Orlando David Henrique dos Santos

Attainment of Emulsions with Liquid Crystal from Marigold Oil Using the Required HLB Method

Development of new formulations for topical use and cosmetic and pharmaceutical delivery agents has increased the complexity of emulsified systems. Liquid crystals, known since the nineteenth century are the third phase of an emulsion, being responsible for increasing its stability and the solubility of substances poorly soluble in water, or the oily phase, modulating the release of drugs imprisoned in its structure and promoting hydration of the skin surface. In the present work we developed oil/water emulsions, making use of Marigold oil (Calendula officinalis L) and ethoxylated fat alcohols as surfactant. The required HLB value for marigold oil was determined to be 6.0. The surfactants were associated in lipophilic/hydrophilic pairs. The lipophilic surfactants were Ceteth‐2 and Steareth‐2 and the hydrophilic surfactants were Steareth‐20, Ceteareth‐20, Ceteareth‐5, and Ceteth‐10. To identify the liquid crystalline phases, the emulsions were analyzed by polarized light microscopy. The physical stability was evaluated by rheology and zeta potential analysis. All emulsions presented lamellar liquid crystal structures. Results showed that this type of surfactant is able to produce liquid crystal in the system, with slight difference in appearance, influencing the physical stability, according to the methods applied.

Physicochemical Characterization of Canola Oil/Water Nano‐emulsions Obtained by Determination of Required HLB Number and Emulsion Phase Inversion Methods

Depending on the emulsion preparation method, different droplet size distributions might be achieved. The EPI method (low‐energy emulsification method) works with water volume fraction changes. Nanometer emulsions can be obtained by this method. The aim of this work was to evaluate the canola oil‐water nano‐emulsion physicochemical characteristics: zeta potential and droplet size values upon preparation and after stability tests. The obtained outcomes suggest that nano‐emulsion yielded by EPI and required HLB methods is quite stable. This can support reported nanometer size droplets and high zeta potential values. Although the emulsions have been submitted to a range of temperatures, the evaluated parameters did not present significant change.

W/O/W Multiple Emulsions Obtained by One‐Step Emulsification Method and Evaluation of the Involved Variables

The effects of some composition variables on the development of multiple emulsions by one‐step method were evaluated and their morphology characterized. The formulations that remained stable during the period of the test were submitted to centrifugation and thermal stress tests. The stability and the morphology of multiple droplets were affected not only by the type and concentration of the surfactants employed, but also by the water/oil ratios used. The results suggest that the formation of multiple droplets could involve a combination of transitional and catastrophic phase inversions. The results provide improved knowledge about the one‐step emulsification method, a simplified process to prepare multiple emulsions when compared to the two‐steps method.

Polyhydroxy Alcohols and Peach Oil Addition Influence on Liquid Crystal Formation and Rheological Behavior of O/W Emulsions

The aim of this study was to develop O/W emulsions with a self‐emulsifying base (SEB) containing liquid crystals (LC) and evaluate the influence of polyhydroxy alcohols and peach oil addition in liquid crystal formation as well as to analyze the rheological behavior of these systems. Formulations containing SEB were supplemented or not with glycerin, sorbitol, propylene glycol, and/or peach oil. All formulations studied had lamellar crystalline phases. Peach oil addition increased the viscosity of SEB, while humectants had different behavior, glycerin enhanced the viscosity of the studied formulations supplemented or not with peach oil, and propylene glycol decreased the viscosity of all formulations studied. On the other hand, sorbitol enhanced the viscosity of formulations containing peach oil. All emulsions presented pseudoplastic behavior and thixotropy.

Development of O/W Emulsions with Annato Oil (Bixa orellana) Containing Liquid Crystal

O/W emulsions with liquid crystals are complex systems for the delivery of actives into the skin surface since they modulate the release rate in the structure, and they increase the stability and solubility of slightly soluble substances in oil or aqueous phase and support moisturing by decreasing the transepidermal water loss (TEWL). The development of emulsions with vegetable oils is interesting due to their properties; in addition it allows the use of natural raw materials of Brazils biodiversity, and it has attracted growing attention in the market because of the marketing value of natural products. Following this trend, emulsions were developed containing annatto oil as oily phase. HLB system was used for selection of emulsifying agents because it aids in the correct determination of the ratio of surfactant in a mixture for a better emulsification. In this study, the HLB value of annatto oil was established using nonionic surfactants, such as oleth‐3 and oleth‐20. With the replacement of these by ceteareth‐5, which presents the same HLB, the formation of liquid crystals phases was observed by polarization microscopy. Cetostearyl alcohol was added to change the rheological characteristics, which was analyzed for the purpose of characterization, which is of great importance for emulsion performance evaluation before use in manufacturing conditions.

