Cossma1607-08_GB

photos and figures: ProDerm ired mer rrier tive eved bus- the tein cor- ated s d a sess oxi- d/or ucts n of rs is nder hen m is tion ates bar- are moke ra- moke that mok- lim- tact ette ther ette the llut- ssed use be- iga- im- nted nts. rom elate vivo ht of sub- nd it re in first contact with smoke exposure in the environment. It is well docu- mented that sebum is oxidised by cigarette smoke to produce in- creased levels of squalene monohy- droperoxide (SQOOH) and malondi- aldehyde (MDA). Furthermore, skin barrier lipids of the stratum corneum are also oxidised by cigarette smoke with measurable increases in MDA. Increased levels of SQOOH have been reported to increase the likeli- hood of skin comedogenicity and the consequences of photo-oxidative stress. Malondialdehyde (MDA) is a good marker of oxidative stress and enzymes that limit free-radical for- mation. As such, it is therefore a good indicator for measuring both oxidative damage and the efficiency of anti-oxidants. Challenges and opportunities Whilst our method is fairly straight- forward to execute, we noted three key challenges in terms of: minimis- ing smoke inhalation by volunteers; the need for standardised and repro- ducible skin pollution exposure at a constant level for several minutes; and the requirement for “fresh” smoke since only fresh smoke ­ contains the pollutants needed for “oxidation”. To overcome these challenges, the method we have ­ developed involves using a smoke-suction device (Fig. 1) in which a pump produces negative pressure and transports smoke to the skin on a defined area of the back (3 cm diameter) for measuring sebum oxidation (Fig. 2), or the vol- ar forearm for barrier lipid oxida- tion. A constant stream of smoke for 15 minutes (app. 89 cigarettes) free- ly interacts with the skin. This short intense application of smoke is akin to the use of intense UV light sources in routine SPF testing, which are 20 times stronger than natural sunlight. Using a swabbing technique, lipids are then removed from the back into a solvent mixture, frozen in liquid nitrogen and analysed using liquid chromatography-mass spectroscopy (LC-MS) in an external laboratory for SQOOH and MDA (Fig. 3 and 4), with statistically significant results. LC-MS combines two selective tech- niques that allow the chemicals of interest in highly complex mixtures to be isolated and measured. LC dif- ferentiates compounds by their physico-chemical properties and MS differentiates compounds by their mass (specifically their mass-to- charge ratio). It is this dual selectiv- ity that makes LC-MS such a power- ful analytical tool. By employing our method, both “short” and “long-term” protection of cosmetic products can be meas- ured as outlined in Table 1* employ- ing the possibility of 2 possible study designs. In an intra-individual study (on the same volunteer), up to 3 cos- metic products can be tested as well as a positive (untreated area ex- posed to smoke) and negative con- trol (untreated area not exposed to smoke). Key advantages in a nutshell The key advantages of this method arethe small number of volunteers required and the reproducibility and sensitivity of the method. The pro- posed method is sufficiently sensi- tive to detect anti-oxidative proper- ties of cosmetic active ingredients and cosmetic formulations. Further- more, pollutant cigarette smoke is a suitable substance that can be used on human volunteers without ethi- cal issues in contrast to other pollu- tion sources. Whilst major compo- nents of cigarette smoke are common to indoor and outdoor pollutants, our method enables us to induce a pollution stress on “living skin” un- der standardised clinical laboratory conditions. □ * The table with the typical test method design can be found on the Internet – see download panel Figure 3: SQOOH found in test samples Fig. 4: MDA found in test samples SPOTLIGHT: ANTI-POLLUTION www.cossma.com  l  45 “Only human studies can provide real benefits” COS1607_42_Proderm_Antipol.indd 45 26.07.16 10:39 COS1607_42_Proderm_Antipol.indd 4526.07.1610:39

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