Modulation of metallic oxide particle behaviour in a formulation: physicochemical and/or sensory properties of emulsions as a tool to identify particles interactions within the matrix

International audienceParticles of metal oxides such as silica (SiO2), alumina (Al2O3) or titanium dioxide (TiO2) are nowadays widely used in manufactured products. The interest of these solid particles lies in the possibility tovary their size (a few nanometers to several micrometers), their shape, and their state of aggregation, as well as their specific surface. In addition, these metal oxides are good candidates for surface modification (coating with other metal oxides, silanization) to also modulate their surface properties [1-2].Thus, incorporated in a complex medium such as an emulsion, these solid particles, due to their varied physicochemical properties, will be able to interact with all the constituents of the matrix. This represents asubject of great scientific interest, from both applied and fundamental point of view. Depending on its surface properties, the particle can manifest more affinity with the continuous phase, the dispersedone, or can be placed at the interface [3]. In the latter situation, the particle can act as a surfactant and can even replace the molecular surfactants conventionally used.The aim of this study lays on its multiscale approach: from microscopic scale through the investigation of the ingredients interactions (guided by the type of particle used) to macroscopic scale with the characterization of stable, homogeneous and totally emulsified systems (as it was a required condition to provide an adapted system for macroscopic evaluations). Rheological, textural and sensory behavior, as well as emulsion colloid size and size distribution, were used as a tool to identify the role of the particles on the matrix organization.One objective was to find the emulsions optimal formulation process and composition to accomplish the desired requirements for this study.The obtained results clearly showed the importance of the particle properties in emulsion formation and stabilization. Interactions created inside the matrix were governed by the specific surface andthe coating type of the particles. Thus, the modulation of the emulsion can be possible relying on the particle/emulsifier/oil phase interaction and ratio.[1] S. Björkegren, L. Nordstierna, A. Törncrona and A. Palmqvist, Journal of Colloid and Interface Science, 2017, 487, 250.[2] C. Picard, A. Larbot, E. Tronel-Peyroz and R. Berjoan, Solid State Sciences, 2004, 6, 605.[3] B. P. Binks, Current Opinion in Colloid & Interface Science, 2002, 7, 21

PHYSICAL AGING OF EMULSIONS CONTAINING COATED TIO2-NANOPARTICLES: INTERACTION BETWEEN NANOPARTICLES AND OTHER INGREDIENTS

International audienceTiO2-nanoparticles (NPs) are usually added to cosmetic emulsions because they procure a good UV-protection1. In this study, two natures of NPs surfaces were explored: a hydrophilic silica-coated particle and a hydrophobic one covered with a large organic coating. During emulsion aging and depending on their surfacenature and properties, NPs might interact with the formula by inducing adsorption of formula’s compounds2 or by undergoingcoatings damages. These phenomenamay change the nanoparticle surface properties, their behavior in emulsion, and finally, led to the emulsionsdestabilization. The impact of TiO2-NP surfaces on the physical aging of emulsions was here studied.For this purpose, threeemulsions were formulated differing only by the presence and type of NPs: one NP-free as blank, and two containing hydrophilic and hydrophobic commercial TiO2-NPs, respectively.The emulsification process was optimized to obtain a blank emulsion physically stable and to improve the NPs dispersions. Effects of coatings on fresh emulsions were depicted on the micro and macro scales by several physico-chemical methods.Then, emulsions physical evolutions onnormal or accelerate aging conditionswere monitored.Droplets sizes were similar between the three fresh emulsions, whereas slight differences in term of networksorganization highlighted the impact of the coating nature on the emulsion microstructure. However, initial emulsions properties looked similar by applying rheological and textural analyses. Although the blank emulsion and the one with hydrophilic NPs remained similar after the aging step, the microstructure of the emulsion with hydrophobic NPsquickly evolved: aggregates of both droplets and NPs made the formula less homogeneous. As will be illustrated, this evolution in term of colloids sizes strongly affects the functional properties, as viscosity, consistency or spreading quality of this aged emulsion. These results revealed the impact of coating nature in this kind of complex media. Afterinnovative NPs extractions3 from fresh and aged formulae, their surfaces were characterized. By an original physico-chemical approach, quick surface modifications appeared and changed the surface charges and wettability of particles. These variations might cause the differences in term of stability between emulsions.(1) Serpone, N.; Dondi, D.; Albini, A. Inorganica Chim. Acta2007, 360 (3), 794–802.(2) Rossano, M.; Hucher, N.; Picard, C.; Colleta, D.; Le Foll, F.; Grisel, M. Int. J. Pharm.2014, 461 (1-2), 89–96.(3) Rossano, M. Ph.D thesis: Utilisation des nanoparticules de dioxyde de titane dans les émulsions cosmétiques : impact sur la santé humaine et l’environnement, Université du Havre: Le Havre, 2014

