Structure and rheology of semisolid o/w creams containing cetyl alcohol/non-ionic surfactant mixed emulsifier and different polymers

Protonation State of a Bioactive Compound Regulates Its Release from Lamellar Gel-Phase Bilayers

Lamellar gel networks (LGNs) in personal care or pharmaceutical lotions and creams provide an opaque cream appearance and a creamy texture to these products. Within the LGNs, the lamellar gel (Lβ) phase composed of regularly spaced bilayers of surfactants and long-chain fatty alcohols is predominately responsible for the unique rheological properties of the LGNs. To extend the shelf life of LGN-containing products, bioactive compounds with antimicrobial properties are often incorporated into the formulation. However, how the protonation state of the bioactive compounds regulates their release from the Lβ-phase bilayers is currently unknown. Using molecular dynamics simulations, we found that the protonated (neutral) form of cinnamic acid, a common antimicrobial food additive, has a retention ratio higher than that of its deprotonated (charged) counterpart in the Lβ-phase bilayer. From free energy calculations, we determined that not only is the protonated molecule more stable in the hydrophobic interior of the bilayer but also the formation of hydrogen-bonded dimers significantly enhances its stability within the bilayer. Thus, the protonation state has a profound impact on bioavailability of the compounds. Our results also highlight the importance of considering possible oligomeric states of molecules when performing calculations to estimate the permeability of molecules within various bilayers.

Equivalence assessment of creams with quali-quantitative differences in light of the EMA and FDA regulatory framework

EMA and FDA are upgrading guidelines on assessing the quality and the equivalence of topically applied drug products for developing copies of originator products and supporting post-marketing variations. For topical products having remarkably similar composition, both EMA and FDA accept the equivalence on the bases of the comparison of rheological properties and in vitro drug release constant (k) and skin permeation flux (J) values, instead of clinical studies. This work aims to evaluate the feasibility to expand this approach to variations of the composition of complex semi-solid preparations. Ibuprofen (IB) creams at two different strengths (i.e., 1 % and 10 %) were used as a model formulation. Two formulative changes were performed: (a) the addition of the humectant to simulate a minor post-marketing variation; (b) the substitution of the emulsifying system to simulate a major one. These variations impacted only in 1 % IB formulations where both the equivalences of rheological data and J-values failed. At the highest concentration, the presence of IB crystals broke down the differences in rheological patterns and lead the IB thermodynamic activity at the maximum figuring out an overlapping of the J-values. Such data suggest the combination of these studies, which are thought mainly for the development of copies, could be also applied to the management of post-marketing variations that involve product composition.

Emollients in dermatological creams: Early evaluation for tailoring formulation and therapeutic performance

The targeted choice of the emollient of a cream determines its physicochemical properties and clinical effectiveness. This work researched the effects of emollient properties on the final characteristics and potential performance of oil-in-water dermatological creams. Seven emollients with different chemical characteristics and structures (alkane, triglyceride, ether, silicone, vegetable oils, and mineral oil) were tested in a model formulation. Early stability, pH, droplet size distribution, rheology, tackiness, adhesivity, spreadability, tribology, and release profile of a lipophilic substance model (in Franz cells, through a synthetic membrane, for six hours) were assessed. The creams had acid epicutaneous pH and a "shear-thinning" "solid-like" viscoelastic behavior. Among the seven emollients' properties, polarity, density, and viscosity were the most influential. Droplet parameters were the most impacted, pH and release were moderately affected, and the textural properties were lowly to moderately impacted. The emollient substitution in the model formulation affected the experimental parameters differently, allowing formulation optimization and tailoring its potential therapeutic performance regarding drug release, coadjutant effects, and dwell time on the skin. By looking at the creams' characteristics, it was possible to select the best-suited emollients for releasing a lipophilic drug, applying on painful skin, and formulation in wash-off products or leave-on protective barrier creams.

