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.

Sensory signature of lignins, new generation of bio-based ingredients in cosmetics.

Lignins represent a high interest in cosmetics as promising multifunctional ingredients. Despite this, uncovering the sensory profile of lignin-based emulsions has remained an unexplored frontier. This study aims to bridge this gap by employing expert sensory evaluation and instrumental characterization to assess the sensory attributes of lignin-based emulsions. A comparative analysis with commercial tinted products and discrimination among lignin derivatives were integral components of the research. Results underscored the distinctive sensory properties of lignin emulsions, exhibiting significantly higher "Integrity of shape" (7.0 ± 0.1) compared to commercial products (4.8 ± 0.1). Additionally, lignin emulsions displayed longer play-time until skin absorption (4.3 ± 0.1), contrasting with the quicker absorption of commercial products (2.7 ± 0.4) and their shorter play-time. Depending on application requirements, lignin derivatives offer formulators a versatile sensory toolbox. Discrimination of lignin emulsions on certain texture properties was achieved using various instrumental tools. Despite the complex formulation of commercial products compared to lignin emulsions, similar texture properties were observed, showcasing lignins' potential to replace multiple ingredients in tinted cosmetics. Beyond their established antioxidant, anti-UV, anti-bacterial, and emulsifying properties, this study reveals additional advantageous sensory properties of lignins, positioning them as promising plant-based sensory ingredients in sustainable cosmetic applications.

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.

Understanding of the residual odour of fatty esters used as emollient in cosmetic products.

OBJECTIVE: Fatty esters are known for their versatility, but in addition to their performance as emollients, emulsifiers, solubilizers, or dispersing agents, they have to meet more and more criteria to be used in cosmetic products. Thus, their olfactory characteristics are expected to be as neutral as possible. However, despite a step of deodorization during the synthesis of fatty esters, a residual odour is currently still perceived at the end of the process. METHODS: In this study, a specific analytical methodology combining sensory with chemical analyses was implemented to characterize the residual odour of two fatty esters and to determine its origin. Ethyl oleate and isononyl isononanoate were selected and underwent a sensory analysis to evaluate their odour intensity and odour profile. Volatile compounds released by these esters were assessed by GC-MS after solid-phase microextraction and among them, odouractive compounds were brought into light using gas chromatography coupled with mass spectrometry and olfactometry analyses. RESULTS: On the isononyl isononanoate chromatogram, only peaks corresponding to the different isomeric ester forms were evidenced while around 70 volatile compounds were detected in the ethyl oleate headspace, including esters, aldehydes, hydrocarbons, and ketones. Isononyl alcohol used as raw material in the synthesis was proven to be responsible for isononyl isononanoate final odour. As for ethyl oleate, of the 23 odour-active compounds perceived, 14 have been identified; they are mainly esters and saturated as well as unsaturated aldehydes. CONCLUSION: A novel measurement approach was presented to analyse trace odours of fatty esters and the results will be useful to control their deodorization by targeting appropriate strategies with the aim to either avoid the formation or remove the identified odorant compounds. This study may be further expanded by investigating the impact of deodorization on odour-active compounds for a complete understanding of their contribution to the fatty ester global odour.

OBJECTIF: Les esters gras sont connus pour leur polyvalence, mais en plus de leurs performances en tant qu'émollients, émulsifiants, solubilisants ou agents dispersants, ils doivent répondre à de plus en plus de critères pour être utilisés dans les produits cosmétiques. Ainsi, une odeur la plus neutre possible est recherchée par les formulateurs. Cependant, malgré une étape de désodorisation lors de la synthèse, une faible odeur résiduelle est souvent encore perçue à la fin du processus. METHODES: Dans cette étude, une méthodologie analytique spécifique combinant des analyses sensorielles et chimiques a été mise en œuvre pour caractériser l'odeur résiduelle de deux esters gras et déterminer son origine. L'oléate d'éthyle et l'isononanoate d'isononyle ont été sélectionnés et une analyse sensorielle a été menée pour évaluer l'intensité et le profil descriptif de leur odeur. Les composés volatils libérés par ces deux esters ont été identifiés par GC-MS après microextraction en phase solide (SPME) et parmi eux, les composés odorants ont été mis en évidence à l'aide de la chromatographie en phase gazeuse couplée à des analyses de spectrométrie de masse et d'olfactométrie (GC-MS-O). RESULTATS: Sur le chromatogramme de l'isononanoate d'isononyle, seuls des pics correspondant aux différentes formes isomériques de l'ester ont été mis en évidence tandis qu'environ 70 composés volatils ont été détectés dans l'espace de tête de l'oléate d'éthyle, parmi lesquels des esters, des aldéhydes, des hydrocarbures et des cétones. Il a été montré que l'alcool isononylique utilisé comme matière première dans la synthèse était responsable de l'odeur finale de l'isononanoate d'isononyle. Pour l'oléate d'éthyle, sur les 23 composés odorants perçus, 14 ont été identifiés ; il s'agit principalement d'esters et d'aldéhydes saturés ou insaturés. CONCLUSION: Ce travail présente une approche efficace pour analyser les traces d'odeur des esters gras. Les résultats obtenus permettront de contrôler la désodorisation de ces ingrédients cosmétiques en ciblant des stratégies appropriées dans le but d'éliminer spécifiquement les composés odorants identifiés. Cette étude pourra être élargie en étudiant l'impact de la désodorisation sur les composés odorants pour une meilleure compréhension de leur contribution à l'odeur globale des esters gras.

