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Abstract
The fibrous silk produced by bees, wasps, ants, or hornets is known to form a four-strand α-helical coiled coil superstructure. We have succeeded in showing the formation of this coiled coil structure not only in natural fibers, but also in artificial films made of regenerated silk of the hornet Vespa simillima xanthoptera using wide- and small-angle X-ray scatterings and polarized Fourier transform infrared spectroscopy. On the basis of time-resolved simultaneous synchrotron X-ray scattering observations for in situ monitoring of the structural changes in regenerated silk material during tensile deformation, we have shown that the application of tensile force under appropriate conditions induces a transition from the coiled α-helices to a cross-β-sheet superstructure. The four-stranded tertiary superstructure remains unchanged during this process. It has also been shown that the amorphous protein chains in the regenerated silk material are transformed into conventional β-sheet arrangements with varying orientation.
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Affiliation(s)
- Taiyo Yoshioka
- Silk Materials Research Unit, National Agriculture and Food Research Organization (NARO) , 1-2 Ohwashi, Tsukuba, Ibaraki 305-8634, Japan
| | - Tsunenori Kameda
- Silk Materials Research Unit, National Agriculture and Food Research Organization (NARO) , 1-2 Ohwashi, Tsukuba, Ibaraki 305-8634, Japan
| | - Kohji Tashiro
- Department of Future Industry-Oriented Basic Science and Materials, Graduate School of Engineering, Toyota Technological Institute , Tempaku, Nagoya 468-8511, Japan
| | - Noboru Ohta
- Japan Synchrotron Radiation Research Institute, 1-1 Koto, Mikazuki-Cho, Sayo-Gun, Hyogo 679-5198, Japan
| | - Andreas K Schaper
- Center for Materials Sciences, Philipps University of Marburg , 35032 Marburg, Germany
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2
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Ramzan R, Schaper AK, Weber P, Rhiel A, Siddiq MS, Vogt S. Mitochondrial cytochrome c oxidase is inhibited by ATP only at very high ATP/ADP ratios. Biol Chem 2017; 398:737-750. [PMID: 27926476 DOI: 10.1515/hsz-2016-0218] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2016] [Accepted: 11/30/2016] [Indexed: 11/15/2022]
Abstract
In the past, divergent results have been reported based on different methods and conditions used for enzymatic activity measurements of cytochrome c oxidase (CytOx). Here, we analyze in detail and show comparable and reproducible polarographic activity measurements of ATP-dependent inhibition of CytOx kinetics in intact and non-intact rat heart mitochondria and mitoplasts. We found that this mechanism is always present in isolated rat heart mitochondria and mitoplasts; however, it is measurable only at high ATP/ADP ratios using optimal protein concentrations. In the kinetics assay, measurement of this mechanism is independent of presence or absence of Tween-20 and the composition of measuring buffer. Furthermore, the effect of atractyloside on intact rat heart mitochondria confirms that (i) ATP inhibition occurs under uncoupled conditions [in the presence of carbonly cyanide m-chlorophenyl hydrazone (CCCP)] when the classical respiratory control is absent and (ii) high ATP/ADP ratios in the matrix as well as in the cytosolic space are required for full ATP inhibition of CytOx. Additionally, ATP inhibition measured in intact mitochondria extends in the presence of oligomycin, thus indicating further that the problem to measure the inhibitory effect of ATP on CytOx is apparently due to the lack of very high ATP/ADP ratios in isolated mitochondria.
