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  • 1
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    Amsterdam : Elsevier Academic Press
    Call number: QH585:104(3)
    Keywords: Tissue Engineering ; Biocompatible Materials ; Cell Transplantation ; Tissue Culture Techniques ; Tissue Transplantation
    Pages: xxvii, 1307 p. : ill. (chiefly col.)
    Edition: 3rd ed.
    ISBN: 9780123706157
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  • 2
    Electronic Resource
    Electronic Resource
    [s.l.] : Macmillian Magazines Ltd.
    Nature 434 (2005), S. 879-882 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Materials are said to show a shape-memory effect if they can be deformed and fixed into a temporary shape, and recover their original, permanent shape only on exposure to an external stimulus. Shape-memory polymers have received increasing attention because of their scientific and ...
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  • 3
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The proto-oncogene c-myb is homologous to the transforming gene product of the avian myeloblastosis virus and was originally thought to be present only in haematopoietic cells1'2. But c-myb and its various family members are synthesized in diverse cell types and regulate cell growth and ...
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  • 4
    ISSN: 1573-904X
    Keywords: water-soluble drug delivery system ; controlled release ; polyanhydride ; biodegradable microspheres ; gelatin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A new method to prepare polyanhydride microspheres capable of near-constant sustained release of low molecular weight, water-soluble molecules is presented. The polyanhydrides used were poly-(fatty acid dimer) (PFAD), poly(sebacic acid) (PSA), and their co-polymers [P(FAD-SA)]. Acid orange 63 (AO), acid red 8 (AR), and p-nitroaniline, were used as model release molecules. P(FAD-SA) microspheres containing the molecules with or without gelatin were prepared by a modified solvent evaporation method using a double emulsion. The microspheres were spherical with diameters of 50–125 µm and encapsulated more than 85% of the molecule, irrespective of the compound used. Near-zero-order degradation kinetics were observed for 5 days as judged by sebacic acid (SA) release. Microsphere degradation was pH sensitive, being enhanced at high pH, and became more stable in acidic conditions, irrespective of the incorporation of gelatin in the matrix. For the gelatin-free microspheres, a close correlation of SA release and AO release was observed (2% loading), suggesting a release mechanism that was controlled dominantly by degradation. However, the incorporation of gelatin into the microsphere significantly extended the periods of molecule release from P(FAD-SA) microspheres, although the degradation profile of the microspheres themselves was quite similar to that of gelatin-free microspheres. It is possible that an interaction between FAD monomers and gelatin molecules causes continued release, even after the polymer matrix completely degrades (even after complete degradation, FAD monomers remain because of their poor water solubility). Thermal analysis of polyanhydride microspheres at different degradation stages demonstrated that a crystalline structure was formed between gelatin and the FAD monomers produced with microsphere degradation. This gelatin effect on the extended period of drug release was not observed for microspheres prepared from other polyanhydrides: poly (sebacic acid) and its co-polymer of bis(p-carboxyphenoxy) propane and sebacic acid. It is therefore likely that the crystalline structure formed between gelatin and FAD monomers may function as a reservoir for water-soluble drugs, leading to an extended period of molecule release from the gelatin-loaded P(FAD-SA) microspheres.
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  • 5
    ISSN: 1573-904X
    Keywords: vaccine delivery system ; controlled release ; poly(lactic/glycolic acid) ; biodegradable microspheres ; tetanus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Controlled-release formulations based on poly(lactic) (PLA) and poly(lactic/glycolic) acid (PLGA) microspheres containing tetanus vaccine were designed. The polymers forming the microspheres were L-PLA of different molecular weights and DL-PLGA, 50:50. These microspheres were prepared by two solvent elimination procedures, both using a double emulsion, and were characterized for size, morphology, and toxoid release kinetics. The influence of formulation variables such as polymer type, vaccine composition, and vaccine/polymer ratio was also investigated. Both techniques yielded microspheres with similar size, morphology, and release properties. Microsphere size was dependent on the type of polymer and the presence of the surfactant L-α-phosphatidylcholine, which led to a reduction in microsphere size. On the other hand, the release kinetics of encapsulated protein were affected by the polymer properties (ratio lactic/glycolic acid and molecular weight) as well as by the vaccine composition, vaccine loading, and microsphere size. Moreover, for some formulations, a decrease in microsphere size occurred simultaneously, with an increase in porosity leading to an augmentation of release rate. The changes in the PLA molecular weight during in vitro release studies indicated that release profiles of tetanus toxoid from these microspheres were only marginally influenced by polymer degradation. A significant fraction of protein (between 15 and 35%) was initially released by diffusion through water-filled channels. In contrast, the decrease in the PLGA molecular weight over the first 10 days of incubation suggested that erosion of the polymer matrix substantially affects protein release from these microspheres. Among all formulations developed, two differing in microsphere size, polymer hydrophobicity, and release profile were selected for in vivo administration to mice. Administration of both formulations resulted in tetanus neutralizing antibody levels that were higher than those obtained after administration of the fluid toxoid.
