Chimie

Alzheimer's disease is characterized by the presence of β-amyloid fibril formation. The inhibition of this peptide accumulation may be a prevention method for Alzheimer's disease. Several classes of molecules have been reported to inhibit β-amyloid fibril formation and among them carbazoles. However, very few studies have been performed to determine the destination of such molecules in vivo and especially if they can pass the blood brain barrier. The aim of this paper is to study whether carbazoles could pass the blood brain barrier, i.e. if they can circumvent ATP Binding Cassette (ABC) transporters such as P-glycoprotein (P-gp) and Multidrug Resistance-associated protein (MRP1) which efficiently limit drug brain uptake. For this purpose we have synthesized a fluorescent derivative of carbazole benzothiazolium iodide 1,2 disubstituted ethylene (referred as carbazole thiazole: CT), which can be easily detected and followed in the pre-trial study phases in cells or in tissue. We use cellular models overexpressing P-gp and MRP1. Our results show that: i) CT is able to cross membranes and to penetrate rapidly inside the cells, ii) CT is a P-gp substrate and consequently its accumulation in P-gp overexpressing cells is very low, iii) CT is a poor MRP1 substrate. In addition once inside the cells, CT rapidly binds to DNA and is then slowly reduced by intracellular reducing agents. In conclusion, the efficiency of carbazole derivatives in inhibiting the β-amyloid formation in vivo could be highly compromised because, as P-gp substrates, they will probably not cross the blood brain barrier.

Biomaterials-centered infections are serious complications associated with the use of implants. The infection risk of biomaterials varies between different materials and is determined by the chemical composition of materials, the host proteins and the type of bacteria. In this study we measured the initial adhesion of Sfaphy/ococcus aureus onto polystyrene derivatives containing carboxylate and sulfonate groups. Five polymers were synthesized and characterized. We studied the role of the host protein fibronectin in promoting adhesion of Staphylococcus aureus. Fibronectin adsorption was comparable on all the tested polymers (pKd=7.2*0.2) whereas bacterial adhesion was dependent on surfaces chemical compositions. Polymers substituted with sulfonate groups showed the most important inhibition of initial bacterial adhesion. 0 2002 Editions scientifiques et medicales Elsevier SAS bacterial adhesion I biomaterials / biomimetic polymers / fibronectin R&urn6 -Modulation de I'adhkrence de Sfaphylococcus aureus par des copolym&res biofonctionnels d&iv& du polystyr&ne. L'adhkrence des bact&ies 2 la surface des biomakkiaux implantables aboutit dans la plupart des cas B la colonisation, &ape prkkdant /'infection en pathologic humaine. Le risque d'infection dgpend de la composition chimique des biomatkriaux, des protkines adsorb&es g la surface de ces mat.&iaux et du type de micro-organisme. Dans cette Etude, nous avons Btudih et quantifib I'adhkrence de Staphylococcus aureus, un des principaux responsables de /'infection sur corps &ranger, sur des polymkres d&iv& du polystyrkne porteurs de groupes carboxylate et sulfonate. Cinq polym&es de compositions diffgrentes ont Bt6 synth@tis& et caract&is6s Le r&e de la fibronecfine en tant que prot&ne mkdiatrice de l'adhbrence bactkrienne a &S &al&. Les r&u/fats obtenus montrent que /'adsorption de la fibronectine radiomarquee est identique sur /es cinq polym&res (pKd = 7.2 k 0.2) alors que l'adhkrence de Staphylococcus aureus sur /es surfaces prkadsorbkes de fibronectine dkpend de la composition chimique du polymkre. La pksence des groupements sulfonate permet d'obtenir I'effet inhibiteur de I'adhkrence bactkienne le plus important. 0 2002 Editions scientifiques et medicales Elsevier SAS adherence bacterienne / biomateriaox / fibronectine I polymeres biomimetiques * Correspondence and reprints.

