Sensory perception of textural properties of cosmetic Pickering emulsions

Innovative Emulsifiers in Cosmetic Products: A Patent Review (2013-2023)

The cosmetics industry, characterized by innovation and dynamism, is constantly undergoing research, often guided by market trends. Although it covers various sectors, emulsifiers have had a notable impact on its development. Numerous products depend on these components, and continuous research has led to the creation of ever-better products. This Review analyzes emulsifiers for cosmetic use patented between 2013 and 2023, using Espacenet as the main database. Fifty-one patents were examined, considering the annual growth in publications, their geographic distribution, types of emulsifiers, their chemical and physical properties, chemical structures, emulsification mechanisms, and systems formed. An increase in the publication of patents was observed, with some decreases in certain years, highlighting that 86% of the patents come from China. The classification of emulsifiers revealed a predominance of those of natural origin, followed by polymeric, synthetic, and defined molecule compounds. The emulsification mechanisms of each group and the systems they formed according to the patents were also reviewed. In addition, trends in the physical and chemical properties of the emulsifiers were identified. This characterization demonstrates the growth in emulsifier research, which allows for the improvement of emulsions on the market, offering greater stability and functionality to develop superior cosmetic products.

Transitioning from Pickering emulsions to Pickering emulsion hydrogels: A potential advancement in cosmeceuticals

Cosmeceuticals, focusing on enhancing skin health and appearance, heavily rely on emulsions as one of the common mediums. These emulsions pose a challenge due to their dependence on surfactants which are essential for stability but are causing concerns about environmental impact as well as evolving consumer preferences. This has led to research focused on Pickering emulsions (PEs), which are colloidal particle-based emulsion alternatives. Compared to conventional emulsions, PEs offer enhanced stability and functionality in addition to serving as a sustainable alternative but still pose challenges such as rheological control and requiring further improvement in long-term stability, whereby the limitations could be addressed through the introduction of a hydrogel network. In this review, we first highlight the strategies and considerations to optimize active ingredient (AI) absorption and penetration in a PE-based formulation. We then delve into a comprehensive overview of the potential of Pickering-based cosmeceutical emulsions including their attractive features, the various Pickering particles that can be employed, past studies and their limitations. Further, PE hydrogels (PEHs), which combines the features between PE and hydrogel as an innovative solution to address challenges posed by both conventional emulsions and PEs in the cosmeceutical industry is explored. Moreover, concerns related to toxicity and biocompatibility are critically examined, alongside considerations of scalability and commercial viability, providing a forward-looking perspective on potential future research directions centered on the application of PEHs in the cosmeceutical field.

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.

Unconventional and conventional Pickering emulsions: Perspectives and challenges in skin applications

Pickering emulsions are free from molecular and classical surfactants and are stabilized by solid particles, creating long-term stability against emulsion coalescence. Additionally, these emulsions are both environmentally and skin-friendly, creating new and unexplored sensorial perceptions. Although the literature mostly describes conventional emulsions (oil-in-water), there are unconventional emulsions (multiple, oil-in-oil and water-in-water) with excellent prospects and challenges in skin application as oil-free systems, permeation enhancers and topical drug delivery agents, with various possibilities in pharmaceutical and cosmetic products. However, up to now, these conventional and unconventional Pickering emulsions are not yet available as commercial products. This review brings to the discussion some important aspects such as the use of phases, particles, rheological and sensorial perception, as well as current trends in the development of these emulsions.

Preparation of Pickering emulsion stabilized by lauroyl lysine

In this paper, the effect of Nε-lauroyl lysine (LL) on stabilizing W/O Pickering emulsions was investigated, and the effect of crystallization temperature on the particle size of LL was explored. The Pickering emulsion was prepared with LL as particle emulsifier, and the effects of homogenization rate, emulsification temperature, particle concentration, oil-water volume ratio and other factors on the preparation of emulsion were discussed. The results showed that the LL particles were the smallest for a crystallization temperature of 30 °C with a size of (1.3 ± 0.2) µm. The oil-water-LL contact angle was 142.9° ± 1.6°, and the prepared emulsion was of W/O type. The most stable emulsions were obtained under the following conditions: homogenization rate = 11,000 r min−1, emulsification temperature = 20 °C, particle concentration = 2 wt%, oil-water volume ratio = 1:1. In addition, LL showed good tolerance to the aqueous phases with different pH values. The LL-stabilized emulsion system proved to be stable over the long term in the stand tests.

