or phototoxic effects in human keratinocytes (HaCaT cells) and BABL/c 3T3 fi broblasts, whereas PCL nanoparticles with BP-3 revealed phototoxic potential in HaCaT cells. The studies of skin permea tion were made over 24 h in a Franz diffusion cell with the human skin, donated from plastic surgery. After this, the BP-3 amounts were measured in epidermis/dermis by the tapping-stripping method, as described in the receptor fl uid by HPLC. During the skin permeation study, it was observed that BP-3 encapsulation in the PCL nanostructure decreased its penetration into the skin. PCL nanoparticles decreased BP-3 skin permeation by 70% in the epidermis and dermis and 80% in the receptor fl uid. However, the skin permeation of SLN-BP-3 was not signifi cantly different from that of free BP-3 (78). Vettor et al., evaluated O MC distribution in skin compartments from OMC-loaded poly-D,L-lactic acid (PLA) nanoparticles formulated in an emulsion gel (OMC-NP emulgel) comparatively to a nonencapsulated OMC emulsion gel (OMC emulgel). Both formulations contained 5% OMC. The classical Franz cell method was fi rst applied, and OMC amounts in each skin strata [SC, epidermis (E), and dermis (D), in the receptor fl uid (RF) and at the skin surface (unpenetrated dose)] were determined after 1, 2, and 3 h exposure time. The results showed the in vitro distribution of OMC in skin compartments for both formulations using either “ACET” (extraction of OMC with acetone) or “IPM” (extrac- tion of OMC with isopropyl myristate) methods. Comparison between OMC emulgel and OMC-NP emulgel gave useful information on the cutaneous uptake of OMC in the skin depending on both formulations. When applied encapsulated in NP, the major part of OMC was retained at the skin surface over time. After 2 and 3 h, 85 and 80% of the applied OMC were, respectively, recovered on the skin surface with NP. These amounts were much higher than those obtained when OMC emulgel was applied (62 and 56%, respectively, after 2 and 3 h). This result demonstrated the nanoparticle ac- cumulation at the skin surface. High amounts of OMC were detected in the SC (be- tween 12 and 26% for OMC emulgel and 5–8% for OMC-NP emulgel with ACET method. More than 80% of OMC conce ntrated on the top of the skin and in the SC after 3 h exposure time. The main difference between the OMC emulgel and the OMC-NP emulgel was OMC distribution between these two compartments. In the case of NP, the percentage of accumu- lated OMC was 10-fold higher on the top of the skin than that in the SC. This value dropped to twofold with OMC emulgel. Consequently, OMC amounts in viable skin layers (Qabs = E + D + RF) were superior for OMC emulgel than for OMC-NP emulgel (~3.5 vs. ~2% after 3 h) because the SC may play a role of reservoir. This result confi rmed the higher affi nity of OMC (lipophilic substance, logp = 5.68) for the lipophilic skin layers, and second that the transport of NP was clearly impeded by the SC (39). Luppi et al. synthesized l ipophilic polymers composed of polyvinyl alcohol (PVA) and various fatty acids (FAs) and investigated in vitro the infl uence of the different nanopar- ticles prepared on percutaneous absorption of BP-3. PVA was selected as a starting material for the preparation of such polymers due to its biocompatibility and the pos- sibility for substitution through chemical linkage to its oxy-residues able to modify its physicochemical properties. PVA was substituted, at two different substitution degrees (40 and 80%), with saturated FAs (myristic, palmitic, stearic, and behenic acid) to give to the polymer suffi cient lipophilicity to allow preparation of nanomatrices for sun- screen delivery. JOURNAL OF COSMETIC SCIENCE 316
The diffusion of BP-3 acros s excised pig-ear skin was studied using a static diffusion cell based on the Franz design and analyzed by HPLC. Results indicated the nanoparticles’ ability to limit sunscreen absorption. Moreover, nanoparticles with a low degree of sub- stitution provided the highest amounts of BP-3 in the receiver compartment. Among these, nanoparticles with short chain length provided higher amounts of BP-3 than nanoparticles with high chain length. There was a correlation between the size of the nanoparticles and the fractional amount of BP-3 recovered in the skin 6 h after topical application: the amount of BP-3 decreased with increasing substitution degree and, for each degree of substitution, increasing nanoparticles size. This indicated the ability of low-substituted formulations to enhance the location of sunscreen in the epidermis, achieving high protection (79). CYCLODEXTRIN DERIVATIVES Th e interaction between 4-M BC and hydrophilic α-, β-, and γ-cyclodextrin derivatives was investigated in water by phase-solubility analysis. Among the studied cyclodextrins, random methyl-β-cyclodextrin (RM-β-CD) had the greatest solubilizing activity. The light-induced decomposition of 4-MBC, in emulsion vehicles, was markedly decreased by complexation with RM-β-CD. The infl uence of RM-β-CD on human skin penetration of the sunscreen was investigated in vivo, using the tape-stripping method. Considerable quantities (21.2–25.1% of the applied dose) of 4-MBC permeated in the SC. However, no signifi cant differences in the amounts of UV fi lter in the 10 fi rst strips of the horny layer were observed, between the formulations containing 4-MBC free or complexed with RM- β-CD. Therefore, RM-β-CD complexation did not alter the retention of 4-MBC in the superfi cial layers of the SC, where its action is more desirable (18). So the complexation with RM beta CD seems to be not effective. COMBINATION OF ORGANIC UV FILTERS Coz zi et al. carried out an investiga tion and made a comparison on how sunscreen formu- lations (whether free or encapsulated) with the common combination of organic UV fi l- ters, BMDBM and OCR, behave. This comparison was made concerning photostability, skin penetration, and retention on the surface of the skin. UV fi lters were enclosed in sol–gel silica glass microcapsules. Free and encapsulated UV fi lters were incorporated in a water-based cold lotion divided into three preparations: formulation without actives (F1), formulation containing UV fi lters (BMDBM 3% and OCR 9%) in free form (F2), and formulation F3 containing encapsulated UV fi lters. To examine the UV fi lter perme- ation in the SC and their retention on the skin surface, the Fourier transform infrared spectroscopy (FTIR) imaging spectroscopy and attenuated total refl ection Fourier trans- form infrared spectroscopy techniques were applied. Skin samples were treated with 2 mg/c m2 of sunscreen formulations applied topically with 1 min of massage to cover the entire skin surface uniformly and mounted in diffusion Franz cell system. The skin samples were maintained in this condition for 2 h for the pen- etration measurement and during 4 h for the retention measurement on the skin surface. At the end of the 2-h treatment, the skin samples were removed from the diffusion cells, and the sunscreen remaining on the skin surface was gently removed before analysis. The tape- stripping technique was used. DISTRIBUTION OF UV FILTERS ON THE SKIN 317
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