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  • 6
    ISSN: 1573-904X
    Keywords: insulin ; lyophilization ; aggregation ; β-elimination ; disulfide interchange
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A critical problem in the storage and delivery of pharmaceutical proteins is aggregation in the solid state induced by elevated temperature and moisture. These conditions are particularly relevant for studies of protein stability during accelerated storage or for proteins loaded in polymeric delivery devices in vivo. In the present investigation, we have found that, when exposed to an environment simulating these conditions, lyophilized insulin undergoes both covalent and noncovalent aggregation. The covalent process has been elucidated to be intermolecular thiol-catalyzed disulfide interchange following β-elimination of an intact disulfide bridge in the insulin molecule. This process is accelerated by increasing the temperature and water content of the insulin powder or by performing lyophilization and/or dissolution of insulin in alkaline media. The aggregation can be ameliorated by the presence of Cu 2+ , which presumably catalyzes the oxidization of free thiols. The water sorption isotherm for insulin reveals that the extent of aggregation directly correlates with the water uptake by the lyophilized insulin powder, thus pointing to the critical role of protein conformational mobility in the aggregation process.
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  • 7
    ISSN: 1573-904X
    Keywords: oral drug delivery ; polymerized liposomes ; Peyer's patches ; stability in G-I fluids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The physical characteristics of polymerized liposomes for potential use as an oral drug delivery system were examined in vitro. The trap efficiency in monomeric liposomes composed of 1,2-di (2,4-octadecadienoyl) phosphatidylcholine was increased from 3% for original multilamellar vesicles to 35% for freeze-thaw treated liposomes. Polymerized liposomes with azobis (isobutyronitrile) and azobis (2-amidinopropane) hydrochloride as radical initiators showed complete stability against solubilization by Triton X-100, a detergent chosen to mimic bile salts. Release rates of 14C-BSA and 14C-sucrose in media simulating the gastro-intestinal fluids was 50% less than from regular liposomes composed of hydrogenated egg phosphatidylcholine mixed with cholesterol (molar ratio 1:1), which can be regarded as one of the most stable types of regular liposomes. It was estimated that, when administered orally, polymerized liposomes can reach the intestine while maintaining their vesicle structure and keeping at least 75% of their original content.
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  • 8
    ISSN: 1573-904X
    Keywords: liposomes ; oral delivery ; drug carrier ; magnetically-responsive
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1573-904X
    Keywords: pulmonary drug delivery ; dry powder ; large porous particles ; excipients ; aerosolization properties
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. Relatively large (〉5 µm) and porous (mass density 〈 0.4 g/cm3) particles present advantages for the delivery of drugs to the lungs, e.g., excellent aerosolization properties. The aim of this study was, first, to formulate such particles with excipients that are either FDA-approved for inhalation or endogenous to the lungs; and second, to compare the aerodynamic size and performance of the particles with theoretical estimates based on bulk powder measurements. Methods. Dry powders were made of water-soluble excipients (e.g., lactose, albumin) combined with water-insoluble material (e.g., lung surfactant), using a standard single-step spray-drying process. Aerosolization properties were assessed with a Spinhaler TM device in vitro in both an Andersen cascade impactor and an AerosizerTM.. Results. By properly choosing excipient concentration and varying the spray drying parameters, a high degree of control was achieved over the physical properties of the dry powders. Mean geometric diameters ranged between 3 and 15 µm, and tap densities between 0.04 and 0.6 g/cm3. Theoretical estimates of mass mean aerodynamic diameter (MMAD) were rationalized and calculated in terms of geometric particle diameters and bulk tap densities. Experimental values of MMAD obtained from the AerosizerTM most closely approximated the theoretical estimates, as compared to those obtained from the Andersen cascade impactor. Particles possessing high porosity and large size, with theoretical estimates of MMAD between 1−3 µm, exhibited emitted doses as high as 96% and respirable fractions ranging up to 49% or 92%, depending on measurement technique. Conclusions. Dry powders engineered as large and light particles, and prepared with combinations of GRAS (generally recognized as safe) excipients, may be broadly applicable to inhalation therapy.
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  • 10
    ISSN: 1573-904X
    Keywords: ultrasound ; sonophoresis ; transdermal ; diagnostics ; interstitial fluid
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. Transdermal extraction of clinically relevant analytes offersa potentially non-invasive method of diagnostics. However,development of such a method is limited by the low skin permeability. In thispaper, we report a potential method for non-invasive diagnostics basedon ultrasonic skin permeabilization and subsequent extraction ofinterstitial fluid (ISF) across the skin.Methods. In vivo experiments were performed using Sprague Dawleyrats to assess ultrasound-induced skin permeabilization and subsequentextraction of various analytes. Serum and ISF concentrations of variousanalytes were measured.Results. Application of low-frequency ultrasound rapidly increasedskin permeability. Skin remained in a state of high permeability for atleast three hours. During this period, application of vacuum extractedISF across rat skin in vivo at a rate of 25.7 μl/cm2/hr. We measuredconcentrations of various analytes including glucose, albumin, calcium,urea, triglycerides, lactate, and dextran in transdermally extracted fluid.The composition of the fluid extracted transdermally is similar to thatof ISF.Conclusions. Application of low-frequency ultrasound allows skin permeabilization and extraction of ISF across the skin.
    Type of Medium: Electronic Resource
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