Maria Elena Santos Taqueda

Hydrating effects of moisturizer active compounds incorporated into hydrogels: in vivo assessment and comparison between devices

Background  Water is an important factor on the appearance and function of the skin and, when dehydrated, it becomes rough and flaky. The measurement of stratum corneum hydration is widely employed to verify the moisture effect of topical products.

Climate as the most important factor determining anti-fungal biocide performance in paint films

The effect of Pigment Volume Content (PVC) on fungal growth on acrylic paint formulations with and without biocide, exposed to weathering in three different climatic regions in Brazil for four years, was studied. Latex paints, with PVC of 30%, 35% and 50%, were applied to autoclaved aerated concrete blocks pre-covered with acrylic sealer and acrylic plaster. They were exposed to equatorial, tropical and temperate climates in north, south-east, and south Brazil. Cladosporium was the most abundant fungal genus detected in the biofilm on the surfaces of all paint formulations at all sites after four years. Heaviest fungal colonization occurred in the tropical south-east and lightest in the temperate south of the country, but more phototrophs, principally cyanobacteria, were detected in the equatorial region. PVC and presence of biocides were shown to be of less importance than environmental conditions (irradiance, humidity and temperature) for biofilm formation and consequent discolouration. These results have important implications for testing of paint formulations.

Optimization of Pothomorphe umbellata (L.) Miquel topical formulations using experimental design

Pothomorphe umbellata is a native plant widely employed in the Brazilian popular medicine. This plant has been shown to exert a potent antioxidant activity on the skin and to delay the onset and reduce the incidence of UVB-induced skin damage and photoaging. The aim of this work was to optimize the appearance, the centrifuge stability and the permeation of emulsions containing P. umbellata (0.1% 4-nerolidylchatecol). Experimental design was used to study ternary mixtures models with constraints and graphical representation by phase diagrams. The constraints reduce the possible experimental domain, and for this reason, this methodology offers the maximum information while requiring the minimum investment. The results showed that the appearance follows a linear model, and that the aqueous phase was the principal factor affecting the appearance; the centrifuge stability parameter followed a mathematic quadratic model and the interactions between factors produced the most stable emulsions; skin permeation was improved by the oil phase, following a linear model generated by data analysis. We propose as optimized P. umbellata formulation: 68.4% aqueous phase, 26.6% oil phase and 5.0% of self-emulsifying phase. This formulation displayed an acceptable compromise between factors and responses investigated.

Evaluation of in vitro percutaneous enhancement effect of papain and pequi oil on diclofenac sodium permeation through human skin

The purpose of this research was to determine the potential of papain and pequi oil as penetration enhancers for diclofenac sodium (DS) across human skin in vitro. The permeation studies were conducted with vertical diffusion cells. The enhancers were associated or not in gels in different concentrations. In vitro studies reveled that papain 0.2% (w/v) presented an elevated enhancer property for diclofenac sodium (J = 0.3369 mg/cm2x h). Pequi oil 10% (w/v) generated a reduced flux value (J = 0.1848 mg/cm2x h) and a combination of both enhancers presented a medium value of J = 0.2187 mg/cm2x h. Papain was found to be better enhancer than pequi oil.

Purification of glucose oxidase from Aspergillus niger by liquid-liquid cationic reversed micelles extraction.

The aim of this work was to select the operating conditions for the extraction and recovery of glucose oxidase (GOX) by reversed micelles from mixtures of commercial enzyme and Aspergillus niger homogenates. For this purpose, the influence of the main operating parameters (pH, surfactant concentration, and presence of cell debris or not) on GOX extraction was investigated at 25 °C. Without cell debris, the highest yield of GOX activity recovery (90.8%) was obtained performing (a) the forward extraction in isooctane as solvent and hexanol and butanol as cosolvents at 76/6/18 ratio, pH 7.0, 0.2 M cetyl trimethylammonium bromide as cationic surfactant, and electric conductivity of 5.0 mS cm−1 and (b) the backward extraction at pH 5.5. Forward and backward extractions furnished comparable results when using raw homogenate, which demonstrates a negligible impact of the presence of cell debris on the process. The highest extraction yield (94%) was obtained under the same forward and backward conditions adopted without cell debris. The promising results of this work suggest that the proposed methodology could be profitably exploited at an industrial level.

