Study of the influence of alcohol on the photostability of four UV filters.

OBJECTIVE: Spray formulations are currently under development in the field of topical photoprotection. Such forms are characterized by their high fluidity, a property that is obtained by the presence of alcohol in the formula. The purpose of this work was to study the influence of ethanol in sunscreens on the photoprotective efficacy as well as the photostability of UV filters. MATERIALS AND METHODS: The filters tested were octyl methoxycinnamate (OMC), PEG-25 PABA, octyl salicylate and butyl methoxydibenzoylmethane (BMDBM) at their maximum concentration authorized by European regulations and in the presence of increasing amounts of alcohol, up to 15% (w/w). RESULTS: The effect of the presence of alcohol on the efficacy of the filters and their photostability varies depending on the molecule considered. Alcohol has no effect on octyl salicylate, either on its efficacy or its photostability. However, filter stabilization is seen for BMDBM and PEG-25 PABA. CONCLUSIONS: Although these differences are significant, they are not great enough to justify large-scale use of ethanol in sunscreen products due to some of its properties, such as flammability.

Study of the influence of substrate and spectrophotometer characteristics on the in vitro measurement of sunscreens efficiency.

All the methods used for the in vitro measurement of the SPF, the universal indicator of sunscreens efficiency, rely on a spectrophotometric analysis. What can vary about the experimental protocol used is mainly the substrate and the type of spectrophotometer chosen. We decided to work with polymethylmetacrylate plates that we analyzed using two spectrophotometers equipped with integrating spheres, the UV1000S and the UV2000 apparatus. Two marketed products were such tested, after spreading 2 mg/cm2 on the plates, using one apparatus after another. We applied a non-parametric Wilcoxon test for paired data to the measures realized on 10 plates (as we systematically used the 2 apparatus), in order to compare the series of measures obtained with the two machines. This way, we were able to show a significant difference between the SPF values respectively obtained with the UV1000S and the UV2000 spectrophotometers. This difference could be explained by the decrease of the stray light in the case of the UV2000 apparatus.

[Comparison of various topical sun protection formulations, based on cosmetic vs medical device status, using in vitro methods to assess their efficacy, photo-stability and water resistance]. / Comparaison de produits de protection solaire ayant un statut de cosmétique ou de dispositif médical par détermination de leur efficacité, de leur photo-stabilité et de leur résistance à l'eau grâce à une méthode in vitro.

BACKGROUND: Within the European Union, sun protection products have long been considered cosmetics whereas in other parts of the world, such as the United States, they are considered as medicinal products. In France, sun protection products with medical device status have recently appeared. Our aim was to compare medical and cosmetic sun protection products. MATERIALS AND METHODS: We subjected 4 sun protection products to in vitro testing in order to determine their efficacy in the UVB and UVA ranges, as well as their photo-stability and water resistance. We tested two cosmetic products (Dépiwhite S Soin photoprotecteur(®) SPF 50+ and Urgo cicatrices(®) SPF 30) and two class I medical devices (MD) (Actinica lotion(®) and Kelocote UV(®) Gel for scars). The main in vitro method used involved measuring the transmittance of a sample of each product applied to a dish containing poly(methyl methacrylate) using a spectrophotometer with integrating spheres. This method enabled us to determine the SPF of the various products as well as their photo-stability and degree of water resistance. RESULTS: Regarding efficacy, three of the four test products met the European recommendations governing sun protection products, i.e. a ratio between UVB and UVA protection of 3 or less, and a critical wavelength (λc) of 370 nm or higher. Actinica lotion(®) was the more effective of the two medical devices tested, and was also the most photo-stable, at least within the UVB range. All four products tested were water-resistant. DISCUSSION: The products tested, while having different status and different claims, exhibited equivalent filtration properties under the study conditions.

Tris-biphenyl triazine, a new ultraviolet filter studied in terms of photoprotective efficacy.

