Blood-brain barrier disruption with focused ultrasound enhances delivery of dopamine transporter tracer (PE2I) into the brain

International audiencePE2I is one of the most selective ligands for dopamine transporter. However it is associated with blood-brain barrier (BBB) permeability limitations. The aim of this study was to investigate the use of ultrasound and microbubbles to increase its delivery through the BBB and by determining the optimal experimental conditions that achieve a transient and safe BBB disruption. First, we stablished the ultrasound conditions that achieved a transient BBB disruption in rats using a non-permeant marker, Evans blue. Hence SonoVue® (450μL/kg) and Evans blue (100mg/kg) were intravenously administered. BBB leakage was obtained using ultrasound insonation through the rat skull at 1.6MPa, PRF 1Hz, duty cycle 1%, burst 10ms during 120sec. BBB disruption was observed in all treated animals (N=4) by histological analysis. The same experimental conditions were applied to enhance brain uptake of PE2I. Biological samples were analyzed using a scintillation counter apparatus. The results showed 50% and 20% increase of 125I-PE2I uptake in the striatum and cerebral cortex, respectively, in the treated rats (N=5) versus control (N=4). Similar enhancements were observed using SonoVue® at half concentration. This innovative method provides a great potential for intracerebral delivery of molecular ligands that could be used for the therapy of brain diseases

Doxorubicin-liposomes loaded microbubbles for ultrasound-triggered doxorubicin delivery

International audienceDoxorubicin (Dox) is a potent chemotherapeutic whose severe side effects limit its clinical efficacy. Microbubble-assisted ultrasound has become a promising strategy for non-invasive local drug delivery to increase the drug concentration locally and to reduce systemic side effects. The aim of this study is to evaluate the effectiveness of administration of Dox-liposomes loaded on MB combined with ultrasound in human glioblastoma cells. Experiments were carried out with free Dox or Dox-loaded MBs on a cell suspension of U-87MG cells. Ultrasound waves were transmitted at 1MHz frequency with a pulse repetition period of 100µs, 40 cycles per pulse and for 30s. Cell viability was evaluated by Trypan blue assay 24h and 48h later. Using Dox alone, the cell viability was 63±3% and 26±2% at 24h and 48h later, respectively. The combination of ultrasound at 600 kPa and Dox-loaded MBs induced a 2.5-fold decrease of cell viability compared to the incubation of Dox-loaded MBs alone at 24h and 48h after treatment, respectively. At 24h, this combination was 3 times more efficient than the doxorubicin treatment alone. The conclusions drawn from this study show the potential of this strategy for a controlled, efficient, and safe drug delivery. Project funded by the EU Project SONODRUGS (NMP4-LA-2008-213706)

Visualization of membrane loss during the shrinkage of giant vesicles under electropulsation

We study the effect of permeabilizing electric fields applied to two different types of giant unilamellar vesicles, the first formed from EggPC lipids and the second formed from DOPC lipids. Experiments on vesicles of both lipid types show a decrease in vesicle radius which is interpreted as being due to lipid loss during the permeabilization process. We show that the decrease in size can be qualitatively explained as a loss of lipid area which is proportional to the area of the vesicle which is permeabilized. Three possible mechanisms responsible for lipid loss were directly observed: pore formation, vesicle formation and tubule formation.Comment: Final published versio

Ultrasound-Responsive Cavitation Nuclei for Therapy and Drug Delivery

Therapeutic ultrasound strategies that harness the mechanical activity of cavitation nuclei for beneficial tissue bio-effects are actively under development. The mechanical oscillations of circulating microbubbles, the most widely investigated cavitation nuclei, which may also encapsulate or shield a therapeutic agent in the bloodstream, trigger and promote localized uptake. Oscillating microbubbles can create stresses either on nearby tissue or in surrounding fluid to enhance drug penetration and efficacy in the brain, spinal cord, vasculature, immune system, biofilm or tumors. This review summarizes recent investigations that have elucidated interactions of ultrasound and cavitation nuclei with cells, the treatment of tumors, immunotherapy, the blood–brain and blood–spinal cord barriers, sonothrombolysis, cardiovascular drug delivery and sonobactericide. In particular, an overview of salient ultrasound features, drug delivery vehicles, therapeutic transport routes and pre-clinical and clinical studies is provided. Successful implementation of ultrasound and cavitation nuclei-mediated drug delivery has the potential to change the way drugs are administered systemically, resulting in more effective therapeutics and less-invasive treatments

