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Abstract  

Composites of poly(vinyl pyrrolidone)/hydroxyapatite (PVP/HA), at variable proportions (100/0; 80/20; 50/50; 20/80 wt%) were prepared and characterized by Fourier transformer-infrared spectroscopy (FT-IR), wide angle X-ray diffraction (WAXD), differential scanning calorimetry (DSC), and thermogravimetry/differential thermogravimetry (TG/DTG). PVP carbonyl stretching was slightly shifted to lower frequency in composites indicating the formation of hydrogen bonding with HA hydroxyl groups. At the first cycle of heating, the calorimetric curves revealed a broad peak the intensity of which was reduced insofar as the amount of PVP decreased in the composites. This peak was attributed to the PVP enthalpy relaxation. According to the TG/DTG curves, PVP degraded into two steps sharply perceivable in the composites. The first decay was ascribed to the release of the pyrrolidone pendant groups and the following one concerned the burning of the hydrocarbon chains. The HA molecules seem to exert a catalytic action on the PVP degradation.

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Quercetin-PVP K25 solid dispersions

Preparation, thermal characterization and antioxidant activity

Journal of Thermal Analysis and Calorimetry
Authors: Ana Rita de Mello Costa, Flávia Silva Marquiafável, Mirela Mara de Oliveira Lima Leite Vaz, Bruno Alves Rocha, Paula Carolina Pires Bueno, Pedro Luiz M Amaral, Hernane da Silva Barud and Andresa Ap Berreta-Silva

, and efficient delivery system is necessary to assure that the increasing of quercetin solubility be warranted. The polyvinylpyrrolidone Kollidon ® 25 (PVP K25) is a polymer used to improve the solubility and bioavailability of little soluble

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inclusion complexes of drug with cyclodextrins (CDs) [ 9 – 11 ] are the most frequently employed. In fast-release solid dispersions, a hydrophilic polymer of first choice is polyvinylpyrrolidone (PVP), which is commercially available with various average

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Journal of Thermal Analysis and Calorimetry
Authors: M. I. Loría-Bastarrachea, W. Herrera-Kao, J. V. Cauich-Rodríguez, J. M. Cervantes-Uc, H. Vázquez-Torres and A. Ávila-Ortega

Introduction Poly( N -vinyl-2-pyrrolidone), PVP, has been attracted a great deal of attention in these days as it has been widely used for applications in various fields. This polymer is a synthetically derived vinyl polymer

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Journal of Thermal Analysis and Calorimetry
Authors: Imre Miklós Szilágyi, Eero Santala, Mikko Heikkilä, Marianna Kemell, Timur Nikitin, Leonid Khriachtchev, Markku Räsänen, Mikko Ritala and Markku Leskelä

. Here we present a model study on the heat treatment of electrospun polyvinylpyrrolidone [PVP, (C 6 H 9 NO) n ] and ammonium metatungstate [AMT, (NH 4 ) 6 [H 2 W 12 O 40 ]· n H 2 O] nanofibers. It clearly demonstrates the importance of finding the

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Abstract  

The miscibility of poly(N-isopropylacrylamide) (PNIPA) with poly(vinyl pyrrolidone) (PVP) and a cross-linked poly(acrylic acid) (Carbopol 971P) was evaluated from the rheological data of aqueous dispersions and the temperature of glass transitions of films made of binary mixtures. PNIPA has a low critical solubility temperature (LCST) of about 33C, below which 1% dispersion behaves as a viscous system. At temperatures above LCST, the hydrophobic interactions among the isopropyl groups initially provide transient networks of greater elasticity. The LCST of PNIPA as well as its T g (144C, estimated by DSC and MTDSC of films) were not modified by the presence of PVP. The immiscibility of PNIPA and PVP was confirmed by the absence of interaction between both polymers as shown by FTIR analysis of the films. In contrast, PNIPA and carbopol were miscible and the behaviour of their mixtures differed significantly from that of the parent polymers; i.e. a strong synergistic effect on the viscoelasticity of the dispersions was observed below the LCST. As temperature increased, the blends showed a decrease in the loss and storage moduli, especially those with greater PNIPA proportions. The fall was smoother as the PNIPA proportion decreased. This behaviour may be explained as the result of the balance between PNIPA/carbopol hydrogen bonding interactions (as shown in the shift of C=O stretch in FTIR spectra) and PNIPA/PNIPA hydrophobic interactions. The T g values of the films of the blends showed a positive deviation from the additivity rule; the mixtures containing more than 1:1 amide:carboxylic acid groups have a notably high Tg (up to 181C). This increase is related to the stiffness induced in the films by the PNIPA/carbopol interactions.

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The effect of physical state on the drug dissolution rate

Miscibility studies of Nimodipine with PVP

Journal of Thermal Analysis and Calorimetry
Authors: G. Papageorgiou, A. Docoslis, M. Georgarakis and D. Bikiaris

Abstract  

In this work, the enhancement of drug dissolution rate through the preparation of new formulations containing Nimodipine in molecular level dispersion or in nanodispersion into poly(vinyl pyrrolidone) (PVP) matrix, was investigated. Differential scanning calorimetry (DSC) and modulated-temperature differential scanning calorimetry (MTDSC) in combination with X-ray powder diffractometry (XRPD) and scanning electron microscopy (SEM) studies showed that Nimodipine was amorphous in solid dispersions of 10 or 20 mass%, and mainly dispersed on a molecular level. This behaviour is attributed to the strong interactions taking place between the amine group of Nimodipine and carbonyl group of PVP. At higher drug loadings, crystal reflections in XRPD patterns and melting peaks of Nimodipine in DSC traces, indicated presence of drug in crystalline form. Micro-Raman studies in combination with SEM micrographs showed that the mean particle size increases with drug content in the formulations, up to 10 μm. Moreover, both XRPD patterns and micro-Raman spectra seem to indicate that Nimodipine crystallized in a second, thermodynamically stable, crystal modification II. The physicochemical characteristics of Nimodipine and the particle size distribution directly affect the dissolution rate enhancement, which is higher in amorphous dispersions.

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Abstract  

We apply a range of techniques (thermal methods, microscopy, X-ray diffraction, IR spectroscopy) to characterize a drug (atenolol), several excipients (PVP=polyvinylpyrrolidone, MGST=magnesium stearate, Avicel©) and drug-excipients mixtures either as prepared, annealed, and exposed to moisture. We compare the data of the mixtures with those computed from a weighted average of similarly treated pure compounds to find evidence of drug properties modified by the interaction with the excipient. We find that thermal response is by far the most sensitive indicator of interaction while IR is the least sensitive one. Avicel© has essentially no interaction with atenolol, while MGST modifies significantly only the thermal response of the drug in the MGST-rich mixtures. PVP interacts strongly with atenolol, and this interaction appears to be mediated by the substantial amount of hydration water the excipient brings in its mixtures with a water-free drug.

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, i.e., the addition of a small amount of tough carboxyl-terminated butadiene acrylonitrile rubber (CTBN) or biocompatible polyvinylpyrrolidone (PVP) polymeric additives, can also result in different changes and improvements of the crystallization and

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another 1 h. The Hap suspensions for electrospaying were prepared as follows: 0.5 g Hap was dispersed in 100 mL of ethanol under vigorous mixing (30 min) and ultrasonication (30 min). The Hap–PEG and Hap–PVP suspensions were obtained after

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