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Characterization of phospholipid vesicles containing lauric acid: physicochemical basis for process and product development

Farkuh, Laura; Hennies, Paulo T.; Nunes, Cláudia; Reis, Salette; Barreiros, Luisa; Segundo, Marcela A.; Oseliero Filho, Pedro L.; Oliveira, Cristiano L. P.; Cassago, Alexandre; Portugal, Rodrigo V.; Muramoto, Rodrigo A.; Carretero, Gustavo P. B.; Schreier, Shirley; Chaimovich, Hernan; Cuccovia, Iolanda M.

Heliyon, 2019, vol 5, 10, pp. e02648

DOI:10.1016/j.heliyon.2019.e02648

Abstract

Lauric acid (LAH) strongly inhibits the growth of acne-causing bacteria. LAH is essentially water-insoluble and the solubility of laurate (LA) salts are medium and temperature dependent. Hence, LAH/LA preparations are difficult to formulate. Here we fully characterized phospholipid vesicles containing up to 50 mol% LAH. Vesicles of dipalmitoylphosphatidylcholine (DPPC) containing LAH, at pHs 7.4 and 5.0, were characterized measuring size, charge, bilayer phase transition temperature (Tm) and permeability of water-soluble probes. Small angle X-ray scattering and cryotransmission electron microscopy showed multilamellar vesicles at low LAH %. Increasing LAH % had a negligible effect on particle size. An internal aqueous compartment in all vesicle’s preparations, even at equimolar DPPC: LAH fractions, was demonstrated using water-soluble probes. At pH 5.0, the interaction between DPPC and LAH increased the Tm and phase transition cooperativity showing a single lipid phase formed by hydrogen-bonded DPPC: LAH complexes. At pH 7.4, vesicles containing 50 mol% LAH exhibited distinct phases, ascribed to complex formation between LAH and LA or LAH and DPPC. LAH incorporated in the vesicles minimally permeated a skin preparation at both pHs, indicating that the primary sites of LAH solubilization were the skin layers. These results provide the foundations for developing processes and products containing DPPC: LAH.

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