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3
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Kameda T, Nemoto T, Ogawa T, Tosaka M, Kurata H, Schaper AK. Evidence of α-helical coiled coils and β-sheets in hornet silk. J Struct Biol 2014; 185:303-8. [DOI: 10.1016/j.jsb.2013.12.005] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2013] [Revised: 12/10/2013] [Accepted: 12/11/2013] [Indexed: 11/25/2022]
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4
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Zheng M, Pavan GM, Neeb M, Schaper AK, Danani A, Klebe G, Merkel OM, Kissel T. Targeting the blind spot of polycationic nanocarrier-based siRNA delivery. ACS Nano 2012; 6:9447-54. [PMID: 23036046 PMCID: PMC3882193 DOI: 10.1021/nn301966r] [Citation(s) in RCA: 74] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/16/2023]
Abstract
Polycationic nanocarriers attract increasing attention to the field of siRNA delivery. We investigated the self-assembly of siRNA vs pDNA with polycations, which are broadly used for nonviral gene and siRNA delivery. Although polyethyleneimine (PEI) was routinely adopted as siRNA carrier based on its efficacy in delivering pDNA, it has not been investigated yet why PEI efficiently delivers pDNA to cells but is controversially discussed in terms of efficacy for siRNA delivery. We are the first to investigate the self-assembly of PEI/siRNA vs PEI/pDNA and the steps of complexation and aggregation through different levels of hierarchy on the atomic and molecular scale with the novel synergistic use of molecular modeling, molecular dynamics simulation, isothermal titration calorimetry, and other characterization techniques. We are also the fist to elucidate atomic interactions, size, shape, stoichiometry, and association dynamics for polyplexes containing siRNA vs pDNA. Our investigation highlights differences in the hierarchical mechanism of formation of related polycation-siRNA and polycation-pDNA complexes. The results of fluorescence quenching assays indicated a biphasic behavior of siRNA binding with polycations where molecular reorganization of the siRNA within the polycations occurred at lower N/P ratios (nitrogen/phosphorus). Our results, for the first time, emphasize a biphasic behavior in siRNA complexation and the importance of low N/P ratios, which allow for excellent siRNA delivery efficiency. Our investigation highlights the formulation of siRNA complexes from a thermodynamic point of view and opens new perspectives to advance the rational design of new siRNA delivery systems.
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Affiliation(s)
- Mengyao Zheng
- Department of Pharmaceutics and Biopharmacy, Philipps-Universität Marburg, Germany
| | - Giovanni M. Pavan
- Laboratory of Applied Mathematics and Physics (LamFI), University for Applied Sciences of Southern Switzerland (SUPSI), Switzerland
| | - Manuel Neeb
- Department of Pharmaceutical Chemistry, Philipps-Universität Marburg, Germany
| | | | - Andrea Danani
- Laboratory of Applied Mathematics and Physics (LamFI), University for Applied Sciences of Southern Switzerland (SUPSI), Switzerland
| | - Gerhard Klebe
- Department of Pharmaceutical Chemistry, Philipps-Universität Marburg, Germany
| | - Olivia M. Merkel
- Department of Pharmaceutics and Biopharmacy, Philipps-Universität Marburg, Germany
- Address correspondence to ;
| | - Thomas Kissel
- Department of Pharmaceutics and Biopharmacy, Philipps-Universität Marburg, Germany
- Address correspondence to ;
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Yoshioka T, Kawahara Y, Schaper AK. Cyclic or Permanent? Structure Control of the Contraction Behavior of Regenerated Bombyx mori Silk Nanofibers. Macromolecules 2011. [DOI: 10.1021/ma2014172] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Affiliation(s)
- Taiyo Yoshioka
- Materials Science Center, EM&Mlab, Philipps University of Marburg, Hans-Meerwein-Str., 35032 Marburg, Germany
| | - Yutaka Kawahara
- Department of Biological and Chemical Engineering, Gunma University, 1-5-1 Tenjin-cho, Kiryu, Gunma 376-8515, Japan
| | - Andreas K. Schaper
- Materials Science Center, EM&Mlab, Philipps University of Marburg, Hans-Meerwein-Str., 35032 Marburg, Germany
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6
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Schaper AK, Wang MS, Xu Z, Bando Y, Golberg D. Comparative studies on the electrical and mechanical behavior of catalytically grown multiwalled carbon nanotubes and scrolled graphene. Nano Lett 2011; 11:3295-300. [PMID: 21755963 DOI: 10.1021/nl201655c] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
The electrical and mechanical properties of multiwalled carbon nanotubes and of scrolled graphene structures, synthesized from iron-phthalocyanine in a catalytic chemical vapor deposition process, were investigated in situ in a transmission electron microscope. These experiments enabled us to get a more detailed quantitative picture of the peculiarities of the two different types of carbon nanostructures. The nanoscrolls showed superior conductance >10G(o), against ≤1G(o) of the nested tubes, and a much enhanced electric sustainability (∼10(8) A/cm(2)). While the pronounced nonlinear increase in current in the nested tube structure with increasing applied voltage is directly related to an increasing number of tubes involved, the electric breakdown has correspondingly been characterized by fractional ablation of the successive layers. Scrolls, on the contrary, do not show any fractional electric response. Mechanical bending has been found easier with scrolled graphenes than with nested tubes. This observation confirms the prediction of higher flexibility of the scroll structure in interesting phenomena like intercalation and electroactuation.
