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Berlin Brandenburg

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  • 1
    Language: English
    In: Journal of Controlled Release, 20 July 2012, Vol.161(2), pp.264-273
    Description: The central nervous system is well protected by the blood–brain barrier (BBB) which maintains its homeostasis. Due to this barrier many potential drugs for the treatment of diseases of the central nervous system (CNS) cannot reach the brain in sufficient concentrations. One possibility to deliver drugs to the CNS is the employment of polymeric nanoparticles. The ability of these carriers to overcome the BBB and to produce biologic effects on the CNS was shown in a number of studies. Over the past few years, progress in understanding of the mechanism of the nanoparticle uptake into the brain was made. This mechanism appears to be receptor-mediated endocytosis in brain capillary endothelial cells. Modification of the nanoparticle surface with covalently attached targeting ligands or by coating with certain surfactants enabling the adsorption of specific plasma proteins are necessary for this receptor-mediated uptake. The delivery of drugs, which usually are not able to cross the BBB, into the brain was confirmed by the biodistribution studies and pharmacological assays in rodents. Furthermore, the presence of nanoparticles in the brain parenchyma was visualized by electron microscopy. The intravenously administered biodegradable polymeric nanoparticles loaded with doxorubicin were successfully used for the treatment of experimental glioblastoma. These data, together with the possibility to employ nanoparticles for delivery of proteins and other macromolecules across the BBB, suggest that this technology holds great promise for non-invasive therapy of the CNS diseases. Reprinted from Begley et al. with permission of the copyright holder, Elsevier, Amsterdam.
    Keywords: Nanoparticles ; Drug Delivery ; Brain Targeting ; Pharmacy, Therapeutics, & Pharmacology
    ISSN: 0168-3659
    E-ISSN: 1873-4995
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  • 2
    Language: English
    In: Journal of Controlled Release, 2011, Vol.154(1), pp.103-107
    Description: Drug delivery to the brain is restricted due to the blood–brain barrier (BBB). Previously, it has been shown that surfactant-coated doxorubicin-loaded nanoparticles were successful in overcoming the BBB and were effective in the treatment of rat brain tumours. However, drug distribution in brain tissue after crossing the BBB was never determined. To distinguish between the amounts of drug in the whole brain and the fraction of drug in the brain parenchyma after crossing the BBB a capillary depletion technique was employed. For this purpose rats were intravenously treated with a doxorubicin solution in 1% polysorbate 80, or doxorubicin-loaded poly-(n-butyl cyanoacrylate) (PBCA) nanoparticles without and with 1% polysorbate 80 coating, respectively. The dosage of doxorubicin was 5 mg per kg of rat body weight. At 30 min, 2 h, and 4 h following intravenous injection into the tail vein, the rats were sacrificed and their brains removed. Homogenates of the brains were prepared. In addition, one part of the homogenate was separated by centrifugation into a pellet (vascular elements) and supernatant (parenchyma) using a well established capillary depletion technique. The time-dependent distribution of doxorubicin in these brain fractions was studied. Clinically effective concentrations in all investigated brain fractions could only be detected in rats treated with surfactant-coated nanoparticles, indicating a significant transcytosis across the BBB. Only low concentrations were observed after 0.5 and 2 h with the uncoated nanoparticles. No uptake of doxorubicin into the brain was observable after administration of drug solution alone. These observations demonstrate the great potential of surface-coated PBCA nanoparticles for the delivery of drugs to the central nervous system. Doxorubicin concentration in different rat brain fractions 2 h after intravenous injection of 5 mg/kg doxorubicin solution, doxorubicin-loaded poly(butyl cyanoacrylate) (PBCA) nanoparticles (NP), or doxorubicin-loaded PBCA-NP coated with polysorbate 80 (PS80).