Structure of Cellulose Ether Affected by Ionic Surfactant and Solvent: A Small-Angle Neutron Scattering Investigation

Polysaccharides and their derivatives are commonly used in pharmaceutical and agricultural formulations as rheology modifiers. Their performance is related to their conformation in solution, which in turn is affected by other ingredients present in the formulation. This study focuses on modulating the conformation of relatively rigid cellulose chains in aqueous solutions. In particular, we have investigated the nonionic cellulose derivative ethyl(hydroxyethyl)cellulose (EHEC) in water in the presence of the ionic surfactant sodium dodecyl sulfate (SDS) and/or ethanol acting as modulating agents. We have used small angle neutron scattering (SANS) with contrast variation to determine the EHEC chain conformation in the presence of (but not masked by) ethanol and SDS. In dilute and semidilute aqueous solutions, EHEC exhibits worm-like chain conformation due to the rigid cellulose backbone. Addition of ethanol does not impact the polymer conformation to a great extent. Addition of SDS alters the EHEC chain conformation, resulting in polyelectrolyte-like scattering behavior due to repulsive interactions between bound charged micelles which show similar structure as the free SDS micelles in solution (in the absence of polymers). Ethanol affects the polymer + surfactant system primarily by acting on the surfactant (bound on polymer) which, in turn, affects the polymer conformation. At higher ethanol concentrations (20 wt %), EHEC regains the worm-like chain conformation because of the detachment of the bound SDS micelles. To the best of our knowledge, this is the only study providing details on chain conformation of the rigid polymer EHEC in dilute or semidilute aqueous solutions in the presence of surfactant and alcohol and one of very few papers utilizing SANS for the characterization of polymer + surfactant + water + alcohol interactions. Such fundamental understanding of interactions and structure in multicomponent mixtures supports the design of industrial formulations.

Assessing and Predicting Physical Stability of Emulsion-Based Topical Semisolid Products: A Review

The emulsion-based topical semisolid dosage forms present a high degree of complexity due to their microstructures which is apparent from their compositions comprising at least two immiscible liquid phases, often times of high viscosity. These complex microstructures are thermodynamically unstable, and the physical stability of such preparations is governed by formulation parameters such as phase volume ratio, type of emulsifiers and their concentration, HLB value of the emulsifier, as well as by process parameters such as homogenizer speed, time, temperature etc. Therefore, a detailed understanding of the microstructure in the DP and critical factors that influence the stability of emulsions is essential to ensure the quality and shelf-life of emulsion-based topical semisolid products. This review aims to provide an overview of the main strategies used to stabilize pharmaceutical emulsions contained in semisolid products and various characterization techniques and tools that have been utilized so far to evaluate their long-term stability. Accelerated physical stability assessment using dispersion analyzer tools such as an analytical centrifuge to predict the product shelf-life has been discussed. In addition, mathematical modeling for phase separation rate for non-Newtonian systems like semisolid emulsion products has also been discussed to guide formulation scientists to predict a priori stability of these products.

Green Surfactants (Biosurfactants): A Petroleum-Free Substitute for Sustainability-Comparison, Applications, Market, and Future Prospects

Surfactants are a group of amphiphilic molecules (i.e., having both hydrophobic and hydrophilic domains) that are a vital part of nearly every contemporary industrial process such as in agriculture, medicine, personal care, food, and petroleum. In general surfactants can be derived from (i) petroleum-based sources or (ii) microbial/plant origins. Petroleum-based surfactants are obvious results from petroleum products, which lead to petroleum pollution and thus pose severe problems to the environment leading to various ecological damages. Thus, newer techniques have been suggested for deriving surfactant molecules and maintaining environmental sustainability. Biosurfactants are surfactants of microbial or plant origins and offer much added advantages such as high biodegradability, lesser toxicity, ease of raw material availability, and easy applicability. Thus, they are also termed "green surfactants". In this regard, this review focused on the advantages of biosurfactants over the synthetic surfactants produced from petroleum-based products along with their potential applications in different industries. We also provided their market aspects and future directions that can be considered with selections of biosurfactants. This would open up new avenues for surfactant research by overcoming the existing bottlenecks in this field.

Synergistic studies of Cassia tora gum with xanthan and guar gum: Carboxymethyl synthesis of cassia gum-xanthan synergistic blend and characterization

The present study describes the study of synergistic behavior of the Cassia tora (CTG) gum with xanthan gum (XG) and comparison with CTG and guar gum (GG) at varying temperatures. A carboxymethyl derivative of CTG: XG blend, having synergistic activity was synthesized and the reaction conditions were optimized using Taguchi's L'9 statistical design. The effect of solvent medium on the degree of substitution (DS) and the gelling property was also studied. The results reveal that synergistic interaction was found in the CTG: XG mixture whereas CTG: GG blend did not show synergistic behavior. The CTG: XG blend shows a highly viscous solution having 8371.9 cps viscosity at ambient temperature and gel is obtained by heating the blending solution and thereafter lowering the temperature. In continuum, an optimized carboxymethyl derivative (DS 0.16) also exhibits gelling properties. The carboxymethyl derivative was characterized by ¹H NMR, FTIR spectroscopy and FESEM analysis. The synergistic action of gums may be utilized in food, cosmetics and pharmaceutical applications.

