Etude de l'influence des facteurs de formulation sur les propriétés viscoélastiques d'un gel à base de Carbopol

Le carbopol est un polymère souvent utilise comme agent viscosifiant et stabilisant clans la formulation des produits pharmaceutiques et cosmétiques. Il est introduit sous forme de gel, avec les autres excipients pour conférer au produit l'aspect semi-solide. Ses propriétés rhéologiques, en matière de consistance et de cohésion, sont très sensibles aux facteurs de formulation, à la concentration du carbopol et au procède de fabrication à savoir, la température et la vitesse d'agitation. Ainsi, on s'est propose clans le cadre de ce travail d'effectuer une étude de débroussaillage des différents facteurs de contrôle lies au procède de formulation, en déterminant leur influence sur les caractéristiques viscoélastiques.Mots clés: Carbopol- Gel-Formulation -Interactions- Viscoélasticité -Plans d'expériences. Carbopol is a polymer often used as viscosifying and stabilizing agent in the pharmaceutical and cosmetic product formulations. It is introduced in the form of a gel, with the others ingredients to confer a semi-solid aspect to the product. Its rheological properties, such as consistency and cohesion, are very sensitive to the formulation factors, carbopol concentration and manufacturing processes, such as temperature and stirring velocity. Thus, the aim of this work is to investigate the effects of controlling factors on the viscoelastic properties of a gel formulated with carbopol.Keywords: Carbopol - Gel - Formulation - Interactions - Viscoelasticity - Experimental design

Propriétés physicochimiques et rhéologiques d’un mélange aqueux de biopolymères et d’un tensioactif non ionique

Dans ce travail, on s‟intéresse à l‟effet des concentrations du xanthane, du caséinate de sodium et du tween 20 sur les propriétés rhéologiques, zétamétriques et de surface de leurs mélanges, dans un milieu aqueux à pH neutre. Il a été mis en évidence, à l‟issue de l‟utilisation de la méthodologie des plans d‟expériences, de l‟existence des interactions répulsives de ségrégation entre les biopolymères, générant un affaiblissement du module de conservation viscoélastique, G‟o et par la même une fragilisation de la structure du système colloïdal. Dans cette situation, il a été observé que le potentiel zêta diminue, ce qui laisse supposer que les interactions répulsives électrostatiques entre les deux espèces anioniques ne sont pas responsables du relâchement de la structure. Par ailleurs, il a été observé que la tension de surface du mélange dépend essentiellement de la concentration du tween 20.Mots clés :Biopolymères - Tween 20 – Rhéologie - Tension de surface - Potentiel zêta

Extraction and characterization of chitin and chitosan from crustacean by-products: Biological and physicochemical properties

Chitin has been extracted from two Tunisian crustacean species. The obtained chitin was transformed into the more useful soluble chitosan. These products were characterized by their biological activity as antimicrobial and antifungal properties. The tested bacterial strains were Escherichia coli American Type Cell Culture (ATCC) 25922, Pseudomonas aeruginosa ATCC 27950 and Staphylococcus aureus ATCC 25923. Four fungi strains were also tested Candida glabrata, Candida albicans, Candidaparapsilensis and Candida kreusei. Squilla chitosan showed a minimum inhibitory concentration (MIC) against the different fungi exceptionally for C. kreusei. Their antioxidant activity was investigated with 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity and inhibition of linoleic acid peroxidation. Parapenaeus longirostris Chitosan showed the highest radical scavenging properties. Chitin and chitosan produced were also characterized with Fourier Transform Infrared Spectroscopy (FTIR).Key words: Antibacterial, antifungal, antioxidant, chitin, chitosan, crustacean

Rapid patterning of 1-D collagenous topography as an ECM protein fibril platform for image cytometry.

