title: Coagels from alkanoyl-6-O-ascorbic acid derivatives as drug carriers: structure and rheology.
abstract: 6-O-Ascorbic acid alkanoates (ASCn, where n is the number of carbon atoms in the alkyl chain) behave as surfactants and form stable supramolecular assemblies in water, depending on chemical structure, concentration and temperature. In concentrated water dispersions, ASCn form liquid crystalline structures ('coagels'), below the critical micellar temperature (CMT), with a typical Krafft phenomenon. Such semisolid systems incorporate and stabilize drugs like anthralin, which is insoluble and unstable in aqueous media. The rheological behavior of coagels obtained from aqueous ASC8, ASC10, ASC11, ASC12, ASC14 and ASC16 was evaluated and related to the coagel structure. For ASC8, ASC12, ASC14 and ASC16 complex rheology was observed and spur values were determined. This behavior is indicative of a high three-dimensional structure. The spur value represents a sharp point of structural breakdown at low shear rate. At this point the semisolids acquire pseudoplastic flow with a very low viscosity. Instead, ASC10 and ASC11 coagels showed pseudoplastic flow and--in the case of ASC11--thixotropy was observed. The ASCn coagel rheological behavior and their capability to load pharmacologically active compounds point to a potentially valuable capacity for such systems as drug carriers.
authors: Departamento de Farmacia, Fac. de Ciencias Químicas, Universidad Nacional de Córdoba, Ciudad Universitaria, 5000 Córdoba, Argentina.
authors: Santiago
authors: S
authors: Palma
authors: Alvaro
authors: A
authors: Jiménez-Kairuz
authors: Laura
authors: L
authors: Fratoni
authors: Pierandrea
authors: P
authors: Lo Nostro
authors: Ruben
authors: R
authors: Manzo
authors: Daniel
authors: D
authors: Allemandi
mesh_terms: D001205:Ascorbic Acid / Q000737:chemistry*; D004337:Drug Carriers / Q000737:chemistry*; D005782:Gels / Q000737:chemistry*; D012212:Rheology
chemical_list: D004337:Drug Carriers; D005782:Gels; D001205:Ascorbic Acid