    Keywords: Nanoparticles ; Capillary Depletion ; Drug Targeting ; Blood–Brain Barrier ; Pharmacy, Therapeutics, & Pharmacology
    ISSN: 0168-3659
    E-ISSN: 1873-4995
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  • 3
    Language: English
    In: PLoS ONE, 2011, Vol.6(5), p.e19121
    Description: Chemotherapy of glioblastoma is largely ineffective as the blood-brain barrier (BBB) prevents entry of most anticancer agents into the brain. For an efficient treatment of glioblastomas it is necessary to deliver anti-cancer drugs across the intact BBB. Poly(lactic-co-glycolic acid) (PLGA) nanoparticles coated with poloxamer 188 hold great promise as drug carriers for brain delivery after their intravenous injection. In the present study the anti-tumour efficacy of the surfactant-coated doxorubicin-loaded PLGA nanoparticles against rat glioblastoma 101/8 was investigated using histological and immunohistochemical methods. ; The particles were prepared by a high-pressure solvent evaporation technique using 1% polyvinylalcohol (PLGA/PVA) or human serum albumin (PLGA/HSA) as stabilizers. Additionally, lecithin-containing PLGA/HSA particles (Dox-Lecithin-PLGA/HSA) were prepared. For evaluation of the antitumour efficacy the glioblastoma-bearing rats were treated intravenously with the doxorubicin-loaded nanoparticles coated with poloxamer 188 using the following treatment regimen: 3×2.5 mg/kg on day 2, 5 and 8 after tumour implantation; doxorubicin and poloxamer 188 solutions were used as controls. On day 18, the rats were sacrificed and the antitumour effect was determined by measurement of tumour size, necrotic areas, proliferation index, and expression of GFAP and VEGF as well as Isolectin B4, a marker for the vessel density. ; The results reveal a considerable anti-tumour effect of the doxorubicin-loaded nanoparticles. The overall best results were observed for Dox-Lecithin-PLGA/HSA. These data demonstrate that the poloxamer 188-coated PLGA nanoparticles enable delivery of doxorubicin across the blood-brain barrier in the therapeutically effective concentrations.
    Keywords: Research Article ; Biology ; Medicine ; Immunology ; Oncology
    E-ISSN: 1932-6203
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  • 4
    Language: English
    In: International Journal of Pharmaceutics, 2011, Vol.415(1), pp.244-251
    Description: Glioblastomas belong to the most devastating cancer diseases. For this reason, polysorbate 80 (Tween 80 )-coated poly(isohexyl cyanoacrylate) (PIHCA) (Monorex ) nanoparticles loaded with doxorubicin were developed and tested for their use for the treatment of glioblastomas. The preparation of the nanoparticles resulted in spherical particles with high doxorubicin loading. The physico-chemical properties and the release of doxorubicin from the PIHCA-nanoparticles were analysed, and the influence on cell viability of the rat glioblastoma 101/8-cell line was investigated. In vitro, the empty nanoparticles did not show any toxicity, and the anti-cancer effects of the drug-loaded nanoparticles were increased in comparison to doxorubicin solution, represented by IC values. The in vivo efficacy was then tested in intracranially glioblastoma 101/8-bearing rats. Rats were treated with 3 × 1.5 mg/kg doxorubicin and were sacrificed 18 days after tumour transplantation. Histological and immunohistochemical analyses were carried out to assess the efficacy of the nanoparticles. Tumour size, proliferation activity, vessel density, necrotic areas, and expression of glial fibrillary acidic protein demonstrated that doxorubicin-loaded PIHCA-nanoparticles were much more efficient than the free drug. The results suggest that poly(isohexyl cyanoacrylate) nanoparticles hold great promise for the non-invasive therapy of human glioblastomas.
    Keywords: Doxorubicin ; Nanoparticles ; Poly(Isohexyl Cyanoacrylate) ; Glioblastoma ; Histology ; Pharmacy, Therapeutics, & Pharmacology
    ISSN: 0378-5173
    E-ISSN: 1873-3476
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  • 5
    Language: English
    In: European Journal of Pharmaceutics and Biopharmaceutics, 2010, Vol.74(2), pp.157-163
    Description: Poly(lactide-co-glycolide) (PLGA) nanoparticles coated with poloxamer 188 (Pluronic F-68) or polysorbate 80 (Tween 80) enable an efficient brain delivery of the drugs after intravenous injection. This ability was evidenced by two different pharmacological test systems employing as model drugs the anti-tumour antibiotic doxorubicin and the agonist of opioid receptors loperamide, which being P-gp substrates can cross the blood–brain barrier (BBB) only in pharmacologically insignificant amounts: binding of doxorubicin to the surfactant-coated PLGA nanoparticles, however, enabled a high anti-tumour effect against an intracranial 101/8 glioblastoma in rats, and the penetration of nanoparticle-bound loperamide into the brain was demonstrated by the induction of central analgesic effects in mice. Both pharmacological tests could demonstrate that therapeutic amounts of the drugs were delivered to the sites of action in the brain and showed the high efficiency of the surfactant-coated PLGA nanoparticles for brain delivery. The results of the study also demonstrated that the efficacy of brain delivery by nanoparticles not only is influenced by the coating surfactants but also by other formulation parameters such as core polymer, drug, and stabilizer.
