Odyssée au fil des interfaces: de la physico-chimie des macromolécules à l'enveloppe bactérienne, plate-forme interactive du micro-organisme avec son micro-environnement

This find is registered at Portable Antiquities of the Netherlands with number PAN-0001909

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

The Hidden Face of Nitrogen Oxides Species: From Toxic Effects to Potential Cure?

Nitrogen oxide (NOx) species represent ones of the most threatening air pollutants due to their prevalence and harmful impact on the environment and human health. The term NOx gathers mainly nitric oxide (NO) and nitrogen dioxide (NO2), mostly produced by anthropogenic activities such as transport and industries. Several cellular constituents were already described as NOx targets. These include membranes, proteins, respiratory chain enzymes, lipids, and DNA. Such damages lead to pathologies of lungs, cardiovascular system, and skin because these organs represent the first barrier toward the environment. On the other hand, NOx is also naturally synthetized by several organisms, playing a mediator role in essential cellular functions. However, few data are yet available on NOx activity toward microorganisms. Here, we review data concerning the double face of NOx, including their use in the medical field against pathogens’ infections that highlight the versatility of these compounds

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 gaseous no 2 on P. fluorescens strain in the membrane adaptation and virulence

International audienceNowadays air pollution is increasing due to anthropogenic activity. Among all air pollutants, nitrogen oxides (NOx) such as NO are predominant. It is well known that those compounds exhibit direct toxic effects on human health. However, microorganisms are also exposed to them, but the effect of NOx on the virulence of air microbiota is still poorly understood. In this study, we evaluated the impact of NO on the adaptability and virulence of an airborne strain of P. fluorescens, MFA76a, by exposition of this strain to 45 ppm of NO2. The growth kinetics and cultivability were analysed. A decrease of cultivability coupled with an increase of the lag phase was observed suggesting a potential toxicity of NO2. Since NOx particularly target lipids, the membrane permeability was assessed thanks to Live Dead tests and confocal microscopy. A significant alteration of membrane permeability was observed. Furthermore, more abundant bacterial aggregates were detected compared to the control. Thus, a lipidomic study was performed using MALDI-TOF MS Imaging coupled to HPTLC. Interestingly, bacteria exposed to NO were lacking one putative glycerophospholipid molecule. In agreement with a previous study from Kondakova et al., these data demonstrate the adaptation potential of P. fluorescens MFAF76a to an air pollutant such as NO

Airborne fluorescent pseudomonads : What potential for virulence?

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Novel Application of Cyclolipopeptide Amphisin: Feasibility Study as Additive to Remediate Polycyclic Aromatic Hydrocarbon (PAH) Contaminated Sediments

To decontaminate dredged harbor sediments by bioremediation or electromigration processes, adding biosurfactants could enhance the bioavailability or mobility of contaminants in an aqueous phase. Pure amphisin from Pseudomonas fluorescens DSS73 displays increased effectiveness in releasing polycyclic aromatic hydrocarbons (PAHs) strongly adsorbed to sediments when compared to a synthetic anionic surfactant. Amphisin production by the bacteria in the natural environment was also considered. DSS73’s growth is weakened by three model PAHs above saturation, but amphisin is still produced. Estuarine water feeding the dredged material disposal site of a Norman harbor (France) allows both P. fluorescens DSS73 growth and amphisin production

Interactions [nano]particules et micro-organismes cutanés

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Evaluation du potentiel applicatif en cosmétique de biosurfactants microbiens secrétés par des souches de Pseudomonas fluorescent aéroportées

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