Multifunctional active ingredient-based delivery systems for skincare formulations: A review.

Nowadays, there is a growing demand for effective cosmetic skincare products that can address the specific skin problems of consumers. Delivery systems play an important role in the effective action of cosmetic skincare formulations. Delivery systems are attractive and smart technologies used as carriers for cosmetic ingredients, which are sensitive to various physical factors such as light, oxygen, pH and temperature. Delivery systems offer several advantages: transport and protection of sensitive active compounds, controlled and targeted release of active ingredients. Several delivery systems, varying in chemical composition, with adaptable physicochemical characteristics (size, morphology, zeta potential, structure) as well as great advantages as carriers, are developed and described in the literature. This article reviews the current cosmetic active ingredients used in skincare products due to their beneficial properties such as antioxidant, anti-aging, photo-protective, anti-inflammatory, anti-microbial, etc.). In addition, the main advantages of several classes of delivery systems (emulsions, lipid nanoparticles, polymeric particles) are described, as well as some recent approaches used to ensure their efficacy (long-term stability, controlled release of the active, skin penetration/permeation) are reviewed. Finally, new trends to be considered for the development of delivery systems and cosmetic formulations are discussed.

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.

Leather Dyeing by Plant-Derived Colorants in the Presence of Natural Additives.

This research aimed to dye leather fabric samples with the application of plant-derived colorants and natural additives. Two grades of chitosan were used as additives, in addition to caffeine, nettle extract, and shellac solution. The ability of colorants to dye leather fabric and the impact of additives on leather fabric properties such as structure, color intensity, color stability under exposure to UVC irradiation, and mechanical properties were examined. For this purpose, dyed samples were tested by a colorimeter, ATR-FTIR spectrophotometer, mechanical testing machine, and X-ray diffractometer. The results indicated that the applied colorants of plant origin have the potential to dye leather fabrics without affecting their structure and without a negative impact on the environment. Applied natural additives can, therefore, beneficially influence the effects of the dyeing process, such as color intensity, colorfastness after exposure to UV irradiation, or tensile strength of the material.

Plant-Derived Colorants for Food, Cosmetic and Textile Industries: A Review.

This review provides a report on properties and recent research advances in the application of plant-derived colorants in food, cosmetics and textile materials. The following colorants are reviewed: Polyphenols (anthocyanins, flavonol-quercetin and curcumin), isoprenoids (iridoids, carotenoids and quinones), N-heterocyclic compounds (betalains and indigoids), melanins and tetrapyrroles with potential application in industry. Future aspects regarding applications of plant-derived colorants in the coloration of various materials are also discussed.

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.

Impact of cigarette smoke on physical-chemical and molecular proprieties of human skin in an ex vivo model.

BACKGROUND: This is a study about the skin ageing exposome, focusing on the effect of cigarette smoke. Human living skin explants (HSE) were exposed to cigarette smoke (CS) of two cigarettes for 2 hours using a custom-made exposure chamber, the Pollubox® . Effects on the surface physico-chemistry and molecular properties of the skin were analyzed and reported for the first time. BASIC PROCEDURES: To this end, transcriptomic study followed by immunohistochemistry, MDA (Malondialdehyde Dosage), and surface physio-chemistry data: surface free energy determination, TEWL (Trans Epidermal Water Loss), skin pH and FT-IR (Fourier Transform-Infrared) spectroscopy of the explant were collected from untreated and treated HSE. MAIN FINDINGS: Results showed a decrease of the total surface free energy of the treated HSE. This decrease reflected higher interactions with polar compounds from the environment and consequently a decrease of the surface hydrophobicity. Additionally, an increase of TEWL and skin pH was observed after treatment. The transcriptomic analysis showed downregulation of mitochondrial genes (PON2-NDUFA4L2-ATP1A1-ALDH2-PRODH) combined with an increase of MDA in CS-treated HSE. CONCLUSIONS: CS-induced oxidation of lipids at HSE surface alters the skin barrier: interactions with polar products are enhanced and the lipid chain packing at the surface is modified. Consequently, skin permeability could increase which correlated with repression of CA9 and AQP1 genes. Beside activation of AHR-NRF2 pathway in CS-exposed HSE, our results suggested that mitochondrial functions were strongly impacted and oxidized lipids failed to be eliminated promoting skin barrier alteration. A mitophagy activity was suggested through the confirmation of PINK1 accumulation in the epidermis by immunostaining.

