Notes: To show the benefits of retinol encapsulation in cosmetic industry, we compared the diffusion of two different retinol preparations through skin:oil-in-water (o/w) emulsions of retinol, also called ‘free retinol’, and suspension of Cylasphere® including retinol, also called ‘encapsulated retinol’. Two methods were used: Franz cell elucidated retinol release and storage in a hairless mouse skin according to time for the two types of preparations. The dosage of retinol by high performance liquid chromatography (HPLC) showed that encapsulated retinol was maintained into the skin for a longer time than free retinol. Raman microspectrometry measurements established a spectral image of the skin and determined the localization of retinol. Maps were collected according to time. They detailed the shifts of free and encapsulated retinol in the epidermis of a human biopsy. Spheres were smaller than droplets and they moved two times faster at this level of the skin.

Notes: The face is composed of complicated anatomical components, presenting unique portions, such as the eyes, nose and mouth in a relatively narrow area. Moreover, the facial skin is densely populated by the pilosebaceous units and sweat glands, and its stratum corneum (SC) is much thinner than that of the trunk and limbs, although it is always exposed to the environment. Among various portions of the facial skin, some are more easily irritated than others by environmental stimuli, or are more often affected by certain dermatoses. However, the functional aspects of the different portions of the facial skin have not been studied in detail under a strictly controlled environment in sufficiently large numbers of subjects covering different age groups. Thus, we conducted studies in winter with various biophysical techniques, such as transepidermal water loss (TEWL), as a parameter for SC barrier function, high-frequency conductance as that for skin surface hydration state, skin surface lipids, pH, blood flow and skin surface temperature on the forehead, mid-portion of the cheek (cheek in short), nasal tip (nose in short), nasolabial fold and chin of 20 healthy Japanese females aged 22–37 years (average 25 years) in a climate chamber adjusted to 21 °C and 50% relative humidity. Thereafter, we studied the influence of ageing on these biophysical parameters by collecting data of TEWL, high-frequency conductance and size of superficial corneocytes on the cheek, nasolabial fold and chin of 303 healthy Japanese female volunteers of different ages. The obtained results showed that the barrier function of the SC was best on the cheek, presenting the lowest TEWL, which was significantly higher on the nasolabial fold and chin than on the cheek. TEWL showed a decrease with age. In contrast, skin hydration state was higher on the nose, but it tended to be lower on the nasolabial fold, showing a mild age-related increase. The corneocytes on the nasolabial fold and chin were smaller than those on the cheek. They revealed a clear increase in size with age. Skin surface lipids were richest on the nose, whereas the superficial pH on the nose was the lowest among the regions tested. The skin temperature was lowest on the cheek than on other areas of the face; although, together with the nose, its blood flow was higher than that of the others. These data indicate great regional differences observable in SC functions on the face. In general, the SC barrier function increases with age, probably because of a decreased epidermal turnover rate as recognized by the increase in corneocyte size. Among the various sites, the skin of the nasolabial fold and chin, whose SC consisted of the smallest corneocytes, showed poorest SC properties in barrier function, suggesting the presence of mild invisible inflammation. It is understandable that this area easily develops not only the complaint of sensitive skin to cosmetics but also dermatitis because of various external agents.

