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H Windhagen - One of the best experts on this subject based on the ideXlab platform.

  • bioDegradable magnesium based screw clinically equivalent to titanium screw in hallux valgus surgery short term results of the first prospective randomized controlled clinical pilot study
    Biomedical Engineering Online, 2013
    Co-Authors: H Windhagen, Kerstin Radtke, Andreas Weizbauer, Julia Diekmann, Yvonne Noll, Ulrike Kreimeyer, Robert Schavan, Christina Stukenborgcolsman, Hazibullah Waizy
    Abstract:

    Purpose: NonDegradable steel-and titanium-based implants are commonly used in orthopedic surgery. Although they provide maximal stability, they are also associated with interference on imaging modalities, may induce stress shielding, and additional explantation procedures may be necessary. Alternatively, Degradable Polymer implants are mechanically weaker and induce foreign body reactions. Degradable magnesium-based stents are currently being investigated in clinical trials for use in cardiovascular medicine. The magnesium alloy MgYREZr demonstrates good biocompatibility and osteoconductive properties. The aim of this prospective, randomized, clinical pilot trial was to determine if magnesium-based MgYREZr screws are equivalent to standard titanium screws for fixation during chevron osteotomy in patients with a mild hallux valgus. Methods: Patients (n=26) were randomly assigned to undergo osteosynthesis using either titanium or Degradable magnesium-based implants of the same design. The 6 month follow-up period included clinical, laboratory, and radiographic assessments. Results: No significant differences were found in terms of the American Orthopaedic Foot and Ankle Society (AOFAS) score for hallux, visual analog scale for pain assessment, or range of motion (ROM) of the first metatarsophalangeal joint (MTPJ). No foreign body reactions, osteolysis, or systemic inflammatory reactions were detected. The groups were not significantly different in terms of radiographic or laboratory results.

  • evaluation of the skin sensitizing potential of bioDegradable magnesium alloys
    Journal of Biomedical Materials Research Part A, 2008
    Co-Authors: Frank Witte, Volker Kaese, Andrea Meyerlindenberg, Inken Abeln, Elinor Switzer, H Windhagen
    Abstract:

    Corroding metals made of magnesium alloys represent a new class of Degradable implants for musculoskeletal surgery. These implants may be associated with skin sensitizing reactions because of the release of metal ions. This study was conducted to compare the sensitizing potential of four different magnesium alloys (AZ31, AZ91, WE43, and LAE442) to current implant materials such as titanium (TiAl6V4) and a Degradable Polymer (SR-PLA96). Solutions and solid chips of these materials were prepared and tested in 156 guinea pigs according to the Magnusson-Kligman test. A standard allergen (hydroxy-cinnamon-aldehyde) causing allergic erythema was used as positive control and a standard irritant (sodium-lauryl-sulfate) causing local skin irritation for less than 24 h was used as negative control. All erythema were graded immediately and 24 h after patch removal by three independent observers. Histomorphological analyses were performed on skin biopsies taken 24 h after patch removal. We found that initial erythema in animals treated with solid chips diminished within 24 h and were caused by local skin irritation. Local skin irritation was also determined in erythema remaining for 24 h after patch removal in animals treated with dissolved test materials. No allergenic reactions according to the histomorphological criteria were observed in skin biopsies. We conclude that no skin sensitizing potential were detected for standard materials as well as for all tested magnesium alloys by the used methods.

  • in vivo corrosion of four magnesium alloys and the associated bone response
    Biomaterials, 2005
    Co-Authors: Frank Witte, Volker Kaese, Heinz Haferkamp, E Switzer, Andrea Meyerlindenberg, Carl Joachim Wirth, H Windhagen
    Abstract:

    Degrading metal alloys are a new class of implant materials suitable for bone surgery. The aim of this study was to investigate the degradation mechanism at the bone-implant interface of different degrading magnesium alloys in bone and to determine their effect on the surrounding bone. Sample rods of four different magnesium alloys and a Degradable Polymer as a control were implanted intramedullary into the femora of guinea pigs. After 6 and 18 weeks, uncalcified sections were generated for histomorphologic analysis. The bone-implant interface was characterized in uncalcified sections by scanning electron microscopy (SEM), element mapping and X-ray diffraction. Results showed that metallic implants made of magnesium alloys degrade in vivo depending on the composition of the alloying elements. While the corrosion layer of all magnesium alloys accumulated with biological calcium phosphates, the corrosion layer was in direct contact with the surrounding bone. The results further showed high mineral apposition rates and an increased bone mass around the magnesium rods, while no bone was induced in the surrounding soft tissue. From the results of this study, there is a strong rationale that in this research model, high magnesium ion concentration could lead to bone cell activation.