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Affiliation(s)
- Andreas K Schaper
- Center for Materials Science, Philipps University of Marburg, 35032 Marburg, Germany.
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7
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Schaper AK, Kurata H, Yoshioka T, Tsuji M. Composite structure of liquid crystal/polymer nanotubes revealed by high-angle annular dark-field scanning transmission electron microscopy. Microsc Microanal 2007; 13:336-41. [PMID: 17900383 DOI: 10.1017/s1431927607070729] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/17/2006] [Accepted: 04/24/2007] [Indexed: 05/17/2023]
Abstract
We have applied high-angle annular dark-field microscopy to the characterization of the structure of template-grown nanotubes composed of a polymer and a discotic liquid crystalline material. Selective staining of the liquid crystal phase with ruthenium tetroxide was used to develop adequate Z-contrast that allows us to distinguish between the two phases. At appropriate staining conditions, we could clearly visualize, in the annular dark-field mode, a 5-15-nm thin liquid crystalline layer precipitated on the inner surface of the polymer tubes. Cryo-electron diffraction has shown high alignment of the discotic columns within the layer parallel to the tube axis. However, although the polymer/liquid crystal phase separation is almost complete, the wetting behavior of the polymer in relation to the template appears to be sensitively influenced by kinetic factors.
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Affiliation(s)
- Andreas K Schaper
- Material Sciences Center, Philipps University, Hans-Meerwein-Str., 35032 Marburg, Germany.
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8
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Abstract
Soft matter research of natural organic and synthetic nanomaterials is an area in nanoscience and technology that has been growing particularly quickly in recent years. The materials under investigation are sensitive to high-energy electrons. Any structure characterization using electron microscopy thus requires special care. First, we illustrated this on naturally grown nanotubes observed by normal and cryogenic scanning electron microscopy. Second, we studied the ordering and orientation of the mesophase in template-grown nanotubes and nanorods containing discotic liquid crystals without and with doping, as desired. For these studies, we mainly used transmission electron diffraction and microscopy at low-dose conditions, high-efficiency image acquisition, and cryoprotection of the structures at liquid helium temperature. Additional analytical information was obtained by electron energy filtering observations.
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Affiliation(s)
- A K Schaper
- Material Sciences Centre, Philipps University, Hans-Meerwein-Str., 35032 Marburg, Germany.
