SUNSCREEN 105
Non-nanometric mineral filter for water and oily phase
n Blanca Motos, Rocío Pérez, Ismael Santamaría – ADPCosmetics, Spain
The sunlight spectrum is made up of UV, VIS and IR light (10, 40 and 50% respectively).1 UV light (100-400 nm) has the highest energy and is mostly absorbed by oxygen and the tropospheric ozone. Thus, the Earth’s surface is protected from UVC light (λ 100-290 nm) but is reached by the more energetic and seasonal UVB radiation (λ290-320 nm, which is concentrated in the middle of the day and is more intense in summer) and UVA radiation (λ 320-400nm, more penetrating due to its greater wavelength, constant throughout the day, all year round). Depending on its wavelength, UV radiation reaches various layers of the skin (epidermis - most superficial-, dermis, or hypodermis- deepest): the UVB radiation acts mainly on the epidermis, causing erythema (sunburn), and partially penetrating the dermis; while the UVA radiation passes through the dermis and is responsible for photoageing. Both types of radiation, through direct or indirect DNA damage, are associated with cellular damage and can have carcinogenic effects. However, it would be wrong to ignore the fact that the UV light that reaches us has beneficial health effects such as promoting vitamin D (UVB) synthesis, boosting the immune response and the haemoglobin in the blood. It also boosts cardiovascular health and brings about wellbeing and good humour. In addition, heliotherapy is used to treat psoriasis, vitiligo or atopic dermatitis.
Balance, therefore, should be sought
through moderate exposure, according to medical recommendations, and the use of suitable photo-protection for each skin type. For that purpose, the classical solutions of the cosmetics market are the incorporation of chemical or physical filters in their formulas. The chemical filters contain aromatic groups and carbonyl groups that absorb UV radiation (mainly UVB) and disperse it through conformational changes in the molecules, emission of radiation with larger wavelength and energy in the form of heat.2 The physical filters are of titanium oxide TiO2
and zinc oxide ZnO, and act through
the dispersion, reflection and absorption of November 2019
n Enhance U•S 12wt% n Nano 12wt% n Micro 12wt% 50 40 30 20 10
0 300 320 340 (nm) Figure 1: Comparison of filters.
the UV radiation (they form a physical barrier on the skin). They are primarily known as TiO2
nanoparticles for UVB
protection and ZnO for UVA protection. They are often used in combination with chemical filters to facilitate the preparation of formulas.
In this context, ADPCosmetics proposes the use of latest generation non-nanometric mineral sun filters as an alternative to chemical or traditional physical filters. The features of enhanceU filters make them suitable to meet the major challenges in formulation, which are cited below:
High-SPF and broad spectrum protection With the minimum filter concentration (ca. 12- 15wt%) reaching SPF 30-50+ and ratio UVA/UVB>0.6 (regulations state UVA/UVB>0.3, with a concentration of no more than 25wt% of filter in formula). Figure 1 compares the performance of one of the enhanceU filters (now referred to as ‘the non- nano filter’) from ADPCosmetics with other commercial filters, incorporated into a
reference cream, in the same concentration (12wt%) to show broad spectrum protection and high SPF against nanoparticles and commercial particles of the INCI itself. The non-nano filters for high SPF and broad spectrum protection are shown in Table 1.
Photo-stability
The covering of silica ensures the photo- stability of the mineral filters as can be seen when irradiating samples that contain mineral filters (INCI: Titanium dioxide, Silica) or chemical filters (avobenzone stabilised with octocrylene). The graphs show that the mineral filters maintain the SPF and UVA values while the organic filters do not. The analysis was carried out with a simulator Solar Oriel LCS-100TM Small Area Sol1A (solar simulator) with Xenon 100W CW lamp generating 1 Sol of irradiation with an AM1.5G filter (intensity of 166 mW/cm2
). A
specific filter for UVA/UVB radiation was used. The SPF measurements were obtained at time 0 and after 1, 2, 3 hours of irradiation with a spectrophotometer fitted
PERSONAL CARE ASIA PACIFIC 360 380 400
SPF
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