Evaluation du pH à l'intérieur de mini-granules enrobées par spectrométrie de fluorescence

Les systèmes à libération contrôlée tels que les mini-granules enrobées sont exposés à des changements de pH lors de leur passage dans le tractus gastro-intestinal. Il peut s agir d un problème lorsque les bases faibles présentant une solubilité aqueuse pH-dépendant doivent être libérées. Actuellement, peu de connaissances sur les changements de pH dans les systèmes réservoirs sont disponibles. La micro-électrode de pH et la résonance paramagnétique électronique sont proposées pour contrôler ces modifications. Néanmoins, ces méthodes restent invasives. Il existe également la microscopie confocale à balayage laser qui utilise un marqueur fluorescent incorporé dans des systèmes matriciels. L objectif de cette étude est d évaluer les changements de pH à l intérieur de mini-granules enrobées contenant du verapamil hydrochloride par une approche non-invasive, la spectroscopie à fluorescence. Les mini-granules ont été fabriquées par un procédé d extrusion-sphéronisation et enrobées avec un mélange de polymères à base de Kollicoat SR et de Kollicoat IR. Une fois les fluorophores appropriés à l étude via une phase de screening, deux d entre eux ont été sélectionnés pour l analyse fluorimétrique. Ces derniers incorporés à l intérieur des mini-granules ont été par la suite enrobées. Le pH à l intérieur de ces systèmes réservoirs après exposition dans le milieu de dissolution a pu être déterminé par spectroscopie à fluorescence.Controlled release systems such as coated pellets are exposed to environmental changes in pH during their passage through the gastrointestinal tract. This can be an issue, when weakly basic drugs with strongly pH-dependent solubility are to be released. So far, relatively little is known about the pH changes occuring within the reservoirs. Microprobes and electron paramagnetic resonance measurements have been proposed to monitor potential alterations. Nevertheless, these methods are invasive. Also, confocal laser scanning microscopy using a fluorescent marker in matrix pellets has been suggested. That is why, the purpose of this study was to monitor pH changes inside coated pellets containing verapamil HCl using a non-invasive approach, the fluometric method. The pellets were produced by extrusion-spheronisation process and coated with a polymer blend of Kollicoat SR:Kollicoat IR. Once the fluorophores suited for this study analyzed via a screening phase, two of them were selected for the fluometric method. The latter were incorporated into pellets, which were subsequently coated and the pH changes within the reservoir systems upon exposure to the dissolution medium could have been determined by fluorescence spectroscopy.ANGERS-BU Médecine-Pharmacie (490072105) / SudocSudocFranceF

Mise au point de microparticules biodégradables en vue de la libération prolongée d'une protéine

ANGERS-BU Médecine-Pharmacie (490072105) / SudocSudocFranceF

How to achieve sustained and complete protein release from PLGA-based microparticles?

International audienceOne of the most challenging tasks in the delivery of therapeutic proteins from PLGA-based microparticles is the sustained and complete release of the protein in its native form. The mechanisms responsible for incomplete protein release from these devices are numerous and complex; the beneficial effect of different formulations has often been evaluated in vitro. Strategies employed for overcoming protein destabilization during the release step are reviewed in this paper. Proteins have been protected in the deleterious environment by adding stabilizers to the formulation, or by modifying the protein or the polymer. Alternatively, some strategies have aimed at avoiding the formation of the destabilizing environment. As experimental conditions may influence the results from in vitro release studies, we initially report precautions to avoid adverse effects

Effect of process parameters on morphology and release profile of Penta-block PLGA-based Microspheres

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Behavior of poly(d,l-lactic-co-glycolic acid) (PLGA)-based droplets falling into a complex extraction medium simulating the prilling process

International audienceHypothesisPrilling process is one of advanced techniques for manufacturing microspheres of controlled and uniform size. In this process, homogenous polymer droplets fall into an extraction medium. The aim of this study was to identify the key parameters influencing the behavior of PLGA polymer-based droplets falling into a complex extraction medium, to select appropriate conditions for prilling.ExperimentsPolymer solutions and extraction media were characterized by determining their viscosity, density and surface tension. A simple model simulating the prilling process was developed to study droplet behavior. Particle shape and velocity at the air-liquid interface and during sedimentation in the container were analyzed step by step. The correlations between the variables studied were visualized by principal component analysis (PCA).FindingsDroplet deformation at the interface greatly affected the recovery and final particle shape. It depended on the viscosity ratio of polymer solution/extraction medium. The particle shape recovery depended on the viscosity and density of extraction media and polymer solutions. The solidification speed is also an important parameter. In media which the solvent diffused slowly, particles were able to relax and recover their shape, however, they can also deform during sedimentation and collision with the bottom of the cuvette