Frank Caruso - One of the best experts on this subject based on the ideXlab platform.

  • A paradigm for peptide vaccine delivery using viral epitopes encapsulated in Degradable Polymer hydrogel capsules
    Biomaterials, 2009
    Co-Authors: Siow-feng Chong, Alexander N. Zelikin, Amy Sexton, Robert De Rose, Stephen J. Kent, Frank Caruso
    Abstract:

    Abstract We report on the use of Degradable Polymer capsules as carriers for the delivery of oligopeptide antigens to professional antigen presenting cells (APCs). To achieve encapsulation, oligopeptide sequences were covalently linked to a negatively charged carrier Polymer via bioDegradable linkages and the resulting conjugate was then adsorbed onto amine-functionalized silica particles. These peptide-coated particles were then used as templates for the layer-by-layer (LbL) deposition of thiolated poly(methacrylic acid) (PMA SH ) and poly(vinylpyrrolidone) (PVPON) multilayers. Removal of the silica core and disruption of the hydrogen bonding between PMA SH and PVPON by altering the solution pH yielded disulfide-stabilized PMA capsules that retain the encapsulated cargo in an oxidative environment. In the presence of a natural reducing agent, glutathione, cleavage of the disulfide bonds causes release of the peptide from the capsules. The developed strategy provides control over peptide loading into Polymer capsules and yields colloidally stable micron- and submicron-sized carriers with uniform size and peptide loading. The conjugation and encapsulation procedures were proven to be non-degrading to the peptide vaccines. The peptide-loaded capsules were successfully used to deliver their cargo to APCs and activate CD8 T lymphocytes in a non-human primate model of SIV infection ex vivo . The reported approach represents a novel paradigm in the delivery of peptide vaccines and other therapeutic agents.

  • disulfide stabilized poly methacrylic acid capsules formation cross linking and degradation behavior
    Chemistry of Materials, 2008
    Co-Authors: Alexander N. Zelikin, Frank Caruso
    Abstract:

    We report the preparation of monodisperse, single-component Degradable Polymer capsules for potential applications in encapsulation, catalysis, and controlled drug delivery. The synthesized capsules, composed entirely of poly(methacrylic acid) (PMA), are obtained by the sequential deposition of thiolated poly(methacrylic acid) (PMASH) and poly(vinylpyrrolidone) (PVPON) onto silica particles, controlled oxidation of thiol groups into bridging disulfide linkages in the PMASH, removal of the silica particles, and finally, release of PVPON by altering the solution pH to disrupt hydrogen bonding between PMASH and PVPON. The PMA capsules are held together solely through bioDegradable disulfide linkages. We demonstrate that the capsules undergo reversible swelling in response to changes in external pH, and degrade in the presence of a physiological concentration of a natural thiol-containing peptide, glutathione. These capsules are of interest for in vivo applications, where degradation of the capsules, through ...

  • A General Approach for DNA Encapsulation in Degradable Polymer Microcapsules
    ACS nano, 2007
    Co-Authors: Alexander N. Zelikin, Alisa L. Becker, Angus P. R. Johnston, Kim L. Wark, Fabio Turatti, Frank Caruso
    Abstract:

    We report a general and facile method for the encapsulation of DNA in nanoengineered, Degradable Polymer microcapsules. Single-stranded (ss), linear double-stranded (ds), and plasmid DNA were encapsulated into disulfide-cross-linked poly(methacrylic acid) (PMA) capsules. The encapsulation procedure involves four steps: adsorption of DNA onto amine-functionalized silica (SiO2+) particles; sequential deposition of thiolated PMA (PMASH) and poly(vinylpyrrolidone) to form multilayers; cross-linking of the thiol groups of the PMASH in the multilayers into disulfide linkages; and removal of the sacrificial SiO2+ particles. Multilayer growth was dependent on the surface coverage of DNA on the SiO2+ particles, with stable capsules formed from particles with up to 50% DNA surface coverage. The encapsulation strategy applies to nucleic acids with varied size and conformation and allows DNA to be concentrated over 100-fold from dilute solutions into monodisperse, uniformly loaded Polymer capsules. The capsule loadin...