A major complication of intraocular lens surgery is diminished visual acuity caused by the regrowth of lens epithelial cells (secondary cataract). Polymethylmethacrylate (PMMA) is a commonly used intraocular lens material. This study addresses the mechanisms underlying the initial adhesion of lens epithelial cells to PMMA and a functionalized PMMA-based terpolymer known to inhibit cell proliferation. Rabbit lens epithelial cells were cultured on the test polymer surfaces in medium containing serum depleted of either fibronectin or vitronectin (or both) to identify the role of these proteins in the initial process of cell adhesion. Adherent cells were quantitated after 60 min, and the actin cytoskeleton and focal contact formation were compared in each serum treatment on both polymers. Vitronectin was significantly more effective for initial cell attachment to both polymers than fibronectin. Normal cell spreading on PMMA required vitronectin and was independent of fibronectin, whereas cell spreading on the terpolymer was abnormal and required the presence of fibronectin and vitronectin together. Together, these results help to explain the inhibition of cell proliferation previously shown on the functionalized PMMA. This work contributes to the design of a polymer for use in intraocular lenses that inhibits proliferation of the target cells.

It is known that protein adsorption is the initial interaction between implanted biomaterials and biological environment. Generally, a complex protein layer will be formed on material surfaces within a few minutes and the composition of this layer at the interface determines the biological response to the implanted material, and therefore the long-term compatibility of the biomaterial. Despite different techniques exist to observe protein adsorption on biomaterials, none of them led to the identification of adsorbed proteins. In this paper, we report a chromatographic technique coupled to proteomics to analyse and identify proteins from complex biological samples adsorbed on biomaterial surfaces. This approach is based on (1) elaboration of the chromatographic support containing the biomaterial (2) a chromatography step involving adsorption of proteins on the biomaterial (3) the high-resolution separation of eluted proteins by 2-DE gel and (4) the identification of proteins by mass spectrometry. Experiments were performed with proteins from platelets rich plasma (PRP) adsorbed on a biomaterial which consist in titanium bioactivated with PolyNaSS. Our results show that chromatographic approach combined to 2-DE gels and mass spectrometry provides a powerful tool for the analysis and identification of proteins adsorbed on various surfaces.

Biomaterial surface properties, via alterations in the adsorbed protein layer, and the presence of specific functional groups can influence integrin binding specificity, thereby modulating cell adhesion and differentiation processes. The adsorption of fibronectin, a protein directly involved in osteoblast adhesion to the extracellular matrix, has been related to different physical and chemical properties of biomaterial surfaces. This study used blasting particles of different sizes and chemical compositions to evaluate the response of MG63 osteoblast-like cells on smooth and blasted titanium surfaces, with and without fibronectin coatings, by means of real-time reverse transcription-polymerase chain reaction (qRT-PCR) assays. This response included (a) expression of the a 5 , a v and a 3 integrin subunits, which can bind to fibronectin through the RGD binding site, and (b) expression of alkaline phosphatase (ALP) and osteocalcin (OC) as cell-differentiation markers. ALP activity and synthesis of OC were also tested. Cells on SiC-blasted Ti surfaces expressed higher amounts of the a 5 mRNA gene than cells on Al 2 O 3 -blasted Ti surfaces. This may be related to the fact that SiC-blasted surfaces adsorbed higher amounts of fibronectin due to their higher surface free energy and therefore provided a higher number of specific cell-binding sites. Fn-coated Ti

Des travaux antérieurs ont montré que les interactions établies entre des polymères solubles et des récepteurs membranaires pouvaient moduler la prolifération et/ou la différenciation cellulaire in vitro. De ce fait, ces polymères peuvent être considérés comme bioactifs. Ce travail vise à établir les conséquences des interactions entre des cellules MCF7, cellules tumorales mammaires humaines et différents polymères solubles de composition variable sur la prolifération cellulaire, ainsi que sur la capacité d'adhésion cellulaire sur le support de culture. Ces polymères solubles en milieu physiologique sont synthétisés par voie radicalaire et composés d'unités acide méthacrylique et styrène sulfonate de sodium. Nous avons évalué la modulation de l'activité biologique des cellules MCF7 par ces polymères de compositions variables en groupements sulfonate et carboxylate. Les cinétiques de prolifération et l'analyse des aires d'étalement cellulaire ont été établies en fonction de la composition des polymères. Les résultats font apparaître une réponse dose-dépendante, une forte inhibition de la prolifération cellulaire induite par ces polymères solubles en milieu physiologique à des concentrations de 100 mg/mL et un changement de la morphologie des cellules MCF7 qui se traduit par une inhibition de l'étalement cellulaire. La nature des interactions polymères solubles/lignée cellulaire MCF7 varie avec la proportion en groupements sulfonate et carboxylate présents sur les chaînes macromoléculaires. # 2008 Elsevier Masson SAS. Tous droits réservés.