There are relatively few authorized ultraviolet filters in Europe and this presents a certain number of problems when we want to formulate a sun protection product which both ensures a high level of protection and respects the recommendations in force in terms of broad-spectrum efficacy, with, in particular, a critical wavelength (λc) greater than or equal to 370 nm. A new ultraviolet filter has just been launched on the market. Known as tris-biphenyl triazine, it is the first filter to be registered on Annexe VI of "Cosmetics Regulation" (EC) No. 1223/2009 of the European Parliament and of the Council, which gives a list of the ultraviolet filters allowed in cosmetic products, since the regulation came into force in July 2013. This filter is both very effective (as it enables 2 SPF units and 1 UVA-PF units to be obtained respectively, by percentage of use) and very photostable (since the SPF and UVA-PF do not vary after 2h of irradiation in a solar simulator). Its broad spectrum associated with its qualities in terms of efficacy and photostability make it a choice ingredient for the formulation of sun protection products.

Study of the persistence of the anti-inflammatory effect observed after application of preparations containing organic ultraviolet filters.

Given that previous studies have highlighted the anti-inflammatory nature, which is influenced by UV radiation, of a certain number of ultraviolet filters currently used in Europe, it seemed interesting to evaluate the persistence of this type of effect. The persistence of the anti-inflammatory effect of fourteen preparations, each containing one of the ultraviolet filters authorized by Regulation (CE) No. 1223/2009, and of 10 commercially-available sun products was studied using the phorbol-myristate-acetate test on mice, up to 6 and a half hours after application. We can observe that a benzophenone, oxybenzone, a PABA derivative, octyldimethylPABA and a derivative of cinnamic acid, OMC as well as 3 commercially-available products, display a very marked anti-inflammatory effect at the end of our experimentation phase. The type of effect observed could encourage users to prolong the time that they are exposed to the sun, due to there being no warning signs, namely sunburn.

Sun oils: effect of the applied dose on SPF determined by using in vitro method.

The relationship between skin cancer and exposure to the sun is now clearly established. It is therefore necessary to ensure that consumers have effective sun protection. The effectiveness of the anti-solar products is quantified using a universal indicator, the SPF (sun protection factor). This value can be given in two different ways: by in vivo (standard ISO 24444:2010) and in vitro methods. The in vitro method was adopted for this study, for ethical reasons. The protective effect regarding non-melanoma cancers given by sun products has been proven. It is nevertheless a fact that consumers need to be made aware. Indeed, the quantity of sun protection product applied in reality by the consumer is clearly lower than the recommended amount. Under these conditions, the following question can be asked: What is the level of protection attained if half or even a quarter of the recommended dose of product is applied? In order to answer this question, 20 oils available on the market were tested in vitro at five different doses (5, 7.5, 10, 12.5, 15.0 mg over a surface of 25 cm(2)). We showed that a ratio of two polynomial functions exists between the SPF and the final mass of the product. The factors reducing the efficacy when the dose is divided by 2 are very variable, ranging from 2 to 4 according to which product is studied.

The effect of ultraviolet radiation on the anti-inflammatory effect of filters.

A certain number of filters have notable anti-inflammatory properties with percentage inhibition of PMA-induced edema in mice at over 70%. The question arose as to whether this effect was likely to continue after UV irradiation. It can be noted that 7 filters retain an equivalent anti-inflammatory effect before and after 2h of irradiation in a Suntest device (650 W/m(2)). For 9 filters, the anti-inflammatory effect decreases and for 5 filters, the anti-inflammatory effect increases. Various behaviors should be noted. 3 groups of substances can be distinguished: such as phenylbenzimidazole sulfonic acid which loses its anti-inflammatory character after irradiation (the percentage inhibition falls from 80 to 44%), oxybenzone which retains a constant anti-inflammatory character (89% inhibition before and after irradiation and also octyl methoxycinnamate which becomes very anti-inflammatory (with a percentage inhibition of 93%). The same phenomenon is observed in the case of commercial products. This should be made known as it can have a considerable impact on the results which are displayed on the packaging of sun products.

Influence on SPF of the quantity of sunscreen product applied.