Sergey K Filippov - One of the best experts on this subject based on the ideXlab platform.

  • hydrolytically Degradable Polymer micelles for drug delivery a saxs sans kinetic study
    Biomacromolecules, 2013
    Co-Authors: Sergey K Filippov, John M Franklin, Petr V Konarev, Petr Chytil, Tomas Etrych, Anna Bogomolova, Margarita Dyakonova, Christine M Papadakis, Aurel Radulescu, Karel Ulbrich
    Abstract:

    We report kinetic studies of therapeutically highly potent Polymer–drug conjugates consisting of amphiphilic N-(2-hydroxypropyl) methacrylamide (HPMA)-based coPolymers bearing the anticancer drug doxorubicin (Dox). Highly hydrophobic cholesterol moieties as well as the drug were attached to the Polymer backbone by a pH-sensitive hydrazone bond. Moreover, the structure of the spacer between the Polymer carrier and the cholesterol moiety differed in order to influence the release rate of the hydrophobic moiety, and thus the disintegration of the high-molecular-weight micellar nanoparticle structure. We performed time-dependent SAXS/SANS measurements after changing pH from a typical blood value (pH 7.2) to that of tumor cells (pH 5.0) to characterize the drug release and changes in particle size and shape. Nanoparticles composed of the conjugates containing Dox were generally larger than the drug-free ones. For most conjugates, nanoparticle growth or decay was observed in the time range of several hours. It ...

  • thermoresponsive hydrolytically Degradable Polymer micelles intended for radionuclide delivery
    Macromolecular Bioscience, 2009
    Co-Authors: Martin Hruby, Cestmir Konak, Jan Kucka, Miroslav Vetrik, Sergey K Filippov, David Vetvicka, Hana Mackova, Goran Karlsson, Katarina Edwards, Blanka Rihova
    Abstract:

    Novel Polymer micelles, prepared by self-assembling thermoresponsive poly(N-isopropylacrylamide)-graft-poly[N-(2-hydroxypropyl)methacrylamide] coPolymers with hydrolytically Degradable N-glycosylamine groups between the Polymer blocks are proposed for delivery of diagnostic and therapeutic radionuclides into solid tumors. The micelles are formed by fast heating of an aqueous solution of the coPolymer to 37 degrees C. They have a hydrodynamic diameter of 128 nm (measured using dynamic light scattering) and slowly degrade during incubation in aqueous buffer at pH = 7.4. Labeling with both (131)I and (90)Y proceeds with high yields (>85%). The unlabeled Polymers are not cytotoxic for any of the tested murine and human cell lines.

Suthenthira Veerappa Vimalanand - One of the best experts on this subject based on the ideXlab platform.

  • determination of stress intensity factor of banana fibre reinforced hybrid Polymer matrix composite using finite element method
    Periodica Polytechnica Mechanical Engineering, 2016
    Co-Authors: Ravi Tumkur Suryawanshi, Gopala Venkatachalam, Suthenthira Veerappa Vimalanand
    Abstract:

    In the current scene on material field, designers are focusing on the development of lightweight, high strength, recyclable and environment friendly materials. Due to increasing environmental admiration, ecological concerns and new statutory laws, natural fibre reinforced Polymer matrix composites have found increasing attention from the recent decades. Past studies show that synthetic and natural fibres such as glass, carbon, jute, coir etc., have been used in fibre reinforced Polymer matrix composite. In this work, banana fibre is used as reinforcement. An investigation is carried out to make use of banana fibre made hybrid Polymer matrix composite. Bio-Degradable Polymer like Cashew Nut Shell Liquid (CNSL) in different percentage is used with General Purpose (GP) resin to make a hybrid Polymer matrix. This work intends to study the fracture analysis of composite by using experimental and Finite Element methods. The critical stress intensity factor (KIC or critical SIF) has been evaluated and validated.

