Using cephalopod-inspired chemistry to extend long-wavelength ultraviolet and visible light protection of mineral sunscreens.

OBJECTIVE: The emergence of new human and environmental-related toxicity data associated with some common UV filters has catalysed growing interest in the inclusion of boosters and stabilizing ingredients in sunscreens. One approach is to incorporate alternative materials inspired by or mimetic of systems in biology, which offer a notable evolutionary advantage of multifunctionality and stability with increased biocompatibility. We describe the use of a natural product, Xanthochrome® (INCI: Ammonium Xanthommatin), in a series of studies designed to not only assess its safety with marine systems but also its formulation compatibility and function in water-in-oil mineral sunscreens. Xanthochrome is the synthetic form of the naturally occurring chromophore xanthommatin (XA) present in cephalopod skin, which doubles as a photostable antioxidant; however, it has never been explored in combination with mineral UV filters in finished formulations. METHODS: Given the recent controversies associated with the environmental toxicological effects of some chemicals used in sunscreens, the safety of XA with coral cuttings was first validated at concentrations 5× above those used in our formulations. Next, a particle-based delivery of XA was designed and incorporated into a zinc oxide (ZnO)-based water-in-oil sunscreen, where the SPF, critical wavelength, and visible light (VL) blocking potential were measured. RESULTS: We observed no adverse effects of XA at 100 mg/L when tested with coral cuttings, demonstrating its safety at concentrations exceeding those used in our sunscreens. When formulated with ZnO-based sunscreens, the inclusion of XA increased the total UV absorbance profile by 28% and the total blocking potential of VL by 45%. The formulations also elicited no dermal irritation or sensitization in a human insult repeat patch test (N = 100 subjects). CONCLUSIONS: XA is differentiated as a photostable, water-soluble compound that is a VL booster proven safe for skin and coral cuttings. To the best of our knowledge, there are no other boosters that can be classified as such, despite a growing body of literature highlighting the need in the industry.

OBJECTIF: L'émergence de nouvelles données de toxicité liées à l'environnement et à l'homme associées à certains filtres UV courants a suscité un intérêt croissant pour l'inclusion d'agents rehausseurs et d'ingrédients stabilisants dans les écrans solaires. Une approche consiste à intégrer des matériaux alternatifs inspirés ou mimétiques des systèmes en biologie, ce qui offre une biocompatibilité accrue et un avantage évolutif notable en matière de multifonctionnalité et de stabilité. Nous décrivons l'utilization d'un produit naturel, le Xanthochrome® (INCI: ammonium de xanthommatine), dans une série d'études conçues non seulement pour évaluer sa sécurité d'emploi avec les systèmes marins, mais également sa compatibilité et sa fonction de formulation dans les écrans solaires minéraux à base d'eau en huile. Le xanthochrome est la forme synthétique de la xanthommatine chromophore (XA) naturellement présente dans la peau des céphalopodes, qui fait office d'antioxydant photostable; cependant, il n'a jamais été étudié en association avec des filtres minéraux UV dans des formulations finies. MÉTHODES: Compte tenu des controverses récentes associées aux effets toxicologiques environnementaux de certains produits chimiques utilisés dans les écrans solaires, la sécurité d'emploi de l'XA sur les coupes de corail a été d'abord validée à des concentrations 5 fois supérieures à celles utilisées dans nos formulations. Ensuite, une application d'XA à base de particules a été conçue et incorporée dans un écran solaire à base d'oxyde de zinc (ZnO), dans lequel le facteur SPF, la longueur d'onde critique et le potentiel bloquant de la lumière visible (LV) ont été mesurés. RÉSULTATS: Nous n'avons pas observé d'effets indésirables de l'XA à raison de 100 mg/L lors de tests sur des coupes de corail, ce qui démontre sa sécurité d'emploi à des concentrations supérieures à celles utilisées dans nos écrans solaires. Lorsqu'il est formulé avec des écrans solaires à base de ZnO, l'inclusion de XA a augmenté le profil d'absorbance totale des UV de 28% et le potentiel bloquant total de la LV de 45%. Les formulations n'ont également entraîné aucune irritation ou sensibilisation cutanée lors d'un test épicutané d'exposition répétée chez l'homme (N = 100 sujets). CONCLUSIONS: Le XA se différencie par un composé soluble dans l'eau et photostable qui est un amplificateur de la LV éprouvé sans danger pour les coupes de peau et de corail. À notre connaissance, il n'existe aucun autre agent rehausseur pouvant être classé comme tel, malgré un corpus croissant de littérature soulignant le besoin dans l'industrie.

Evaluation of Biologically Inspired Ammonium Xanthommatin as a Multifunctional Cosmetic Ingredient.