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9
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Jia ZH, Schaper AK, Massa W, Treutmann W, Rager H. Structure and phase transitions in Ca2CoSi2O7–Ca2ZnSi2O7 solid-solution crystals. Acta Crystallogr B Struct Sci 2006; 62:547-55. [PMID: 16840804 DOI: 10.1107/s0108768106016612] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/23/2005] [Accepted: 05/05/2006] [Indexed: 11/11/2022]
Abstract
While the incommensurability in melilites is well documented, the underlying atomic configurations and the composition-dependent phase behavior are not yet clear. We have studied the transition from the incommensurate phase to the high-temperature normal phase (IC-N), and to the low-temperature commensurate phase (IC-C) of selected members of the Ca2Co1 − x
Zn
x
Si2O7 system using X-ray and single-crystal electron diffraction, as well as calorimetric measurements. The space group of the unmodulated normal phase and of the basic structure of the incommensurate phase is P\bar 4 2_1m; the commensurate lock-in superstructure was refined as a pseudomerohedral twin in the orthorhombic space group P21212. We found that the commensurate modulation is mainly connected with a sawtooth-like periodicity of rotations of the T
1 tetrahedra in the 3 × 3 superstructure. In this structure, the clustering of the low-coordinated Ca2+ ions is not complete so that only imperfect octagons were detected. Generally, the effect of increasing substitution of Co by Zn was a continuous reduction of the IC-N and IC-C transition temperatures.
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Affiliation(s)
- Z H Jia
- Department of Geosciences, Material Sciences Center, Philipps University Marburg, Hans-Meerwein-Strasse, D-35032 Marburg, Germany
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Lottermoser W, Schaper AK, Treutmann W, Redhammer G, Tippelt G, Lichtenberger A, Weber SU, Amthauer G. 57Fe Mössbauer spectroscopy on multiwalled carbon nanotubes with metal filling. J Phys Chem B 2006; 110:9768-71. [PMID: 16706424 DOI: 10.1021/jp061803x] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Mössbauer measurements at different temperatures are reported for MWCNTs with metallic encapsulations ("nanowires"). The spectra can reasonably be refined with two subpatterns: one providing clear evidence of an iron carbide Fe(3)C (cementite) phase as the main nanowire component and the other yielding a relaxation doublet most probably belonging to the same phase. Whereas the former one displays a well resolved magnetic hyperfine spectrum with Brillouin type temperature dependence, the latter one gains importance with rising temperature or onset of an inhomogeneous external magnetic field. The comparably large incoherent scattering is attributed to the graphene layers of the tube walls. The experimental results are discussed on the background of an interpretation model trying to explain unusual magnetometric results published elsewhere.
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Westedt U, Wittmar M, Hellwig M, Hanefeld P, Greiner A, Schaper AK, Kissel T. Paclitaxel releasing films consisting of poly(vinyl alcohol)-graft-poly(lactide-co-glycolide) and their potential as biodegradable stent coatings. J Control Release 2006; 111:235-46. [PMID: 16466824 DOI: 10.1016/j.jconrel.2005.12.012] [Citation(s) in RCA: 117] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2005] [Revised: 12/12/2005] [Accepted: 12/14/2005] [Indexed: 12/20/2022]
Abstract
Although substantial progress in catheter and stent design has contributed to the success of percutaneous transluminal angioplasty (PTA) of atherosclerotic disease, the incidence of restenosis caused by in-stent neointimal hyperplasia remains a serious problem. Therefore, stents with a non-degradable polymer coating showing controlled release of active ingredients have become an attractive option for the site-specific delivery of anti-restenotic agents. Biodegradable coatings using polyesters, namely poly(lactic-co-glycolic acid) (PLGA) and different poly(vinyl alcohol)-graft-poly(lactic-co-glycolic acid) (PVA-g-PLGA) as paclitaxel-eluting stent coating materials were investigated here to evaluate their influence on the release kinetic. Whereas PLGA showed sigmoid release behavior, the paclitaxel release from PVA-g-PLGA films was continuous over 40 days without initial drug burst. Wide angle X-ray diffraction confirmed that paclitaxel is dissolved in the polymer matrix. Paclitaxel crystallization can be observed at a drug load of > or =10%. The effect of drug loading on polymer degradation was studied in films prepared from PVA300-g-PLGA30 with paclitaxel loadings of 5% and 15% over a time period of 6 weeks. The results suggest a surface-like erosion mechanism in films. A model stent (Jostent peripheral) coated with Parylene N, a poly(p-xylylene) (PPX) derivate, was covered with a second layer of PVA300-g-PLGA15, and PVA300-g-PLGA30 by using airbrush method. Morphology of coated stents, and film integrity after expansion from 3.12 to 5 mm was investigated by scanning electron microscopy (SEM). The devices resisted mechanical stress during stent expansion and merit further investigation under in vivo conditions.
