Mise en forme d'un biomatériau par auto-assemblage colloïdal : modification de surface de nanoparticules à base d'hydrogel par un copolymère à blocs thermosensible

Les progrès réalisés dans le domaine de la médecine régénérative sont intimement liés à la conception de nouveaux biomatériaux répondant à des cahiers des charges spécifiques. Les biomatériaux doivent maintenir l'intégrité du tissu sain environnant et être facilement implantés ou injectés chez les patients. Dans ce contexte, les biomatériaux à base de particules colloïdales thermosensibles sont très prometteurs car ils peuvent être injectés et, en réponse à un stimulus comme la température du corps, s'auto-assembler au niveau du site d'injection pour une application localisée. Nous proposons une stratégie innovante de mise en forme d'un biomatériau par auto-assemblage colloïdal : une modification de surface de nanoparticules à base d'hydrogel par un copolymère thermosensible qui permettrait un auto-assemblage thermo-induit. L'objectif de la thèse est de répondre à la problématique suivante : est-ce que la modification de surface des particules par un copolymère thermosensible leur apporte des propriétés d'auto-assemblage thermo-induit ? Dans un premier temps, le copolymère pH- et thermosensible PVAm-b-PNIPAM a été synthétisé et caractérisé dans le but de mettre en évidence l'influence du caractère pH-sensible du copolymère sur sa thermosensibilité et les conséquences sur l'auto-assemblage du copolymère en solution. Cette étude a permis de mettre au point des conditions de greffage du copolymère à la surface de nanoparticules composites cœur-couronne SiNP@CS/ALG, composées d'un cœur de silice recouvert d'un assemblage multicouche d'hydrogel de polyélectrolytes naturels, le chitosane et l'alginate et de diamètre hydrodynamique d'environ 500 nm. La modification de surface des nanoparticules a été caractérisée, la présence du copolymère thermosensible a été mise en évidence par RMN 1H et par XPS et quantifiée par spectrofluorimétrie. Enfin, l'évaluation des propriétés thermosensibles des nanoparticules modifiées en suspension a permis de montrer une déstabilisation de la suspension lorsque la température est élevée au-delà de la température critique du copolymère thermosensible. Ce résultat confirme l'intérêt d'un tel système thermosensible pour des applications biomédicales.Progress in regenerative medicine is closely related to the elaboration of new biomaterial tailored to suit certain specifications. Biomaterials are expected to maintain and/or restore the healthy tissu's function and be easily implanted into patients. In this context, thermosensitive nanoparticles-based biomaterials are promising as they can be injected and, in response to a stimulus such as body temperature, they undergo in-situ self-assembly. We proposed an innovative strategy aiming at the design of a biomaterial by colloidal self-assembly based on the surface modification of hydrogel-based nanoparticles with a thermoresponsive copolymer. This work objective is to answer the following question: does surface modification of nanoparticles with a thermoresponsive copolymer induce to the particles thermosensitive properties? First, pH- and thermoresponsive copolymer PVAm-b-PNIPAM was synthetized and characterized to study its physico-chemical properties in aqueous medium, including its critical temperature and self-assembly properties. Hydrogel-based core/shell particles with diameter of around 500 nm were obtained by the layer-by-layer assembly of two natural polyelectrolytes, chitosan and alginate, coated onto silica core. Surface modification was characterized, 1H NMR and XPS confirmed the copolymer's presence onto the particles surface and a quantification was carried out by spectrofluorimetry. Finally, thermosensitive properties of the modified nanoparticles suspension was investigated and showed that a rise of temperature above the copolymer's critical temperature induced the destabilization of the suspension. This result answered positively to the problematic and confirmed the interest of such system for biomedical applications

Experimental Infection of Ticks: An Essential Tool for the Analysis of Babesia Species Biology and Transmission

International audienceBabesiosis is one of the most important tick-borne diseases in veterinary health, impacting mainly cattle, equidae, and canidae, and limiting the development of livestock industries worldwide. In humans, babesiosis is considered to be an emerging disease mostly due to Babesia divergens in Europe and Babesia microti in America. Despite this importance, our knowledge of Babesia sp. transmission by ticks is incomplete. The complexity of vectorial systems involving the vector, vertebrate host, and pathogen, as well as the complex feeding biology of ticks, may be part of the reason for the existing gaps in our knowledge. Indeed, this complexity renders the implementation of experimental systems that are as close as possible to natural conditions and allowing the study of tick-host-parasite interactions, quite difficult. However, it is unlikely that the development of more effective and sustainable control measures against babesiosis will emerge unless significant progress can be made in understanding this tripartite relationship. The various methods used to date to achieve tick transmission of Babesia spp. of medical and veterinary importance under experimental conditions are reviewed and discussed here

Experimental Infection of Ticks: An Essential Tool for the Analysis of Babesia Species Biology and Transmission