We describe the investigation of an organic natural product, ammonium xanthommatin (Xanthochrome), in a series of studies designed to not only assess its impact on endocrine receptor function in vitro but also interrogate its mutagenic potential using bacterial reverse mutation assays. As a multifunctional raw material, ammonium xanthommatin functions as an antioxidant with a broad absorption profile spanning the UV through the visible spectrum, making it an interesting target for cosmetic applications. In solution, ammonium xanthommatin contributes to <30% inhibition of hormonal activities, indicating that it is not an endocrine disruptor. Furthermore, the compound does not cause gene mutations in the bacterial strains used, indicating that it is nonmutagenic. Applications are also described, highlighting xanthommatin's ability to boost the UVA and UVB absorptive properties of traditional chemical UV filters by >50% across all filters tested. In addition to these features, xanthommatin exhibited no phototoxic hazards in vitro when irradiated with UVA and visible light, demonstrating its utility as a multifunctional cosmetic ingredient. Although these findings encourage the use of xanthommatin in cosmetics, they represent only the beginning of the complete in vitro and in vivo data package needed to support safety and efficacy claims for future applications in skin health.

Biomimetic Colorants and Coatings Designed with Cephalopod-Inspired Nanocomposites.

Brilliant and dynamic colors in nature have stimulated the design of dyes and pigments with broad applications ranging from electronic displays to apparel. Inspired by the nanostructured pigment granules present in cephalopod chromatophore organs, we describe the design and fabrication of biohybrid colorants containing the cephalopod-specific pigment, xanthommatin (Xa), encased within silica-based nanostructures. We employed a biomimetic approach to encapsulate Xa with amine-terminated polyamidoamine (PAMAM) dendrimer templates, which helped stabilize the pigment during encapsulation. Depending on the concentration of Xa used in the reaction, the resultant biohybrid nanomaterials generated a range of neutral colors of differing hues. When applied as coatings, these colorants can be triggered to change color from yellow/gold to red in the presence of a chemical reducing agent, as we leverage the natural redox-dependent color change of Xa. Altogether, these capabilities demonstrated the ability to process biochromes like Xa as nanomaterials that can be applied as coatings with a tunable and dynamic range.

A bioinspired, photostable UV-filter that protects mammalian cells against UV-induced cellular damage.

While commercially available suncare products are effective at absorbing ultraviolet (UV)-light, recent studies indicate systemic toxicities associated with many traditional chemical and physical UV-filters. We demonstrate the application of xanthommatin, a biochrome present in arthropods and cephalopods, as an alternative chemical UV-filter that is cytocompatible while maintaining its photostability and photoprotective properties.

Dynamic pigmentary and structural coloration within cephalopod chromatophore organs.

Chromatophore organs in cephalopod skin are known to produce ultra-fast changes in appearance for camouflage and communication. Light-scattering pigment granules within chromatocytes have been presumed to be the sole source of coloration in these complex organs. We report the discovery of structural coloration emanating in precise register with expanded pigmented chromatocytes. Concurrently, using an annotated squid chromatophore proteome together with microscopy, we identify a likely biochemical component of this reflective coloration as reflectin proteins distributed in sheath cells that envelop each chromatocyte. Additionally, within the chromatocytes, where the pigment resides in nanostructured granules, we find the lens protein Ω- crystallin interfacing tightly with pigment molecules. These findings offer fresh perspectives on the intricate biophotonic interplay between pigmentary and structural coloration elements tightly co-located within the same dynamic flexible organ - a feature that may help inspire the development of new classes of engineered materials that change color and pattern.

Xanthommatin-Based Electrochromic Displays Inspired by Nature.

Color is a signature visual feature in nature; however, the ability to trigger color change in the presence of different environmental stimuli is unique to only a handful of species in the animal kingdom. We exploit the natural color-changing properties of the predominant pigment in arthropods and cephalopods-xanthommatin (Xa)-and describe its utility as a new broad-spectrum electrochromic material. To accomplish this goal, we explored the spectroelectrochemical properties of Xa adsorbed to an indium-doped tin oxide-coated substrate chemically modified with poly(3,4-ethylene dioxythiophene) doped with poly(styrenesulfonate) (PEDOT:PSS). We identified a synergistic role between PEDOT:PSS and Xa that contributed to its absorption profile, which could be modulated across multiple cycles. By varying the ratio of the two electroactive components, we also altered the perceived visible color of Xa-based devices, which cycled from different shades of red to yellow under reducing and oxidizing potentials, respectively. Together, our data illustrate the utility of Xa-based devices as new broad-spectrum electrochromic materials.