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Affiliation(s)
- Ulrich Westedt
- Philipps University Marburg, Faculty of Pharmacy and Biopharmaceutics, Ketzerbach 63, 35032 Marburg, Germany
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Yosef M, Schaper AK, Fröba M, Schlecht S. Stabilization of the Thermodynamically Favored Polymorph of Cadmium Chalcogenide Nanoparticles CdX (X = S, Se, Te) in the Polar Mesopores of SBA-15 Silica. Inorg Chem 2005; 44:5890-6. [PMID: 16060644 DOI: 10.1021/ic050517h] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A versatile synthetic approach to cadmium chalcogenide nanoparticles in the mesopores of SBA-15 silica as a host matrix was developed. The use of cadmium organochalcogenolates of the type Cd(XPh)(2).TMEDA (X = S, Se, Te) allowed the preparation of nanoparticles of all three cadmium chalcogenides following the same experimental protocol. Particles of CdS, CdSe, and CdTe with a particle size of 7 nm were prepared from this class of single-source precursors. The incorporation of the precursor molecules into the pores was achieved by melt infiltration at a temperature of 140 degrees C. Subsequent pyrolysis of the precursors in the mesopores yielded the semiconductor particles. Owing to the high polarity of the silanol-covered pore walls, which lower the surface energy of the particles to a large extent, the dimorphic cadmium chalcogenides are obtained in their thermodynamically favored modifications; e.g., CdS particles crystallize in the wurtzite type, CdTe particles are obtained in the zinc blende structure, and CdSe (where no unambiguous preference exists) crystallizes as a "mixture" of both structures with a rather random stacking sequence.
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Affiliation(s)
- Maekele Yosef
- Fachbereich Chemie, Philipps-Universität Marburg, Germany
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Oster CG, Kim N, Grode L, Barbu-Tudoran L, Schaper AK, Kaufmann SHE, Kissel T. Cationic microparticles consisting of poly(lactide-co-glycolide) and polyethylenimine as carriers systems for parental DNA vaccination. J Control Release 2005; 104:359-77. [PMID: 15907586 DOI: 10.1016/j.jconrel.2005.02.004] [Citation(s) in RCA: 85] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2004] [Revised: 02/01/2005] [Accepted: 02/02/2005] [Indexed: 11/19/2022]
Abstract
Cationic microparticles for DNA adsorption were formulated by blending poly(lactide-co-glycolide) (PLGA) (50:50), with different cationic agents, either PEI 25 kDa (polyethylenimine) or CTAB (cetyl-trimethyl-ammonium-bromide). The aim was to create adjuvant delivery systems increasing the efficiency of DNA vaccines. Microparticles formulated with 10% PEI exhibited a highly positive zeta-potential, small particle sizes, in contrast to particles prepared with CTAB, which revealed highly aggregated structures in scanning electron micrographs. PEI 10% microparticles efficiently adsorbed DNA and protected DNA from enzymatic degradation. Microparticles with up to 10% PEI did not affect membrane integrity whereas CTAB particles showed higher LDH release. Transfection efficiencies were assessed using a luciferase reporter gene assay compared to naked DNA and PEI/DNA polyplexes. DNA adsorbed onto microspheres with 10% or 50% PEI generally had higher transfection efficiencies than CTAB but reached lower expression levels than PEI/DNA polyplexes alone. This documented the intact release of DNA. The mechanism of gene delivery to non-phagocytic cells was studied via covalent fluorescence labeling of both the DNA and PEI by confocal microscopy and suggested uptake of DNA. Immunization of mice was performed using plasmids encoding immunodominant antigens of Listeria monocytogenes adsorbed onto RG 502 H+PEI 10% microparticles. The efficiency was tested by intravenous challenge with an otherwise lethal dose of L. monocytogenes. PLGA+PEI microspheres can be used as adjuvant delivery systems for DNA but further optimization is necessary to exploit their full potential.
