Hypercortisolisme infra-clinique dans le diabète de type 2

BORDEAUX2-BU Santé (330632101) / SudocPARIS-BIUM (751062103) / SudocSudocFranceF

Etude comparative et rétrospective du traitement de la maladie de Basedow par activité calculée et activité standard d'iode 131

BORDEAUX2-BU Santé (330632101) / SudocPARIS-BIUM (751062103) / SudocSudocFranceF

Evaluation de la mise en place d'un suivi médical et éducatif de la mesure continue du glucose dans la prise en charge du diabète de type 1 instable

BORDEAUX2-BU Santé (330632101) / SudocSudocFranceF

Nanogels de polysaccharides pour la délivrance d'insuline

Les nanogels sont de bons candidats pour la délivrance d actifs. Ces réseaux de polymères réticulés et de taille nanométrique, sont gonflés d eau. Ils sont donc capables d encapsuler une protéine à l intérieur de leurs pores et de la libérer en fonction de l état de gonflement du réseau. Cet état peut être modulé par la densité de réticulation du réseau ou par l application d un stimulus externe tel que le pH, la température ou encore une biomolécule telle que le glucose. Ainsi, les nanogels sensibles au glucose se présentent comme des candidats idéaux pour administrer l insuline de façon asservie à la glycémie. Afin de satisfaire aux critères de biocompatibilité et de biorésorption des vecteurs, nous avons choisi de développer des nanogels à base de polysaccharide, en particulier à base d acide hyaluronique (HA). Ceux-ci sont obtenus par réticulation du HA, préalablement modifié par des fonctions réticulables telles que les méthacrylates, dans des nanogouttes d'émulsion eau-dans-huile. Des nanogels de taille et de porosité modulables ont été synthétisés grâce à un bon contrôle 1) de la modification chimique des précurseurs par des fonctions réticulables (taux de méthacrylation), 2) de l émulsion matricielle (taille, stabilité), 3) des conditions de réticulation par photopolymérisation gouvernant le taux de conversion des méthacrylates. Ce savoir-faire a ensuite été appliqué à la synthèse de nanogels modifiés par des dérivés de l acide phénylboronique, ligand du glucose, afin d obtenir des matériaux dont le taux de gonflement varie en fonction de la glycémie. L intérêt applicatif de ces objets a été évalué vis-à-vis des propriétés d encapsulation de l insuline, de dégradabilité enzymatique, et de biocompatibilité.Nanogels are an attractive class of delivery systems. These soft particles, made of highly swollen polymer network, can physically entrap a drug and release it at a rate depending on its diffusion though the network. Therefore, any change in the swelling degree can trigger the release kinetics. This parameter can be tuned by modifying the density of cross-links in the gel matrix or by changing the environmental conditions such as pH, temperature or analyte such as glucose. Thus, glucose-responsive nanogels are good candidates to be used as self-regulated systems for insulin delivery. To fulfill both biocompatibility and biodegradability criteria, our attention has been focused on the design of new nanogels made of polysaccharides, in particular made of hyaluronic acid (HA), as a main constituent. HA was at first covalently modified with polymerizable methacrylate functions and confined in nanoreactors during photopolymerization using water-in-oil miniemulsions as template. Biodegradable nanogels with a well-defined size and various cross-linking degrees were thus achieved, thanks to a good control of 1) the chemical modification of HA with methacrylates (degree of methacrylation) 2) the emulsion template (size, stability), 3) the photopolymerization conditions which governed the conversion rate of the polymerization. Further modification of the polysaccharide with phenylboronic acid as a glucose-sensitive group yielded nanogels whose swelling behavior could vary as a function of glucose concentration. These systems were further studied as insulin delivery systems. Moreover, their biodegradability, stability and biocompatibility were assessed.BORDEAUX1-Bib.electronique (335229901) / SudocSudocFranceF