Pickering Emulsions: A Novel Tool for Cosmetic Formulators

The manufacturing of stable emulsion is a very important challenge for the cosmetic industry, which has motivated intense research activity for replacing conventional molecular stabilizers with colloidal particles. These allow minimizing the hazards and risks associated with the use of conventional molecular stabilizers, providing enhanced stability to the obtained dispersions. Therefore, particle-stabilized emulsions (Pickering emulsions) present many advantages with respect to conventional ones, and hence, their commercialization may open new avenues for cosmetic formulators. This makes further efforts to optimize the fabrication procedures of Pickering emulsions, as well as the development of their applicability in the fabrication of different cosmetic formulations, necessary. This review tries to provide an updated perspective that can help the cosmetic industry in the exploitation of Pickering emulsions as a tool for designing new cosmetic products, especially creams for topical applications.

Optical Properties of Pickering Emulsions and Foams

A significant number of studies have been conducted on particle adhesion phenomena as pertaining to the oil-water interface of droplets and the air-liquid interface of bubbles, known as Pickering emulsions and Pickering foams, respectively. However, few of the literature reports have discussed the optical properties of these materials. In this study, the optical properties of Pickering particles were calculated by using an electromagnetic field analysis via a finite element method, and their optical responses are discussed. The changes in scattering due to the differences in the number of adhering particles and particle size are compared for three composition systems: an oil-in-water Pickering emulsion, a water-in-oil Pickering emulsion, and a Pickering foam. It was determined that changes in the amount of scattering are due to the mixing of the phases in the scattering field. This effect is more pronounced when the size of the scatterer is significantly smaller than the wavelength. For systems with particles larger than the wavelength, changes in the amount of scattering were suppressed because of destructive interference of the electromagnetic waves. This work revealed that the variation in the amount of scattering due to the constituent material and size of the Pickering particles is affected by two different factors, and the change in the amount of scattering is 10 times greater than in a uniformly dispersed system.

Textural and Thermal Properties of the Novel Fucoidan/Nano-Oxides Hybrid Materials with Cosmetic, Pharmaceutical and Environmental Potential

The main purpose of the research was to obtain and study hybrid materials based on three different nano-oxides commonly used in the cosmetic and pharmaceutical industries: Al₂O₃, TiO₂, and ZnO, with the natural bioactive polysaccharide fucoidan. Since the mentioned oxides are largely utilized by industry, there is no doubt that the presented studies are important from an environmental point of view. On the basis of the textural studies (dynamic light scattering DLS, low temperature nitrogen adsorption, X-ray diffraction analysis XRD, scanning electron microscopy SEM) it was proved that the properties of the hybrid materials differ from the pure components of the system. Moreover, the advanced thermal analysis (TG-DTG-DSC) combined with the evolved gas analysis using Fourier transformed infrared spectroscopy (FTIR) and mass spectrometry were applied to describe the thermal decomposition of fucoidan, oxides and hybrid materials. It was found that the interactions between the polymer and the oxides results in the formation of the hybrid materials due to the functionalization of the nanoparticles surface, and that their thermal stability increased when compared to the pure substrates. Such findings definitely fill the literature void regarding the fucoidan based hybrid materials and help the industrial formulators in the preparation of new products.

