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Objectives: Diethyltoluamide and ethylhexyl p-methoxycinnamate (OMC) are two active ingredients in insect repellent and sunscreen products, respectively. The concurrent application of these two substances often increases their systemic absorption, compromising the safety and efficiency of the cosmetic product. In this study, diethyltoluamide and OMC were incorporated into solid lipid nanoparticles, a colloidal drug delivery system, to reduce percutaneous absorption and avoid toxic effects and also maintain the efficacy of the two active compounds on the skin surface for a long duration., Methods: Solid lipid nanoparticles were prepared based on an ultrasonication technique and characterized by differential scanning calorimetry (DSC) analyses. In-vitro studies determined the percutaneous absorption of diethyltoluamide and OMC., Key Findings: DSC data carried out on unloaded and diethyltoluamide- and/or OMC-loaded solid lipid nanoparticles highlighted that diethyltoluamide and OMC modified the temperature and the enthalpy change associated to the calorimetric peak of solid lipid nanoparticles. The concurrent presence of the two compounds in the solid lipid nanoparticles caused a synergic effect, indicating that the lipid matrix of nanoparticles guaranteed a high encapsulation of both diethyltoluamide and OMC. Results from the in-vitro study demonstrated that the particles were able to reduce the skin permeation of the two cosmetic ingredients in comparison with an oil-in-water emulsion., Conclusions: This study has provided supplementary evidence as to the potential of lipid nanoparticles as carriers for topical administration of cosmetic active compounds.

Three oily extracts, obtained by acetone extraction from the entrails of different varieties of Mediterranean fishes, such as mackerel (Scomber scombrus), sardine (Sardina pilchardus) and horse mackerel (Trachurus mediterraneus), were characterized to determine their unsaturated fatty acid content. In an in-vitro model, their inhibitory effect was then evaluated against protein aggregation and their protective efficacy against heat-induced albumin denaturation assessed. The fish oil extracts tested in this study presented a significant amount of unsaturated fatty acids; in particular the extract obtained from the entrails of horse mackerel proved to have higher concentrations of DHA (docosahexaenoic acid) and oleic acid compared with the other two oils. The in-vitro study revealed an interesting protective effect of the oil extracts (particularly the horse mackerel extract) against heat-induced denaturation of albumin.

Novel polyoxyethylene esters of 18 beta-glycyrrhetic acid (GA) were synthesized and evaluated as potential dermal prodrugs. The permeation of these prodrugs (1a-e) was studied in-vitro, using excised human skin membranes (SCE; stratum corneum/epidermis) mounted in Franz type cells, and in-vivo, evaluating the ability of these compounds to inhibit methyl nicotinate (MN)-induced skin erythema in healthy human subjects. All the esters synthesized showed a good water stability, while the enzymatic hydrolysis rate was significantly affected by the length of the polyoxyethylenic chain used as promoiety. In in-vitro percutaneous absorption studies, only esters 1b and 1c (respectively triethylen- and tetraethylenglycol derivatives) showed an increased flux through SCE membranes compared with GA. Furthermore, we observed an appreciable and sustained in-vivo topical anti-inflammatory activity of esters 1b and 1c compared with the parent drug.

We have investigated the influence of charge and lipid concentration on the in-vivo percutaneous absorption of a model compound, methyl nicotinate (MN), from liposomal vesicles. MN-loaded liposomes were produced by the reverse-phase evaporation method (REV) using different concentrations of phosphatidyl choline (PC), in association with surfactants such as dioctadecyl dimethyl ammonium bromide (DDAB18) and dicetyl phosphate (DCP), which impart a positive or negative charge to the systems, respectively. The liposomal suspensions were then processed to hydrogels and used to study in-vivo the MN permeation profile. MN was chosen as the model compound since it was capable of causing cutaneous erythema, the intensity and duration of which was proportional to the amount entering the living epidermis over time. The extent of the erythema was monitored by reflectance spectrophotometry, a non-invasive technique. In-vivo findings showed an interesting MN delayed release, which was proportional to the amount of phospholipids in each liposomal formulation. Furthermore, it could be noted that the erythematous effect was more prolonged when MN was delivered from neutral or negatively-charged liposomal forms.

The aim of this study was to evaluate the in-vivo drug release profile of indometacin-loaded liposomes into the skin. Large unilamellar vesicles (LUVs), composed of dipalmitoyl-L-alpha-phosphatidylcholine and cholesterol (9:1), were obtained using the extrusion method and then incorporated in hydrogels (LUV-A and LUV-B). The delivery of indometacin from the liposomal system was evaluated by determining its in-vivo local anti-inflammatory activity after cutaneous application of liposomal gel formulations; the anti-inflammatory activity is directly proportional to the amount of drug that actually crosses the skin. UVB-induced erythema on healthy human volunteers was chosen as the inflammatory model and the extent of erythema was monitored by the non-invasive technique of reflectance spectrophotometry. The results showed that LUV dispersions containing indometacin provided a high percentage of entrapped drug (approximately 84%). Furthermore, in-vivo findings revealed that the anti-inflammatory effect was more prolonged when indometacin was delivered from a liposomal gel formulation rather than from a gel formulation without liposomes. In particular, the indometacin-loaded gel formulation LUV-A showed a sustained effect, probably related to an interaction between LUV lipids and stratum corneum lipid structure. This interaction produces a depot in the stratum corneum that ensures sustained release of the drug to deeper skin layers.

Sedum telephium L. is a medicinal plant used in antiquity to cure many types of inflammatory skin diseases. The leaves (without the external cuticle), are used to promote healing and reduce skin inflammation and pain, and contain various components. We found two major components: flavonol glycosides and polysaccharides, with molecular weight between 13,000 and 13,500 Da. We evaluated the in-vitro antioxidant and in-vivo skin photoprotective effects of three lyophilized extracts obtained from the juice of S. telephium L. leaves: a total lyophilized juice, a lyophilized flavonolic fraction, and a lyophilized polysaccharidic fraction. Two in-vitro models were used: the bleaching of the stable 2,2-diphenyl-1-picrylhydrazyl (DPPH*) radical, and the protective effect against UV-induced peroxidation on phosphatidylcholine multilamellar vesicles, as model membranes. The antioxidant/radical scavenging activity of each lyophilized extract was also assessed in-vivo by determining their ability to reduce UVB-induced skin erythema (monitored by reflectance spectrophotometry) in healthy human volunteers. The findings of the in-vitro experiments clearly demonstrated that, unlike the lyophilized polysaccharidic fraction, the lyophilized flavonolic fraction and total lyophilized juice possess strong antioxidant/free radical scavenging properties, which are likely due to phenolic compounds. Consistent with these findings, gel formulations of both the total lyophilized juice and, to a greater degree, the lyophilized flavonolic fraction appeared to possess a strong protective effect against UV-induced skin erythema in-vivo, whereas the lyophilized polysaccharidic fraction was completely ineffective. The in-vitro and in-vivo results suggest that, both the total lyophilized juice and, in particular, the lyophilized flavonolic fraction, but not the lyophilized polysaccharidic fraction of S. telephium L. leaves, have photoprotective effects against UVB-induced skin damage.