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Browsing by Author "Almeida, IF"

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  • Bacterial cellulose membranes as drug delivery systems: An in vivo skin compatibility study
    Publication . Almeida, IF; Pereira, T; Silva, NH; Gomes, FP; Silvestre, AJ; Freire, CS; Sousa-Lobo, JM; Costa, PC
    Bacterial cellulose (BC) is a highly pure form of cellulose, produced in the form of a swollen membrane by several bacteria that demonstrated to be able to modulate the skin release of model drugs. In the present study, the skin irritation potential of BC was evaluated in human subjects. BC membranes with and without glycerin (acting as plasticizer) were tested. No significant differences were observed for transepidermal water loss (TEWL) measurements in comparison with negative control, 2 and 24h after patch removal, which is an indicator of an absence of barrier disruption. Similar results were found for erythema. Clinical scores were zero at both times for all volunteers, with the exception of five volunteers that exhibited weak reactions. BC with glycerin provided a skin moisturizing effect statistically higher than the negative control (p=0.044), which was not observed for BC alone. The good skin tolerance found after a single application under occlusion reinforces the putative interest of BC membranes as supports for drug topical delivery. Besides modifying the mechanical properties, the inclusion of glycerin results in a skin moisturizing effect which could be clinically relevant for the treatment for skin diseases characterized by dryness, such as psoriasis and atopic dermatitis.
    2013Journal article Open access Show more
  • In vivo Skin Irritation Potential of a Castanea sativa (Chestnut) Leaf Extract, a Putative Natural Antioxidant for Topical Application
    Publication . Almeida, IF; Valentão, P; Andrade, PB; Seabra, RM; Pereira, TM; Amaral, MH; Costa, PC; Bahia, MF
    Topical application of natural antioxidants has proven to be effective in protecting the skin against ultraviolet-mediated oxidative damage and provides a straightforward way to strengthen the endogenous protection system. However, natural products can provoke skin adverse effects, such as allergic and irritant contact dermatitis. Skin irritation potential of Castanea sativa leaf ethanol:water (7:3) extract was investigated by performing an in vivo patch test in 20 volunteers. Before performing the irritation test, the selection of the solvent and extraction method was guided by the 1,1-diphenyl-2-picryl hydrazyl (DPPH) free radical scavenging test and polyphenols extraction (measured by the Folin Ciocalteu assay). Iron-chelating activity and the phenolic composition (high performance liquid chromatography/diode array detection) were evaluated for the extract obtained under optimized conditions. The extraction method adopted consisted in 5 short extractions (10 min.) with ethanol:water (7:3), performed at 40 degrees. The IC(50) found for the iron chelation and DPPH scavenging assays were 132.94 +/- 9.72 and 12.58 +/- 0.54 microg/ml (mean +/- S.E.M.), respectively. The total phenolic content was found to be 283.8 +/- 8.74 mg GAE/g extract (mean +/- S.E.M.). Five phenolic compounds were identified in the extract, namely, chlorogenic acid, ellagic acid, rutin, isoquercitrin and hyperoside. The patch test carried out showed that, with respect to irritant effects, this extract can be regarded as safe for topical application.
    2008Journal article Open access Show more