    Keywords: Blood–Brain Barrier ; Doxorubicin ; Glioblastoma ; Loperamide ; Mice ; Nanoparticles ; Poly(Lactide-Co-Glycolide) ; Poloxamer 188 ; Polysorbate 80 ; Rats ; Tail-Flick Test ; Pharmacy, Therapeutics, & Pharmacology
    ISSN: 0939-6411
    E-ISSN: 1873-3441
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  • 6
    In: Biotropica, May 2016, Vol.48(3), pp.405-412
    Description: Hunting and trade of wild animals for their meat (bushmeat), especially mammals, is commonplace in tropical forests worldwide. In West and Central Africa, bushmeat extraction has increased substantially during recent decades. Currently, such levels of hunting pose a major threat to native wildlife. In this paper, we compiled published data on hunting offtake of mammals, from a number of studies conducted between 1990 and 2007 in Cameroon, Central African Republic, Democratic Republic of Congo, Equatorial Guinea, Gabon, and Republic of Congo. From these data sources, we estimated annual extraction rates of all hunted species and analyzed the relationship between environmental and anthropogenic variables surrounding each hunting rate and levels of bushmeat extraction. We defined hunting pressure as a function of bushmeat offtake and number of hunted species and confirm that hunting pressure is significantly correlated with road density, distance to protected areas and population density. These correlations are then used to map hunting pressure across the Congo Basin. We show that predicted risk areas show a patchy distribution throughout the study region and that many protected areas are located in high‐risk areas. We suggest that such a map can be used to identify areas of greatest impact of hunting to guide large‐scale conservation planning initiatives for central Africa. La chasse et le commerce d'animaux sauvages pour la viande de brousse, en particulier les mammifères, sont des activités courantes dans les forêts tropicales à travers le monde. En Afrique occidentale et centrale, l'extraction de la viande de brousse a considérablement augmenté au cours des dernières décennies. Actuellement, cette pression de chasse significative constitue une menace majeure pour la faune indigène. Dans cet article, nous avons compilé les données publiées sur le prélèvement de la chasse des mammifères, à partir d'un certain nombre d’études effectuées entre 1990 et 2007 au Cameroun, en République Centrafricaine, en République Démocratique du Congo, en Guinée Equatoriale, au Gabon et en République du Congo. Au regard de ces données, nous avons estimé les taux d'extraction annuels de toutes les espèces chassées, ainsi que la relation des variables environnementales et anthropiques par rapport au taux de chasse et aux niveaux d'extraction de la viande de brousse. Nous avons défini la pression de chasse en fonction du prélèvement de la viande de brousse et le nombre d'espèces chassées et ainsi nous avons pu confirmer que la pression de chasse est significativement corrélée avec la densité routière, la distance aux aires protégées et la densité de population. Ces corrélations ont ensuite été utilisées pour cartographier la pression de chasse à travers le bassin du Congo. Ainsi, nous avons démontré que les zones à risque prédites révèlent une distribution inégale dans toute la région d’étude et que de nombreuses aires protégées sont situées dans des zones à haut risque. C'est pourquoi nous suggérons qu'une telle carte puisse être utilisée pour identifier les zones de grand impact de la chasse afin de guider les initiatives de planification de la conservation à grande échelle pour l'Afrique centrale.
    Keywords: Gis ; Hunting Offtake ; Mammals ; Random Forests
    ISSN: 0006-3606
    E-ISSN: 1744-7429
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