Babesiosis is one of the most important tick-borne diseases in veterinary health, impacting mainly cattle, equidae, and canidae, and limiting the development of livestock industries worldwide. In humans, babesiosis is considered to be an emerging disease mostly due to Babesia divergens in Europe and Babesia microti in America. Despite this importance, our knowledge of Babesia sp. transmission by ticks is incomplete. The complexity of vectorial systems involving the vector, vertebrate host, and pathogen, as well as the complex feeding biology of ticks, may be part of the reason for the existing gaps in our knowledge. Indeed, this complexity renders the implementation of experimental systems that are as close as possible to natural conditions and allowing the study of tick-host-parasite interactions, quite difficult. However, it is unlikely that the development of more effective and sustainable control measures against babesiosis will emerge unless significant progress can be made in understanding this tripartite relationship. The various methods used to date to achieve tick transmission of Babesia spp. of medical and veterinary importance under experimental conditions are reviewed and discussed here

Meal size and energy costs of digestion: insights from an omnivorous non-human primate (Microcebus murinus)

International audienc

Ajustement du budget énergétique à la contrainte alimentaire chez un primate frugivore (Microcebus murinus)

International audienc

A deeper insight into the dual temperature- and pH-responsiveness of poly(vinylamine)-b-poly(N-isopropylacrylamide) double hydrophilic block copolymers

International audienceBlock copolymers based on poly(vinylamine) and poly(N-isopropylacrylamide), PVAmm-b-PNIPAMn, were synthetized by hydrazinolysis of poly(N-vinylphthalimide) based copolymers, PVPIm-b-PNIPAMn, obtained by RAFT polymerization. The effect of molar mass and pH on the thermoresponsive and aggregation properties of these polymers in aqueous solution was studied with UV–vis spectroscopy, differential scanning calorimetry, NMR spectrometry, light and X-ray scattering experiments. For the first time it was demonstrated that at room temperature, these copolymers are prone to self-assemble and tend to form larger aggregates upon heating. Hence core-shell nanostructures with a dense PNIPAM core and a hydrophilic PVAm shell, were notably observed above Tc when pH < pKa

Spatial and Temporal Circulation of <i>Babesia caballi</i> and <i>Theileria equi</i> in France Based on Seven Years of Serological Data

Caused by two blood parasites, Babesia caballi and Theileria equi, equine piroplasmosis is a tick-borne disease that poses major health and economic issues for the equine industry. Our objective was to gain insight into the spatio-temporal variations of parasite circulation in France, where the disease is known to be enzootic, but has been the subject of few studies. Seroprevalence was assessed for each parasite thanks to 16,127 equine sera obtained between 1997 and 2003 from all over France and analysed through complement fixation tests. Results indicated that 13.2% (5–27% depending on the region) of horses were seropositive for T. equi and 9.5% (3–25%) for B. caballi. Regardless of the year, horses from the southern regions of France were the most affected by B. caballi or T. equi infection, while the proportion of horses having antibodies against T. equi increased over time. These results highlight the heterogeneity of the circulation of both piroplasms, which may be linked with ecological diversity and vector distribution. Our data provide baseline information regarding the sero-epidemiology of B. caballi and T. equi infection in horses in France, making it now possible to select regions for future studies on risk factors, and design and implement effective targeted measures against equine piroplasms

RAFT Polymerization of N -Methyl- N -vinylacetamide and Related Double Hydrophilic Block Copolymers

International audienc

Polymer/silica core–shell nanoparticles with temperature-dependent stability properties

International audienc

Protein sustained release from isobutyramide-grafted stellate mesoporous silica nanoparticles

International audienceProteins are great therapeutic candidates as endogenous biomolecules providing a wide range of applications. However, their delivery suffers from some limitations and specifically designed delivery systems having an efficient protein anchoring and delivery strategy are still needed. In this work, we propose to combine large pore stellate mesoporous silica (STMS) with isobutyramide (IBAM), as a "glue" molecule which has been shown promising for immobilization of various biomacromolecules at silica surface. We address here for the first time the ability of such IBAM-modified NPs to sustainably deliver proteins over a prolonged time. In this work, a quantitative loading study of proteins (serum albumin (HSA), peroxidase (HRP), immunoglobulin (IgG) and polylysine (PLL)) on STMS@IBAM is first presented using three complementary detection techniques to ensure precision and avoid protein quantification issues. The results demonstrated a high loading capacity for HSA and HRP (≥ ca. 350 μg.mg-1) but a moderate one for IgG and PLL. After evaluating the physicochemical properties of the loaded particles and their stability over scaling-up and washings, the ability of STMS@IBAM to release proteins over prolonged time was evaluated in equilibrium (static) and flow mimicking (dynamic) conditions and at different temperatures (25, 37, 45 °C). Results show not only the potential of such "glue" functionalized STMS to release proteins in a sustained way, but also the retention of the biological activity of immobilized and released HRP, used as an enzyme model. Finally, an AFM-force spectroscopy study was conducted to decipher the interactions between IBAM and proteins, showing the involvement of different interactions in the adsorption and release processes