Physical gels of a carboxymethyl derivative of scleroglucan: Synthesis and characterization
ABSTRACT A carboxymethyl derivative of scleroglucan (Scl-CM) was synthesized and characterized through FT-IR, 1H NMR and potentiometer titration. Rheological studies allowed evidencing the effect produced by the introduction of the carboxymethyl moiety on the native polymer. The mechanical spectrum of the scleroglucan solution showed a weak gel behaviour, while the derivative one looked like a system near the gel point, that evolved to a gel state depending on the concentration. This difference could be related to conformational changes due to the introduction of the negative charges on the chains. Different concentrations of Ca2+, added to the aqueous solutions of Scl-CM, were able to deeply modify the resulting system, showing a sharp transition toward a gel like behaviour. Acyclovir was loaded into the hydrogels obtained with different amounts of polymer and salt. The release rate of the drug from these systems was strictly related to both concentrations of salt and polymer. The obtained results suggest a possible employment of these new hydrogels for topical formulations or in situ implantation.
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ABSTRACT: High field NMR characterization of carboxymethyl scleroglucan (Scl-CM) recently synthesized through reaction of the native polymer (Scl) with chloroacetic acid in basic conditions is discussed, reporting the position of the carboxymethyl groups in the scleroglucan moiety. The comparison between the Scl-CM and the Scl structures can be useful to comprehend their different profiles in the viscosity-shear rate curves and their different ability to form physical gels.International Journal of Polymer Analysis and Characterization 11/2013; 18(8). DOI:10.1080/1023666X.2013.842286 · 1.49 Impact Factor
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ABSTRACT: The effects of lipid concentration and composition on the physicochemical properties, aerosol performance and in vitro toxicity activity of several rifampicin-loaded liposomes were investigated. To this purpose, six liposome formulations containing different amounts of soy phosphatidylcholine and hydrogenated soy phosphatidylcholine, with and without cholesterol and oleic acid, were prepared and fully characterized. Uni- or oligo-lamellar, small (~100 nm), negatively charged (~60 mV) vesicles were obtained. Lipid composition affected aerosol delivery features of liposomal rifampicin; in particular, the highest phospholipid concentration led to a better packing of the vesicular bilayers with a consequent higher nebulization stability. The retention of drug in nebulized vesicles (NER%) was higher for oleic acid containing vesicles (55% ± 1.4%) than for the other samples (~47%). A549 cells were used to evaluate intracellular drug uptake and in vitro toxicity activity of rifampicin-loaded liposomes in comparison with the free drug. Cell toxicity was more evident when oleic acid containing liposomes were used.
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ABSTRACT: The aim of this work was to develop new microparticles for drug delivery to lungs by coating liposomes with chitosan (CH)–xanthan gum (XG) polyelectrolyte complexes to obtain chitosomes. To this purpose, two groups of liposomes were prepared using a mixture of soy phosphatidylcholine and hydrogenated soy phosphatidylcholine in two different concentrations to evaluate their capability to entrap appropriate amounts of the model drug rifampicin. The obtained vesicles were then coated with different CH–XG weight ratios and liposomes and chitosomes were characterized in terms of morphology, size, size distribution, zeta potential, drug entrapment, and rheological properties. The efficiency of chitosomes and liposomes during nebulization was also studied. Results of this study indicated that nebulization and rheological properties of chitosomes are affected by the CH–XG weight ratio. In particular, CH–XG 1:0.5 (w/w) coating was able to greatly improve drug total mass output and drug deposition in the lower stages of the impinger. © 2011 Wiley Periodicals, Inc. and the American Pharmacists Association J Pharm Sci 101:566–575, 2012