Mécanismes moléculaires et cellulaire de l'électrotransfert de plasmides in vitro

Le transfert de plasmides au sein d'une cellule cible représente un outil clé dans l'étude de fonctions biologiques et dans le développement de nouvelles approches thérapeutiques. Cependant, le transfert de plasmides doit être réalisé avec un minimum d'effets secondaires au niveau de la cellule cible. La technique d'électroperméabilisation est une méthode physique fondée sur la modulation du potentiel électrique transmembranaire natif de la cellule par un champ électrique externe. Cependant, l'utilisation rationnelle de l'électroperméabilisation en pharmacologie et en médecine ne pourra se faire que grâce à une parfaite compréhension des mécanismes impliqués lors de l'électroperméabilisation au niveau membranaire et de ses conséquences cellulaires. Le mécanisme de l'électrotransfert de plasmides est un processus multi-étapes avec une étape d'interaction plasmide/membrane perméabilisée pendant l'application des impulsions électriques, suivi après ces dernières, d'une étape de translocation du plasmide à travers la membrane plasmique. Ce travail de recherche pluridisciplinaire vise à une meilleure compréhension du mécanisme de l'électrotransfert de plasmides. Il intègre l'étude des conséquences membranaires de l'électrotransfert de plasmide et l'étude de l'interaction plasmide/membrane perméabilisée. L'application d'impulsions électriques millisecondes et perméabilisantes induit un désordre membranaire et une rapide translocation des phospholipides dans les régions perméabilisées. La translocation électro-induite des phospholipides n'est pas associée à une perte de la viabilité cellulaire. L'existence du processus multi-étapes de l'électrotransfert de plasmide (perméabilisation membranaire, interaction plasmide/membrane et expression génique) a été confirmé dans différentes lignées cellulaires. Pendant l'application de la première impulsion électrique, les molécules de plasmide migrent par électrophorèse et viennent interagir dans des sites distincts de la région membranaire faisant face à la cathode. L'interaction des molécules de plasmide avec la membrane perméabilisée serait donc un processus rapide (de l'ordre d'une centaine de microsecondes). Les complexes plasmide/membrane se stabilisent en un délai de 200 ms. Un rôle distinct de l'intensité du champ électrique et du nombre d'impulsions électriques a été mis en évidence. Si l'intensité du champ électrique définit la surface membranaire où l'interaction des molécules de plasmide a lieu et de fait, le nombre de spots d'interaction, le nombre d'impulsions électriques définit la quantité de molécules de plasmide présente par complexe. Les complexes plasmide/membrane ainsi formés ne diffusent pas latéralement dans la membrane. Le cytosquelette d'actine n'est pas impliqué dans la formation de ces complexes mais pourrait être impliqué dans le transport intracellulaire des molécules de plasmides. L'électroperméabilisation et l'interaction plasmide/membrane perturbent la mobilité latérale des protéines membranaire du feuillet externe de la membrane plasmique. La combinaison de la sonoporation avec l'électroperméabilisation permet d'améliorer l'efficacité de transfection obtenue par l'électroperméabilisation seule. Le transfert de plasmides par électro-sonoporation est une stratégie prometteuse en thérapie génique.Plasmid transfer within a target cell represents a key tool in the study of biological functions and the development of new therapeutic strategies. However, the transfer of plasmids must be carried out with a minimum of side effects on the level of the target cell. The technique of electropermeabilization is a physical method based on the modulation of the native transmembrane electric potential of the cell by an external electric field. However, the rational use of the electropermeabilization in pharmacology and medicine could be done only thanks to one perfect comprehension of the mechanisms involved in the electropermeabilization at the membrane level and its cellular consequences. The mechanism of the plasmid electrotransfer is a multi-steps process with a step of plasmid/membrane interaction during the application of the electric pulses, followed after these last, of a step of plasmid translocation through the plasma membrane. This multi-disciplinary research task aims at a better comprehension of the mechanism of the plasmid electrotransfer. It integrates the study of the membrane consequences of the electropermeabilization and the study of the plasmid/ membrane interaction. The application of milliseconds and permeabilizing electric pulses induces a membrane disorder and a fast phospholipid translocation in the permeabilized regions. The electro-induced translocation of phospholipids is not associated with a loss of cell viability. The existence of the multi-steps process of the plasmid electrotransfer (membrane permeabilization, plasmid/membrane interaction and gene expression) was confirmed in various cell lines. During the application of the first electric pulse, the plasmids migrate by electrophoresis and come to interact in distinct sites from the membrane region facing the cathode. The interaction of plasmids with the permeabilized membrane would be thus a fast process (about a hundred microseconds). The plasmid/membrane complexes are stabilized in a delay of 200 ms. A distinct role from the intensity of the electric field and the number of electric pulses was highlighted. If the intensity of the electric field defines membrane surface where the interaction of the plasmid molecules takes place and in fact, the number of spots of interaction, the number of electric pulses defines the amount of plasmids presents by complex. The plasmid/membrane complexes thus formed do not diffuse laterally in the membrane. The actine cytoskeleton is not involved in the formation of these complexes but could be involved in the intracellular traffic of plasmids. Electropermeabilization and plasmid/membrane interaction disturbed the lateral mobility of membrane proteins of outer leaflet of plasma membrane. The combination of the sonoporation with the electropermeabilization makes it possible to improve the effectiveness of transfection obtained by the electropermeabilization alone. The transfer of plasmids by electro-sonoporation is a promising strategy in gene therapy

