Milica Lukic

A combined approach in characterization of an effective w/o hand cream: the influence of emollient on textural, sensorial and in vivo skin performance

To formulate a consumer‐acceptable cosmetic product, numerous demands have to be fulfilled, and as the most important, efficacy (both real and perceived), adequate aesthetic (visual perception) and all sensorial characteristics have to be achieved. In this study, four model water‐in‐oil creams intended for hand care, varying in one emollient component, were submitted to rheological, sensory and textural characterization, and their efficacy was evaluated in in vivo study on human volunteers. Our results indicate that certain alteration restricted to the oil phase induced a change in all investigated characteristics, showing that each instrumental measurement can be used as a sensitive tool in the characterization of cream samples. Regarding the correlation between physical measurements and certain sensory attributes, it is possible to formulate a product with specific sensory characteristics by using pre‐defined rheological or textural parameters. To obtain a complete sensory profile of a cosmetic product, a detailed sensory evaluation should be carried out according to the existing standard practices, which are both time‐ and money‐consuming. However, a modified sensory study could be useful for fast in‐line screening along with instrumental characterization of a novel cosmetic emulsion product and could be particularly helpful in the process of distinguishing a single formulation from several differing in one component.

Lactobionic acid in a natural alkylpolyglucoside-based vehicle: assessing safety and efficacy aspects in comparison to glycolic acid

Background/aims  Lactobionic acid (LA) is a newer cosmeceutical active belonging to the class of alpha‐hydroxyacids (AHAs), showing advantages over them. The aim of part I of this study was to compare efficacy and irritation potential of LA vs. glycolic acid (GA) from two types of vehicles – gel and emulsion. In part II, effects of LA‐containing emulsions based on a new, natural emulsifier of alkylpolyglucoside (APG) type were evaluated.

Moisturizing emulsion systems based on the novel long-chain alkyl polyglucoside emulsifier

Mesomorphic behavior of the novel long-chain alkyl polyglucoside emulsifier comprising arachidyl alcohol (C20), behenyl alcohol (C22), and arachidyl glucoside was investigated in order to determine the prevalent stabilization mechanism and moisturizing capacity of emulsion systems based on it. For this to be accomplished thermoanalytical methods (differential scanning calorimetry and thermogravimetric analysis) coupled with microscopy, rheological, X-ray diffraction methods and a short-term in vivo study of skin hydration level were performed. Obtained results have proved that C20/C22 alkyl polyglucoside mixed emulsifier is able to provide the synergism between the two main types of lamellar phases, the liquid-crystalline (Lα), and the gel crystalline (Lβ) one, building the emulsion systems of different stability and performance. Formation of lamellar structures influenced for more than one half of water within the system to be entrapped. Conducted investigation of hydration potential in real-time conditions provided valuable information on the investigated emulsion vehicles’ moisturizing potential as well as their contribution to the skin barrier improvement. Therefore, it could be expected that emulsions based on this alkyl polyglucoside emulsifier could influence the delivery of active ingredients of both the lipophilic and hydrophilic type. The employment of thermoanalytical methods in our work suggests the possibility for thermal methods to be used more frequently in the characterization of both the novel raw materials and the belonging emulsion systems.

Lactobionic acid as antioxidant and moisturizing active in alkyl polyglucoside‐based topical emulsions: the colloidal structure, stability and efficacy evaluation