Application of Confocal Raman Microscopy for the Characterization of Topical Semisolid Formulations and their Penetration into Human Skin Ex Vivo

PURPOSE

The quality testing and approval procedure for most pharmaceutical products is a streamlined process with standardized procedures for the determination of critical quality attributes. However, the evaluation of semisolid dosage forms for topical drug delivery remains a challenging task. The work presented here highlights confocal Raman microscopy (CRM) as a valuable tool for the characterization of such products.

METHODS

CRM, a laser-based method, combining chemically-selective analysis and high resolution imaging, is used for the evaluation of different commercially available topical acyclovir creams.

RESULTS

We show that CRM enables the spatially resolved analysis of microstructural features of semisolid products and provides insights into drug distribution and polymorphic state as well as the composition and arrangement of excipients. Further, we explore how CRM can be used to monitor phase separation and to study skin penetration and the interaction with fresh and cryopreserved excised human skin tissue.

CONCLUSION

This study presents a comprehensive overview and illustration of how CRM can facilitate several types of key analyses of semisolid topical formulations and of their interaction with their biological target site, illustrating that CRM is a useful tool for research, development as well as for quality testing in the pharmaceutical industry.

Investigating the influence of excipient batch variation on the structure, consistency and physical stability of polysorbate 60-based topical vehicles

Fatty alcohol-polysorbate 60-water ternary systems were used as models to represent the continuous phases of the respective semisolid oil-in-water emulsions for topical delivery of cosmetic and medicinal agents. The influence of batch variation of polysorbate 60 and fatty alcohol on structure and consistency of these systems was investigated using microscopy, rheology, differential scanning calorimetry and X-ray scattering techniques. The polysorbate 60 : cetostearyl alcohol mixed emulsifying wax showed swelling in water, that is, the lamellar repeat distance continually augmented from 93 to 125 Å with water percentage 20-90%. Cetostearyl alcohol ternary systems were thicker than cetyl alcohol ones independently of polysorbate 60 batches used. All the ternary systems showed an initial increase in consistency over the first 2 weeks of storage, which was followed by slight changes in consistency (cetostearyl alcohol systems) due to the re-allocation of polysorbate 60 molecules in the gel network or significant breakdown of structure (cetyl alcohol systems) due to the transformation of swollen α-lamellar gel phase into β, γ crystals on 25°C storage. With all fatty alcohols, the consistency of polysorbate 60 ternary system was directly dependent upon interlamellar water thickness as governed by the length and distribution of polyoxyethylene groups within polysorbate 60 molecules. In relation with the composition of polysorbate 60 batches used, the consistency of ternary systems was higher when prepared with the polysorbate 60 batch containing a greater amount of sorbitan polyoxyethylene monoesters. It was proposed that the swollen α-crystalline gel phase could be better formed by sorbitan polyoxyethylene monoesters rather than sorbitan polyoxyethylene diesters.

Spectral analysis and Antibacterial activity of the bioactive principles of Sargassum tenerrimum J. Agardh collected from the Red sea, Jazan, Kingdom of Saudi Arabia

Seaweeds are a major marine resource that can be explored to develop novel pharmaceutical molecules. The present study showed the presence of unique bioactive components in the petroleum ether extract (PEE) and methanolic extract (ME) of Sargassum tenerrimum. The gas chromatography-mass spectrometry analysis suggested that the PEE of S. tenerrimum contained antibacterial biomolecules: hexadecanoic acid, methyl ester, 17-pentatriacontene, dasycarpidan-1-methanol, and acetate (ester). However, the ME of S. tenerrimum exhibited better antibacterial effect than the PEE due to the presence of the bioactive compounds 1,2-benzenedicarboxylic acid, diisooctyl ester, tetratetracontane, 1-docosene, 1,2-benzenediol, and benzoic acid. Thus, promising antibacterial molecules can be isolated from S. tenerrimum for better therapeutic use.