Characterization and Evaluation of Electrolyte Influence on Canola Oil/Water Nano‐Emulsion

Emulsion stability is controlled by the physicochemical properties of the adsorbed layers formed on the surface of the droplets. Zeta potential and droplet size measured initially and during storage can estimate O/W emulsion stability. The aim of this study was to characterize and evaluate the effects of different hydrolyzable compounds employed in pharmaceutical and cosmetic preparations on the zeta potential and droplet size of canola O/W nano‐emulsions and, consequently, the emulsion stability. The samples containing additives demonstrated significant change in zeta potential, but in spite of that, no macroscopic instability was observed. Yet the droplet size values did not undergo significant change.

Some Fundamentals of the One-Step Formation of Double Emulsions

The recently introduced one-step process to form double emulsions is analyzed using generalized phase diagrams of water, ethylene oxide adduct surfactants, and hydrocarbons. With the process used, we found three factors to be involved in the successful formation of double emulsions. Temporary ultra-low interfacial tension allowed drops of irregular shape to exist, a large part of the emulsion formed a bicontinuous microemulsion at intermediate times, and the interfacial tension was temporarily reduced extremely by significant amounts of all three compounds transferred over the interfaces in different directions depending on the stage of the process.

Attainment of O/W Emulsions Containing Liquid Crystal from Annatto Oil (Bixa orellana), Coffee Oil, and Tea Tree Oil (Melaleuca alternifolia) as Oily Phase Using HLB System and Ternary Phase Diagram

Emulsions containing liquid crystals present interesting properties and advantages such as the skin moisturize increase, active release modulation, and emulsion stabilization. In this work, emulsions containing annatto, coffee and tea tree oils, and nonionic surfactants were developed. The HLB method was used for selection of surfactants. The required HLB value was established (9.0). Liquid crystals were attained when used the surfactant mixture Ceteareth‐5 and Steareth‐2 and identified as lamellar. The emulsions showed pseudoplastic behavior and tixotropy. The ternary diagram was useful in the selection of the proportion of surfactant and oily phase considering skin compatibility and liquid crystal presence.

Development of Vegetable Oil Emulsions with Lamellar Liquid-Crystalline Structures

Emulsions containing vegetable oils and anisotropic phases have especially attractive properties in pharmaceutical technology. They are use as vehicle for different kind of drugs, especially those of topical application. Apart from that, many vegetable oil have pharmacological activity, increasing the necessity for the development of new delivery systems for them. We developed emulsions with vegetable oils at a fixed surfactant ratio and observed the formation of liquid crystalline phases. Nine vegetable oils: Andiroba, Apricot, Avocado, Brazil Nut, Buriti, Cupuassu, Marigold, Passion Fruit and Pequi and mineral oil were tested. Surfactant system was consisted by Steareth-2 and Ceteareth-5. Emulsions were prepared by the emulsion phase inversion (EPI) method, presenting high stability independent on the HLB value. Results indicate that this method could be employed to attain stable emulsions, even if the required HLB value is not known.

Influence of Surfactant on the Thermal Behavior of Marigold Oil Emulsions with Liquid Crystal Phases

ABSTRACT Vegetable oils have been largely consumed owing to the interest of pharmaceutical and cosmetic industries in using natural raw materials. The production of stable emulsions with vegetable oils challenges formulators due to its variability in composition and fatty acids constitution within batches produced. In the present work, it was studied that the influence of the size of carbon chain and the number of ethylene oxide moieties of the surfactant on the thermal behavior of eight emulsions prepared with marigold oil stabilized by liquid crystal phases. Differential scanning calorimetry (DSC) was used to determine the thermal behavior of the emulsions. The ratio of bound water was calculated, being between 29.0 and 42.0%, confirming the extension of the liquid-crystalline net in the external phase. Changing the lipophilic surfactant from Ceteth-2 to Steareth-2, there was an increase in the temperature of phase transition of the liquid crystal influencing the system stability. Calorimetric study is very useful in understanding the performance of liquid crystals with the increase of temperature and to estimate emulsions stability.Vegetable oils have been largely consumed owing to the interest of pharmaceutical and cosmetic industries in using natural raw materials. The production of stable emulsions with vegetable oils challenges formulators due to its variability in composition and fatty acids constitution within batches produced. In the present work, it was studied that the influence of the size of carbon chain and the number of ethylene oxide moieties of the surfactant on the thermal behavior of eight emulsions prepared with marigold oil stabilized by liquid crystal phases. Differential scanning calorimetry (DSC) was used to determine the thermal behavior of the emulsions. The ratio of bound water was calculated, being between 29.0 and 42.0%, confirming the extension of the liquid-crystalline net in the external phase. Changing the lipophilic surfactant from Ceteth-2 to Steareth-2, there was an increase in the temperature of phase transition of the liquid crystal influencing the system stability. Calorimetric study is very useful in understanding the performance of liquid crystals with the increase of temperature and to estimate emulsions stability.