Residual film formation after emulsion application: Understanding the role and fate of excipients on skin surface.

This study focuses on the fate of excipients contained in topical emulsions once applied on the skin. The aim was thus to develop a methodology to characterize the residue left on the skin shortly after emulsion application. To this end, both the role and the impact of the different excipients on the formation and properties of the residue left on the skin surface once a product is applied were investigated. To that purpose, an O/W emulsion composed of an ester as oily phase, an emulsifier (alkylpolyglucoside-based vehicles), a polymer and a humectant (hydrophilic excipient) was first developed. Then, systems with fewer ingredients were prepared to understand their respective role in the residual film. This residual film was studied in vivo by means of biophysical instrumental methods, all being performed on the participants' forearm. Results highlighted the major role of the ester giving a bright and hydrophobic residue. While the surfactant structuration as the presence of glycerin and polymer provided a specific water distribution inside the residue on the skin surface. Finally, this work evidenced the ingredients organization in the residue depending on the systems composition, with a particular stratification on skin surface which could be considered in the formulation strategy for efficient active delivery and skin protection.

Design of a Lipid-Coated Polymeric Material Mimic Human Skin Surface Properties: a Performing Tool to Evaluate Skin Interaction with Topical Products.

An original nonbiological skin model (NBSM) has been developed to mimSic skin surface properties. This skin model presents several improvements when compared to existing ones: it has a topography identical to that of in vivo skin and a lipid composition close to that of the skin face. This imparts to the model surface a physicochemistry similar to in vivo skin. The concept and design of the skin model are presented, followed by an instrumental characterization performed using 3D microscopy, attenuated total reflectance-Fourier transformed infrared spectroscopy, and contact angle measurements. Surface free energy components are calculated for the NBSM using the Van Oss approach and compared to ex vivo experiments performed on human living skin explants. A comparison was made with the commercial skin model VITRO-SKIN, this latter being a reference in terms of the NBSM. The effect of several emollients on skin physicochemistry was investigated in vivo and on both nonbiological models. The study focused on several emollients and oils, including silicones and esters, and three emulsions (oil-in-water or water-in-oil). The results obtained confirm the high reliability of the developed model as it shows a skin-like surface behavior. This very interesting tool shows promising results concerning the study of the residual film present after product application or to study skin/product interactions.

Impact of backbone stiffness and hydrophobic chain length of modified xanthan on oil in water emulsion stabilization.

The impact of xanthan chemical modification under both ordered and disordered conformations on oil-in-water (O/W) emulsion stabilization was investigated. While both hydrophobically modified xanthan (HMX) are able to stabilize the O/W interface, a dramatic difference was observed macroscopically. When HMXord (ordered conformation) could produce stable emulsions at concentrations down to 0.2% w/w, HMXdis (disordered conformation) led to unstable systems mostly by creaming whatever the concentration studied. Moreover, in the case of HMXdis, the role of the grafted chain length was investigated and two different behaviors were observed depending on the grafting unit. It was demonstrated that the cornerstone of these emulsion stability was the rheological properties of the continuous phase which was governed by two main factors: the partitioning of HMXdis between the interface and the continuous phase and the viscosifying ability of the polymer, the latter being directly linked to the backbone stiffness.

Instrumental and sensory methodologies to characterize the residual film of topical products applied to skin.

BACKGROUND: The work is aimed at the development of a methodology to characterize the tactile properties of topical products during application. Specific attention was paid to the study of the residual properties left at the surface of the skin. This approach was interestingly used to better understand the formulation factors governing the skinfeel of topical preparations. MATERIALS AND METHODS: Cosmetic and pharmaceutical topical products were selected based on their various texture, galenic form (gel or emulsion), and composition (polymer used as texturing agent). Key texture attributes namely Firmness, Stickiness, Spreadability, and Amount of residue were objectively evaluated using sensory analysis. Additionally, texture analysis (compression test), rheology (flow test), and tribology (in vivo friction test) were carried out. RESULTS: Sensory evaluations highlighted a great diversity of tactile properties among products when applied to skin. For example, assessors perceived an important amount of residue left by emulsions whereas gels were not leaving any residue after application to the skin. These results were confirmed by in vivo tactile friction measurements with two distinct evolutions in time of the residual film properties. CONCLUSION: The present investigation shows how the tactile properties of topical gels and emulsions are studied using complementary tests in order to understand and improve the skinfeel of topical preparations.