Cosmeceutical antioxidants may protect the skin against oxidative injury, involved in the pathogenesis of many skin disorders. However, an unsuitable topical delivery system with compromising safety profile can affect the efficacy of an antioxidant active. This study investigated the antioxidant potential of lactobionic acid (LA), a newer cosmeceutical active, per se (in solution) and incorporated into natural alkyl polyglucoside (APG) emulsifier‐based system using 1,1‐diphenyl‐2‐picrylhydrazyl free radical scavenging and lipid peroxidation inhibition assays. The α‐tocopherol was used as a reference compound. The physical stability (using rheology, polarization microscopy, pH and conductivity measurements) of an Alkyl glucoside‐based emulsion was evaluated with and without the active (LA); colloidal structure was assessed using polarization and transmission electron microscopy, rheology, thermal and texture analysis. Additionally, the safety profile and moisturizing potential were investigated using the methods of skin bioengineering. Good physical stability and applicative characteristics were obtained although LA strongly influenced the colloidal structure of the vehicle. LA per se and in APG‐based emulsion showed satisfying antioxidant activity that promotes it as mild multifunctional cosmeceutical efficient in the treatment and prevention of the photoaged skin. Employed assays were shown as suitable for the antioxidant activity evaluation of LA in APG‐based emulsions, but not for α‐tocopherol in the same vehicle.

An Overview of Novel Surfactants for Formulation of Cosmetics with Certain Emphasis on Acidic Active Substances

Abstract Novel surfactants which are nowadays available for incorporation into various formulations of personal care and cosmetic products are numerous, implying a permanent need for their classification. This overview provides essential information relating to synthesis, basic physicochemical characteristics, application and other relevant data on surfactants currently used in cosmetic products. In the second part of the paper an outline of acidic active substances with significant application in cosmetic products is given, as well as the problems that arise during preparation/manufacture of the containing formulations, accompanied with the review of scientific publications and other available reliable data dealing with the incorporation of these actives in the cosmetic formulations stabilized with novel (mainly natural) surfactants.

Tacrolimus loaded biocompatible lecithin-based microemulsions with improved skin penetration: Structure characterization and in vitro/in vivo performances

In order to improve skin penetration of tacrolimus we aimed to develop potentially non-irritant, lecithin-based microemulsions containing ethanol, isopropanol and/or propylene glycol as cosurfactants, varying caprylic/capric triglycerides and propylene glycol monocaprylate as oil phase. The influence of excipients on the size of microemulsion region in pseudo-ternary phase diagrams and their ability to form different types of microemulsions was evaluated. The comprehensive physicochemical characterization of microemulsions and the evaluation of their structure was performed, while the localization of tacrolimus in microemulsions was further investigated using electron paramagnetic resonance spectroscopy. Moreover, stability studies proved no change in tacrolimus content during one year of storage at room temperature. In addition, in vivo skin performance indicated no skin irritation potential of blank microemulsions, whereas in vitro release testing using Franz diffusion cells showed superior release rate of tacrolimus from microemulsions (0.98±0.10 and 0.92±0.11μg/cm2/h for two bicontinuous and 1.00±0.24μg/cm2/h for oil-in-water microemulsion) compared to referent Protopic ointment (0.15±0.08μg/cm2/h). Furthermore, ex vivo penetration assessed through porcine ear skin using tape stripping, confirmed superiority of two microemulsions related to the reference, implying developed microemulsions as promising carriers for dermal delivery of tacrolimus.

Effect of small changes in natural origin-based emulsion systems on hydrocortisone skin absorption and performance: a comparison of two in vivo methods

Abstract Context: Alkyl polyglucoside surfactants (APG) remain prominent natural origin stabilizers offering a prospect of combining satisfactory stability with mild dermatological properties and complete biodegradability. Objective: With the purpose of adjusting the dose to a patient’s needs, dilution of commercial corticosteroid formulations is a practice which may modify efficacy uncontrolledly. The rational of the study was to investigate whether a simple change in ready-to-use bases (co-solvent addition) could address these needs in a more predictive manner. Methods: Hydrocortisone (HC) delivery from such emulsion systems was comparatively assessed employing two in vivo methods: the established human skin blanching assay versus skin stripping technique. Results: HC permeation data obtained after three dose durations showed better overall performance of the APG-stabilized bases relative to reference ones. Although the solubility study showed that all the assessed active samples retained equal thermodynamic activity, diverse HC permeation/penetration implies the importance of the applied base’s colloidal structure and/or changes endured. Isopropyl alcohol (IPA) addition offered faster drug penetration enhancement, while glycerol as a moisturizing agent influenced HC penetration through the increase in skin hydration. Conclusion: Although the performed in vivo methods cannot be considered alternative, skin stripping technique proved to be a cost-efficient mode of percutaneous penetration assessment, providing additional information on vehicle–skin interactions.