Cellular behavior is strongly influenced by the architecture and pattern of its interfacing extracellular matrix (ECM). For an artificial culture system which could eventually benefit the translation of scientific findings into therapeutic development, the system should capture the key characteristics of a physiological microenvironment. At the same time, it should also enable standardized, high throughput data acquisition. Since an ECM is composed of different fibrous proteins, studying cellular interaction with individual fibrils will be of physiological relevance. In this study, we employ near-field electrospinning to create ordered patterns of collagenous fibrils of gelatin, based on an acetic acid and ethyl acetate aqueous co-solvent system. Tunable conformations of micro-fibrils were directly deposited onto soft polymeric substrates in a single step. We observe that global topographical features of straight lines, beads-on-strings, and curls are dictated by solution conductivity; whereas the finer details such as the fiber cross-sectional profile are tuned by solution viscosity. Using these fibril constructs as cellular assays, we study EA.hy926 endothelial cells' response to ROCK inhibition, because of ROCK's key role in the regulation of cell shape. The fibril array was shown to modulate the cellular morphology towards a pre-capillary cord-like phenotype, which was otherwise not observed on a flat 2-D substrate. Further facilitated by quantitative analysis of morphological parameters, the fibril platform also provides better dissection in the cells' response to a H1152 ROCK inhibitor. In conclusion, the near-field electrospun fibril constructs provide a more physiologically-relevant platform compared to a featureless 2-D surface, and simultaneously permit statistical single-cell image cytometry using conventional microscopy systems. The patterning approach described here is also expected to form the basics for depositing other protein fibrils, seen among potential applications as culture platforms for drug screening

Sorption Study of a Basic Dye “Gentian Violet” from Aqueous Solutions Using Activated Bentonite

AbstractVarious industries like textiles, papers, food, plastics, leather, etc are great water and organic colorant users. Hence, the resulting effluents could be an important source of environmental problems, since they may contain stable and non biodegradable contaminants, like organic dyes. The treatment of which is the main scope of the present study. Different ways of dye removal from these effluents do exist, such as flotation, reverse osmosis, chemical flocculation and adsorption etc. Adsorption is used in this work for the removal of a particular basic dye, known as Gentian violet (GV) from an aqueous solution, by means of a natural clay material. The influence of various key parameters like contact time, temperature, ionic strength, etc. on the adsorbed amount of the dye was investigated, for batch conditions. A kinetic study was also carried out, the obtained experimental results were tested against the pseudo first order and the pseudo second order equations. An analysis of the obtained equilibrium data showed that the dye adsorption is best described by the Langmuir model. The obtained results showed that temperature did enhance the Gentian violet dye retention process onto the considered bentonite whereas the obtained thermodynamic parameters indicated that the adsorption process is spontaneous and endothermic. The simultaneous presence of methylene blue, which is another colorant compound, with the Gentian violet was also considered. The clay materials showed a better affinity for the first one i e. methylene blue. In conclusion and according to the obtained results, the clay material may be recommended as an industrial adsorbent for the treatment of effluents containing Gentian violet (GV)

In Vitro Bioactivity of Astaxanthin and Peptides from Hydrolisates of Shrimp (Parapenaeus longirostris) By-Products: From the Extraction Process to Biological Effect Evaluation, as Pilot Actions for the Strategy "From Waste to Profit"

Non-edible parts of crustaceans could be a rich source of valuable bioactive compounds such as the carotenoid astaxanthin and peptides, which have well-recognized beneficial effects. These compounds are widely used in nutraceuticals and pharmaceuticals, and their market is rapidly growing, suggesting the need to find alternative sources. The aim of this work was to set up a pilot-scale protocol for the reutilization of by-products of processed shrimp, in order to address the utilization of this valuable biomass for nutraceutical and pharmaceuticals application, through the extraction of astaxanthin-enriched oil and antioxidant-rich protein hydrolysates. Astaxanthin (AST) was obtained using "green extraction methods," such as using fish oil and different fatty acid ethyl esters as solvents and through supercritical fluid extraction (SFE), whereas bioactive peptides were obtained by protease hydrolysis. Both astaxanthin and bioactive peptides exhibited bioactive properties in vitro in cellular model systems, such as antioxidant and angiotensin I converting enzyme (ACE) inhibitory activities (IA). The results show higher astaxanthin yields in ethyl esters fatty acids (TFA) extraction and significant enrichment by short-path distillation (SPD) up to 114.80 ± 1.23 µg/mL. Peptide fractions of <3 kDa and 3-5 kDa exhibited greater antioxidant activity while the fraction 5-10 kDa exhibited a better ACE-IA. Lower-molecular-weight bioactive peptides and astaxanthin extracted using supercritical fluids showed protective effects against oxidative damage in 142BR and in 3T3 cell lines. These results suggest that "green" extraction methods allow us to obtain high-quality bioactive compounds from large volumes of shrimp waste for nutraceutical and pharmaceutical applications