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.

Skin surface physico-chemistry: Characteristics, methods of measurement, influencing factors and future developments.

Physico-chemical properties such as surface free energy, polarity or hydrophobicity of solid surfaces have been largely studied in literature because they are involved in many physical phenomena: adhesion, friction, wetting … Nowadays, the study of biointerfaces is of great interest for the medical, the pharmaceutical or the cosmetic field but also for material design researches, especially for the development of biomimetic surfaces. The present paper focuses on a particular biointerface, namely skin, which is the most extended organ of the human body. The different ways for the study of skin physico-chemistry are first reviewed, followed by their practical uses, from pharmaceutical to cosmetic science. Those properties depict the ways skin interacts with topical products, its lipid composition but also its hydration state. In addition, this article aims to present recent approaches using original model materials in order to mimic human skin; indeed, in vivo experiments are often limited by the inter and intra individual variability, the safety regulation and above all the time and the cost of such studies. Finally, further data clearly highlight the importance of skin surface properties for dermatological and pharmaceutical researches.

Hydrophobically modified xanthan: Thickening and surface active agent for highly stable oil in water emulsions.

Oil-in-water (O/W) emulsions were prepared using exclusively a hydrophobically modified xanthan (HMX) under ordered conformation without any surfactant. A series of HMX differing in grafting density were utilized at different concentrations. It was demonstrated that HMX stabilizes O/W emulsions where pristine xanthan do not. Indeed, in some cases, emulsions with HMX proved to be homogeneous and stable over months. Emulsions microstructure and rheological properties were investigated over time as a function of HMX concentration and grafting density in order to determine the mechanisms governing this efficient stability. The higher the HMX concentration is, the better the emulsions stability. However, unexpectedly, increasing the HMX grafting density leads to faster destabilization. The whole set of results demonstrate that the stability of the emulsions against coalescence and creaming is explained by partitioning of HMX molecules between bulk and interface, thus split between viscosifying the aqueous phase and stabilizing the interface.

Prediction of residual film perception of cosmetic products using an instrumental method and non-biological surfaces: The example of stickiness after skin application.

Prediction of sensory texture attributes using instrumental measurements is a very important challenge for cosmetic industry because in vivo sensory studies are expensive, time consuming and limited by the safety issue of applied products. The aim of this work is to investigate how residual sensory properties of cosmetic products can be predicted without using a panel of assessors, focusing on the residual film attribute "Stickiness". 10 cosmetic products with different galenics have been selected and evaluated in vivo using a classical sensory protocol, developed according to the Spectrum™ Descriptive Analysis method. In addition to this study, products were evaluated after their application on non-biological skin models in order to compare perceptions onto in vivo skin and artificial surfaces. Results obtained show that in vivo perceptions can be compared with the ones on artificial surfaces meaning that residual film stickiness is similar between in vivo skin and non-biological skin models. An instrumental protocol using a texture analyzer has been set up to evaluate residual film adhesiveness. This protocol has been tested and validated in vivo (r²adjusted = 0.90; RPD = 3.07) before being optimized on a selected non-biological skin model Bioskin® (Beaulax, Co. Ltd. Tokyo, Japan) owning good correlation with in vivo perceptions. Established model shows excellent predictive ability with a r²adjusted of 0.94 and a RPD of 3.38, as highlighted by the 4 steps cross-validation performed. It proves that physical stimulus responsible for cosmetic film stickiness can be instrumentally measured on both in vivo skin and artificial skin.

Chemical modification of xanthan in the ordered and disordered states: An open route for tuning the physico-chemical properties.

The impact of the chain stiffness on physicochemical properties has been studied by chemical modification of xanthan under both ordered and disordered conformations. Corresponding rheological properties were studied and results showed that amphiphilic xanthan exhibited completely different behaviors depending on its conformation during modification. Xanthan, when modified under ordered conformation, exhibits similar behavior to non-modified one, only the chain relaxation being strongly slowed down. Therefore, the high stiffness of xanthan helices does not allow hydrophobic moieties to associate. Oppositely, xanthan modified under its disordered conformation displayed a chemical gel-like behavior without any relaxation of the chain within the studied frequency range nor with temperature, which is unexpected for this length of alkyl chains. These different viscoelastic properties can be correlated to the regioselectivity of the grafting; the latter can be controlled by the conformation of xanthan during modification, thus by the synthesis conditions.

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.