  • determination of stress intensity factor of banana fibre reinforced hybrid Polymer matrix composite using finite element method
    Periodica Polytechnica Mechanical Engineering, 2016
    Co-Authors: Ravi Tumkur Suryawanshi, Gopala Venkatachalam, Suthenthira Veerappa Vimalanand
    Abstract:

    In the current scene on material field, designers are focusing on the development of lightweight, high strength, recyclable and environment friendly materials. Due to increasing environmental admiration, ecological concerns and new statutory laws, natural fibre reinforced Polymer matrix composites have found increasing attention from the recent decades. Past studies show that synthetic and natural fibres such as glass, carbon, jute, coir etc., have been used in fibre reinforced Polymer matrix composite. In this work, banana fibre is used as reinforcement. An investigation is carried out to make use of banana fibre made hybrid Polymer matrix composite. Bio-Degradable Polymer like Cashew Nut Shell Liquid (CNSL) in different percentage is used with General Purpose (GP) resin to make a hybrid Polymer matrix. This work intends to study the fracture analysis of composite by using experimental and Finite Element methods. The critical stress intensity factor (KIC or critical SIF) has been evaluated and validated.

Haewon Kim - One of the best experts on this subject based on the ideXlab platform.

  • synthesis characterization and 3d printing of an isosorbide based light curable Degradable Polymer for potential application in maxillofacial reconstruction
    ACS Biomaterials Science & Engineering, 2020
    Co-Authors: Nazanin Owji, Haewon Kim, Alaa Aldaadaa, Jaeryung Cha, Taleen Shakouri, Elena Garciagareta, Jonathan C Knowles
    Abstract:

    Although emergence of bone tissue engineering techniques has revolutionized the field of maxillofacial reconstruction, the successful translation of such products, especially concerning larger sized defects, still remains a significant challenge. Light-curable methacrylate-based Polymers have ideal properties for bone repair. These materials are also suitable for 3D printing which can be applicable for restoration of both function and aesthetics. The main objective of this research was to synthesize a mechanically stable and biologically functional Polymer for reconstruction of complex craniofacial defects. The experimental work initially involved synthesis of (((3R,3aR,6S,6aR)-hexahydrofuro[3,2-b]furan-3,6-diyl)bis(oxy))bis(ethane-2,1-diyl)bis((4-methyl-3-oxopent-4-en-1-yl)carbamate), CSMA-1, and ((((((((((((3R,3aR,6S,6aR)-hexahydrofuro[3,2-b]furan-3,6-diyl)bis(oxy))bis(ethane-2,1 diyl))bis(oxy))bis(carbonyl))bis(azanediyl))bis(methylene))bis(3,3,5-trimethylcyclohexane-5,1-diyl))bis(azanediyl))bis(carbonyl))bis(oxy))bis(ethane-2,1-diyl)bis(2-methylacrylate), CSMA-2; nuclear magnetic resonance analysis confirmed formation of the monomers, and composite samples were fabricated respectively by exposing 11 mm diameter discs to blue light. Modulus of elasticity was determined using a biaxial flexural test and the values were found to be between 1 and 3 GPa in CSMA-1, CSMA-2, and their composites. In vitro cell culture, using human bone marrow-derived mesenchymal stem cells, confirmed nontoxicity of the samples and finally 3D printing allowed direct photo-Polymerization and setting of the bio ink into a 3D construct.

  • biomedical nanocomposites of poly lactic acid and calcium phosphate hybridized with modified carbon nanotubes for hard tissue implants
    Journal of Biomedical Materials Research Part B, 2011
    Co-Authors: Haehyoung Lee, Ueon Sang Shin, Jaeho Lee, Haewon Kim
    Abstract:

    Degradable Polymer-based materials are attractive in orthopedics and dentistry as an alternative to metallic implants for use as bone fixatives. Herein, a Degradable Polymer poly(lactic acid) (PLA) was combined with novel hybrid nanopowder of carbon nanotubes (CNTs)-calcium phosphate (CP) for this application. In particular, CNTs-CP hybrid nanopowders (0.1 and 0.25% CNTs) were prepared from the solution of ionically modified CNTs (mCNTs), which was specifically synthesized to be well-dispersed and thus to effectively adsorb onto the CP nanoparticles. The mCNTs-CP hybrid nanopowders were then mixed with PLA (up to 50%) to produce mCNTs-CP-PLA nanocomposites. The mechanical tensile strength of the nanocomposites was significantly improved by the addition of mCNTs-CP hybrid nanopowders. Moreover, nanocomposites containing low concentration of mCNTs (0.1%) showed significantly stimulated biological responses including cell proliferation and osteoblastic differentiation in terms of gene and protein expressions. Based on this study, the addition of novel mCNT-CP hybrid nanopowders to PLA bioPolymer may be considered a new material choice for developing hard tissue implants. © 2011 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2011.