An Innovative Methodology to Characterize, at the Molecular Scale, Interactions in Polysaccharide Aqueous Solutions.

Characterizing molecular interactions at the microscopic level remains difficult and, therefore, represents a key target to better understand macromolecule and biomacromolecule behaviors in solution, alone, or in mixtures with others. Therefore, accurate characterization in liquid media, especially in aqueous solutions, without causing any perturbation of the system in which they are studied, is quite difficult. To this purpose, the present paper describes an innovative methodology based on fluorescence spectrophotometry. Two molecular fluorescent probes, namely 8-anilino-1-naphtalenesulfonic acid (ANS) and 2-benzofuryl-3-hydroxy-4(1H)-quinolone (3HQ-Bf), were selected to characterize, respectively, the dipole-dipole interactions and hydrophobic micro-domains, for the first one, and hydrogen bonding, for the second. As a support to study molecular interactions, xanthan, galactomannan, and corresponding mixtures of these substances which are well known to exhibit a synergy of interactions in well-defined mixture conditions were chosen. Once the methodology was set up, the existence of the three types of interactions in these systems was demonstrated, thus allowing the elucidation of the mechanisms of interactions at the molecular scale.

Topical pickering emulsion versus classical excipients: A study of the residual film on the human skin.

The interest in Pickering emulsions is based on the possibility of replacing classical emulsifiers with solid particles. These emulsions are very attractive in the pharmaceutical field for their stability virtues and as a vehicle to deliver active ingredients. The study aimed to analyze the properties of the residual film of the Pickering emulsions on the human skin compared to conventional systems. For this project, three types of solid particles were used: titanium dioxide, zinc oxide and silicon dioxide. All of them are capable of stabilizing the oil/water interface and thus forming totally emulsified systems. To create an emulsion of reference, a classical surfactant was used as an excipient. Complementary systems containing both particles and the emulsifier were also analyzed. Then, a combined approach between physicochemical and biometrological in vivo analysis was employed. The study proved that Pickering emulsions stabilized by the metal oxides were distinct from the reference emulsion in terms of droplet sizes and organization, rheological and textural responses. Consequently, it impacted the properties of the residual film once the product was applied to the skin. The particle-stabilized emulsions formed a hydrophobic film counter to conventional excipients. Also, the Friction parameter (or the roughness of the film) was directly linked to the quantity of the particles used in the formulation and their perception on the skin surface. The use of the particles blurs the glossy effect of the oil phase. Finally, it was observed that the appearance of the residual film was impacted by the type of the particle, namely TiO2 and ZnO particles.

Triumfetta cordifolia Gum as a Promising Bio-Ingredient to Stabilize Emulsions with Potentials in Cosmetics.

The cosmetics industry is searching for efficient and sustainable substances capable of stabilizing emulsions or colloidal dispersions that are thermodynamically unstable because of their high surface energy. Therefore, surfactants are commonly used to stabilize the water/oil interface. However, the presence of a surfactant is not always sufficient to obtain stable emulsions on the one hand, and conventional surfactants are often subject to such controversies as their petroleum origin and environmental concerns on the other hand. As a consequence, among other challenges, it is obvious that research related to new-natural, biodegradable, biocompatible, available, competitive-surfactants are nowadays more intensive. This study aims to valorize a natural gum from Triumfetta cordifolia (T. cordifolia) as a sustainable emulsifier and stabilizer for oil-in-water (O/W) emulsions, and to evaluate how the nature of the fatty phase could affect this potential. To this end, O/W emulsions were prepared at room temperature using three different oils varying in composition, using a rotor-stator mixer. Resulting mixtures were characterized using optical microscopy, laser granulometry, rheology, pH and stability monitoring over time. The results demonstrated good potential for the gum as an emulsifying agent. T. cordifolia gum appears efficient even at very low concentrations (0.2% w/w) for the preparation and stabilization of the different O/W emulsions. The best results were observed for cocoglyceride oil due to its stronger effect of lowering interfacial tension (IFT) thus acting as a co-emulsifier. Therefore, overall results showed that T. cordifolia gum is undoubtedly a highly promising new bio-sourced and environmentally friendly emulsifier/stabilizer for many applications including cosmetics.

Original tools for xanthan hydrophobization in green media: Synthesis and characterization of surface activity.

