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Whereas in the studies based in basal TEWL measurements only discrete differences were reported, the dynamic approach followed in this study provided unequivocal evidence of barrier impairment. The methodology enabled a more objective characterization of sensitive skin and can potentially be applied to the diagnosis/prediction of sensitivity; as well as the efficacy assessment of cosmetic products that are specifically designed to fulfill the needs of consumers with this skin condition.

Spent coffee grounds and green coffee defective beans, which are industrial sub-products of coffee processing, have a potential use for cosmetic applications, due to their safety and high content in lipids that present interesting physicochemical properties. Sunscreen formulations in the form of water-in-oil emulsions might be a suitable application for these sub-products because providing a higher sun protection factor (SPF) for the same concentration of sunscreen activities than oil-in-water emulsions. The purpose of this work was to assess the biological effects of using the oil fraction of spent coffee grounds extracted with supercritical CO 2 and green coffee oil in the development of new generation of sunscreens with improved sun protection performance. The oil fractions were used to prepare w/o sunscreens involving a cold emulsification process, with purified water as disperse aqueous phase and TiO 2 and ZnO particles as stabilizers. The sunscreens were characterized in terms of mechanical, rheological and skin adhesion properties. In addition, the in vitro and in vivo biological properties of the formulations were evaluated, including safety and sunscreen water resistance tests. The use of two types of solid particles proved to be useful in the developed formulations, ensuring a high SPF with UVB/A protection, conferred by TiO 2 and ZnO, respectively. Moreover, the emulsion containing 35% w/w of the spent coffee grounds oil fraction presented promising characteristics in the improvement of water performance with a broad spectrum sun protection when compared to an emulsion containing 35% w/w of green coffee oil which improved the SPF in physical sunscreens. The formulations are industrial-scalable and suitable for topical use according to the rheological, mechanical and safety assessment. The use of spent coffee oil in cosmetic industry seems to be a suitable approach for the valorisation of waste from the coffee industry and presents promising characteristics in the improvement of sunscreen performance.

Background/aims: The evaluation of transepidermal water loss (TEWL) is one of the methods most frequently used in studies involving skin water dynamics. However, TEWL does not provide a direct measurement of epidermal barrier function, being rather a surrogate effect of it. In particular, when external stimuli change cutaneous water balance, these stimuli must be taken into account in order to achieve a rigorous interpretation of the results. Since TEWL is primarily attributed to the water flux from the deepest layers of the skin, through the epidermis, and towards the external environment, this whole process is reasonably compliant with Fick's first law of diffusion. Within this perspective, the aim of this work was to develop a two compartment mathematical model capable of quantitatively describing cutaneous water mass balance over time and thus to provide practical and objective comparable parameters that are particularly useful for studies critically depending on a precise evaluation of TEWL. Methods: The theoretical basis for the proposed model was tested with data collected from different protocols that use TEWL as the main indicator of induced cutaneous alterations. Those alterations involved either external inputs or intrinsic changes on the cutaneous pathway capable of changing the whole water balance across the skin, either altering epidermal cohesion or promoting a significant influx of external water. Results: Both the evaporation and the hydration equilibrium processes, merged within the TEWL curve profiles, were thoroughly described in a quantitative fashion using a mathematical model. Direct parameters were calculated, such as kinetic rate constants (khydr and kevap) and half‐life times (t1/2 hydr and t1/2 evap) chosen to describe the hydration and evaporation processes. Secondary parameters, such as time to reach the maximum and an area under the curve derived parameter, the dynamic water mass (DWM), were also calculated, providing additional data particularly useful for comparisons. Conclusion: Modelling TEWL experimental data in a compartmental analysis framework provides valuable parameterized information for characterising and comparing results. Numerical parameters derived on solid theoretical assumptions are reliable indicators for many situations, as long as those assumptions are not violated. The proposed bicompartmental model may also be suitable for other cutaneous water balance related variables, such as capacitance or conductance, although eventually based on distinct model assumptions. In any case, this modelling conceptualisation seems to render valuable insights into the kinetic description of the main processes involved in the net evaporation and water distribution within the complex human skin hydration process.

Context: Based on its antioxidant activity, melatonin was recently found to have a protection effect against photocarcinogenesis. Objective: This work aimed to develop an innovative sunscreen formulation based on the Pickering emulsions concept, stabilized by physical UV filters, modified starch and natural oils associated to melatonin as a key strategy for prevention against UV-induced skin damage. Materials and methods: For this purpose, melatonin was incorporated in Pickering emulsions that were characterized using physicochemical, in vitro and in vivo testing. Physicochemical studies included physical and chemical stability by a thorough pharmaceutical control. The possible protective effects of melatonin against UV-induced cell damage in HaCaT cell lines were investigated in vitro. The safety assessment and the in vivo biological properties of the final formulations, including Human Repeat Insult Patch Test and sunscreen water resistance tests were also evaluated. Results and discussion: These studies demonstrated that melatonin sunscreen Pickering emulsion was beneficial and presented a powerful protection against UVB-induced damage in HaCat cells, including inhibition of apoptosis. The inclusion of zinc oxide, titanium dioxide, green coffee oil and starch ensured a high SPF (50+) against UVA and UVB. Conclusion: The combination of melatonin, multifunctional solid particles and green coffee oil, contributed to achieve a stable, effective and innovative sunscreen with a meaningful synergistic protection against oxidative stress.

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Background/purpose: Dynamic methods, such as the mathematical modelling of the transepidermal water loss curves that result from a plastic occlusion stress test (POST), enable the complete characterization of the dynamic water balance established between the deep and the superficial skin structures. Previous studies have indicated that this methodology was able to detect impaired barrier function and differentiate normal and dry skin. The objective of the present study is to apply the discriminative capacity of the model to the efficacy testing of moisturizing products. Methods: A moisturizing cream containing urea was applied for 2 weeks to the lower leg of volunteers with dry skin. After this period, a POST was performed in the treated and control untreated site and a mathematical model was adjusted to the resulting desorption curves. Results: Results indicate that, after treatment of the skin with the cream for 2 weeks, statistically different kinetic parameters are obtained in the treated site, which suggests

Quercus Suber Bark from Quercus suber L. is a natural, renewable and biodegradable biomaterial with multifunctional proprieties. In this study, we used it as solid particles to stabilize a Pickering emulsion. The main goal was to produce an optimized topical formulation using biocompatible organic particles as stabilizers of the emulsion instead of the common surfactants, whilst benefiting from Quercus suber L. proprieties. In this work, a Quality by Design (QbD) approach was successfully applied to the production of this emulsion. A screening design was conducted, identifying the critical variables of the formula and process, affecting the critical quality attributes of the emulsion (droplet size distribution). The optimization of the production was made through the establishment of the design space. The stability was also investigated during 30 days, demonstrating that Quercus Suber Bark-stabilized emulsions are stable since the droplet size distribution lowers. In vitro studies were performed to assess antioxidant and antiaging efficacy, which revealed that the formulation had indeed antioxidant proprieties. A physicochemical characterization demonstrated that the formulation presents a shear-thinning fluid, ideal for topical administration. The in vivo compatibility study confirmed that the final formulation is not skin irritant, being safe for human use. A sensorial analysis was also performed, using a simple sensory questionnaire, revealing very positive results. Thus, the use of Quercus Suber Bark particles as a multifunctional solid ingredient contributed to achieve a stable, effective and innovative Pickering emulsion with a meaningful synergistic protection against oxidative stress.