Microgels sensibles au glucose pour la delivrance d'insuline

Le traitement du diabète de type 1 en boucle fermée représente un enjeu majeur tant sur le plan sociétal que thérapeutique. L une des solutions consiste en une formulation thérapeutique basée sur des microvéhicules capables de délivrer la bonne dose d insuline selon une cinétique adaptée aux variations de la glycémie. Les microgels sont des particules de polymère réticulé formant des édifices submicrométriques tridimensionnels gonflés par un solvant, dont le taux de gonflement dépend des conditions environnementales. Leur porosité permet à la fois l encapsulation d espèces et leur libération à une vitesse dépendant de leur diffusion à travers le réseau. Nous avons synthétisé des microgels à base de poly(N-alkylacrylamide) fonctionnalisés par des récepteurs du glucose dérivés de l acide phénylboronique. Ces microgels, à la base thermosensibles, présentent la propriété de changer de volume en fonction de la concentration en glucose et se présentent comme d excellents candidats pour la délivrance auto-régulée d insuline dans le cadre du traitement du diabète. Ils permettent la délivrance répétée de doses d insuline modulée par la glycémie. La quantité d insuline encapsulée a pu être améliorée en structurant les microgels en architecture cœur-écorce ou capsule.En outre, nous avons utilisé ces microgels pour développer des capteurs au glucose, sélectifs vis-à-vis des autres saccharides et quelques études de cytotoxicité ont été amorcées et ont permis d établir avec satisfaction que certains de nos objets n étaient pas toxiques.Les résultats obtenus ont donc permis d affirmer que la technologie des microgels sensibles au glucose peut répondre de manière conceptuelle aux attentes des patients diabétiques pour permettre la délivrance d insuline en boucle fermée.Bioresponsive hydrogels can change many of their physical properties in response to the recognition of a target in the solution. In particular, changes in hydrogel swelling lead in turn to controllable changes in shape, volume, pore size, mechanical and optical properties. We focus our research on the development of glucose-responsive microgels which hold promising interest in the field of both sensing and drug delivery. These cross-linked polymer particles, made of highly swollen networks, can swell proportionally to the concentration of glucose in the surrounding medium. Since they are porous, they can entrap a drug and release it a rate dependent on their swelling degree, which is of particular interest in the case of insulin as a drug. Such systems could be used as self-regulated insulin delivery systems for diabetes treatment. With that aim, we have designed microgels able to sense glucose concentrations in the patho-physiological range, under physiological conditions. Insulin was successfully loaded into the nanogels and was shown to be released at a rate dependent on glucose concentration. Furthermore, microgels with a controlled internal structure were synthesized, such as core-shell microgels and capsules. These latter developments led to improvements in terms of insulin encapsulation efficiency and glucose-triggered delivery. Besides, other nanogel formulations were investigated, in order to improve both their biocompatibility as well as the selectivity of their response to glucose compared to other saccharides.BORDEAUX1-Bib.electronique (335229901) / SudocSudocFranceF

Differential beta cell coupling patterns drive biphasic activity

Background and aims: After food intake, pancreatic islets secrete insulin with a biphasic pattern, which is impaired in type 2 diabetic patients. The mechanisms underlying this pattern have not been fully elucidated and the presence of distinct vesicle pools has been proposed as explanation. Electrical activity of islets consists of individual β cell activity (action potentials, APs) and the multicellular electrical response due to coupling between β cells (slow potentials, SPs). We addressed here the contribution of these two distinct activities to the 1 st and the 2 nd phase of β cell activity, and their modulation by physiological concentrations of GLP-1. Materials and methods: Electrical activity (SPs and APs) of entire mice (C57Bl6/J, age 10-14 weeks) or human islets have been recorded on polymer-coated microelectrode arrays (MEA). These new electrodes allow simultaneous detection of APs (of very low amplitude) and SPs at a high time resolution (10'000 points/s x60 electrodes) for a prolonged period mimicking physiological digestion (2 h). Specific filters differentially detect SPs and APs and 3 parameters were analyzed at the same time: SP frequencies, SP amplitudes and AP frequencies. To investigate synchrony of SPs between different regions of the same islet, we used high density MEAs with an inter-electrode distance of 30 instead of 200 µm followed by analysis via Matlab. Results: Islets were stimulated with glucose concentrations in the physiological range (5.5-8.2 mM). Electrical responses were biphasic for both SPs and APs. APs were mainly present during the 1 st phase while the transition between the 1 st and the 2 nd phase is driven by SPs. In 2 nd phase, the SP amplitude and synchronisation increased significantly (1 st phase: 18.1±2.3 µV; 2 nd phase: 47.4±5.5 µV, p<0.0001), reflecting further electrical coupling and synchronisation of β cells. The intra-islet synchronisation was also further correlate using high density MEAs. The incretin GLP-1, at a physiological postprandial concentration (50 pM), did not change the individual activity of cells (APs) but increased specifically coupling (SPs) and only in the 2nd phase (37.7±3.0 µV vs 47.0±4.2 µV with GLP-1, p<0.0001). Furthermore, when GLP-1 was applied in the presence of a subthreshold glucose concentration (5.5 mM), the hormone triggered only a 2 nd phase. The biphasic electric profile was confirmed in human islets. Their exposure to a glucotoxic medium (20 mM glucose, 65 h) considerably increased basal activity and abolished the biphasic response as well as the discrimination between glucose concentrations. These glucotoxic effects were partially reversible. Conclusion: Our data show that (i) electrical activity pattern shape the biphasic secretion and (ii) the transition period between the 1 st and the 2 nd phase results from increasing electrical synchronisation. Thus biphasic secretion is primarily dictated by changes in electrical activity rather than vesicle pools. The effects of GLP-1 on only coupling SP signals and only during the 2 nd phase explain its clinical effects