Xanthan gum (XG) was modified through esterification using various alkenyl succinic anhydrides in green media. FTIR and NMR spectroscopy confirmed that the alkenyl succinic hydrophobic groups were successfully grafted on octenyl-grafted (XG-C8), dodecenyl-grafted (XG-C12), and hexadecenyl-grafted (XG-C16) xanthan backbone. Grafted chains were evaluated by degree of succinylation (DS). Modification enhance the surface activity of xanthan by decreasing surface tension from 72 until 37 and 58 mN/m due to respectively long alkenyl chain for XG-C16 (DS = 2.2 ± 0.2%) and high grafting rate for XG-C12 (DS = 16.9 ± 1.9%). These original tools are of great interest to optimize both the DS and the properties of xanthan gum by varying reaction parameters like pH range, reaction time and the mole excess of the grafting reagents to xanthan monomeric units.

Bio-sourced polymers in cosmetic emulsions: a hidden potential of the alginates as thickeners and gelling agents.

OBJECTIVE: The present work aims to investigate the impact of the alginates on the texture properties of cosmetic emulsions. For this purpose, five systems were selected: a classical emulsion without polymer and four emulsions containing polymers, as texture modifiers, at the level of 1%. Two different grades of alginates were chosen: one rich in mannuronic acid and one rich in guluronic acid. The objective was also to evaluate the potential of in-situ gelation during formulation. The guluronic rich sample was gelled to evaluate the effect on the texture properties. Finally, alginates-based systems were compared to the xanthan gum as a bio-sourced polymer reference. METHODS: The sensory profile of the systems was established through a combination of prediction models and sensory analysis. The emulsion residual films obtained with natural polymers, Alginates and Xanthan Gum used as thickeners, as well as with the gelled version, were similar. However, the structural differences between polymers intervene during the characterisation of the sensory properties "before" and "during" application. A multi-scale physicochemical analysis was used to explain these differences. RESULTS: Due to a controlled formulation process, the use of the polymers did not affect the microstructure of the emulsion which remained similar to the control one. The main impact of the polymers was observed on the macroscopic level: both alginates showed their unique textural signature, different from the classical Xanthan Gum. Due to weak structural differences, mechanical and textural properties were very close between the mannuronic rich and guluronic rich samples, when not gelled, compared to other emulsions. However, the molar mass and the mannuronic/guluronic acids ratio were proved to be crucial for the stretching and consistency properties, showing that this structural difference may have an impact when products are handled in traction and compression. CONCLUSION: Meanwhile, the viscoelastic properties and the dynamic viscosity were greatly increased for the emulsion containing the gelled version of the alginate when compared to the classical polymers. The emulsion was also more consistent as proved by the textural analysis, pointing at better stability and suspension potential of the gelled emulsion versus the classical one containing the usual natural thickening agents.

OBJECTIF: Ce document vise à étudier l'impact des alginates sur les propriétés de texture des émulsions cosmétiques. À cet effet, cinq systèmes ont été sélectionnés: une émulsion classique sans polymère et quatre émulsions contenant des polymères, qui jouent le rôle de modificateurs de texture, à raison d'une teneur de 1%. Deux grades différents d'alginates ont été choisis : un alginate riche en acide mannuronique et un autre riche en acide guluronique. L'objectif était également d'évaluer le potentiel de gélification in situ pendant la formulation. L'échantillon riche en guluronique a été gélifié pour évaluer l'effet sur les propriétés de texture. Enfin, les systèmes à base d'alginates ont été comparés à la gomme xanthane, prise comme polymère d'origine biologique de référence. MÉTHODES: Le profil sensoriel des systèmes a été établi par une combinaison de modèles de prédiction et d'analyse sensorielle. Les films résiduels d'émulsion obtenus avec les polymères naturels, les alginates et la gomme de xanthane utilisés comme épaississants, ainsi qu'avec la version gélifiée, étaient similaires. Cependant, des différences structurelles entre les polymères se manifestent lors de la caractérisation des propriétés sensorielles « avant ¼ et « pendant ¼ l'application. Une analyse physico-chimique à échelles multiples a été utilisée pour expliquer ces différences. RÉSULTATS: En raison d'un procédé de formulation contrôlé, l'utilisation des polymères n'a pas affecté la microstructure de l'émulsion qui est restée la même que celle du témoin. Le principal impact des polymères a été observé au niveau macroscopique: les deux alginates ont montré leur signature texturale propre, laquelle diffère de la gomme de xanthane classique. En raison de faibles différences structurelles, comparées à d'autres émulsions, les propriétés mécaniques et texturales étaient très proches entre les échantillons riches en mannuronique et en guluronique, lorsqu'ils n'étaient pas gélifiés. Cependant, la masse molaire et le rapport acides gluturoniques/acides mannuroniques se sont avérés essentiels pour les propriétés d'étirement et de consistance, ce qui montre que cette différence structurelle peut avoir un impact lorsque les produits sont manipulés en traction et compression. CONCLUSION: Pendant ce temps, les propriétés viscoélastiques et la viscosité dynamique ont été considérablement augmentées pour l'émulsion contenant la version gélifiée de l'alginate par rapport aux polymères classiques. L'émulsion présentait également une plus grande uniformité, comme le prouve l'analyse texturale, indiquant un potentiel de stabilité et de suspension de l'émulsion gélifiée supérieur à celui de l'émulsion classique contenant les agents épaississants naturels habituels.

