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Wischke C.,University of Michigan | Wischke C.,Research Center Geesthacht GmbH | Zhang Y.,University of Michigan | Mittal S.,Merck And Co. | Schwendeman S.P.,University of Michigan
Pharmaceutical Research | Year: 2010

Purpose: Although efficient in vitro, fenretinide has not been successful clinically for either of the targeted indications-cancer prevention and dry age-related macular degeneration-because of various issues, such as low oral bioavailability. Therefore, controlled release carriers for parenteral delivery of fenretinide were developed. Methods: After examining the solubility profile of fenretinide, the drug was encapsulated in poly(lactic-co-glycolic acid) (PLGA) microparticles at 20% drug loading by an s/o/w methodology as well as into in situ-forming PLGA implants. The carrier morphology and drug release kinetics in an elevated polysorbate 80-containing release medium were studied. Results: Preformulation studies revealed increased fenretinide solubility in various PLGA solvents including N-methylpyrrolidone (NMP) and 1:9 v/v methanol:methylene chloride. Co-solvent emulsion methods resulted in low encapsulation efficiency. With a s/o/w method, fenretinide release rates from injectable microparticles were adjusted by the o-phase concentration of end-capped PLGA, the drug particle size, and the particle porosity. In situ implants from non-capped PLGA in NMP exhibited a continuous release of ~70% drug over 1 month. Conclusions: Injectable carriers for fenretinide were successfully prepared, exhibiting excellent drug stability. Based on the in vitro release properties of the different carriers, the preferred injection sites and in vivo release rates will be determined in future preclinical studies. © 2010 Springer Science+Business Media, LLC. Source


Da Conceicao T.F.,Helmholtz Center Geesthacht | Scharnagl N.,Research Center Geesthacht GmbH | Dietzel W.,Helmholtz Center Geesthacht | Kainer K.U.,Helmholtz Center Geesthacht
Corrosion Science | Year: 2011

In this study, investigations on the protectiveness of poly(ether imide) coatings against corrosion of magnesium AZ31 alloy sheets are performed. The coatings were prepared in different pre-treated substrates by the dip coating method using N'N'-dimethyl acetamide (DMAc) and N'-methyl pyrrolidone solutions. The optimal performance was obtained for hydrofluoric acid treated substrates coated using DMAc solution (coating thickness 13μm) which showed impedances in the order of 10 7Ωcm 2 even after more than 3300h of exposure to a 3.5wt.% NaCl solution. This high performance is associated to an acid-base interaction at the interface as observed by X-ray photoelectron spectroscopy. © 2010 Elsevier Ltd. Source


Behl M.,Research Center Geesthacht GmbH | Lendlein A.,Research Center Geesthacht GmbH
Journal of Materials Chemistry | Year: 2010

Shape-memory polymers (SMPs) are an emerging class of active materials, which are able to change their shape in a predefined way upon appropriate stimulation. As SMPs can switch from a temporary to their permanent shape they are dual-shape materials. Recently, multiphase polymer networks were explored, which are able to switch from a first shape (A) to a second shape (B) and from there to a third shape (C). Here we highlight this triple-shape effect (TSE) as a thermally triggered effect. The generality of the concept will be explained by describing suitable polymer network architectures and appropriate triple-shape creation processes (TSCPs). TSCP is a thermomechanical treatment typically consisting of two consecutive deformation steps resulting in shapes B and A. The molecular architecture of triple-shape polymers (TSPs) also contains the essential elements for the dual-shape effect (DSE), which therefore was systematically investigated. The understanding of the underlying mechanisms recently led to the discovery of a system, where a thermomechanical treatment with only one single deformation step resulted in a TSE. TSPs enable complex, active deformations on demand, having a high potential as enabling technology for application fields including intelligent medical devices, textile and assembling systems. © The Royal Society of Chemistry 2010. Source


Zotzmann J.,Research Center Geesthacht GmbH | Zotzmann J.,Berlin Brandenburg Center for Regenerative Therapies | Behl M.,Research Center Geesthacht GmbH | Hofmann D.,Research Center Geesthacht GmbH | Lendlein A.,Research Center Geesthacht GmbH
Advanced Materials | Year: 2010

A reversible triple-shape effect is achieved for multi-phase polymer networks based on two different crystallizable segments. The reversibility of the two shape-changes is based on crystallization induced elongation (CIE) occurring during cooling and melting-Induced contraction (MIC) during heating under constant stress. (Figure Presented). Source


Behl M.,Research Center Geesthacht GmbH | Zotzmann J.,Research Center Geesthacht GmbH | Lendlein A.,Research Center Geesthacht GmbH
Advances in Polymer Science | Year: 2010

The ability of polymers to respond to external stimuli is of high scientific and technological significance. In the last few years, research activities have been intensified substantially, exploring whether stimuli-sensitive polymers can be designed that move actively. In this review actively-moving materials were classified according to the underlying mechanisms enabling the shape changes: shape-memory polymers and shape-changing polymers/shape-changing gels were identified. The application spectra of these materials as well as the current developments were elucidated and general molecular design principles presented. When applicable, a further distinction according to the applied stimulus was made. © 2009 Springer-Verlag Berlin Heidelberg. Source

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