Journal of Colloid and Interface Science

A simple route to deliver on demand hydrosoluble molecules such as peptides, packaged in biocompatible and biodegradable microgels, is presented. Hyaluronic acid hydrogel particles with a controlled structure are prepared using a microfluidic approach. Their porosity and their rigidity can be tuned by changing the crosslinking density. These negatively-charged polyelectrolytes interact strongly with positively-charged linear peptides such as poly-l-lysine (PLL). Their interactions induce microgel deswelling and inhibit microgel enzymatic degradability by hyaluronidase. While small PLL penetrate the whole volume of the microgel, PLL larger than the mesh size of the network remain confined at its periphery. They make a complexed layer with reduced pore size, which insulates the microgel inner core from the outer medium. Consequently, enzymatic degradation of the matrix is fully inhibited and non-affinity hydrophilic species can be trapped in the core. Indeed, negatively-charged or small neutral peptides, without interactions with the network, usually diffuse freely across the network. By simple addition of large PLL, they are packaged in the core and can be released on demand, upon introduction of an enzyme that degrades selectively the capping agent. Single polyelectrolyte layer appears as a simple generic method to coat hydrogel-based materials of various scales for encapsulation and controlled delivery of hydrosoluble molecules

Adsorption of microgels at an oil–water interface: correlation between packing and 2D elasticity

International audienceThe aim of this paper is to determine how microgels adsorb at a model oil–water interface and how they adapt their conformation to compression, which gives rise to surface elasticity depending on the microgel packing. The structure of the film is determined by the Langmuir films approach (forced compression) and compared to spontaneous adsorption using the pendant drop method. The behaviour of microgels differs significantly from that of non-deformable particles but resembles that of linear polymers or proteins. We also correlate the properties of microgels spontaneously adsorbed at model interfaces to their forced adsorption during emulsification. Finally we propose a route to easily control a posteriori the microgel packing at the surface of droplets and the flow properties of emulsions stabilised by the microgels

Biosensors & bioelectronics

On-line and real-time analysis of micro-organ activity permits to use the endogenous analytical power of cellular signal transduction algorithms as biosensors. We have developed here such a sensor using only a few pancreatic endocrine islets and the avoidance of transgenes or chemical probes reduces bias and procures general usage. Nutrient and hormone-induced changes in islet ion fluxes through channels provide the first integrative read-out of micro-organ activity. Using extracellular electrodes we captured this read-out non-invasively as slow potentials which reflect glucose concentration-dependent (3-15mM) micro-organ activation and coupling. Custom-made PDMS-based microfluidics with platinum black micro-electrode arrays required only some tens of islets and functioned at flow rates of 1-10microl/min which are compatible with microdialysis. We developed hardware solutions for on-line real-time analysis on a reconfigurable Field-Programmable Gate Array (FPGA) that offered resource-efficient architecture and storage of intermediary processing stages. Moreover, real-time adaptive and reconfigurable algorithms accounted for signal disparities and noise distribution. Based on islet slow potentials, this integrated set-up allowed within less than 40mus the discrimination and precise automatic ranking of small increases (2mM steps) of glucose concentrations in real time and within the physiological glucose range. This approach shall permit further development in continuous monitoring of the demand for insulin in type 1 diabetes as well as monitoring of organs-on-chip or maturation of stem-cell derived islets