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Mihranyan A.,Uppsala University | Esmaeili M.,Uppsala University | Razaq A.,Uppsala University | Razaq A.,COMSATS Institute of Information Technology | And 2 more authors.
Journal of Materials Science | Year: 2012

Paper-based conductive electrode materials of polypyrrole (PPy) and nanocellulose (NC) have received much attention lately for applications in non-metal-based energy storage devices, ion exchange, etc. The aim of this study was to study how the primary characteristics of NC raw materials impact and electrochemical properties of conductive NC-PPy composite sheets. Three NC raw materials were used: Cladophora cellulose (NCUU) produced at Uppsala University, Cladophora cellulose (NCFMC) produced at FMC Biopolymer, and microfibrillated cellulose (NC INN) produced at Innventia AB. Composite paper sheets of PPy coated on the substrate NC material were produced. The NC raw materials and the composites were characterized with a battery of techniques to derive their degree of crystallinity, degree of polymerization, specific surface area, pore size distribution, porosity, electron conductivity, charge capacity and tensile properties. It was found that the pore size distribution and overall porosity increase upon coating of NC fibres for all the samples. The charge capacity of the composites was found to decrease with the porosity of the samples. It was further found that the mechanical strength of the pristine NC sheets was largely dependent on the overall porosity, with NC INN having the highest mechanical strength and lowest porosity in the series. The mechanical properties of the composite NC-PPy sheets were significantly diminished as compared with pristine NC sheets because of the impaired H-bonding between fibres and PPy-coated nanofibres. It was concluded that to improve the mechanical properties of PPy-NC sheets, a fraction of additive bare NC fibres is beneficial. Future study may include the effect of both soluble and insoluble additives to improve the mechanical strength of PPy-NC sheets. © Springer Science+Business Media, LLC 2012. Source


Moroni A.,Glaxo SmithKline CHRandD | Drefko W.,International Specialty Products | Thone G.,FMC BioPolymer
Drug Development and Industrial Pharmacy | Year: 2011

Background: Matrix type, monolithic, dosage forms suitable for controlled release that exhibit pH-dependent behavior are considerably less common than similarly behaving multiparticulated, enterically coated dosage forms, although simpler and less expensive to make. Aim: Evaluate the properties of alginates and alginate-containing systems to produce pH-sensitive, monolithic, controlled release dosage forms that perform acceptably and determine their limits of application in regard with stability, pH and Ca ++ sensitivity, and appropriated rate of release. Method: Mixtures of the ionic gum sodium alginate (Na Alg.) with other gel-forming gums such as propylene glycol alginate (PGA), xanthan, or hydroxypropyl methylcellulose have been evaluated for applicability in the manufacture of controlled release dosage forms with three drugs of different solubility and ionic character. Mixture have been compressed into tablets and tested under a variety of pHs to simulate transit through the GI tract, in the presence of Ca ++, and for stability. Results: These mixtures have been able to sustain drug release for up to 12 hours with acceptable performance going from acidic to alkaline pHs to simulate travel through the GI tract and in the presence of Ca ++. Release rate has been adjusted by selecting a suitable Na Alg./other gum combination at an appropriated ratio. Conclusions: Mixtures of Na Alg. with a number of other gums have been demonstrated suitable to manufacture pH sensitive, matrix-type solid dosage forms with release-controlling properties for up to 12 hours. © 2011 Informa UK, Ltd. Source


Rosiaux Y.,University of Lille Nord de France | Rosiaux Y.,French Institute of Health and Medical Research | Velghe C.,University of Lille Nord de France | Velghe C.,French Institute of Health and Medical Research | And 8 more authors.
Pharmaceutical Research | Year: 2014

Purpose: To elucidate the mass transport mechanisms controlling drug release from recently proposed, ethanol-resistant, polymeric film coatings. Methods: Theophylline matrix pellets were coated with ethylcellulose: guar gum blends. Drug release from single pellets and ensembles of pellets was measured in various release media. Changes in the systems' morphology, composition and mechanical properties were monitored using SEM, gravimetrical analysis and a texture analyzer. Based on the obtained experimental results a mechanistically realistic mathematical model was identified and used to quantitatively predict drug release from coated pellets in ethanol-free and ethanol-containing bulk fluids. Results: Drug diffusion though the intact polymeric film coatings is likely to be the dominant mass transport mechanism in the investigated systems, irrespective of the ethanol content in the surrounding environment. An appropriate solution of Fick's law could be used to quantitatively predict theophylline release from pellets coated with different ethylcellulose:guar gum blends at different coating levels. Importantly, independent experiments confirmed the theoretical predictions. Conclusions: In silico simulations can help facilitating the optimization of the novel ethanol-resistant polymeric film coatings, avoiding time-consuming and cost-intensive series of trial-and-error experiments. The presence/absence of ethanol does not affect the underlying drug release mechanisms. © 2013 Springer Science+Business Media New York. Source


Muschert S.,University of Lille Nord de France | Muschert S.,French Institute of Health and Medical Research | Siepmann F.,University of Lille Nord de France | Siepmann F.,French Institute of Health and Medical Research | And 3 more authors.
European Journal of Pharmaceutics and Biopharmaceutics | Year: 2011

When using aqueous polymer dispersions for the preparation of controlled-release film coatings, instability during long-term storage can be a crucial concern. Generally, a thermal after treatment is required to assure sufficient polymer particle coalescence. This curing step is often performed under static conditions in an oven, which is a time-consuming and rather cumbersome process. Dynamic curing in the fluidized bed presents an attractive alternative. However, yet little is known on the required conditions, in particular: temperature, time, and relative humidity, to provide stable film structures. The aim of this study was to better understand the importance of these key factors and to evaluate the potential of dynamic curing compared with that of static curing. Recently proposed ethylcellulose:poly(vinyl alcohol)-poly(ethylene glycol) graft copolymer (PVA-PEG graft copolymer) dispersions were coated on theophylline and metoprolol succinate-loaded starter cores, exhibiting different osmotic activity. Importantly, processing times as short as 2 h were found to be sufficient to provide long-term stable films, even upon open storage under stress conditions. For instance, 2-h dynamic curing at 57 °C and 15% relative humidity are assuring stable film structures in the case of theophylline matrix cores coated with 15% ethylcellulose:PVA-PEG graft copolymer 85:15. Importantly, the approach is also applicable to other types of drugs and starter cores, and the underlying drug release mechanisms remain unaltered. © 2011 Elsevier B.V. All rights reserved. Source


Muschert S.,University of Lille Nord de France | Siepmann F.,University of Lille Nord de France | Leclercq B.,FMC BioPolymer | Carlin B.,FMC BioPolymer | Siepmann J.,University of Lille Nord de France
Drug Development and Industrial Pharmacy | Year: 2010

Background: Food effects might substantially alter drug release from oral controlled release dosage forms in vivo. Methods: The robustness of a novel type of controlled release film coating was investigated using various types of release media and two types of release apparatii. Results: Importantly, none of the investigated conditions had a noteworthy impact on the release of freely water-soluble diltiazem HCl or slightly water-soluble theophylline from pellets coated with ethylcellulose containing small amounts of PVAPEG graft copolymer. In particular, the presence of significant amounts of fats, carbohydrates, surfactants, bile salts, and calcium ions in the release medium did not alter drug release. Furthermore, changes in the pH and differences in the mechanical stress the dosage forms were exposed to did not affect drug release from the pellets. Conclusion: The investigated film coatings allowing for oral controlled drug delivery are highly robust in vitro and likely to be poorly sensitive to classical food effects in vivo. © Informa UK, Ltd. Source

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