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Viscoelastic Parameters (viscoelastic + parameter)
Selected AbstractsAcyclovir delivery matrices based on poly(ethylene glycol)/chitosan semi-interpenetrating networksJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 6 2007O. Diez-Sales Abstract Chitosan matrix systems have been studied as potential vehicles for the prolonged release of acyclovir (ACV). The influence of chitosan concentration (from 0.83% to 1.67%) on viscoelastic properties of formulations with and without glyoxal was analyzed. For chitosan-poly(ethylene glycol) 400 formulations loss modulus (G,) are greater than storage modulus (G,). This corresponds to the characteristic behavior of nonstructured systems. When glyoxal was added to the chitosan-poly(ethylene glycol) 400 formulations, gelled matrix was obtained (i.e., G, is higher than G,), except for the lowest chitosan concentration. ACV release rates for the both types of systems, with and without glyoxal, were also determined. The ACV diffusion coefficient values from matrices are less than for the respective formulation without glyoxal and it was found to depend on the crosslink density within the matrices. Viscoelastic parameters, dynamic moduli (G,, G,), and complex viscosity (,*), were correlated with the ACV diffusion coefficients (D). The complex viscosity (,*) could be used as a parameter of predictive value for the release rate of drugs. © 2007 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 96:1653,1657, 2007 [source] Effects of lipid nanocarriers on the performance of topical vehicles in vivoJOURNAL OF COSMETIC DERMATOLOGY, Issue 2 2009Mojgan Moddaresi PharmD Summary Background/aims, Nanocarrier systems have been extensively studied for their suitability in personal care formulations. Theoretically, they could enhance skin delivery of active compounds, thereby improving in vivo efficacy of the products. As such the aim of this study was to evaluate the effect of a lipid nanocarrier (LNC) system loaded with tocopheryl acetate (TA) on the hydration, biomechanical properties, and antioxidant capacity of human skin, when used in two different vehicles, and compare it with a non-LNC formulation. Methods, TA-loaded lipid nanocarriers (TA-LNCs) were produced by the phase inversion method, using physiological lipids and purified by ultra-centrifugation. They were incorporated into a hydrophilic gel and foam, and their performance compared with a saturated TA solution in silicon oil. Skin hydration and biomechanical properties were measured by means of a corneometer and a cutometer, respectively, while a high-resolution spectrophotometer was used to assess skin redness after stimulation by methyl nicotinate in a micro-inflammatory test. Both short-term (3 h) and long-term trials (4 weeks) were performed. Results, The results confirmed that the LNCs enhanced skin hydration in both studies, while skin viscoelastic parameters remained practically unchanged during the 4-week study. The antioxidant assessment failed to show significant difference between the test sites. Conclusions, TA-loaded LNCs exhibited the ability to enhance skin hydration, while their effect on skin biomechanical properties and on antioxidant efficacy could not be statistically proved. [source] VISCOELASTIC PROPERTIES OF WHITE FRESH CHEESE FILLED WITH SODIUM CASEINATEJOURNAL OF TEXTURE STUDIES, Issue 4 2000C. LOBATO-CALLEROS ABSTRACT The yield, moisture loss and viscoelastic properties of white fresh cheeses containing sodium caseinate were determined and compared to those of a reference cheese without sodium caseinate. Added sodium caseinate resulted in higher cheese yields and lower moisture losses during aging. Creep compliance tests were performed on the cheeses using a parallel plate viscoelastometer. Multiple regression analysis of the experimental data provided first order models that explain the variation of most of the viscoelastic parameters of the white fresh cheeses in terms of sodium caseinate level, moisture content, aging and pH. The instantaneous elastic compliance and the Newtonian viscosity increased with moisture content and pH, respectively. The retarded elastic compliances increased and the first retardation time decreased during aging. The influence of sodium caseinate on most of the viscoelastic parameters was significant. [source] Rheological properties of three different vitamin D ointments and their clinical perception by patients with mild to moderate psoriasisJOURNAL OF THE EUROPEAN ACADEMY OF DERMATOLOGY & VENEREOLOGY, Issue 2005JP Marty ABSTRACT Background, Ointments, classically used for the treatment of dermatological diseases, are monophasic viscous semisolid formulations. According to the proportion of their compounds, they have physicochemical and organoleptic properties and when applied on skin show a specific behaviour allowing to be spread more or less easily. Objective, To measure in vitro rheological characteristics of three vitamin D derivative ointments prescribed for the treatment of psoriasis, and to compare their viscosity and clinical acceptability when applied on the diseased skin. Methods, Rheological characteristics of tacalcitol 4 µg/g, calcipotriol 50 µg/g and calcitriol 3 µg/g ointments were assessed by measuring the oscillatory viscoelastic parameters and the permanent flow analysis. Clinical acceptability was studied in 20 psoriatic male or female subjects, aged 18 years or older. A survey evaluated the acceptability of calcitriol vs. tacalcitol and calcipotriol. Questions included information about fluidity, spreading capacity and stickiness after application. Results, We demonstrated that viscoelastic parameters were four times higher for ointment tacalcitol than for calcipotriol and calcitriol, corresponding to a higher consistency of ointment tacalcitol compared to calcipotriol and calcitriol showing both similar results; better fluidity was demonstrated by calcitriol than by tacalcitol and calcipotriol. Comparable results were obtained for the quality to be spread. The sensation of stickiness, significantly different between tacalcitol and calcitriol, was not different between calcipotriol and calcitriol. Conclusion, The above results confirm the relationship between rheological in vitro and sensorial in vivo results: variations between different formulations may have an important influence on non-adherence and treatment failure. [source] Viscoelastic and Histologic Properties in Scarred Rabbit Vocal Folds After Mesenchymal Stem Cell Injection,THE LARYNGOSCOPE, Issue 7 2006S Hertegård MD Abstract Objective/Hypothesis: The aim of this study was to analyze the short-term viscoelastic and histologic properties of scarred rabbit vocal folds after injection of human mesenchymal stem cells (MSC) as well as the degree of MSC survival. Because MSCs are antiinflammatory and regenerate mesenchymal tissues, can MSC injection reduce vocal fold scarring after injury? Study Design: Twelve vocal folds from 10 New Zealand rabbits were scarred by a localized resection and injected with human MSC or saline. Eight vocal folds were left as controls. Material and Methods: After 4 weeks, 10 larynges were stained for histology and evaluation of the lamina propria thickness. Collagen type I content was analyzed from six rabbits. MSC survival was analyzed by fluorescent in situ hybridization staining from three rabbits. Viscoelasticity for 10 vocal folds was analyzed in a parallel-plate rheometer. Results: The rheometry on fresh-frozen samples showed decreased dynamic viscosity and lower elastic modulus (P < .01) in the scarred samples injected with MSC as compared with the untreated scarred group. Normal controls had lower dynamic viscosity and elastic modulus as compared with the scarred untreated and treated vocal folds (P < .01). Histologic analysis showed a higher content of collagen type 1 in the scarred samples as compared with the normal vocal folds and with the scarred folds treated with MSC. MSCs remained in all samples analyzed. Conclusions: The treated scarred vocal folds showed persistent MSC. Injection of scarred rabbit vocal folds with MSC rendered improved viscoelastic parameters and less signs of scarring expressed as collagen content in comparison to the untreated scarred vocal folds. [source] | |||||||||||||