Biomedical subjects

Isabelle Bertholon

Publications and source records attributed to Isabelle Bertholon.

3 recordsLinked to original sources

PubMed2006

Properties of polysaccharides grafted on nanoparticles investigated by EPR.

The in vivo fate of nanoparticles developed as drug delivery systems is influenced by the surface characteristics of the colloidal particles. In the present work, surface characteristics of a series of poly(isobutylcyanoacrylate) nanoparticles prepared by redox radical emulsion polymerization with polysaccharides of different molecular weight and nature were characterized by EPR. To this aim, a spin label was grafted on the polysaccharide chains after synthesis of the nanoparticles. The percentage of label showing fast movements was evaluated from EPR spectra which were analyzed according to the Kivelson theory. The results showed that mobility depended on temperature, type, and molecular weight of the polysaccharides. Differences between nanoparticles appeared with low-molecular-weight polysaccharides, while over a defined molecular weight which depended on the nature of the polysaccharide, the spin label behaved almost the same way in the different types of nanoparticles. Paradoxically, the percentage of fast moving label was the highest when linked to the shortest chitosan, which was the most rigid polysaccharide tested in this study. Thus, it was concluded that the apparent mobility of the polysaccharide evaluated by the EPR method depended on the capacity of the polysaccharide chains to fold making possible hydrophobic interactions between the label and the nanoparticle core. The transition between the unfolded-folded regiment depended on the molecular weight and on the nature of the polysaccharide. Results of this study may be useful to improve the understanding of the nanoparticle interactions with blood proteins and complement which in turn influence the in vivo fate of nanoparticles used as drug delivery systems.

Cyanoacrylates↗

PubMed2006

Complement activation by core-shell poly(isobutylcyanoacrylate)-polysaccharide nanoparticles: influences of surface morphology, length, and type of polysaccharide.

PURPOSE: Biodistribution of intravenously administered nanoparticles depends on opsonization. The aim of this study was the evaluation of complement activation induced by nanoparticles coated with different polysaccharides. Influences of size and configuration of dextran, dextran sulfate, or chitosan bound onto nanoparticles were investigated. METHOD: Core-shell nanoparticles were prepared by redox radical or anionic polymerization of isobutylcyanoacrylate in the presence of polysaccharides. Conversion of C3 into C3b in serum incubated with nanoparticles was evaluated. RESULTS: Cleavage of C3 increased with size of dextran bound in "loops" configuration, whereas it decreased when dextran was bound in "brush." It was explained by an increasing steric repulsive effect of the brush, inducing poor accessibility to OH groups. The same trend was observed for chitosan-coated nanoparticles. Nanoparticles coated with a brush of chitosan activated the complement system lesser than nanoparticles coated with a brush of dextran. This was explained by an improved repelling effect. Dextran-sulfate-coated nanoparticles induced a low cleavage of C3 whereas it strongly enhanced protein adsorption. CONCLUSION: Complement activation was highly sensitive to surface features of the nanoparticles. Type of polysaccharide, configuration on the surface, and accessibility to reactive functions along chains are critical parameters for complement activation.

Chitosan↗

PubMedDate not supplied

Bioadhesive properties of poly(alkylcyanoacrylate) nanoparticles coated with polysaccharide.

Development of bioadhesive nanoparticles is of great interest to improve drug absorption through the intestinal barrier. Various Polysaccharide-coated poly(alkylcyanoacrylate) nanoparticles were prepared. The bioadhesive properties of the nanoparticles coated with dextran or chitosan in end-on or side-on conformation were evaluated with an ex-vivo adsorption experiment on rat intestine. Results show that diffusion of nanoparticles in mucus layer was governed by the nanoparticle diameter and isotherms of adsorption were influenced by the nature of polysaccharide used. High amount of nanoparticles coated with chitosan can be entrapped in the mucus layer even at low nanoparticle concentration in suspension. When nanoparticle concentration increased, a pseudo-plateau was reached. In the case of dextran-coated nanoparticles, linear increase of adsorption was observed and no saturation phenomenon was highlighted over the range of nanoparticle concentration used in this study. These results suggested that interactions involved in bioadhesion mechanism depended on the nature of polysaccharide. Electrostatic interactions are enhanced between chitosan-coated nanoparticles and glycoproteins of mucus leading to a saturated adsorption phenomenon whereas dextran-coated nanoparticles interacted by non-electrostatic interactions with mucus resulting in a non-saturated phenomenon. Polysaccharides grafted at the nanoparticle surface in the brush conformation appeared more favorable to promote interactions of nanoparticles with glycoproteins of mucus in comparison with the more compact loop conformation of polysaccharide chains.

Adhesiveness↗