Investigations of Olive Oil Industry By-Products Extracts with Potential Skin Benefits in Topical Formulations

The by-products of olive oil industry are a major ecological issue due to their phenolic content, highly toxic organic load, and low pH. However, they can be recovered and reused, since their components have antioxidant, anti-inflammatory, and photoprotector properties. In this work, oil-in-water creams containing three different olive oil industry by-products extracts were produced without the use of organic solvents. First, the extracts were thoroughly characterized in vitro for cytotoxicity, inhibition of skin enzymes, and antioxidant and photoprotection capacities. Safety studies were then performed, including ocular and skin irritation tests, ecotoxicity evaluation, and in vivo Human Repeat Insult Patch Test. The results obtained in this initial characterization supported the incorporation of the extracts in the cream formulations. After preparation, the creams were characterized for their organoleptic, physicochemical, droplet size and rheological properties, and microbial contamination. The results showed that all formulations were semi-solid creams, with stable pH, compatible with the skin, without microbial contamination, and with the expected droplet size range. The rheological analysis showed shear-thinning behavior with yield stress, with the viscosity decreasing with increasing shear rate. The oscillatory results suggest that the creams have a strong network structure, being easily rubbed into the skin. Finally, compatibility, acceptability and antioxidant efficacy were evaluated in vivo, in human volunteers. No adverse reactions were observed after application of the formulations on skin and the cream with the highest concentrations of phenolic compounds showed the highest antioxidant efficiency. In conclusion, the results suggest that olive oil industry by-products extracts have valuable properties that favor their re-use in the cosmetic industry. The example presented here showed their successful incorporation into creams and their impact in these formulations' appearance, pH, and rheological performance, as well as their in vivo compatibility with skin and antioxidant efficiency.

Rheology by Design: A Regulatory Tutorial for Analytical Method Validation

The increasing demand for product and process understanding as an active pursuit in the quality guideline Q8 and, more recently, on the draft guideline on quality and equivalence of topical products, has unveiled the tremendous potential of rheology methods as a tool for microstructure characterization of topical semisolid dosage forms. Accordingly, procedure standardization is a dire need. This work aimed at developing and validating a methodology tutorial for rheology analysis. A 1% hydrocortisone cream was used as model cream formulation. Through a risk assessment analysis, the impact of selected critical method variables (geometry, temperature and application mode) was estimated in a broad range of rheological critical analytical attributes-zero-shear viscosity, upper-shear thinning viscosity, lower-shear thinning viscosity, infinite-shear viscosity, rotational yield point, thixotropic relative area, linear viscoelastic region, oscillatory yield point, storage modulus, loss modulus, and loss tangent. The proposed validation of the approach included the rheometer qualification, followed by the validation of numerous operational critical parameters regarding a rheology profile acquisition. The thixotropic relative area, oscillatory yield point, flow point and viscosity related endpoints proved to be highly sensitive and discriminatory parameters. This rationale provided a standard framework for the development of a reliable and robust rheology profile acquisition.

Pickering Emulsions Stabilized by Calcium Carbonate Particles: A New Topical Formulation

Pickering emulsions are systems composed of two immiscible fluids stabilized by solid organic or inorganic particles. Pickering emulsions are particularly useful in cosmetics, where the surfactants are unwanted, as well as in the pharmaceutical field, where transdermal and/or dermal drug delivery is difficult to achieve and controlled drug release is desired. Here, we studied calcium carbonate particles as stabilizers of Pickering emulsions for topical use. An optimized formulation was obtained using a Quality by Design approach. First, a screening experiment was performed to identify the formulation and process critical variables that affect the quality properties of the Pickering emulsion. The optimization of the production was then studied by establishing the design space. The final formulation was hereinafter investigated regarding the pH, rheological properties, and in vitro cytotoxicity assays. The results showed the formulation had a pH compatible with human skin and a shear thinning behavior. Moreover, this formulation showed a strong network structure, with a suitable spreadability on the skin, allowing an easy application. The in vitro assays were performed to assess the potential cytotoxicity of the calcium carbonate-stabilized emulsion and the particles themselves, and the results revealed that the formulation did not significantly affect the cell viability. In conclusion, the use of calcium carbonate particles as a stabilizer ingredient contributed to achieve an eco-friendly Pickering emulsion.

