KEYWORDS: organogel, organogelator, LMOG, formulation, cosmetic product, dermo-cosmetic application Abstract Organogels are semi-solid systems in which an organic liquid phase is immobilized by a three-dimensional network composed of low molecular weight or polymeric components. Recently, they have raised an increasing interest in the pharmaceutical, cosmetic and food industry. Numerous cosmetic products based on organogels formulations are marketed. Many studies now focus on new applications of organogels and therefore, aim to develop novel systems of organogels and new generations of organogelators. In this review, methods of preparation and characterization of organogel will be described, as well as different classifications and current applications in the cosmetic field, more particularly in dermo-cosmetics. Organogels for cosmetic and dermo-cosmetic applications Classification, preparation and characterization of organogel formulations - PART 2* FORMULATION PLAMEN KIRILOV 1 *, ANH KHANH LE CONG 1 , ALICE DENIS 1 , HALIMA RABEHI 1 , SILVIA RUM 2 , CARLA VILLA 2 , MAREK HAFTEK 1,3 , FABRICE PIROT 1,4 * Corresponding author 1. Université 1, EA 4169 "Aspects fondamentaux, cliniques et thérapeutiques de la fonction cutanée", SFR Lyon-Est Santé – INSERM US 7 – CNRS UMS 3453 Laboratoire de Pharmacie Galénique Industrielle, ISPB, 8 Avenue Rockefeller, 69737 Lyon, Cédex 08, France 2. DIFAR - Dipartimento di Farmacia dell'Università, Sezione di Chimica del Farmaco e del Prodotto Cosmetico VIale Benedetto XV 3, 16132 Genova, Italy 3. Université Claude Bernard Lyon 1, EA 4169 "Aspects fondamentaux, cliniques et thérapeutiques de la fonction cutanée", SFR Lyon-Est Santé – INSERM US 7 – CNRS UMS 3453 Laboratoire de Dermatologie, ISPB, 8 Avenue Rockefeller, F-69737 Lyon, Cédex 08, France 4. Groupement Hospitalier Eduard Herriot – Service Pharmaceutique – Fabrication et contrôles des médicaments, Pavillon X, Place d’Arsenal, 69437 Lyon, Cédex 03, France bonds between polar molecules and phosphate groups of the lecithin molecules. A further addition of a small amount of water results in the formation of long, fexible and worm- like tubular micellar structures. Tubular micro-structures, thus formed, overlap and entangle with each other to form a three-dimensional gel network of fbrils and fbers, which possesses viscoelasticity and thermo-reversibility properties. The organic liquids get entrapped in the spaces between the entangled reverse micelles (35) (Figure 3). Solid fber mechanism The solid fber mechanism involves the dispersion of the solid organogelator into the apolar solvent by hot emulsifcation and formation of an apolar liquid mixture of organogelator. After cooling to room temperature, organogelator molecules precipitate out as fbrils which undergo non-covalent physical interactions amongst each other and form a three- dimensional fbrillar network structure. The apolar solvent is then immobilized by the gelator fbers and a semi-solid organogel is thus formed (30, 36, 37) (Figure 4). Mechanical homogenization and microirradiation This novel technique consists in a high speed homogenization using Ultra-Turrax ® before microwave heating. Commonly, organogels are formed using PREPARATION OF ORGANOGEL Generally, organogels are prepared by heating a mixture of a gelator and an organic liquid (or organic solvent) in order to obtain a dispersion mixture, which after cooling at room temperature, leads to the formation of a jelly structure. Organogelator molecule interactions induce a gelator organization into well-defned aggregates, such as tubular rods, fbrils and fbers. Mainly three methods are used for the organogel preparation: fuid-flled fber mechanism, solid fber mechanism and mechanical homogenization and microirradiation method. Fluid-flled fber mechanism The gelation process takes place with the addition of a trace amount of water into the solution of apolar solvent and surfactant, such as lecithin molecules. Before the addition of water, the surfactant is dispersed in the organic medium. With the addition of small amount of water, the surfactant molecules assemble themselves together to form micelles. Further addition of water makes the short tubular or cylindrical micellar aggregate. The water molecules bind stoichiometrically to the hydrophilic head of the surfactant molecules. The water molecules link two surfactant molecules together which forms linear networks with the hydrogen 16 H&PC Today - Household and Personal Care Today, vol. 10(4) July/August 2015