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Affiliation(s)
- C G Oster
- Department of Pharmaceutics and Biopharmacy, Philipps-University, Ketzerbach 63, D-35032 Marburg, Germany
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Steinhart M, Zimmermann S, Göring P, Schaper AK, Gösele U, Weder C, Wendorff JH. Liquid crystalline nanowires in porous alumina: geometric confinement versus influence of pore walls. Nano Lett 2005; 5:429-434. [PMID: 15755089 DOI: 10.1021/nl0481728] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Aligned liquid crystalline nanowires within ordered porous alumina templates show a pronounced texture on a macroscopic scale. We have investigated the influence of the geometric confinement and the nature of the pore walls on the mesophase formation by means of X-ray diffraction. The apparent texture is the result of a complex interplay of the pore geometry, interfacial phenomena, and the thermal history. Pores with a diameter of a few hundred nm guide the mesophase formation more efficiently than those with a diameter below 100 nm.
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Affiliation(s)
- Martin Steinhart
- Max Planck Institute of Microstructure Physics, Weinberg 2, D-6120 Halle, Germany.
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Westedt U, Barbu-Tudoran L, Schaper AK, Kalinowski M, Alfke H, Kissel T. Effects of different application parameters on penetration characteristics and arterial vessel wall integrity after local nanoparticle delivery using a porous balloon catheter. Eur J Pharm Biopharm 2005; 58:161-8. [PMID: 15207550 DOI: 10.1016/j.ejpb.2004.03.009] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2003] [Accepted: 03/09/2004] [Indexed: 11/21/2022]
Abstract
Catheter-based local delivery of drug loaded nanoparticles agents offers a potential therapeutic approach to reducing restenosis. However, high delivery pressures and large volumes of infusates may cause severe vascular damage and increase intimal thickening. Therefore, we investigated the penetration pattern and vessel wall integrity of fluorescence-labelled nanoparticles (217 nm in diameter) into the non-atherosclerotic aorta abdominalis of New Zealand white rabbits in dependence of the volume (2.5 and 5 ml) and concentration (0.5 and 1 mg/ml) of the nanoparticle suspension, as well as the infusion pressure (2 and 4 atm) using a channelled balloon catheter (SCIMED REMEDY model RC 20/2.5). The location and penetration characteristics of nanoparticles in the arterial vessel wall were visualized using confocal laser scanning microscopy and transmission electron microscopy (TEM). Catheter design and infusion pressure form a radial particle stream through intima and media into the adventitial layer of the aorta abdominalis. Infusion pressures of 4 atm in combination with high particle concentrations lead to effective nanoparticle delivery without severe vessel wall disruptions. Endothelium of the treated vessel segments was slightly affected during catheter insertion showing partly denudation of the innermost cell layer. TEM micrographs underlines transport functional properties of the vasa vasorum inside the vessel wall. Consequently, local delivery efficiency of nanoparticulate carriers is critically affected by infusion pressure, and concentration of carrier suspensions. These factors need to be taken into consideration for the design of in vivo experiments.