Nα-methyl coprogen B, a potential marker of the airway colonization by Scedosporium apiospermum in patients with cystic fibrosis

International audienceScedosporium apiospermum is an emerging pathogen colonizing the airways of patients with cystic fibrosis (CF). While usually responsible for chronic colonization without clinical signs, this fungus may cause severe and often lethal infections in lung transplant recipients. Early diagnosis of its airway colonization and appropriate treatment are required to eradicate the fungus when a lung transplantation is planned. Here we propose an alternative to mycological examination of sputum samples based on extraction of siderophores by chromatography on Amberlite XAD-4, followed by high performance liquid chromatography analysis of the siderophore extract. Improvement of the extraction procedure was performed in a fractional factorial design which revealed the importance of prior ammonium sulfate precipitation of the proteins, alkalinization of the obtained solution and stirring during extraction. In order to verify the specificity of Nα-methyl coprogen B for S. apiospermum, the method was applied on culture supernatants of different filamentous fungi colonizing the airways of CF patients, including some aspergilli and Exophiala dermatitidis. Nα-methyl coprogen B was detected exclusively for species of the S. apiospermum complex. Likewise, sputum samples from colonized and non-colonized CF patients were analyzed, and the siderophore was detected exclusively in three out of the five specimens which were found by culture to contain S. apiospermum. Together these results confirmed Nα-methyl coprogen B as a marker of the airway colonization by species of the S. apiospermum complex.</p

Development of pharmacologically active microcarriers transporting stem cells and releasing growth factors integrated in a thermosensitive injectable hydrogel for an efficient tissue engineering strategy

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The potential of combinations of drug-loaded nanoparticle systems and adult stem cells for glioma therapy

International audienceThe prognosis of patients with malignant glioma remains extremely poor, despite surgery and improvements in radio- and chemo-therapies. Nanotechnologies hold great promise in glioma therapy as they protect the therapeutic agent and allow its sustained release. However, new paradigms permitting tumor-specific targeting and extensive intratumoral distribution must be developed to efficiently deliver nanoparticles. Modifications and functionalizations of nanoparticles have been developed to specifically track tumor cells. However, these nanoparticles have yielded few clinical results due to intra-patient heterogeneity and inter-patient variability. Stem cells with a specific tropism for brain tumors could be used as delivery vehicles for nanoparticles. Indeed, these cells have a natural tendency to migrate and distribute within the tumor mass and they can also incorporate nanoparticles. Stem cell therapy combined with nanotechnology could be a promising tool to efficiently deliver drugs to brain tumors.</p

Development of prilling process for biodegradable microspheres through experimental designs

International audienceThe prilling process proposes a microparticle formulation easily transferable to the pharmaceutical production, leading to monodispersed and highly controllable microspheres. PLGA microspheres were used for carrying an encapsulated protein and adhered stem cells on its surface, proposing a tool for regeneration therapy against injured tissue. This work focused on the development of the production of PLGA microspheres by the prilling process without toxic solvent. The required production quality needed a complete optimization of the process. Seventeen parameters were studied through experimental designs and led to an acceptable production. The key parameters and mechanisms of formation were highlighted.</p

Mesenchymal stem cells as cellular vehicles for delivery of nanoparticles to brain tumors

The prognosis of patients with malignant glioma remains extremely poor, despite surgery and improvements in radio- and chemo-therapies. Nanotechnologies represent great promise in glioma therapy as they protect therapeutic agent and allow its sustained release. However, new paradigms allowing tumor specific targeting and extensive intratumoral distribution must be developed to efficiently deliver nanoparticles (NPs). Knowing the tropism of mesenchymal stem cells (MSCs) for brain tumors, the aim of this study was to obtain the proof of concept that these cells can be used as NP delivery vehicles. Two types of NPs loaded with coumarin-6 were investigated: poly-lactic acid NPs (PLA-NPs) and lipid nanocapsules (LNCs). The results show that these NPs can be efficiently internalized into MSCs while cell viability and differentiation are not affected. Furthermore, these NP-loaded cells were able to migrate toward an experimental human glioma model. These data suggest that MSCs can serve as cellular carriers for NPs in brain tumors