Progressing Towards the Sustainable Development of Cream Formulations

This work aims at providing the assumptions to assist the sustainable development of cream formulations. Specifically, it envisions to rationalize and predict the effect of formulation and process variability on a 1% hydrocortisone cream quality profile, interplaying microstructure properties with product performance and stability. This tripartite analysis was supported by a Quality by Design approach, considering a three-factor, three-level Box-Behnken design. Critical material attributes and process parameters were identified from a failure mode, effects, and criticality analysis. The impact of glycerol monostearate amount, isopropyl myristate amount, and homogenization rate on relevant quality attributes was estimated crosswise. The significant variability in product droplet size, viscosity, thixotropic behavior, and viscoelastic properties demonstrated a noteworthy influence on hydrocortisone release profile (112 ± 2–196 ± 7 μg/cm²/√h) and permeation behavior (0.16 ± 0.03–0.97 ± 0.08 μg/cm²/h), and on the assay, instability index and creaming rate, with values ranging from 81.9 to 120.5%, 0.031 ± 0.012 to 0.28 ± 0.13 and from 0.009 ± 0.000 to 0.38 ± 0.07 μm/s, respectively. The release patterns were not straightforwardly correlated with the permeation behavior. Monitoring the microstructural parameters, through the balanced adjustment of formulation and process variables, is herein highlighted as the key enabler to predict cream performance and stability. Finally, based on quality targets and response constraints, optimal working conditions were successfully attained through the establishment of a design space.

Novel and Modified Neutrophil Elastase Inhibitor Loaded in Topical Formulations for Psoriasis Management

Human neutrophil elastase (HNE) is a serine protease that degrades matrix proteins. An excess of HNE may trigger several pathological conditions, such as psoriasis. In this work, we aimed to synthesize, characterize and formulate new HNE inhibitors with a 4-oxo-β-lactam scaffold with less toxicity, as well as therapeutic index in a psoriasis context. HNE inhibitors with 4-oxo-β-lactam scaffolds were synthesized and characterized by NMR, FTIR, melting point, mass spectrometry and elemental analysis. In vitro cytotoxicity and serine protease assays were performed. The compound with the highest cell viability (AAN-16) was selected to be incorporated in an emulsion (AAN-16 E) and in a microemulsion (AAN-16 ME). Formulations were characterized in terms of organoleptic properties, pH, rheology, droplet size distribution, in vitro drug release and in vivo psoriatic activity. All compounds were successfully synthesized according to analytical methodology, with good yields. Both formulations presented suitable physicochemical properties. AAN-16 E presented the most promising therapeutic effects in a murine model of psoriasis. Overall, new HNE inhibitors were synthesized with high and selective activity and incorporated into topical emulsions with potential to treat psoriasis.

Flavonoid-Enriched Plant-Extract-Loaded Emulsion: A Novel Phytocosmetic Sunscreen Formulation with Antioxidant Properties

The aim of this study was to develop a phytocosmetic sunscreen emulsion with antioxidant effect, containing a blend of flavonoid-enriched plant extracts. In vitro sun protection factor, antioxidant activity, skin irritation, photostability, cutaneous permeation, and retention of flavonoids were evaluated. Thermodynamically stable emulsions were obtained and tested for sensorial analysis after loading the blend of extracts. The selected emulsion was stable when stored at low temperatures (5 °C), for which after 120 days the concentration of quercetin and rutin were above their limit of quantification, i.e., 2.8 ± 0.39 μg/mL and 30.39 ± 0.39 μg/mL, respectively. Spreadability, low rupture strength and adhesiveness were shown to be similar to a conventional topical product. Higher brittleness, pseudo-plastic, and viscoelastic behaviors were also recorded for the developed phytocosmetic sunscreen. The product presented a critical wavelength of 387.0 nm and ultraviolet rays A and B (UVA/UVB) rate of 0.78, confirming that the developed formulation shows capacity for UVA/UVB protection, protecting skin against damages caused by ultraviolet (UV) radiation. Rutin was shown to permeate the skin barrier and was also quantified in the stratum corneum (3.27 ± 1.92 μg/mL) by tape stripping and retention test (114.68 ± 8.70 μg/mL). The developed flavonoid-enriched phytocosmetic was shown to be non-irritant to skin by an in vitro assay. Our results confirm the antioxidant activity, sun protection, and physical properties of the developed phytocosmetic for topical application.

