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CORDIS - Resultados de investigaciones de la UE

Novel Photoprotective Cosmetics: From Fundamental Science to Product

Periodic Reporting for period 1 - SUNNRL (Novel Photoprotective Cosmetics: From Fundamental Science to Product)

Período documentado: 2020-08-01 hasta 2022-07-31

Sunscreens (lotions, creams, sprays, etc.) contain active ingredients which protect the skin from ultraviolet (UV) radiation, usually classified as UVA and UVB, by absorbing this harmful radiation. Active ingredients such as octocrylene, oxybenzone, octinoxate, octisalate, and ethylhexyl methoxycinnamate are commonly used in sunscreens to provide protection against UVB radiation, but some of these ingredients are potentially damaging to marine environments. There is a much more limited list of ingredients which protect against UVA radiation, and the ones available present challenges related to the ingredient’s stability under light exposure, and their cost.
This project aimed to establish a unique, innovative and interdisciplinary approach to sunscreen development based on a thorough understanding of how molecules dissipate absorbed radiative energy. The goal is to find a more direct avenue towards improved sunscreens, without having to engage in costly and time-consuming ‘trial-and-error’ sunscreen development.
To achieve its goals, the project focused on methyl anthranilate (MA), a food grade flavour and fragrance additive used in personal care products which is also a strong UVA absorber. Its low risk of toxicity to humans, agreeable fragrance, relative ease of extraction from natural products and affordability make MA a strong candidate for use in commercial sunscreen formulations. However, previous studies found MA to be inneficient in dissipating energy from UV radiation, which is a non-optimum behaviour in sunscreen active ingredients. An ideal sunscreen active ingredient should be able to dissipate excess energy quickly and as heat, without generating any reactive species.
In order to harvest the good sunscreen qualities of MA and combat its downsides, this project aims to combine MA with other sunscreen active ingredients, namely, UVB filters such as ethylhexyl methoxycinnamate and octocrylene. The interactions between MA and these UVB filters have been found to facilitate MA’s excess energy dissipation as heat.
The other important goal of this project is to compare the photophysics observed in dilute solution to those observed in complex sunscreen formulations, in order to establish if the findings of fundamental studies are relevant to final product development and indeed if they can be applied to guide and inform sunscreen development.
The dissemination of the project was mainly done through publication of peer-reviewed articles and participation in scientific conferences. Public engagement activities were not possible due to COVID-19 restrictions.
Initially, MA was incorporated into commercial sunscreen formulations to establish its suitability as a replacement for avobenzone. It was found that MA would not be a suitable replacement, since the resulting formulation does not comply with the required levels of UVA protection, and is not sufficiently stable upon irradiation. Nevertheless, MA could be used as a booster for UVA protection, and/or in conjunction with other UVA filters, potentially avoiding the use of avobenzone. In addition, there is evidence that a higher concentration of MA in the sunscreen formulation enhances its photostability.
To evaluate the effects of combining MA with UVB filters, commercial sunscreen formulations containing separate mixtures of MA and EHMC, and MA and OCR, were also prepared. The results suggest that what determines the photophysical behaviour of a commercial sunscreen formulation, i.e. what determines its alterations upon interaction with solar radiation, is the photophysical behaviour of the UV filters themselves – a crucial finding, since it allows for reliable comparisons to be drawn between fundamental science studies and final product development.
The project then sought to understand the behaviour of irradiated sunscreen formulations and explore how the energy resulting from absorption of UV radiation is dissipated within the mixtures. The flash photolysis studies undertaken as part of this project confirmed the same concentration effect observed both in the aforementioned industry standard in vitro study, as well as previously reported dilute solution studies. Furthermore, these flash photolysis experiments revealed that, as is the case in dilute solution, the interaction between MA and either EHMC and OCR significantly speeds up energy dissipation. Understanding these interactions and proving that they are still active even within a complex formulation environment allows for a smarter sunscreen design through which the targeted combination of active ingredients can be used to create more stable and better performing sunscreen products.
The findings in this project also highlight the importance of evaluating each sunscreen active ingredient and its interactions with others on a case-by-case basis, i.e. it cannot be assumed that a given active ingredient always acts as a stabilizer within a sunscreen formulation. For example, while EHMC has been found to significantly improve the performance of MA-containing sunscreen formulations, it is known to have the opposite effect when avobenzone is present.
This project pushed the state-of-the-art of the sunscreen industry by demonstrating the potential of a holistic approach to sunscreen development. There are two main conclusions that arise from this project:
1. The photophysical behaviour of complex commercial sunscreen formulations is dominated by the photophysics of the sunscreen active ingredients and those resulting from their interactions, i.e. the complex mixture environment of the formulation does not significantly alter the observed photophysics. This observation allows for a bridge to be drawn between fundamental science knowledge and sunscreen development. Establishing this relationship is crucial to further understanding the behaviour and performance of current sunscreen formulations, but it also opens a window of opportunity for further studies that can better inform the sunscreen development process.
2. Fundamental science techniques, often used to study single-solvent dilute solutions, can be applied to study complex commercial sunscreen formulations. Having used experimental techniques such as flash photolysis to study sunscreen lotions for the first time, this project offers new tools to the sunscreen industry. The in vitro testing methods currently used by the sunscreen industry are limited in the information they provide and are not sufficient to establish the performance of a sunscreen product; the final regulatory performance indicators for sunscreens, such as SPF and UVAPF values, must be measured in vivo. However, significant efforts are being made to move away from in vivo cosmetic testing towards in vitro alternatives, which the work of the present project is a significant contribution towards.
As such, this project offers new avenues for future innovation, development and research to the sunscreen industry, as well as the cosmetics sector in general. Ultimately, the impact of this work may translate to improved sunscreen products which may better protect human skin against the damaging effects of exposure to UV radiation, which may in turn have an impact in the rising skin cancer incidence.
As far as the researcher's career goes, this project has had tremendous impact, helping her secure a six-year, highly competitive research grant from FCT (Portugal) to setup and establish her own independent research.