Effects of aging on structure and stability of TiO2 nanoparticle-containing oil-in-water emulsions

International audienceFormulations incorporating different cosmetic grade TiO 2 nanoparticles were developed according to a self-produced protocol on the basis of typical sunscreen cream oil-in-water emulsions. Role of nanopar-ticles and, more specifically, the impact of two different lipophilic surface treatments on microstructure and stability of the formulations were assessed. Aging of formulations was performed under classical conditions at room temperature or under accelerated conditions at 50 • C, with or without TiO 2 , and was characterized by several tools such as rheology, microscopy, and particle size measurements. Changes in emulsion stability and aggregation state of nanoparticles were followed over time. Destabilization phenomena were identified: under accelerated aging, the formulation without nanoparticles underwent a coalescence occurrence whereas the formulation incorporating nanoparticles was subjected to aggregation of the colloidal particles. Besides, TiO 2 nanoparticles strongly affected the particle-droplets interactions and thus modified the emulsion microstructure with a coating-dependent effect: destabilization mechanisms occur more rapidly with alumina (and) triethoxycaprylylsilane (coating 1) TiO 2 nanoparticles as compared to alumina (and) isopropyl titanium triisostearate (and) triethoxycaprylylsi-lane crosspolymer (coating 2) nanoparticles

Development of preservative-free nanoparticles-based emulsions: Effects of NP surface properties and sterilization process

International audienceModel emulsions were developed with or without commercial titanium dioxide nanoparticles (NP) carrying various surface treatments in order to get close physicochemical properties whatever the NP surface polarity (hydrophilic and hydrophobic). Rheology and texturometry highlighted that the macroscopic properties of the three formulated emulsions were similar. However, characterizations by optical microscopy, static light scattering and zetametry showed that their microstructures reflected the diversity of the incorporated NP surface properties. In order to use these model emulsions as tools for biological evaluations of the NP in use, they had to show the lowest initial microbiological charge and, specifically for the NP-free emulsion, the lowest bactericidal effect. Hence, formulae were developed preservative-free and a thermal sterilization step was conducted. Efficiency of the sterilization and its impact on the emulsion integrity were monitored. Results highlighted the effect of the NP surface properties: only the control emulsion and the emulsion containing hydrophilic NP fulfilled both requirements. To ensure the usability of these model emulsions as tools to evaluate the 'NP effect' on representative bacteria of the skin microflora (S. aureus and P. fluorescens), impact on the bacterial growth was measured on voluntary inoculated formulae

IMPACT OF A TIO2 [NANO] COSMETICS GRADE ON THE CUTANEOUS MICROBIOTA: NANOPARTICLES BEHAVIOR IN EMULSION AND BACTERIOTOXICITY