A review of environmental odor quantification and qualification methods: The question of objectivity in sensory analysis.

For several years, various issues have up surged linked to odor nuisances with impacts on health and economic concerns. As awareness grew, recent development in instrumental techniques and sensorial analysis have emerged offering efficient and complementary approaches regarding environmental odor monitoring and control. While chemical analysis faces several obstacles, the sensory approach can help overcome them. Therefore, this latter may be considered as subjective, putting the reliability of the studies at risk. This paper is a review of the most commonly sensory methodology used for quantitative and qualitative environmental assessment of odor intensity (OI), odor concentration (OC), odor nature (ON) and hedonic tone (HT). For each of these odor dimensions, the assessment techniques are presented and compared: panel characteristics are discussed; laboratory and field studies are considered and the objectivity of the results is debated. For odor quantification, the use of a reference scale for OI assessment offers less subjectivity than other techniques but at the expense of ease-of-use. For OC assessment, the use of dynamic olfactometry was shown to be the least biased. For odor qualification, the ON description was less subjective when a reference-based lexicon was used but at the expense of simplicity, cost, and lesser panel-training requirements. Only when assessing HT was subjectivity an accepted feature because it reflects the impacted communities' acceptance of odorous emissions. For all discussed dimensions, field studies were shown to be the least biased due to the absence of air sampling, except for OC, where the dispersion modeling approach also showed great potential. In conclusion, this paper offers the reader a guide for environmental odor sensory analysis with the capacity to choose among different methods depending on the study nature, expectations, and capacities.

Objective odor analysis of incidentally emitted compounds using the Langage des Nez® method: application to the industrial zone of Le Havre.

Environmental odor studies are usually done using two approaches: nuisance impact assessment and source identification. The latter may be done using chemical analysis or sensory analysis. While sensory analyses offer many advantages, they also face the main obstacle: odor nature description still uses conventional methods based on subjective evocations as odor descriptors. This makes the sensory method ineffective especially when the expected outcome is the source identification in the context of an industrial accident. This work wants to fulfill this gap proposing to build an objective database including the odor nature description of selected potentially emitted compounds using a promising approach: the Langage des Nez® (LdN). Using definite odorous compounds as odor referents, this work provides the odor nature description of 44 compounds, reported as potential incidentally released chemical compounds in the industrial zone of Le Havre. The city of Le Havre, France, was chosen as a model due to a history of odorous emissions of industrial origins. A trained panel described the odor of each compound using up to three referents of the LdN referents collection and attributed a score to each referent. A data analysis method was developed based on the frequency of citation of the referents and the attributed scores allowing the categorization of each compound in three types of consensus categories. The data analysis results showed that around 80% of compounds were described with a good consensus, showing the LdN as a well-adapted lexicon. This study does not point to any correlation between the chemical structures of the compounds of interest and their relative referents. When compared to conventional methods, LdN revealed a more objective and precise approach. The proposed experimental method and the results provided in this work offer the first insight for time-efficient approaches to objectively describe environmental odors, especially potentially emitted odors during incidents. This work may be supplemented by abatement and mixture effect investigations for a complete understanding of odor dispersion.

