72 TRENDING TECHNOLOGIES The same formulation was tested in vitro
following the ISO24444:2012 standard to assess UV-A PF. The results reported in Figure 3 show average SPF protection value of 33.4 and UV-A protection factor of 13. The UV-A/UV-B protection ratio observed of 0.39 complies with the 1/3 value required to achieve the broad- spectrum label claim.
In vivo SPF test: hybrid sunscreen formulations Hybrid sunscreen formulations containing blends of mineral and organic filters were taken into evaluation to assess the contribution of biomimetic HAP to increase organic filters in vivo SPF and compare it to the SPF increase induced by titanium dioxide. In vitro UV-A protection factor was also assessed. In detail, two formulations were analyzed, with the composition details and final results summarised in Table 2.
Formula 1 The organic filters blend SPF value reported corresponds to 30. By adding to such system 4% of titanium dioxide or 4% of biomimetic HAP, the final SPF recorded of the formulations was 34 after the addition of titanium dioxide and 40 after the addition of HAP. The UV-A/UV-B ratio (data not shown in table) was kept in both cases, with values of 0.5 for titanium dioxide-based formula and 0.35 for HAP-based formulation.
Formula 2 The organic filters blend SPF value reported corresponds to 50. By adding to such system 5% of titanium dioxide or 5% of biomimetic HAP, the final SPF recorded of the formulations was 64 after the addition of titanium dioxide and 65 after the addition of HAP. The UV-A/UV-B ratio (data not shown in table) was kept in both cases, with values of 0.38 for titanium dioxide-based formula and 0.33 for the HAP-based formulation. The results suggest therefore that the +1:1
replacement of titanium dioxide with HAP to organic filters based formulations is expected to keep comparable SPF increase values, while optimizing texture, reducing the formulation whitening and maintaining the UVA/UVB ratio.
Multifunctional SPF booster: anti- ageing tests Biomimetic HAP differentiates from other minerals frequently used in sun care for its in
40 35 30 25 20 15 10 5 0
in vivo SPF Protection In vitro UV-A PF
Figure 3: In vivo SPF test (Colipa international SPF test method 2006 standard) and in vitro UV-A PF (ISO24443:2012 standard)
PERSONAL CARE June 2022
Ethylhexyl methoxycinnamate (10%) Butyl methoxydibenzoylmethane (2%) Ethylhexylsalicylate (4%) Diethylaminohydroxybenzoyl hexylbenzoate (10%) Ethylhexyl triazone (3%)
50
TABLE 1: MINERAL SUNSCREEN BASE FORMULA DEVELOPED IN COLD PROCESS TESTED Phase
INCI 1
2 3 4 5 6 7 8 9
10 11
12 13 14 15
Aqua Bentonite
Olivoil pca foksnab (potassium olivoyl pca, sodium pca, aqua) Refined olive oil (olea europaea fruit oil) Decyl oleate Triheptanoin Zinc oxide
Helianthus annus seed oil, tocopherol Apalight (hydroxyapatite) Propanediol
Sodium levulinate, potassium sorbate, aqua Aqua
Xanthan gum Propanediol Aqua
vivo solubility, triggered by the skin acidic pH and its peculiar external porous surface able to create many anchor points with external substrates. In such a context, HAP time- controlled and partial ions release is suggested to promote several skin benefits, especially following long-term application, given by increased signalling of key ions like calcium and phosphates. Furthermore, its porous mineral surface has been proven to interact with sebum unsaturated fatty acids otherwise exposed to UV rays and converted in lipid peroxides, with a consequent preventive action on the formation of harmful free radicals on the skin.21 Biomimetic HAP was tested at 6% active
matter in emulsion against a placebo cream in order to assess the following parameters: elasticity, firmness - by analyzing the R2 and R6 parameters through a Cutometer SEM 575 made by Courage & Khazaka of Germany - and roughness (through skin surface replicas and image analysis), in order to quantitatively determine its additional benefits. Ten female volunteers (age range: 40 to 70) were included in the study, applying the product twice a day on the entire face for four weeks.
Skin elasticity and firmness The treatment with biomimetic HAP highlighted an increase of the skin elasticity (R2) parameter by 10.3% (Figure 4), and a decrease of visco-elasticity by 17.1%, (value
Formila with Apalight @ 25% a.m. + Zinc Oxide @ 4.0% ■ (%)
To 100 0.6 4.4 6.0
10.0 6.0 4.0 0.2
25.0 3.0 2.0
20.0 0.2 1.0
4.0
R6). The visco-elasticity is a key parameter to assess skin stretchability, whose value is inversely proportional to skin firmness increase (reduction of skin stretchability corresponds to higher skin keratinocytes compactness, hence increased firmness). Elasticity and firmness are key aspects to consider in sun care products, keeping in mind that prolonged sun exposure dries out the skin.
Anti-wrinkle In order to evaluate the anti-wrinkle action, skin replicas were used: in detail a fast-hardening synthetic polymer (SILFLO by Flexico, UK) and adhesive disc were chosen with the aim of having an identical imprinting on the skin. To analyze the results, according to the Corcuff method, some images were taken through a processing software (Quantilines, Monaderm, Monaco). The silicone replica of the skin surface
was illuminated by a light source with an incidental angle of 35°. The images (covering 12x9 mm of each skin replica) were acquired through a video camera (high performance CCD camera, COHU, Monaco). This instrument enables to analyze the following parameters: Ra (roughness value), Rz (maximum roughness value, namely deep wrinkles). The anti-wrinkle efficacy is given by a
decrease of Ra and/or Rz values. The treatment with biomimetic HAP (Figure 5) showed statistically significant deep wrinkle reduction
TABLE 2: FORMULA 1 AND FORMULA 2: EVALUATION OF SPF INCREASE CONTRIBUTION INDUCED BY APALIGHT IN COMPARISON TO TITANIUM DIOXIDE
Organic filter composition
Ethylhexyl methoxycinnamate (10%) Butyl methoxydibenzoylmethane (2%) Ethylhexylsalicylate (4%) Diethylaminohydroxybenzoyl hexylbenzoate (7%) Ethylhexyl triazone (1.5%)
Organic filter composition Inital SPF
SPF after addition of 4% TiO2
30 34
SPF after addition of 4% Apalight
40
Inital SPF
SPF after addition of 4% TiO2
64
SPF after addition of 4% Apalight
65
www.personalcaremagazine.com
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