International audienceTiO2-nanoparticles (NP) commonly used in cosmetics as physical UV-filters, are surface-modified by applying a first coating in order to quench photo-produced radicals. In addition, a second coating is sometimes added to raise their dispersibility in emulsion. Whereas European regulation mentions the obligation to demonstrate the safety of NP, very few studies took interest on their behavior in use. During formulation and storage, NP are exposed to a variety of environmental conditions which can accelerate aging and induce particles aggregation, adsorption of formula’s compounds or coatings deterioration. Consequently, a crucial question remains their safety while layered on skin and particularly their effect on the skin microflora. We will present the impact of TiO2-nanoparticles on the skin microflora in relation to their physicochemical properties in cosmetic emulsions during aging.A series of cosmetic emulsions were formulated with using conventional cosmetic ingredients, with or without Nanoparticles (NPs): one without NPs considered as blank, and two with hydrophilic and hydrophobic commercial TiO2-NPs, respectively. An emulsification process was developed and optimized to obtain a blank emulsion, physically stable, with improved NPs dispersions in emulsion. Then, emulsions were submitted to accelerate aging.Particles were extracted from the fresh/aged emulsions by original protocols allowing recovering particles with possible adsorbed compounds or cleaned surfaces.Skin bacteria growths were evaluated in emulsions or dispersions to check the toxicity of nanoparticles in use. Then, because of NP opacity, protocols were adapted to measure their effect on bacteria virulence toward skin cells.Microscopic and macroscopic characterizations revealed comparable structures and functional properties between the three fresh emulsions. Then, during aging, different behavior were registered and could be related to nanoparticle coating nature.Extracted NP from the fresh/aged formulas showed quick surface modifications in terms of chemical structures and physical properties that might be caused by adsorption or deterioration at their surfaces.For fresh emulsions, both nanoparticles did not have any impact on skin bacteria strains, S. aureus and P. fluorescens. In the case of aged emulsions, part of NPs seemed to allow the S. aureus growth, whereas others still remained with no effect on microflora. Finally, bacteria generation times and virulence toward skin cells differed depending on NPs surface treatments and exposition time.This work dealt with the impact of nanoparticles on skin microflora along cosmetic emulsion shelf-life. This new approach allows taking into account their safety when used in emulsion.First, through innovative extraction and characterization protocols, it was highlighted that chemical nature and physical properties of nanoparticle surfaces might be altered once in emulsion. These physicochemical observations were related to microbiological tests on skin representative bacteria. Effect of some of the NPs on bacteria growth and virulence evolved after aging. Finally, modification of NPs surface treatment seemed to have an effect on skin microflora

ALTERATIONS DE LA MOTRICITE DIGESTIVE ASSOCIEES AUX PROCESSUS INFLAMMATOIRES INDUITS PAR LES RAYONNEMENTS IONISANTS CHEZ LE RAT

PARIS7-Bibliothèque centrale (751132105) / SudocPARIS-BIUSJ-Physique recherche (751052113) / SudocSudocFranceF

Spreading behavior of cosmetic emulsions Impact of the oil phase

International audienceBackground Emollients are an important ingredient in personal care products, they are currently prescribed in skin disorders like eczema, which affects up to 30% of children in developed countries. Methods The aim of the study was to investigate the impact of two emollients (stearic acid and isohexadecane) and their mixtures in the spreadability and frictional effect on films obtained from oil-in-water emulsions. Rheological, textural, sensory and tribological analysis were performed on human skin and artificial substrates. Results The emollients ratio influences the spreading behavior of emulsions more isohexadecane in the oil phase easier to spread the product on the skin. Moreover, significant correlations were obtained for the spreading behavior obtained by textural measurements on artificial substrates and sensory analysis (Pearson coefficient = −0.871). The results obtained by frictiometer showed different developments over time after product application the friction values increase with the stearic acid concentration in emulsion. Discussion This study showed the importance to consider the emollient properties when one emollient is used in the emulsion, but especially their interactions, when several emollients are used, to better understand and anticipate their behavior. First, spreading was governed by the consistency of the emulsion, particularly impacted by the emollients ratio. But then, in a long-time spreading, when the emulsion broke down and residual film was formed, a particular interaction with skin influenced the spreadability. It appears that not only the physical state of the emollient but also its chemical nature, physical state, polarity, temperature might explain these phenomena. © 2018 Elsevier Lt

Characterisation of spreading and penetration of ingredients used in cosmetic emulsions

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Impact of emollients on the spreading properties of cosmetic products: A combined sensory and instrumental characterization

International audienceThis study deals with the impact of emollients on the spreading properties of cosmetic products using a combined sensory-instrumental approach. To that purpose, three esters and one silicone were selected and incorporated separately into an oil phase. Different cosmetic o/w emulsions were then prepared with these different oil phases. Both of them were analyzed by instrumental techniques and in vivo sensory analyses. A significant effect of the emollient used was established in emulsions and in oil phases as well. Concerning emulsions, results reveal a clear correlation between in vivo spreading evaluation and friction coefficient parameters measured by texture analyzer, despite a fairly low correlation coefficient (Pearson coefficient = −0.78). Concerning oil phases, characterization of spreading was done by monitoring the contact angle relaxation of a drop of solution after deposition on a flat PMMA surface whereas sensory procedure was based on spontaneous spreading of oil phases onto the skin. Finally, good correlations between in vivo sensory analysis and instrumental measurements of both oils and emulsions were found, thus promising the possible development of predictive tools to evaluate spreadability