Design and Characterization of a New Quercus Suber-Based Pickering Emulsion for Topical Application

Quercus Suber Bark from Quercus suber L. is a natural, renewable and biodegradable biomaterial with multifunctional proprieties. In this study, we used it as solid particles to stabilize a Pickering emulsion. The main goal was to produce an optimized topical formulation using biocompatible organic particles as stabilizers of the emulsion instead of the common surfactants, whilst benefiting from Quercus suber L. proprieties. In this work, a Quality by Design (QbD) approach was successfully applied to the production of this emulsion. A screening design was conducted, identifying the critical variables of the formula and process, affecting the critical quality attributes of the emulsion (droplet size distribution). The optimization of the production was made through the establishment of the design space. The stability was also investigated during 30 days, demonstrating that Quercus Suber Bark-stabilized emulsions are stable since the droplet size distribution lowers. In vitro studies were performed to assess antioxidant and antiaging efficacy, which revealed that the formulation had indeed antioxidant proprieties. A physicochemical characterization demonstrated that the formulation presents a shear-thinning fluid, ideal for topical administration. The in vivo compatibility study confirmed that the final formulation is not skin irritant, being safe for human use. A sensorial analysis was also performed, using a simple sensory questionnaire, revealing very positive results. Thus, the use of Quercus Suber Bark particles as a multifunctional solid ingredient contributed to achieve a stable, effective and innovative Pickering emulsion with a meaningful synergistic protection against oxidative stress.

Phase Behavior Controlled by the Addition of Long-Chain n-Alcohols in Systems of Cationic Surfactant/Anionic Polyion Complex Salts and Water

Phase behavior of surfactants in water may be affected by the addition of a third component, and the present study discusses how long-chain n-alcohols affect phase transitions of systems formed by the surfactant hexadecyltrimethylammonium bromide, C₁₆TAB, or its complex salts formed with polyacrylate, C₁₆TAPA₃₀, as well as other previously reported complex salts/water/alcohol systems. Structural characterization by X-ray diffraction patterns at small and wide angles and different temperatures was performed for samples containing n-decanol, n-dodecanol, or n-tetradecanol. Differential scanning calorimetry (DSC) was also used to study the phase transition. The results allowed us to observe and understand the coexistence of lamellar gel (L_β) and lamellar liquid-crystal (L_α) phases, elucidating the structure of a previously reported mesophase, proposing an alternative assignment. Whereas the chain-melting transition is well-known to be sharp for lipids, we have found that it is broader for C₁₆TAB and C₁₆TAPA in the presence of these n-alcohols. We have investigated the effects of their composition and chain length on the temperature and enthalpy of transition. This elucidates why the addition of n-alcohols with chains slightly shorter than that of the surfactants leads to the formation of an ordered gel-like lamellar phase (L_β). n-Alcohols act as neutral cosurfactants, leading to more packing, and all of the factors converge to a limit situation, associated with a common critical area occupied by each alkyl chain. We compared our results with other mesophase systems from the literature, demonstrating that the same trends of phase behavior occur for complex salts of other polyelectrolytes with alkyltrimethylammonium surfactants.

Effect of Solvent Dielectric Constant on the Formation of Large Flat Bilayer Stacks in a Lecithin/Hexadecanol Hydrogel

We investigated the effect of dielectric properties of the aqueous medium on the novel type of hydrogel composed of a crude lecithin mixture (PC70) and hexadecanol (HD), in which charged sheet-like bilayers are kept far apart due to interbilayer repulsive interaction. We used dipropylene glycol (DPG) as a modifier of the dielectric properties and examined its effect on the hydrogel by synchrotron X-ray diffraction, differential scanning calorimetry (DSC), polarized optical microscopy, and freeze-fracture electron microscopy. We found that at a DPG weight fraction in the aqueous medium WDPG ≈ 0.4, the bilayer organization is transformed into unusually large flat bilayer stacks with a regular lamellar spacing of 6.25 nm and consequently disintegration of the hydrogel takes place. Semiquantitative calculation of the interbilayer interaction energy based on the Deyaguin-Landau-Verwey-Overbeek (DLVO) theory suggested that the reduction of the aqueous medium dielectric constant ε by DPG may lower the energy barrier preventing flat bilayers from coming closer together. We inferred that the size of the bilayer sheet increases because the reduction of ε promotes protonation of acidic lipids that work as edge-capping molecules.