It is now a clearly established fact that ultraviolet radiation is involved in the induction of skin cancer such as carcinoma and melanoma. The most efficient means of protection is by using clothes. For uncovered areas, it is essential to apply a sun product. For some time, various authors have been wondering about the inefficiency or indeed the dangerousness of sun products. Cases of sunburn are still just as frequent in children. We have chosen to study the influence of the quantity of sun product applied on the skin on the level of efficiency obtained. Twenty commercially-available products with SPFs varying between 10 and 50+ and belonging to all levels of protection, that is to say "low", "medium" and "high", were tested in vitro at 5 different doses (5.0, 7.5, 10.0, 12.5 and 15.0 mg for a surface area of 25 cm(2)). We were able to demonstrate that there was a polynomial relationship between the SPF and the quantity of product on the skin's surface. It can be seen that when the dose is halved, the SPF is divided by a variable factor according to the product, from 1.5 to 3.8.

Comparison of two in vitro methods to evaluate the water resistance of sunscreens.

For a long time, the water resistance of sunscreens has been determined in vivo, according to Colipa's (Comité de Liaison des Industries de la Parfumerie) procedure. This method is not so ethical as healthy volunteers are irradiated, and can be replaced by an in vitro method which is easy and quick to perform. The objective of this work was to correlate the experimental device proposed by Choquenet et al. and the dissolutest (Sotax AT6). This equipment is used in the pharmaceutical industry to control the tablets. The experimental conditions have been fixed to correlate the results obtained with both methods. The stirring speed for the dissolutest was fixed at 75 rpm, which is the speed value recommended by the European Pharmacopeia to study the dissolution over time of tablets.

Interest of external photoprotection by means of clothing and sunscreen products in young children.

BACKGROUND: Protecting young children is a major public health issue. OBJECTIVE: We tested children's clothing and sunscreen products that are specially designed for children. METHODS: The effectiveness of the different types of clothing and sunscreen products was determined using spectrophotometer equipped with an integrating sphere A measure of transmittance carried out, respectively, between 290 and 400 nm and between 320 and 400 nm, allowed us to assess the photoprotective properties in the UVB and UVA range respectively. RESULTS: Although the photoprotective effect varies according to the type of clothing (UV-protection factor [UPF] of approximately 10 for a cotton T-shirt and 500 for a pair of jeans), the effect is constant for any one type of clothing. Placing fabrics in layers is essential and this enables the protective effect to be greatly increased. Moreover, the authors wished to answer the question, 'what makes a good sun cream?' by analysing the formula of each product tested. It turns out that only creams containing both organic filters and inorganic filters have an sun protection factor (SPF) that is the same as the one stated on the product. CONCLUSION: Concerning townwear, the jeans, tracksuits, sweatshirts, pullovers and tights turned out to be very photoprotective. They enable, in effect, to reach a UPF higher than 500. The mere presence of titanium dioxide and/or zinc dioxide does not mean that the product will have a high SPF. Products containing alcohol can be eliminated from the possible choices by carefully reading the label.

In vitro UV-A protection factor (PF-UVA) of organic and inorganic sunscreens.

The objective of this research was to evaluate the efficacy of various sunscreen agents incorporated into an O/W emulsion. Within the scope of this study only an in vitro method was used. According to selected filter UVA, we can obtain more or less effective creams. With the seven available filters, we can cover a range of values between 2 and 12. In addition to these seven filters absorbing in UVA range, variously coated titanium dioxide and zinc oxide were tested as well. So it appears that the best organic UVA filter is anisotriazine at 10% (PF-UVA = 11.82). Its effectiveness is comparable with that of the titanium dioxide forms used at 25%. Photostability in Suntest showed that the more photostable UVA-filters are the benzophenones.

Adaptation of the protocol for determining in vitro the sun protection factor of anti-solar sticks.