Cancer Imaging: Progress and Prospect

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Therapeutic Ultrasound

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Editorial: Biomedical advances in ultrasound-mediated drug/ molecule delivery

Editorial letter on special issue on biomedical advances in ultrasound-mediated drug/ molecule deliveryEditorial on the Research Topic Biomedical advances in ultrasound-mediated drug/molecule delivery Despite the increasing number of innovative drugs and the development of novel targeted methods, therapeutic advances remain modest for many prevalent and costly diseases including neurodegenerative disorders, cancers, and cardiovascular diseases among others. One of the major therapeutic hurdles is the presence of biological barriers in multiple organs (e.g., endothelial and epithelial barriers, plasma membrane, interstitial pressure, detoxification processes, etc.). While they sustain organ/tissue homeostasis in physiological conditions, these barriers substantially impede the delivery of a vast majority of therapeutic molecules (e.g., chemotherapeutics, antibiotics, nucleic acids, antibodies, etc.) in diseased tissues, thus reducing their bioavailability and therapeutic effect. This challenge narrows the landscape of usable therapeutic molecules and drastically influences the design of many therapeutic protocols. Therefore, crossing of biological barriers in drug studies is undoubtedly a source of major RD investments in academia and pharmaceutical industry. For over 2 decades, therapeutic ultrasound (US) applications facilitating gene/drug delivery have been widely investigated, with some approaches being on the brink of reaching the bedside. Among these, using US-responsive particles injected systemically, e.g., microbubbles, to facilitate US-mediated, crossing of biological barriers has been shown to: 1) be applicable in a standardized and non-invasive fashion in laboratory animals and human subjects, and 2) render therapeutically-achievable drug/molecule biodistribution, supporting the clinical translatability of this modality. While these advances foresee a "blue sky" in the field, like in many medical specialties, the translation gap remains challenging to evaluate. One may ask-to what extent is a successful pre-clinical study predictive of the outcome of its clinical counterpart? Before devising a clinical study, it is essential to boost chances of clinical success by conducting impactful in-vitro and preclinical studies that can inform clinical trial design and enable technology translation

Comment on “The Enhancing Effect of Focused Ultrasound on TNK-Tissue Plasminogen Activator-Induced Thrombolysis using an In Vitro Circulating Flow Model”

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