Development and evaluation of an emulsion containing lycopene for combating acceleration of skin aging

Lycopene, a carotenoid and potent antioxidant is found in large quantities in tomatoes. Lycopene combats diseases, such as cardiovascular disease and different types of cancer, including prostate cancer. However, its topical use in emulsion form for the combat of skin aging is under-explored. The aim of the present study was to develop an emulsion containing lycopene extracted from salad tomatoes and evaluate its cytotoxicity, stability, rheological behavior, antioxidant activity and phytocosmetic permeation. The developed cosmetic comprised an oil phase made up of shea derivatives and was evaluated in terms of its physiochemical stability, spreadability, thermal analysis, rheological behavior, microbiological quality, cytotoxicity, antioxidant activity, cutaneous permeation and retention. The results demonstrate that this phytocosmetic is stable, exhibits satisfactory rheological behavior for a topical formula and is a promising product for combating skin aging.

Development of lamellar gel phase emulsion containing marigold oil (Calendula officinalis) as a potential modern wound dressing

Appropriate therapeutics for wound treatments can be achieved by studying the pathophysiology of tissue repair. Here we develop formulations of lamellar gel phase (LGP) emulsions containing marigold (Calendula officinalis) oil, evaluating their stability and activity on experimental wound healing in rats. LGP emulsions were developed and evaluated based on a phase ternary diagram to select the best LGP emulsion, having a good amount of anisotropic structure and stability. The selected LGP formulation was analyzed according to the intrinsic and accelerated physical stability at different temperatures. In addition, in vitro and in vivo studies were carried out on wound healing rats as a model. The LGP emulsion (15.0% marigold oil; 10.0% of blend surfactants and 75.0% of purified water [w/w/w]) demonstrated good stability and high viscosity, suggesting longer contact of the formulation with the wound. No cytotoxic activity (50-1000 μg/mL) was observed in marigold oil. In the wound healing rat model, the LGP (15 mg/mL) showed an increase in the leukocyte recruitment to the wound at least on days 2 and 7, but reduced leukocyte recruitment after 14 and 21 days, as compared to the control. Additionally, collagen production was reduced in the LGP emulsion on days 2 and 7 and further accelerated the process of re-epithelialization of the wound itself. The methodology utilized in the present study has produced a potentially useful formulation for a stable LGP emulsion-containing marigold, which was able to improve the wound healing process.

Cold processed oil-in-water emulsions for dermatological purpose: formulation design and structure analysis

The aim of this work is to develop, optimize and characterize cold process emulsions that are stable at acidic pH. The main surfactant was selected according to the hydrophilic lipophilic balance (HLB) concept and surface tension, whereas polymers were selected by viscoelastic measurements and analytical centrifugation. It was showed that the inclusion of methyl vinyl ether/maleic anhydride copolymer crosslinked with decadiene (PVM/MA) increased the storage modulus (G') of the gels (23.9-42.1 Pa) two-fold and the droplet migration decreased from 3.66% to 0.95%/h. Cetrimide was selected as a preservative based on its microbiological results and additional contribution to the stability of the emulsions. Four emulsions were developed that differed by the co-emulsifier used (PEG-20 glyceril laurate and polyglyceryl-4-isostearate) and the glycol (2-methyl-2,4-pentanediol and ethoxydiglycol). Viscoelastic measurements and droplet size/microscopic analysis showed that the structure of PEG-20 glyceril laurate emulsion (η' = 76.0 Pa.s at 0.01 Hz and 32.9 ± 3.7 µm, respectively) was stronger compared to polyglyceryl-4-isostearate (η' = 37.4 Pa.s at 0.01 Hz and 37.8 ± 15.7 µm, respectively). Differential scanning calorimetry (DSC) results were in accordance with the latter and showed that PEG-20 glyceril laurate with 2-methyl-2,4-pentanediol corresponded to the strongest structure (|224.4| W °C g(-1)). This cold process allowed a total production savings of more than 17% when compared to the traditional hot process.