Impact of the synergistic interaction between xanthan and galactomannan on the stickiness properties of residual film after application on a surface.

The objective was to investigate the influence of synergism between xanthan gum (X) and galactomannans (guar gum (G) and locust bean gum (L)) on the stickiness of the film formed after the application of polysaccharides on a surface. The adhesion of the film was evaluated using a texture analyzer. X, G, and L were examined in concentrated solutions (0.5, 1 and 1.5 %, w/w) and as a function of the gums mixing ratios (0/100, 20/80, 40/60, 50/50, 60/40, 80/20 and 100/0). The film stickiness increased significantly with gum concentration with G exhibiting less sticky films than with X and L. The binary mixture of X/G and X/L confirmed a synergistic interaction, increasing the firmness of mixtures and decreasing the film stickiness. Such findings open interesting applications for skincare product development using natural texturing agents with enhanced consistency with the residual film on the skin being pleasant and not sticky.

Squalene Oxidation Induced by Urban Pollutants: Impact on Skin Surface Physico-Chemistry.

The effect of urban pollutants on skin properties has been revealed through several epidemiological studies. However, comprehension of involved mechanisms remains undetermined. In addition, the impact of such stressors on skin surface properties, especially skin physico-chemistry, has not been investigated. Consequently, the present study aims to develop a new aging protocol able to highlight the impact of selected urban pollutants on a model sebaceous lipid: the squalene. Its quality has been followed during aging using LC-MS analysis. Results showed that the quality of the control solution containing only squalene remains stable during 45 days, whereas the quality of the solution containing squalene mixed with pollutants appears greatly altered, especially in the presence of heavy metals: a large amount of oxidation compounds was evidenced due to oxidation and dehydrogenation mechanisms. In addition, a physicochemical study was performed using a validated nonbiological skin model able to mimic skin physico-chemistry. Surface free energy components were calculated using contact angle measurements according to the Van Oss model. The application of degraded squalene significantly increased skin hydrophilic and monopolar behavior compared to the application of control squalene. Those modifications are essentially explained by the nature of squalene oxidation products. It must be noted from this study that squalene oxidation due to pollutants or due to high temperature did not lead to the same physicochemical consequences neither to the same oxidation products, as shown by thermal analysis. This study gives original and precious information to explain alterations induced by pollutants on skin surface properties, especially skin chemistry and physico-chemistry.

Toxicokinetics, disposition and metabolism of fluoxetine in crabs.

The disposition and metabolism of fluoxetine in the European shore crab and the Dungeness crab were assessed. Crabs received intracardiac doses of either 0.13 µg/kg or 0.5 mg/kg fluoxetine, respectively. In addition, fluoxetine was administered to Metacarcinus cancer by oral gavage at 7.8 mg/kg. The distribution of fluoxetine was quantified in haemolymph and digestive gland for both crabs, as well as brain, muscle, and testis of Carcinus maenas, over 12 days. The metabolite norfluoxetine, was also measured in C. maenas. Fluoxetine was mainly found in lipid rich tissues. Distribution coefficients increased for digestive gland until three days after fluoxetine administration and then decreased until the end of the observations. The highest distribution coefficients were obtained for brain. Norfluoxetine displayed continuously high levels in digestive gland and brain. The strong decrease in fluoxetine and the concomitant increase in norfluoxetine demonstrates that decapod crustaceans metabolise fluoxetine into the more biologically active norfluoxetine. Fluoxetine levels in the haemolymph of M. cancer declined within 20 h, but showed a second peak 25 h later, suggesting remobilisation from tissues sequestering the compound. The steady state volume distribution and the total body clearance of fluoxetine were high, consistent with high diffusion of fluoxetine into the peripheral tissues and biotransformation as an important elimination pathway. Oral administration of fluoxetine prolonged its half-life in M. cancer, but bioavailability was low. These results confirm the high distribution into nervous tissue, extensive biotransformation into the highly active norfluoxetine and a half-life similar to that observed in vertebrates.

Impact of coated TiO2-nanoparticles used in sunscreens on two representative strains of the human microbiota: Effect of the particle surface nature and aging.