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Affiliation(s)
- Ulrich Westedt
- Department of Pharmaceutics and Biopharmacy, Philipps-University, Marburg, Germany
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Oster CG, Wittmar M, Unger F, Barbu-Tudoran L, Schaper AK, Kissel T. Design of Amine-Modified Graft Polyesters for Effective Gene Delivery Using DNA-Loaded Nanoparticles. Pharm Res 2004; 21:927-31. [PMID: 15212155 DOI: 10.1023/b:pham.0000029279.50733.55] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
PURPOSE The purpose of this study was the design of a polymeric platform for effective gene delivery using DNA-loaded nanoparticles. METHODS The polymers were synthesized by carbonyldiimidazole (CDI)-mediated coupling of diamines diethylaminopropylamine (DEAPA), dimethylaminopropylamine (DMAPA) or diethylaminoethylamine (DEAEA) to poly(vinyl alcohol) (PVA) with subsequent grafting of D,L-lactide and glycolide (1:1) in the stoichiometric ratios of 1:10 and 1:20 (free hydroxyl groups/monomer units). The polymers were characterized by 1H-NMR, gel permeation chromatography-multiple-angle laser-light-scattering, and differential scanning calorimetry. DNA-loaded nanoparticles prepared by a modified solvent displacement method were characterized with regard to their zeta (zeta)-potential and size. The transfection efficiency was assessed with the plasmid DNA pCMV-luc in L929 mouse fibroblasts. RESULTS The polymers were composed of highly branched, biodegradable cationic polyesters exhibiting amphiphilic properties. The amine modification enhanced the rapid polymer degradation and resulted in the interaction with DNA during particle preparation. The nanoparticles exhibited positive zeta-potentials up to +42 mV and high transfection efficiencies, comparable to polyethylenimine (PEI) 25 kDa/DNA complexes at a nitrogen to phosphate ratio of 5. CONCLUSIONS The polymers combined amine-functions and short poly(D,L-lactic-co-glycolic acid) (PLGA) chains resulting in water-insoluble polymers capable of forming biodegradable DNA nanoparticles through coulombic interactions and polyester precipitation in aqueous medium. The high transfection efficiency was based on fast polymer degradation and the conservation of DNA bioactivity.
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Affiliation(s)
- Christine G Oster
- Department of Pharmaceutics and Biopharmacy, Philipps-University, D-35032 Marburg, Germany
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Abstract
Cross-linkable di- and triblock copolymers of poly(epsilon-caprolactone) (PCL) and monomethoxyl poly(ethylene glycol) (MPEG) were synthesized. These amphiphilic copolymers self-assembled into nanoscale micelles capable of encapsulating hydrophobic paclitaxel in their hydrophobic cores in aqueous solutions. To further enhance their thermodynamic stability, the micelles were cross-linked by radical polymerization of the double bonds introduced into the PCL blocks. Reaction conditions were found to significantly affect both the cross-linking efficiency and the micelle size. The encapsulation of paclitaxel into the micelles was confirmed by the proton nuclear magnetic resonance (1H NMR) spectroscopy. Encouragingly, paclitaxel-loading efficiency of micelles was enhanced significantly upon micelle core-cross-linking. Both the micelle size and the drug loading efficiency increased markedly with increasing the PCL block lengths, no matter if the micelles were core-cross-linked or not. However, paclitaxel-loading did not obviously affect the micelle size or size distribution. The cross-linked micelles exhibited a significantly enhanced thermodynamic stability against dilution with aqueous solvents. The efficient cellular uptake of paclitaxel loaded in the nanomicelles was demonstrated by confocal laser scanning microscopy (CLSM) imaging. This new biodegradable nanoscale carrier system merits further investigations for parenteral drug delivery.