Mechanism of gelation in the hydrogenated soybean lecithin (PC70)/hexadecanol/water system

The crude phospholipid mixture (PC70) forms a homogeneous gel with hexadecanol (HD) in water, whereas the purified lipid does not. The fact that the crude material PC70 can be utilized for homogeneous gel preparation suits the cosmetic industry very well from the viewpoint of cost performance. In order to clarify the mechanism of the gelation, we investigated the structures and physicochemical properties of the PC70/HD/water system by rheometry, freeze-fracture electron microscopy, differential scanning calorimetry (DSC) and synchrotron X-ray diffraction. Our results suggested that the gelation is induced by change in bilayer morphology from closed vesicles to sheet-like structures with open edges covered by minor lipid components that are stiffened due to intercalation of HD molecules between phospholipids. The morphological change may give rise to homogeneous distribution of the bilayer sheets throughout the solution and formation of water continuum that may work as a network in the gel.

Formulation and in vitro release evaluation of newly synthesized palm kernel oil esters-based nanoemulsion delivery system for 30% ethanolic dried extract derived from local Phyllanthus urinaria for skin antiaging

BACKGROUND

Recently there has been a remarkable surge of interest about natural products and their applications in the cosmetic industry. Topical delivery of antioxidants from natural sources is one of the approaches used to reverse signs of skin aging. The aim of this research was to develop a nanoemulsion cream for topical delivery of 30% ethanolic extract derived from local Phyllanthus urinaria (P. urinaria) for skin antiaging.

METHODS

Palm kernel oil esters (PKOEs)-based nanoemulsions were loaded with P. urinaria extract using a spontaneous method and characterized with respect to particle size, zeta potential, and rheological properties. The release profile of the extract was evaluated using in vitro Franz diffusion cells from an artificial membrane and the antioxidant activity of the extract released was evaluated using the 2, 2-diphenyl-1-picrylhydrazyl (DPPH) method.

RESULTS

Formulation F12 consisted of wt/wt, 0.05% P. urinaria extract, 1% cetyl alcohol, 0.5% glyceryl monostearate, 12% PKOEs, and 27% Tween 80/Span 80 (9/1) with a hydrophilic lipophilic balance of 13.9, and a 59.5% phosphate buffer system at pH 7.4. Formulation F36 was comprised of 0.05% P. urinaria extract, 1% cetyl alcohol, 1% glyceryl monostearate, 14% PKOEs, 28% Tween 80/Span 80 (9/1) with a hydrophilic lipophilic balance of 13.9, and 56% phosphate buffer system at pH 7.4 with shear thinning and thixotropy. The droplet size of F12 and F36 was 30.74 nm and 35.71 nm, respectively, and their nanosizes were confirmed by transmission electron microscopy images. Thereafter, 51.30% and 51.02% of the loaded extract was released from F12 and F36 through an artificial cellulose membrane, scavenging 29.89% and 30.05% of DPPH radical activity, respectively.

CONCLUSION

The P. urinaria extract was successfully incorporated into a PKOEs-based nanoemulsion delivery system. In vitro release of the extract from the formulations showed DPPH radical scavenging activity. These formulations can neutralize reactive oxygen species and counteract oxidative injury induced by ultraviolet radiation and thereby ameliorate skin aging.

Influence of hydration state and homologue composition of magnesium stearate on the physical chemical properties of liquid paraffin lipogels

Lipogels were prepared by dispersing mixed (60:40 C(16)-C(18)) and pure (C(18)) homologue magnesium stearate (MgSt) in liquid paraffin, using three methods of preparation, i.e. addition of water at 95 °C during cooling cycle (method 1), homogenisation upon cooling (method 2) or cooling without addition of water or homogenisation (method 3). The systems were characterised by physical inspection, polarised, hot stage and scanning electron microscopy (SEM), differential scanning calorimetry (DSC), rheology, and X-ray diffraction (XRD). Systems formed stable semisolid lipogels (no syneresis), unstable solids showing syneresis or structured fluids, depending on the type of magnesium stearate used and the preparation technique. The stable semisolid lipogels containing mixed homologue MgSt (commercial-as received, anhydrous or dihydrate) prepared by methods 1 (∼ 1-2% water) and 2 contained α-crystalline lamellar structure. These were not present in the unstable solids formed with method 3 or in systems prepared from pure homologue MgSt which were generally structured fluids rather than semisolids. In addition, semisolid lipogels of pure homologue trihydrate MgSt prepared by method 3 showed plate-like crystals, implying pressure sensitivity. There is significantly more amorphous MgSt in the unstable solids compared to the stable semisolid lipogels, which are mainly crystalline (confirmed by XRD).