Synthesis, characteristics, and applications of modified starch nanoparticles: A review

Nowadays, starch nanoparticles (SNPs) are drawing attention to the scientific community due to their versatility and wide range of applications. Although several works have extensively addressed the SNP production routes, not much is discussed about the SNPs modification techniques, as well as the use of modified SNPs in typical and unconventional applications. Here, we focused on the SNP modification strategies and characteristics and performance of the resulting products, as well as their practical applications, while pointing out the main limitations and recommendations. We aim to guide researchers by identifying the next steps in this emerging line of research. SNPs esterification and oxidation are preferred chemical modifications, which result in changes in the functional groups. Moreover, additional polymers are incorporated into the SNP surface through copolymer grafting. Physical modification of starch has demonstrated similar changes in the functional groups without the need for toxic chemicals. Modified SNPs rendered differentiated properties, such as size, shape, crystallinity, hydrophobicity, and Zeta-potential. For multiple applications, tailoring the aforementioned properties is key to the performance of nanoparticle-based systems. However, the number of studies focusing on emerging applications is fairly limited, while their applications as drug delivery systems lack in vivo studies. The main challenges and prospects were discussed.

Relationship between sensorial and physical characteristics of topical creams: A comparative study on effects of excipients

Rising consumer demands for safer, more natural, and sustainable topical products have led to increased interest in finding alternative excipients, while retaining functionality and cosmetic appeal. Particle-stabilized Pickering creams have emerged as possible alternatives to replace traditional surfactant-stabilized creams and are thus one of the focuses in this study. The aim of this paper was to study relationships between sensorial characteristics and physical properties to understand how different excipients affect these aspects, comparing one starch particle-stabilized and three surfactant-stabilized formulations. A human panel was used to evaluate sensorial perception, while physical properties were deduced by rheology and tactile friction, together with in vivo and ex vivo skin hydration measurements. The results show that sensorial attributes related to the application phase can be predicted with rheology, while afterfeel attributes can be predicted with tactile friction studies. Differences in rheological and sensory properties among surfactant-based creams could mainly be attributed to the type of emollients used, presence of thickeners and surfactant composition. Differences between surfactant-based creams and a Pickering cream were more evident in relation to the afterfeel perception. Presence of starch particles in the residual film on skin results in high tactile friction and low perception of residual coating, stickiness, greasiness, and slipperiness in sensorial afterfeel.

Therapeutic Applications of Metal and Metal-Oxide Nanoparticles: Dermato-Cosmetic Perspectives

Invention of novel nanomaterials guaranteeing enhanced biomedical performance in diagnostics and therapeutics, is a perpetual initiative. In this regard, the upsurge and widespread usage of nanoparticles is a ubiquitous phenomenon, focusing predominantly on the application of submicroscopic (< 100 nm) particles. While this is facilitated attributing to their wide range of benefits, a major challenge is to create and maintain a balance, by alleviating the associated toxicity levels. In this minireview, we collate and discuss particularly recent advancements in therapeutic applications of metal and metal oxide nanoparticles in skin and cosmetic applications. On the one hand, we outline the dermatological intrusions, including applications in wound healing. On the other hand, we keep track of the recent trends in the development of cosmeceuticals via nanoparticle engrossments. The dermato-cosmetic applications of metal and metal oxide nanoparticles encompass diverse aspects, including targeted, controlled drug release, and conferring ultraviolet and antimicrobial protections to the skin. Additionally, we deliberate on the critical aspects in comprehending the advantage of rheological assessments, while characterizing the nanoparticulate systems. As an illustration, we single out psoriasis, to capture and comment on the nanodermatology-based curative standpoints. Finally, we lay a broad outlook and examine the imminent prospects.

Fundamentals and applications of particle stabilized emulsions in cosmetic formulations

The cosmetic industry is one of the fastest growing industrial sectors that is constantly evolving by absorbing new technologies and incorporating innovative yet sustainable products. Cosmetic products are comprised of diverse formulations such as skin care, color cosmetics, hair care, makeup, body care products. Traditionally, cosmetic emulsions are stabilized using surfactants or polymers. Due to its adverse effects on environment, cytotoxicity effects, numerous health hazards, there is a strong drive to shift towards sustainable and surfactant free emulsions. With increasing consumer demand for a safer and more biodegradable products, formulating "surfactant- free" emulsions by replacing conventional stabilizers with particles has gained popularity. In this review, various important aspects and applications of particle stabilized emulsions in cosmetic formulations will be discussed. Importantly, novel ideas on surface modification of particles and use of Janus particles in cosmetic formulations will be discussed.