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Affiliation(s)
- Xintao Shuai
- Department of Pharmaceutics and Biopharmacy, Philipps-University of Marburg, Ketzerbach 63, D-35032 Marburg, Germany
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19
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Westedt U, Barbu-Tudoran L, Schaper AK, Kalinowski M, Alfke H, Kissel T. Deposition of nanoparticles in the arterial vessel by porous balloon catheters: localization by confocal laser scanning microscopy and transmission electron microscopy. AAPS PharmSci 2002; 4:E41. [PMID: 12646012 PMCID: PMC2751330 DOI: 10.1208/ps040441] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Restenosis remains the major limitation of percutaneous transluminal angioplasty (PTA) and stenting in the treatment of patients with atherosclerotic disease. Catheter-based local delivery of pharmacologic agents offers a potential therapeutic approach to reducing restenosis and minimizing undesirable systemic side effects. However, the intramural retention of liquid agents is low. Therefore, to achieve a sustained and regional release of the therapeutic agent it must be encapsulated in nanoparticle carrier systems. The purpose of this study was to investigate the size dependence of the penetration of nanoparticles after local delivery into the vessel wall of the aorta abdominalis of New Zealand white rabbits. Two milliliters of a 0.025% fluorescence-labeled polystyrene nanoparticle suspension with diameters ranging from 110 to 514 nm were infused at 2 atm and at constant PTA pressure of 8 atm into the aorta abdominalis. After the infused segments were removed, the location of nanoparticles was visualized using confocal laser scanning microscopy and transmission electron microscopy. The study demonstrates a size-dependent nanoparticle penetration into the intact vessel wall. While nanoparticles of about 100 and 200 nm were deposited in the inner regions of the vessel wall, 514-nm nanoparticles accumulated primarily at the luminal surface of the aorta. The observations confirm that size plays a critical role in the distribution of particles in the arterial vessel wall. It is additionally influenced by the formation of pressure-induced infusion channels, as well as by the existence of anatomic barriers, such as plaques, at the luminal surface of the aorta or the connective elastic tissue.
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Affiliation(s)
- Ulrich Westedt
- Department of Pharmaceutics and Biopharmacy, Philipps-University, Ketzerbach 63, D-35032 Marburg, Germany
| | | | | | - Marc Kalinowski
- Department of Diagnostic Radiology, Philipps-University, D-35032 Marburg, Germany
| | - Heiko Alfke
- Department of Diagnostic Radiology, Philipps-University, D-35032 Marburg, Germany
| | - Thomas Kissel
- Department of Pharmaceutics and Biopharmacy, Philipps-University, Ketzerbach 63, D-35032 Marburg, Germany
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Schaper AK, Schosnig M, Kutoglu A, Treutmann W, Rager H. Transition from the incommensurately modulated structure to the lock-in phase in Co-åkermanite. Acta Crystallogr B 2001; 57:443-8. [PMID: 11468369 DOI: 10.1107/s0108768101006930] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/03/2000] [Accepted: 04/25/2001] [Indexed: 11/11/2022]
Abstract
The adaptation of the incommensurate structure modulation in Ca(2)CoSi(2)O(7) (dicalcium cobalt disilicate) single crystals to decreasing temperature has been examined using in situ high-resolution transmission electron microscopy and electron diffraction. The transition from the incommensurate to the commensurate lock-in phase of Co-åkermanite exhibits a pronounced hysteresis of a highly strained metastable state with a characteristic microdomain morphology. A network of domain walls surrounding single orientation domains develops out of the room-temperature tartan pattern, the domains increase in size and their alignment changes from crystallographic to random. At 100 K the phase transition becomes almost complete. In parallel, the evolution of the modulation structure can be described by a change from a loose arrangement of octagonal tilings into a close-packed configuration of overlapping octagons in the commensurate low-temperature lock-in phase. Thereby, the octagon represents the ordered distribution of low-coordinated Ca clusters within a nanodomain extending over 4 x 4 subunits, on average [Riester et al. (2000). Z. Kristallogr. 215, 102--109]. The modulation wavevector was found to change from q(1,2) = 0.295 (a* +/- b*) at 300 K to q(1,2) = 0.320 (a* +/- b*) at 100 K.
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Affiliation(s)
- A K Schaper
- Department of Geosciences and Materials Science Center, Philipps University Marburg, Hans-Meerwein-Strasse, D-35032 Marburg, Germany.
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