Optimized extraction of a single-chain variable fragment of antibody by using aqueous micellar two-phase systems

In this work, the purification of a single-chain variable fragment (scFv) of an antibody by using liquid-liquid extraction in aqueous micellar two-phase systems was optimized by means of central composite design. Protein partitioning assays were performed by using the selected system composition in previous works: Triton X-114 at 4% wt/wt, yeast fermentation supernatant at 60% wt/wt, McIlvaine buffer pH 7.00. The other system component concentrations, Cibacron Blue F3GA (CB), Fabsorbent™ F1P HF (HF) and NaCl, were selected as independent variables. ScFv recovery percentage (%R) and purification factor (PF) were selected as the responses. According to the optimization process both, scFv recovery percentage and purification factor were favored with the addition of HF and NaCl in a range of concentrations around the central point of the second central composite design (HF 0.0120% w/w, CB 0.0200% w/w, NaCl 0.200% w/w). These experimental conditions allowed the concentration and pre-purification of scFv in the micelle-rich bottom phase of the systems with a recovery percentage superior to 88% and a purification factor of approximately 3.5. These results improved the previously presented works and demonstrated the convenience of using aqueous micellar two-phase systems as a first step in the purification of scFv molecules.

Optimization of primaquine diphosphate tablet formulation for controlled drug release using the mixture experimental design

A tablet formulation based on hydrophilic matrix with a controlled drug release was developed, and the effect of polymer concentrations on the release of primaquine diphosphate was evaluated. To achieve this purpose, a 20-run, four-factor with multiple constraints on the proportions of the components was employed to obtain tablet compositions. Drug release was determined by an in vitro dissolution study in phosphate buffer solution at pH 6.8. The polynomial fitted functions described the behavior of the mixture on simplex coordinate systems to study the effects of each factor (polymer) on tablet characteristics. Based on the response surface methodology, a tablet composition was optimized with the purpose of obtaining a primaquine diphosphate release closer to a zero order kinetic. This formulation released 85.22% of the drug for 8 h and its kinetic was studied regarding to Korsmeyer–Peppas model, (Adj-R2 = 0.99295) which has confirmed that both diffusion and erosion were related to the mechanism of the drug release. The data from the optimized formulation were very close to the predictions from statistical analysis, demonstrating that mixture experimental design could be used to optimize primaquine diphosphate dissolution from hidroxypropylmethyl cellulose and polyethylene glycol matrix tablets.

Polarisation curves and experiment design as tools in the search of optimised inhibitors mixture formulation for HSLA steel in hydrochloric acid

Corrosion inhibitors are intentionally added to pickling baths in order to prevent metal dissolution during its surface cleaning from oxides and other adherent materials. The main goal of this work is to verify if there is any synergism when the three following inhibitors: benzotriazole (BTAH), N-phenylthiourea (N-PTU) and hexadecyltrimethylammonium chloride (HTAC) are put together in hydrochloric acid (HCl) medium to prevent high strength low alloy (HSLA) steel corrosion and to find an optimised formulation that yields the highest HSLA steel surface protection degree from weight loss measurements and from anodic and cathodic potentiodynamic polarisation curves. The experiment design used was a simplex-lattice type which yields the Sheffe polynomial expressions as the model, with a 16 experiments matrix and the inhibitors concentrations as independent variables and the steel surface protection degree as response or dependent variable for a complete cubic model. A cubic model was obtained from regression analysis with a determination coefficient R 2 = 0.98 and a good agreement between experimental results and the predicted values from the model. The cubic model coefficients demonstrate that there is a significant synergism between BTAH and N-PTU and also between N-PTU and HTAC and a optimised formulation was found. The potentiodynamic curves obtained for inhibitors concentrations that have showed synergism were in close agreement with the results of weight loss measurements from the experiment design.

Mixture screening design to choose formulations for functionally graded fiber cements

This work employing the screening strategy to examine thirteen mix proportions of six-component fiber cement formulations composed of ordinary Portland cement, ultra-fine cement, limestone filler, silica fume, cellulose and polyvinyl alcohol fibers. The vacuum de-watering technique was applied in the production of fiber cement specimens cured for 10 days and submitted to four-point bending tests. The mechanical properties such as limit of proportionality (LOP), modulus of elasticity (MOE), modulus of rupture (MOR) and specific energy (SE) were evaluated and these properties were correlated with the raw material fractions resulting in mixture rules. Results indicate that screening can be a promising methodology with which to generate coherent fiber cement mixture rules, optimize formulations in terms of costs and performance and even facilitate the choosing of formulations for functionally graded fiber cements.