Mannosylated amphiphilic and degradable PEO-b-PCL copolymers for drug delivery systems: preparation and sugar availability characterizations

Over the last decade, polymer micelles and nanoparticles attracted an increasing interest in pharmaceutical research because they can be used as efficient drug delivery systems. In this field, amphiphilic copolymers combining poly(ethylene oxide) and aliphatic polyester (such as poly(ε-caprolactone) (PCL) or polylactide (PLA)) are particularly of interest because (i) PEO has unique protein- repellent properties and thus provides a stealth behaviour to the drug carriers and (ii) aliphatic polyesters are biocompatible and biodegradable hydrophobic matrices well-suited for the incorporation of an hydrophobic drug. By end-capping the hydrophilic segment by a targeting moiety so that they may interact with membrane receptors, the biodistribution of polymeric micelles and nanoparticles stabilized with this copolymer can be modulated and can induce specific cellular uptake by receptor-mediated endocytosis. One class of interesting targeting agent is the saccharides, in particular the mannose, because of its specific interaction with mannose receptor, which are found on peripheral and bone marrow macrophages, dendritic cells and sinusoidal liver cells. In this study, the reductive amination reaction is use to attach this targeting agent. After optimisation of the reaction with amino fluorescein, a model amine, mannosylated copolymer of PEO and PCL has been prepared. The surface availability of the saccharide upon the micelles in aqueous phosphate buffer was then assessed by DLS through binding with the protein Concanavalin A (ConA), a known mannose receptor. The interactions between the Bcla lectin and the mannosylated micelles have then been studied by Isothermal Titration Calorimetry (ITC) and the thermodynamic parameters have been obtained. This polymer is particularly useful for the stabilization of PLGA nanoparticles with the goal to target M cells for oral vaccination

Caractérisation biochimique et structurale des tagatose-1,6-bisphosphate aldolases de classe I d’origine procaryotique

La réaction d’addition catalysée par la D-tagatose-1,6-bisphosphate aldolase (TBPA) de classe I n’est pas spécifique. A partir du dihydroxyacétone phosphate et du D-glycéraldéhyde-3-phosphate, la TBPA génère quatre D-cétohexoses-1,6-bisphosphate qui diffèrent au niveau des carbones 3 et 4 : D-tagatose-1,6-bisphosphate, D-fructose-1,6-bisphosphate, D-psicose-1,6-bisphosphate et D-sorbose-1,6-bisphosphate. Dans le cadre de ce travail, nous contribuons à la compréhension du contrôle stéréochimique de cette enzyme en identifiant des acides aminés impliqués dans sa spécificité. Pour ce faire, une analyse in silico a été réalisée afin de sélectionner des TBPA présentant des particularités dans le site actif. Des alignements de séquences montrent que la lysine à la position 125, décrite comme importante pour la catalyse, est remplacée par une arginine dans une seule TBPA : celle de Streptococcus porcinus. Les paramètres cinétiques révèlent que cette arginine entraine un changement de spécificité en faveur du D-tagatose-1,6-bisphosphate alors que la lysine correspondante est importante pour une spécificité élargie. Cependant, l’arginine diminue fortement l’activité de clivage et de formation des D-cétohexoses-1,6-bisphosphate. La détermination de la structure par cristallographie des rayons-X aide à comprendre le rôle de l’arginine dans la TBPA de S. porcinus. Finalement, des études HPLC révèlent que toutes les TBPA synthétisent principalement du D-tagatose-1,6-bisphosphate et du D-fructose-1,6-bisphosphate.Caractérisation biochimique et structurale des tagatose-1,6-bisphosphate aldolases de classe I d’origine procaryotiqu

Clickable PEG conjugate obtained by ‘‘clip’’ photochemistry: Synthesis and

In this paper, we describe a grafting methodology associated to a quantitative 19F NMR method (qNMR) for the conjugation of small molecules on a PEG building block aimed at click chemistry applications in the domain of drug delivery systems. Acetylenic PEG (PEG-yne) was first derivatized with a fluorinated benzyl amine (TagF6) by means of photografting of a trifluoromethylphenyl diazirine bifunctional linker (TPD-clip). The amount of TagF6 grafted on PEG-yne was calculated by NMR using an internal standard (trifluoroethanol) and adjusting of the acquisition and processing parameters. NMR is used as a valuable alternative to the complex procedures often employed for the quantification of functionalities on biomaterials. The accuracy of the qNMR methodology was attested by controlling its linearity, the determination of limits of quantification and the percentage of recovery. A good assessment of the TagF6 grafting rates was obtained after taking into account the inherent unspecific adsorption that occurs on materials. This versatile methodology that combines simple chemistry and a common analytical tool was, in a second time, applied to the preparation of a PEG conjugated with a RGD (Arg-Gly-Asp) peptidomimetic in a controlled manner

Sugar-labeled and PEGylated (bio)degradable polymers intended for targeted drug delivery systems

This paper aims at giving a comprehensive view of the research effort devoted to the preparation of sugar coated long-circulating degradable polymers intended for drug delivery applications. In the recent past, many research projects have focused on the controlled drug delivery and, therefore, on the design of drug carriers. Among them, polymeric carriers have great potential because they can be chemically modified to a large extent and so endowed with specific properties. For instance, depending on the selected polymer, either the circulation time in the bloodstream can be increased very significantly (long-circulating polymer) or the drug carrier can be completely degraded after administration. Moreover, active targeting, i.e., carriers bearing a ligand known for specific affinity for one tissue, has emerged as a method of choice in targeting the delivery of drugs. This concept is of the utmost importance because the large variety of receptors present in the body makes the selective targeting a must in order to prevent any healthy tissue from being damaged irreversibly. The purpose of this paper is to emphasize that carbohydrates are very promising pilot molecules for the next generation of drug deliver