Notes: Human skin is composed of epidermal and dermal layers, each of which has its own functional importance. Dermis consist of a fine network of collagen fibers, elastic fibers, and other components of the extracellular matrix (ECM). ECM consist primarily of proteins and complex sugars, which form fibrillar networks and a ground substance. Collagen is an important structural component of skin connective tissue and provides the tensile strength of skin.Approximately 70–80% of the dry weight of skin consists of collagen. The most abundant collagen types in skin are types I and III; the former accounts for 80% of the total collagen content of skin and the latter for approximately 15%. The other collagen types present in skin include type IV collagen, which is abundant in the basement membrane (BM); type V collagen, which is located pericellularly; type VI collagen, which plays a role in matrix assembly and is present as microfibrils between collagen fibers; and type VII collagen, which is a structural component of anchoring fibrils. Elastin accounts for only about 1–2% of the dry weight of skin but is important for the maintenance of skin elasticity and resilience. Glycosaminoglycans are of central importance for the maintenance of a water balance in skin, even though the quantities in ECM are small (0.1–0.3% of the dry weight of skin).In the dermis fibroblasts are responsible for the synthesis of ECM proteins. The fibroblasts in the dermis spend majority of time in quiescent state. However in response to activation, the fibroblasts can be reactivated, and certain pool of cell is able to differentiate into myofibroblasts which have important role in repairing skin defects such as during wound healing. During aging the number of fibroblasts is markedly reduced.Also the response of fibroblasts to various growth factors and mechanical or pathological stimulates (wound healing) is diminished.Skin collagen synthesis declines with aging and as the result of such external factors as long-term sun exposure and medications, for example, topical corticosteroids. In aging skin, collagen fibers become thicker and less soluble and the synthesis of collagen declines. Skin thickness remains quite constant between 20 and 70 years of age, after which a marked decrease in skin thickness occurs. During aging the expression of collagenases are increased and inhibitors of collagenases are reduced leading to increased proteolysis of connective tissue. Recent studies have shown that collagen synthesis is declined in the skin of heavy smokers, while collagenases are increased inducing premature skin aging.The elastic properties of skin are also affected by aging. Along with increasing age, dermal elastic fibers become thicker and fragmented and oxytalan fibers appear fragmented and shortened. Disintegration of elastic fibers is already seen in a minority of fibers between ages 30 and 70, but the changes become more profound after the age of 70 years, affecting a majority of the fibers. As a result of the decreased number of elastic fibers in aged skin, the elastic recovery of skin decreases in elderly people. Even though the content of GAGs and proteoglycans is relatively small, they have significant role in collagen fibril formation, water content of dermis and in mechanical properties. During aging there are marked alterations in different proteoglycans. The amount and synthesis of versican (high molecular size) is decreased and small molecular size decorin is increased. In photoaged skin versican is increased and is closely associated to elastin while decorin is decreased.

Notes: As the skin is always in contact with oxygen and is increasingly exposed to environmental and artificial ultraviolet (UV) irradiation the risk of photooxidative damage induced by reactive oxygen species – finally leading to phototoxicity, photoaging and skin cancer – has increased substantially.The term reactive oxygen species (ROS) includes oxygen centered radicals like the superoxide anion radical and the hydroxyl radical, but also non-radical species such as hydrogen peroxide and singlet oxygen – all being produced in skin upon UV irradiation. In response to the attack of reactive oxygen species the skin has developed a complex antioxidant defense system including enzymatic and non-enzymatic antioxidants. As a first line of the enzymatic antioxidative defense, superoxide dismutases reduce superoxide anion radicals to hydrogen peroxide which subsequently is detoxified to water by catalase and glutathione peroxidases.We were interested whether the antioxidant enzymes manganese superoxide dismutase (SOD2) and glutathion peroxidase (GPx1) are inducible upon UV irradiation and whether repetitive UV exposure, as practiced for the light-hardening during phototherapy of photodermatoses, can even enhance the adaptive antioxidant response. To address this question skin fibroblasts and keratinocytes were exposed in vitro to single and repetitive UV low dose irradiation in different time intervals and afterwords challenged by high dose irradiation. The antioxidant response was measured in terms of steady state mRNA levels and activity changes of SOD2 or GPx1 as well as of the viability after challenge with high dose UV-irradiation.Interstingly, only UVA but not UVB irradiation was able to induce the mRNA steady state levels and the activity of SOD2 in fibroblasts. However, fibroblasts incubated with the supernatants from UVB-irradiated epidermal cells responded with an increase in SOD2. This increase on mRNA and activity levels was mediated by paracrine acting secreted factors produced by the keratinocytes. If fibroblasts were exposed repetitively to sublethal UVA doses the further up-regulation of SOD2 correlated with the protection against high UV doses. Importantly, SOD2 basal levels of protein content and activity substantially differed within cultivated cells and skin biopsies from different individuals. These results provide evidence for an adaptive antioxidative UV response of the skin. Interindividual differences might account for differences in the susceptibility to develop photodermatologic disorders related to photosensitivity, photoaging, and skin cancer.

Notes: Human in vivo fragrance evaporation data from a previously published study are reanalysed in terms of compartmental pharmacokinetic models in which the microscopic rate constants are functions of the physicochemical properties of the fragrance components. According to the proposed analysis, which is restricted to low doses, absorption and evaporation of each component are first-order processes occurring from either the skin (one-compartment model) or the skin and a more rapidly depleted vehicle layer (two-compartment models). Evaporation rates of ingredients from a 12-component mixture containing a musk fixative followed single exponential decays that were well described by the one-compartment model. An otherwise identical mixture without fixative yielded evaporation rates that could be characterized as biexponential decays associated with loss from two compartments. This result shows that ingredient interactions qualitatively and quantitatively change evaporation rate profiles of fragrance components; however, an attempt to account for these interactions explicitly by means of activity coefficients inserted as multipliers for the microscopic rate constants was unsuccessful. Re-examination of this approach in the context of a diffusion/evaporation model is suggested. The developed models have potential utility for dermal risk assessment and for prediction of aroma evolution following topical application of complex fragrances.

