanted prostheses are sometimes subject to bacterial infections, which can threat their benefit rule on a long-term basis. Various methods are studied to fight against these infections. Among them, the grafting of bioactive polymers onto the prosthesis surface shows up as a promising way to the problem of infections. This work presents the influence of various water-soluble bioactive polymers on the inhibition of the Staphylococcus epidermidis adhesion on the titanium samples surfaces initially preadsorbed with various proteins. Whatever the studied protein is, it is shown that the bioactive polymer containing sulfonate functions generates an inhibition of the adhesion of Staphylococcus epidermidis. For a plasma preadsorption, the inhibition rate rises up to 68% when the concentration of sulfonate function is 2.5 mu mol/L. Titanium surfaces grafted with the bioactive polymer were also tested. We find an inhibitive activity of the adhesion close to that of the previous case. These preliminary results can point up a clinical interest in the fight against the medical devices infection, because they highlight a clear local effect of S. epidermidis adhesion inhibition. Copolymers containing other functional groups (phosphate or carboxylate) were dissolved in a bacterial suspension to monitor the influence of the composition on the adhesion inhibition. Their inhibition rates are not significantly lower than those of pNaSS homopolymers, as much as the sulfonate function proportion remains higher than 50%. Thus, the sulfonate function is the main responsible for the inhibition of the S. epiderrnidis adhesion. (C) 2010 Elsevier Masson SAS. All rights reserved

Observation de ligaments artificiels de genou après implantation en MEB à pression variable

1 - ArticleRésuméObjectifs Comparer deux techniques de préparation d'échantillons pour l'observation en microscopie électronique à balayage à pression variable (MEB-PV) afin d'évaluer la colonisation cellulaire et tissulaire de ligaments artificiels explantés.Matériels et méthodes Des ligaments artificiels en PET et PET greffé par un polymère bioactif, le poly(styrène sulfonate de sodium) ont été implantés dans le genou de quatre brebis après section du ligament croisé antérieur (LCA) puis explantés trois mois plus tard. L'évaluation qualitative de la colonisation cellulaire et tissulaire des ligaments artificiels a été réalisée sur des explants séchés (MEB-PV) ou non (MEB-PV-Peltier) au point critique.Résultats et discussion Les deux techniques évaluées ont permis de mettre en évidence des différences dans la bio-intégration des deux types de ligaments étudiés. Seule la technique MEB-VP-Peltier a permis l'obtention d'images d'excellente définition à fort grossissement se montrant à ce titre très intéressante pour l'évaluation qualitative rapide de l'intégration cellulaire et tissulaire des ligaments artificiels.Objectives We carried out a comparative study between two methods to prepare explanted artificial ligaments samples before their observation in the variable pressure scanning electron microscope (VP-SEM).Materials and methods Poly(ethylene terephtalate) (PET) artificial ligaments grafted by a bioactive polymer, the poly(sodium styrene sulfonate) were implanted for three months in the knee of four ewes after section of the anterior cruciate ligament (ACL). The qualitative evaluation of the cellular and tissue colonization of the artificial ligaments was carried out on critical point-dried explants (observed by VP-SEM) or not (observed by VP-SEM-Peltier).Results and discussion The results showed differences in the biointegration of the two types of studied ligaments. Only the MEB-VP-Peltier technique allowed obtaining images of excellent resolution with high magnification. For this reason the MEB-VP-Peltier technique is a promising method for the fast qualitative evaluation of the cellular and tissue integration of the artificial ligaments

Oxidative Stress Regulation on Endothelial Cells by Hydrophilic Astaxanthin Complex: Chemical, Biological, and Molecular Antioxidant Activity Evaluation

An imbalance in the reactive oxygen species (ROS) homeostasis is involved in the pathogenesis of oxidative stress-related diseases. Astaxanthin, a xanthophyll carotenoid with high antioxidant capacities, has been shown to prevent the first stages of oxidative stress. Here, we evaluate the antioxidant capacities of astaxanthin included within hydroxypropyl-beta-cyclodextrin (CD-A) to directly and indirectly reduce the induced ROS production. First, chemical methods were used to corroborate the preservation of astaxanthin antioxidant abilities after inclusion. Next, antioxidant scavenging properties of CD-A to inhibit the cellular and mitochondrial ROS by reducing the disturbance in the redox state of the cell and the infiltration of lipid peroxidation radicals were evaluated. Finally, the activation of endogenous antioxidant PTEN/AKT, Nrf2/HO-1, and NQOI gene and protein expression supported the protective effect of CD-A complex on human endothelial cells under stress conditions. Moreover, a nontoxic effect on HUVEC was registered after CD-A complex supplementation. The results reported here illustrate the need to continue exploring the interesting properties of this hydrophilic antioxidant complex to assist endogenous systems to counteract the ROS impact on the induction of cellular oxidative stress state

In vivo and in vitro studies of corn and potato starch thermoplastic materials for biomedical applications

National audienc

Bone tissue response to titanium implant surfaces modified with carboxylate and sulfonate groups