The impact of two differently coated TiO2-nanoparticles (NPs) was evaluated on two representative bacteria from the cutaneous microbiota (Staphylococcus aureus and Pseudomonas fluorescens) in conditions of use. Particles were coated in order to exhibit either hydrophilic or hydrophobic behavior. A first exposure scenario within some fresh/aged model emulsions was developed in order to measure both the impact of the NPs presence and their surface nature during the emulsions conservation. Thanks to this protocol, it was demonstrated that, during aging, the hydrophobic NPs modified the physicochemical characteristics of the emulsions, such as the pH or the colloids sizes, and favored the development of potential pathogenic bacteria. A second scenario was then envisaged, aiming to mimic the exposition of the skin, especially of the cutaneous bacteria, to NPs. Tested NPs were extracted from emulsions with different aging, and results highlighted the importance of both the NP coating nature and their history in emulsion. The different NPs impacts on the bacteria growth were discussed and linked to their surface properties modifications during aging, as polarity and charges. Finally, through two exposition scenarios, this work highlights the major impact of the NPs surface properties on bacteria.

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

Model 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.

Hydrophobically modified xanthan: an amphiphilic but not associative polymer.

Hydrophobic octyl moieties have been grafted in various densities onto the carboxylic acid functions of xanthan under its ordered conformation. The outcoming amphiphilic and associative properties were studied by fluorescence spectroscopy and rheology. Results showed that the conformation of xanthan is not affected by the chemical modification and remains the same as the native one. Additionally, xanthan derivatives do not show any viscoelastic enhancement; nevertheless, their dynamics is strongly slowed down: the higher the grafting density, the slower the relaxation. We proved that hydrophobically modified xanthan, even being amphiphilic, does not exhibit any additional associating properties compared to the unmodified xanthan. The high stiffness of xanthan helices does not allow the derivatives to adopt the organization usually observed for flexible amphiphilic polymers. On the basis of these observations, a model depicting such a singular behavior is proposed.

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

Formulations incorporating different cosmetic grade TiO2 nanoparticles were developed according to a self-produced protocol on the basis of typical sunscreen cream oil-in-water emulsions. Role of nanoparticles 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 TiO2, 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, TiO2 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) TiO2 nanoparticles as compared to alumina (and) isopropyl titanium triisostearate (and) triethoxycaprylylsilane crosspolymer (coating 2) nanoparticles.

Supramolecular assemblies with calix[6]arenes and copper ions: from dinuclear to trinuclear linear arrangements of hydroxo-Cu(II) complexes.

Complexation of copper(II) by calix[6]arene-based ligands bearing either two or three N-benzylimidazole coordinating arms under basic conditions has been studied. Whereas the tris(imidazole) derivative stabilizes dicationic 5-coordinate aqua complexes in a mononuclear state with an intracavity bound guest, in the presence of hydroxide ions, the latter undergo dimerization. An X-ray structure revealed decoordination of one imidazole arm and formation of a bis(hydroxo) bridged Cu(II) core with a square-planar geometry for both metal centers sandwiched by two empty calixarene cavities. Upon methanolysis, the dinuclear complex underwent an unexpected rearrangement leading to the clean formation of a trinuclear complex. X-ray diffraction analyses of this novel species revealed a trinuclear core constructed around a central Cu(II) ion that is doubly bridged through either methoxide or hydroxide anions to two Cu(II) ions hold by two calixarene units. The same complex could be directly synthesized by reacting the ligand with copper(II) perchlorate in a 2:3 ratio in the presence of base. In solution, the tetrahydroxo Cu(3) complex was characterized by UV-vis and (1)H NMR spectroscopies and displayed an electron paramagnetic resonance (EPR) signal only below 100 K that accounts for a S = 1/2 fundamental state. Formation of the same di- and trinuclear species was observed with a calix[6]arene-based bis(imidazole) ligand, which demonstrates the generality of the reaction schemes. All these results emphasize the versatility of the calix[6]arene scaffold for the stabilization of metal complexes with various nuclearities.

A novel receptor based on a C3v-symmetrical PN3-calix[6]cryptand.

A C3v-symmetrical PN3-calix[6]cryptand was prepared in six steps from the known 1,3,5-tris-methylated calix[6]arene through a remarkably efficient [1 + 1] macrocyclization reaction. A 1H NMR study showed that the P,N-crypto cap rigidifies the whole edifice in a cone conformation ideal for molecular recognition applications. The ability of this new receptor to perform selective endo-complexation is illustrated with ammonium guests.