Development of a prospective isopropyl alcohol-loaded pharmaceutical base using simultaneous in vitro/in vivo characterization methods of skin performance.

Abstract Context: Approaching of pharmaceutical and cosmetic industries in some aspects inevitably influence formulation of topical pharmaceuticals, urging researchers to introduce novel excipients with proven benefits over traditional ones. In that context, alkyl polyglucosides (APG) emerge as prominent natural-origin emulsifiers with numerous favorable features (biodegradability, dermatological acceptability, desirable sensory properties). Objective: To evaluate APG-stabilized bases (alone and upon addition of isopropyl alcohol) and their impact on skin performance. A simultaneous in vitro/in vivo skin absorption study was conducted to evaluate whether the tape stripping technique could be recommended as an in vivo tool for skin penetration assessment during formulation optimization process. Materials and methods: After a comprehensive physicochemical characterization, biopharmaceutical properties of APG-bases versus reference ones were assessed through a combined in vitro (release/permeation) and in vivo approach. Results and discussion: Physicochemical characterization revealed substantial difference in structural ordering due to the formation of various mesomorphic phases. The enhancer-loaded APG base resulted in significantly higher drug levels at all depths into the stratum corneum, indicating that the selected enhancer along with specific colloidal structure has increased the extent of drug delivery. Conclusion: Results recommend the investigated emulsifier for stabilization of topical drug delivery systems, not only for their ability to sustain the addition of isopropyl alcohol which proved to be a valuable enhancer, but also satisfactory skin absorption and tolerability when compared to samples stabilized by conventional emulsifier. Tape stripping proved to be a useful and yet inexpensive tool for in vivo trials, able to discriminate subtle differences in dermal availability.

Feasibility of a Natural Surfactant as a Stabilizer for Cosmetics with Liposome-Encapsulated Plant Stem Cells: Pre-Formulation and Formulation Through Stability Studies

Abstract During the formulation of liposome-containing products different problems can occur and the selection of a suitable carrier remains the greatest challenge. To estimate feasibility of a novel alkyl polyglucoside surfactant (hydroxystearyl alcohol and hydroxystearyl glucoside) as an emulsifier for cosmetics with liposome-encapsulated plant stem cells, we performed a two-phase study. In the first, the pre-formulation phase, the emulsifiers critical micelle concentration (CMC) and liposome-encapsulated active-emulsifier interactions were determined. The second phase was carried out to develop and characterize a cosmetic emulsion suitable to serve as a carrier for liposomes. The investigated emulsifier, with the obtained CMC value of 0.0085 wt.%, could be classified as liposome-friendly and can be used to develop stable and aesthetically acceptable cosmetics or even prospective pharmaceutical liposome-containing emulsions.

Physicochemical Characterization and in vivo Skin Performance of a Novel Alkyl Polyglucoside Emulsifier in Natural Cosmetic Cream-Bases

Abstract Alkyl polyglucosides (APGs) are a perfect amphiphilic structure, with excellent surface activity and solubility feature. The aim of this study is to develop a simple system, with a relatively low emulsifier content, composed of materials mainly naturally based and with no additional fatty alcohol. Hydroxystearyl alcohol and Hydroxystearyl glucoside, prepared with Jojoba and Hazelnut oil, medium chain triglycerides with or without Xylitylglucoside and Anhydroxylitol and Xylitol, have been investigated by using microscopy, rheology, thermal analysis, pH and conductimetry. Cyclic stress and in vivo skin irritation tests were also conducted. The investigated natural APG emulsifier has a capacity to form simple and stable emulsions of desirable rheological profile with improved hydration potential and to renew damaged skin, thus it can be safely applied as stabilizer in cosmetic and prospective pharmaceutical cream-bases.