1 - ArticleThe present study assessed in vivo new bone formation around titanium alloy implants chemically grafted with macromolecules bearing ionic sulfonate and/or carboxylate groups. Unmodified and grafted Ti-6Al-4V exhibiting either 100% carboxylate, or 100% sulfonate, or both carboxylate and sulfonate groups in the percent of 50/50 and 80/20 were bilaterally implanted into rabbit femoral condyle. Neither toxicity nor inflammation were observed for all implants tested. After 4 weeks, peri-implant new bone formation varied as a function of the chemical composition of the titanium surfaces. The percent bone-implant contact (BIC) was the lowest (13.4 +/- A 6.3%) for the implants modified with grafted carboxylate only. The value of BIC on the implants with 20% sulfonate (24.6 +/- A 5.2%) was significantly (P < 0.05) lower than that observed on 100% sulfonate (38.2 +/- A 13.2%) surfaces. After both 4 and 12 weeks post-implantation, the BIC value for implants with more than 50% sulfonate was similar to that obtained with the unmodified Ti-6Al-4V. The grafted titanium alloy exhibiting either 100% sulfonate or carboxylate and sulfonate (50% each) groups promoted bone formation. Such materials are of clinical interest because, they do not promote bacteria adhesion but, they support new bone formation, a condition which can lead to osseointegration of bone implants while preventing peri-implant infections

Intracellular delivery of natural antioxidants via hyaluronan nanohydrogels

Natural antioxidants, such as astaxanthin (AX), resveratrol (RV) and curcumin (CU), are bioactive molecules that show a number of therapeutic effects. However, their applications are remarkably limited by their poor water solubility, physico-chemical instability and low bioavailability. In the present work, it is shown that self-assembled hyaluronan (HA)-based nanohydrogels (NHs) are taken up by endothelial cells (Human Umbilical Vein Endothelial Cells, HUVECs), preferentially accumulating in the perinuclear area of oxidatively stressed HUVECs, as evidenced by flow cytometry and confocal microscopy analyses. Furthermore, NHs are able to physically entrap and to significantly enhance the apparent water solubility of AX, RV and CU in aqueous media. AX/NHs, RV/NHs and CU/NHs systems showed good hydrodynamic diameters (287, 214 and 267 nm, respectively), suitable ζ-potential values (−45, −43 and −37 mV, respectively) and the capability to neutralise reactive oxygen species (ROS) in tube. AX/NHs system was also able to neutralise ROS in vitro and did not show any toxicity against HUVECs. This research suggests that HA-based NHs can represent a kind of nano-carrier suitable for the intracellular delivery of antioxidant agents, for the treatment of oxidative stress in endothelial cells

Bioactive poly(ethylene terephthalate) fibers and fabrics: Grafting, chemical characterization, and biological assessment

1 - ArticleThe grafting of poly(sodium styrene sulfonate) (pNaSS) onto ozone-treated poly(ethylene terephthalate) (PET) fabric surfaces was characterized by X-ray photoelectron spectroscopy and toluidine blue, colorimetry. Significant amounts of pNaSS were grafted over the range of experimental conditions examined in this study (30-120 min of ozonation, reaction at 65 or 70 degrees C, and reaction times up to 240 min). Within these ranges the amount of grafted pNaSS increased with both ozonation time and reaction temperature. The amount of grafted pNaSS increased over the first 60 min of reaction, then remained relatively constant from 60 to 240 min. For the biological experiments pNaSS-grafted samples were prepared with 30 min of ozonation and 60 min of reaction at a grafting temperature of 70 degrees C. The ozonation time was limited to 30 min to minimize any possible degradation of the PET fabrics by the ozonation treatment. The pNaSS-grafted PET surface adsorbed a factor of 4 more compared to the nongrafted surfaces. The strength of fibroblast adhesion was an order of magnitude higher on pNaSS-grafted PET fabrics compared to that on nongrafted PET fabrics. This. difference in the cell attachment was correlated to the cell spreading, which was better and more homogeneous on the grafted fibers compared to the nongrafted fibers. Fibroblasts adhered more strongly on surfaces precoated with normal human plasma compared to surfaces precoated with 10% fetal calf serum in Dulbecco's modified Eagle's medium

Shape-memory starch for resorbable biomedical devices

International audienceShape-memory resorbable materials were obtained by extrusion-cooking of potato starch with 20% glycerol under usual conditions. They presented an efficient shape-memory with a high recovery ratio (Rr > 90%).Their recovery could be triggered at 37 C in water. After water immersion at 37 C, the modulus decreased from 1 GPa to 2.4 MPa and remained almost constant over 21 days. Gamma-ray sterilization did not have a dramatic impact on their mechanical properties, despite a large decrease of molecular mass analyzed by asymmetrical flow field-flow fractionation coupled with multi-angle laser light scattering (AFFFF-MALLS). Samples implanted in a rat model exhibited normal tissue integration with a low inflammatory response. Thus, as previously investigated in the case of shape-memory synthetic polymers, natural starch, without chemical grafting, can now be considered for manufacturing innovative biodegradable devices for less-invasive surgery. (C) 2013 Elsevier Ltd. All rights reserved