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Thiols are very important molecules in the biomedical field involved for example in redox homeostasis. Their detection and quantification remain difficult due to their poor stability (oxidation) linked to their strong reactivity towards other thiols (by the formation of S-S bonds) or other interfering molecules in the medium. Cellulose membranes with immobilized gold nanoparticles (AuNP) were developed to capture and quantify thiols in simple and complex matrices. This device was first optimized and characterized in terms of nanostructuration and thiol adsorption. N-Acetylcysteine (NAC) and reduced glutathione (GSH), chosen as model molecules, were filtered through the device demonstrating a maximal adsorption capacity of 270 and 60 nmol respectively. In a second step, the adsorbed species were subjected to ligand exchange using a more reactive thiol, dithiothreitol. The results showed release rates of approximately 90% for NAC and GSH. Finally, the amount of endogenous GSH in rat plasma was determined without any pretreatment. For the first time to our knowledge, a nanostructured device for the capture, selective and sensitive quantification of thiols is proposed. This device is easy to handle and overcomes matrix effects. Moreover, the very large concentration factor induced by this technology will be a valuable asset to decrease the quantification limits of analytical methods.

International audience; Gold nanoparticle (AuNP) interaction with the blood compartment as a function of their charge and the binding energy of their surface ligand was explored. Citrate, polyallylamine and cysteamine stabilized AuNP along with dihydrolipoic acid and polyethylene glycol capped AuNP were synthesized and fully characterized. Their interactions with model proteins (human albumin and human fibrinogen) were studied. Complexes formed between AuNP and protein revealed several behaviors ranging from corona formation to aggregation. Protein fluorescence quenching as a function of temperature and AuNP concentration allowed the determination of the thermodynamic parameters describing these interactions. The hemolysis induced by AuNP was also probed: an increasing or a decreasing of hemolysis ratio induced by AuNP was observed as of function of protein corona formation. Taken together, our results drew up a composite sketch of an ideal surface ligand for blood compatible AuNP. This capping agent should be strongly bound to the gold core by one or more thiol groups and it must confer a negative charge to the particles.

Introduction Alors que le systeme immunitaire adaptatif tolere naturellement les antigenes du soi, plusieurs etudes recentes suggerent qu’il est capable de reagir au peptide amyloide Aβ, aussi bien dans des modeles animaux transgeniques qu’au cours de la maladie d’Alzheimer humaine. Ainsi, des methodes d’immunisation classiques induisent des reponses ayant un effet sur le plan pathologique et eventuellement clinique. La mise au point de vaccins therapeutiques s’avere cependant difficile car les reponses cellulaires T peuvent se compliquer de meningoencephalites graves. Par ailleurs, si les anticorps anti-Aβ seuls semblent efficaces contre l’accumulation des plaques seniles, leur effet therapeutique clinique est moins certain. Dans l’ensemble, il apparait indispensable de mieux connaitre les relations entre le systeme immunitaire et le peptide Aβ pour concevoir des approches immunotherapeutiques efficaces et sures. Un interet particulier a ete porte aux cellules T regulatrices (Treg), responsables des principaux mecanismes de la tolerance immunitaire peripherique. Materiel & methodes Des souris C57BL/6 sauvages ou doubles transgeniques APPPS1 (APP K670N/M671L et PS-1 L166P) ont ete traitees ou non a l’âge de 8 ou 16 semaines par un anticorps anti-CD25 (PC61) pour depleter de facon transitoire les Treg. L’effet de cette depletion sur l’activation des reponses T CD4+ anti-Aβ a ete analyse apres vaccination par Aβ42 en presence d’adjuvant complet de Freund. En parallele, l’impact de la depletion des Treg sur l’evolution naturelle de la maladie a ete etudie par analyses histologiques et comportementales sur un groupe de souris APPPS1 traitees ou non par PC61 mais non-vaccinees. Resultats Apres suppression des Treg les reponses proliferatives T CD4+ anti-Aβ post-vaccinales sont plus augmentees chez les souris transgeniques APPPS1 que chez les souris sauvages. D’autre part, nos resultats preliminaires suggerent que la tolerance due aux cellules Treg peut favoriser la progression des signes pathologiques. Discussion Les cellules Treg inhibent les reponses T CD4+ anti-Aβ se developpant spontanement au cours de la maladie, et pourraient ainsi contribuer a la physiopathologie de la maladie d’Alzheimer. La depletion des cellules T regulatrices represente donc un outil therapeutique potentiel, sous reserve que les reponses immunitaires chez l’homme soient semblables a celles du modele murin APPPS1. Des travaux recents vont dans ce sens, montrant que les reponses immunitaires adaptatives contribueraient au controle des depots amyloides.