Notes: The cornified cell envelope (CE) formed by transglutaminase-mediated ε-(γ-glutamyl)lysine cross-linking of specialized corneocyte proteins is the most insoluble component of the terminally differentiated keratinocyte. Under normal Nomarski optics, two types of CE are readily distinguishable: an irregularly shaped, readily deformed ‘fragile’ envelope (CEf), which predominates in the deepest layers of the stratum corneum, and a polygonal “resilient” or ‘rigid’ envelope (CEr), which represents over 80% of the CE population in the superficial layers. This distinct spatial distribution indicates a maturation of the CE from the fragile to the resilient morphology during stratum corneum maturation. In this study, we have examined morphological and physical changes occurring in the CE during the terminal differentiation. The proportion of CEf and CEr present in superficial samples of stratum corneum were readily distinguishable following staining with Tetrarhodamine isothiocyanate (TRITC) and showed significant body site variation. The percentage of CEf was highest on samples recovered from exposed body sites (back of hand 〉 cheek 〉 inner arm [bicep region]) suggesting innate body site differences or that photodamage and other environmental trauma can reduce or delay normal CE maturation. Soap-induced dryness resulted in a significant decrease in CE maturation coincidental with reduced corneodesmosomal hydrolysis. Effective moisturization of winter-induced dry skin enhanced CE maturation (33% increase in TRITC fluorescence, n = 14 following 4-week treatment). Using a novel micromanipulation instrument, the force required (µN) to maximally deform individual CEf and CEr was compared. CEf recovered from deep stratum corneum were significantly softer and weaker than CEr recovered from superficial layers. These studies indicate that the normal process of CE maturation is associated with an actual strengthening of this insoluble protective structure and that the impairment of this process is associated with poor quality of the stratum corneum.

Notes: Skin-cleansing compositions based on alkyl carboxylates (soaps) have a higher irritation potential than those based on syndet surfactants such as alkyl isethionates or alkyl ether sulphates. Contributing factors include inherent differences in the irritation potential of soaps and syndet surfactants, pH-induced changes in surfactant solution chemistry, and the direct effects of pH on the physical properties of the stratum corneum (SC). Past work has not directly addressed the effect of solution pH on the SC itself and its potential role in cleanser-induced skin irritation. In the current work, alterations to SC properties induced by buffered pH solutions and two strongly ionizable surfactants, sodium dodecyl sulphate and sodium lauryl ether sulphate, at different pH values are measured. By utilizing optical coherence tomography (OCT) and infrared (IR) spectroscopy we have directly measured physical changes in SC proteins and lipids. Our results indicate that SC swelling, which reflects alterations to SC structural proteins, is increased significantly at pH 10, compared to pH 4 and 6.5. The transition temperature (Tm) of SC lipids is found to increase at pH 10, compared to pH 4 and 6.5, suggesting a more rigid SC lipid matrix. Surfactants cause a further increase in swelling and lipid rigidity. Some aspects of what these results mean for SC physical properties as well as their implications to potential mechanisms of surfactant-induced skin irritation are discussed.

Notes: The complex composition of lipstick formulations usually needs the use of organic solvents for sample dissolution. A treatment based on dissolution of cosmetic samples in ethanol-water (70 : 30, v/v) by use of ultrasonic irradiation is proposed. A C18 stationary phase and an isocratic mobile phase of ethanol:water:acetic acid (70 : 29.5 : 0.5, v/v/v) with a flow rate of 1 mL min−1 and an injection volume of 20 µL is proposed for the high-pressure liquid chromatography (HPLC) determination of four UV-filters, and detection was carried out at 309 nm. The limit of the chromatographic detection was 7.0 µg mL−1 for butyl methoxydibenzoylmethane, 1.5 µg mL−1 for benzophenone-3, 1.4 µg mL−1 for octyl dimethyl p-aminobenzoic acid (octyl dimethyl PABA) and 2.7 µg mL−1 for octyl methoxycinnamate. The relative standard deviations of the results were between 1.8 and 2.4%. The results were comparable to those obtained by a procedure based on the use of tetrahydrofuran. The method can be considered as a green analytical procedure because it only requires the use of small quantities of ethanol.