The effect of sarcopenic obesity and muscle quality on complications after DIEP-flap breast reconstruction

Introduction: The aim of this study was to evaluate whether sarcopenic obesity and muscle quality as expressed by skeletal muscle radiodensity (SMD) are associated to postoperative complications in women undergoing DIEP-flap breast reconstruction (BR). Methods: All patients who underwent DIEP-flap BR at our tertiary center between 2010 and 2018 were asked to sign informed consent for the use of their electronic medical records and images. By outlining anatomical skeletal muscle contours on the preoperative abdominal CT-scan at lumbar level L3, SMD and skeletal muscle indices (SMI) were measured by two observers independently. Using logistic regression analyses, the association between sarcopenic obesity (BMI >25 & SMI <39), low SMD (<40HU), and Clavien-Dindo (CD) grade ≥ II complications was evaluated. In this way odds ratios (OR) and adjusted odds ratios (ORadjusted) were provided. Results: Out of the 103 patients included in this study, 36% had CD grade ≥ II complications within 30 days of surgery. Twenty patients (19%) suffered from sarcopenic obesity of whom eleven patients (55%) had CD grade ≥ II complications (OR = 2.7, p = 0.05). In a multivariate analysis, sarcopenic obesity was not significantly related to a higher complication rate (ORadjusted = 2.2, p = 0.14) but women with SMD below average and those with prior radiotherapy had a higher risk for grade ≥ II complications (ORadjusted = 2.9, p = 0.02 and ORadjusted = 2.7, p = 0.02 respectively). Conclusion: Below average SMD (<40HU) was found to be associated with the development of postoperative CD grade ≥ II complications in women undergoing DIEP-flap BR. Future research should evaluate whether improving SMD reduces the complication incidence in this patient group

The transpiration rate sensitivity to increasing evaporative demand differs between soil textures, even in wet soil

Many efforts to improve crop yields in water-limited environments have been directed towards identifying genotypes capable of restricting their transpiration rate (TR) at high vapor pressure deficit (VPD). This has proven challenging due to the dependence of the TR-VPD relationship on environmental conditions. In this context, however, the impact of edaphic properties on the TR response to VPD has largely been overlooked as experiments investigating the TR-VPD relationship are usually performed in wet soil conditions. Hence, the soil is not expected to be limiting the water supply to the canopy at high VPD. Nonetheless, soil (hydraulic) properties are known to shape plant growth and the development of the plant hydraulic system. Thereby, they might indirectly affect plant water use during rising VPD, even in wet soils. To test the soil dependency of the TR-VPD relation, we measured the TR response of genotypes of three important C4 cereals - maize, sorghum, and pearl millet - to increasing VPD in two soil textural classes (sandy loam vs. clay loam). We show that the TR response to rising VPD differed among soil textures in wet conditions. Plants grown in sandy loam exhibited a higher initial slope in TR during increasing VPD (slope1), a restriction in TR at lower VPD (VPDBP), and a greater difference in TR before and after the VPDBP (slopediff. ), compared to plants grown in clay loam. Additionally, plants grown in more conductive soils (i.e., sandy loam) systematically exhibited higher maximum canopy conductance (i.e., slope1) and restricted their transpiration rate at lower VPD levels (VPDBP), resulting in a greater reduction in transpiration. This aligns with a hydraulic mechanism underpinning TR response to VPD. We advocate that considering soil texture is valuable in breeding for water conservation based on TR restriction under increasing VPD