Apart from the protection offered by clothing, the application of sunscreen products suited to each type of skin constitutes one way for decreasing the frequency of skin cancers nowadays. After having adapted an in vitro method for determining the efficacy of sunscreens in emulsion form, we wished to transpose this technique by adapting it for the anti-solar sticks for the evaluation of sun protection factor (SPF) using a spectrophotometer equipped with an integrating sphere. To do this, we tested 14 products in the market as well as sticks that we ourselves fabricated in the laboratory. In a base common to all of these sticks, we added organic (13 filters tested) and inorganic (two filters tested, titanium dioxide and zinc oxide) to their maximum permitted concentration in the European Union. In parallel, emulsions containing the same filters at the same percentage of use were studied; to be in keeping with the results on the products packaging on the one hand, and with the results obtained for the emulsion form on the other hand, we were able to determine the optimal mass which needed to be placed on the support used the in vitro test to determine the SPF.

Development of an in vitro test to determine the water-resistance of sunscreens.

The aim of this work was to develop an in vitro method for testing the water resistance of sun products. For comparison, we used the in vivo method put forward by the Colipa. Standards and commercial products were successive baths. The Sun protection factor of these different creams was determined in vitro both before and after the baths. The result was that two successive baths of 20 min in moderately shaken distilled water, at 29 +/- 2 degrees C and may substitute the in vivo test.

Mineral filters in sunscreen products--comparison of the efficacy of zinc oxide and titanium dioxide by in vitro method.

European legislation currently authorizes 26 sun filters among which, there is only one mineral filter: titanium dioxide. In the United States, two mineral filters are authorized: titanium dioxide in a maximum dose of 25% and zinc oxide. Zinc oxide is authorized in Europe, but its concentration level is not limited. A large number of commercial products are containing one of these mineral filters. The difference between these products lies in the percentage of the active substance, the way they are incorporated into the final product and the size of the primary particles. Depending on the ingredient used, there is a large variation in efficacy. The efficacy of the products tested was determined by an in vitro method using a spectrophotometer equipped with an integration sphere. Titanium dioxide was thus seen to be much more effective than zinc oxide; indeed no commercial form of zinc oxide tested can give a sun protection factor (SPF) higher than 10 at its maximum dose of use, unlike titanium dioxide which in its coated form (coated with alumina and with stearic acid, amongst others) gives a SPF of 38. This study has also allowed us to dispel the theory that talc--a raw material which has been used empirically for years in foundation in the belief that it has photoprotective effects--has an effect against sun rays. Talc proved to be particularly ineffective, as when it is used at a level of 25%, it only gives a totally negligible SPF of one unit.

Study of the efficacy of 18 sun filters authorized in European Union tested in vitro.

In this work, the authors study the influence of filter concentration on the SPF in a topical product measured in vitro. Firstly, the method was adapted by determining that a mass of 15 mg of product must be applied on the PMMA (polymethylmethacrylate) plate in order to have the best correlation with results obtained in vivo. By using the highest concentration allowed by European legislation, the following ranking was drawn up in ascending order of efficacy: 3-Benzylidene camphor (1.66) < oxybenzone (3.01) < octylsalicylate (3.12) < PABA (3.36) < polysilicone 15 (3.64) < methylene bis-benzotriazolyl tetramethylbutylphenol (3.68) < PEG25 PABA (3.81) < benzophenone-4 (3.85) < 4-methylbenzylidene camphor (4.22) < homosalate (4.33) < octyltriazone (7.80) < phenylbenzimidazole sulfonic acid (8.31) < octyldimethyl PABA (8.71) < octocrylene (10.41) < octylmethoxycinnamate (10.42) < diethylhexylbutamidotriazone (12.58)

Effect of the combination of organic and inorganic filters on the Sun Protection Factor (SPF) determined by in vitro method.

This paper describes the effect on Sun Protection Factor (SPF) of the combination of inorganic and organic filters in sunscreen products as determined by an in vitro method. O/W emulsions containing inorganic filters, such as titanium dioxide and zinc oxide, combined with 18 EU-authorized UV-B organic filters were tested. SPF measurements were carried out using a spectrophotometer equipped with an integrating sphere. This study observed a synergic effect when titanium dioxide was combined with either anisotriazine or octyldimethylPABA. The combination of zinc oxide with 11 UV-B organic filters also exhibited a similar synergy; however, the measured SPF was systematically lower than the protection factor achieved with titanium dioxide.