The group of cinnamate analogues also inc ludes the UVB fi lter OCR. Studies showed that 16–24 h after application of OCR (8–10%) on the surface of skin samples, most of the OCR remained on the surface of the skin as non-penetrated material ( 95%), and detectable amounts of the applied dose were found in the SC, and in low amounts or below the detec- tion limit in other skin layers (epidermis, dermis, or receptor medium). None of the authors determined a percentage of dermal absorption. Hayden’s study showed that only 0.4% of OCR was found in the epidermis and approximately 0.05% in the fl uid receptor (40). Therefore, it can be concluded that transdermal absorption of OCR is very low. The sensitizing potential of OCR has been extensively reviewed in the scientifi c literature, and contact al- lergy to OCR is very rare in the general population. Photocontact allergy cases to OCR have been reported but are rare in the general population (66). It is photostable with a good photostabilizing effect, particularly toward BMDBM. BMDBM exhibits high absorptive capacity in the UVA region, but it suffers from marked decom- position under sunlight irradiation, which leads to a reduction in the protective effi cacy of the sunscreen preparation during solar exposure. In addition, its photo-fragmentation results in the formation of free radicals, which may directly or indirectly initiate skin damage. The instability of BMDBM under sunlight can be reduced by the addition of UVB fi lters, such as OCR or methylbenzylidene camphor, with triplet energy similar to BMDBM and acting as quenchers of its triplet state. In the case of irradiation, energy transfer between OCR and BMDBM takes place in the exited state (triplet state). Triazones . The UVB fi lters ethylhexyl triazone (EHT), diethylhexyl butamido triazone (DEBT, iscotrizinol, Uvasorb HEB), and the broad-spectrum UV fi lter bis-ethylhexy- loxyphenol methoxyphenyl triazine (BEMT, bemotrizinol, Tinosorb S/BASF Care Cre- ations, Germany) have a molecular weight over 500 Da because of the extension and multiplication seed in their chromophoric groups. The benefi ts of these UV fi lters in- clude the development of high absorption coeffi cients, anti-infl ammatory properties while being effi cient and also photostable (67,68). Tinosorb S can also optimize the pho- tostability of other UV fi lters in a sunscreen (69). T riazones are an integral part of an increasing number of skincare and sunscreen products, and this has to do with their benefi cial properties. A particle size less than 100 nm and a molecular weight of 823.1 Da make Tris-biphenyl triazine (Tinosorb A2B) the fi rst UV fi lter to be ideally included in care products around Europe. It offers great skin protection against UV radiation between 290 and 340 nm, bridging the gap between “conventional” UVA or UVB fi lters. In addition, it has water-dispersible action, it is broad-spectrum, and it is micronized. Benzo triazoles. The UV fi lters drometrizole trisiloxane (DTS, Mexoryl XL) and methylene bis- benzotriazolyl tetramethylbutylphenol (MBBT, Bisoctrizole, Tinosorb M) are also catego- rized within the 500 Da rule. They have a minor skin penetration property, while they rarely cause (photo) allergic reactions (37,70). Mexoryl XL, the fi rst photostable UV fi l- ter, offers skin protection over the whole UVB and UVA ranges. A combination of Mexo- ryl SX and XL also offers a synergistic effect on their protection properties (71). Tinoso rb M is produced in the form of organic microfi ne particles and can be dispersed in the water phase of a sunscreen. Also, it offers all the properties of organic and inorganic UV fi lters, while it refl ects, scatters, and absorbs UV radiation. Furthermore, it exhibits suffi cient photostability and broad-spectrum ability over the whole UVB, UVA-I, and UVA-II range (72). JOURNAL OF COSMETIC SCIENCE 312

INNOVATIV E SUNFILTER FORMULATIONS AND CARRIERS FOR THE FUTURE. ENCAPSULA TION OF BI2TI2O7 NANOCOMPOSITES WITH DENDRITIC SILICON DIOXIDE MICROSPHERES (DSMS), AND ORGANIC FILTERS INCLUDING SINAPOYL MALATE (SM) AND BAICALIN (BS/BTO-DSM) TiO2 and ZnO particles have been commonly used as inorganic fi lters. Although inorganic fi lters present less skin penetration concerns than organic fi lters, the harmful photocatalytic activity that can induce ROS generation and ultimately damage to cells and DNA eventually may lead to carcinogenesis. Therefore, different surface-coating or encapsulation strategies have been adopted to overcome these challenges to obtain effective and safety inorganic fi lters with low photocatalytic activity. DSMs enca psulated with inorganic fi lter Bi2Ti2O7 nanocomposites (BTO-DSMs) and decorated with organic fi lters including SM and baicalin (BS/BTO-DSM) were rationally designed to effectively enhance UV protection while effectively scavenging the generated ROS and reducing skin permeability (the UV shielding properties were investigated in vitro by the calcein-AM/PI double-staining assay and MTT assay on HaCaT cells). To maintain the amount of active ingredients (Ti and SM) in 0.1 mg/mL, 10 mL of product should contain 22 mg of TiO2-DSM, 25 mg of BTO-DSM, 9 mg of SM/BTO-DSM, and 10 mg of BS/BTO-DSM with 10 mL of emulsion. The baica lin acted as the ROS scavenger to effi ciently eliminate the produced ROS gener- ated from the organic fi lters. The photodegradation of MO (methyl orange) was used to assess the photocatalytic activities of samples. Before the irradiation with UV light, sam- ples (7.5 mg) were added to MO (6 mL, 60 μM) aqueous solution and kept stirring for 0.5 h. Then, the mixture was irradiated with a UVB/UVA (254/365, 16 W) light for 3 h, and the sample was collected at a regular interval (0.5 h). The obtained samples were centrifuged, and the absorbance (465 nm) of solution was measured by a UV-Vis spec- trophotometer. The protect ion effects against UV irradiation on the skin of female BALB/c nude mice were further evaluated. The mice were placed under UVB/UVA (254/365 nm, 16 W) radiation for 0.5 h. Three days after UV radiation, the dorsal skin was re- moved and stained with hematoxylin/eosin (H&E) as well as Masson’s trichome for histology. Moreover, epidermal thickness and relative keratin percentage of each group were measured. To further evaluate the skin penetration in vivo, FITC (fl uorescein isothiocyanate) and FITC/BTO-DSM were applied topically onto the dorsal skin of the mice. Both the FITC and FITC/BTO-DSM samples had the same amount of FITC (0.1 mg/mL). Af- ter applying the samples for 6 h at room temperature, the skin samples were wiped topically fi ve times with PBS buffer and alcohol. After that, the dorsal skin was re- moved, sectioned into slices, mounted on glass slides, and imaged by a laser scanning confocal microscope. Thus, the r esulting BS/BTO-DSM presented excellent in vitro anti-UV performance and in vivo UV protection against keratinocyte apoptosis and epidermal hyperplasia without long-term toxicity. The introduction of SM into BTODSM signifi cantly broadened the UV shield range, which also prevented the SM direct contact with the epidermis and penetration behaviors (73). DISTRIBUTION OF UV FILTERS ON THE SKIN 313