title: Riboflavin-photosensitized changes in aqueous solutions of alginate. Rheological studies.
abstract: Interactions between photoexcited riboflavin (RF), promoted by irradiation in the range of 310-800 nm, and alginate have been studied in air equilibrated aqueous solutions with the aid of rheological methods. Light irradiation of RF causes under aerobic conditions fragmentation of alginate and a decrease in the shear viscosity and other rheological parameters of its solutions. The decrease is most pronounced in concentrated polymer solutions. The photochemical degradation of alginate is inhibited in the presence of the quenchers/scavengers d-mannitol, glutathione, potassium iodide, and sodium azide and in excess oxygen. The addition of thiourea to alginate-RF solutions leads to enhanced degradation of the polymer. Significant shear-thinning effects and deviations from the Cox-Merz rule are observed at higher polymer concentrations.
authors.affiliation: Department of Pharmaceutics, School of Pharmacy, University of Oslo, P.O. Box 1068, Blindern, Norway.
authors.forename: Stefania G
authors.initials: SG
authors.lastname: Baldursdóttir
authors.forename: Anna-Lena
authors.initials: AL
authors.lastname: Kjøniksen
authors.forename: Jan
authors.initials: J
authors.lastname: Karlsen
authors.forename: Bo
authors.initials: B
authors.lastname: Nyström
authors.forename: Jaan
authors.initials: J
authors.lastname: Roots
authors.forename: Hanne H
authors.initials: HH
authors.lastname: Tønnesen
mesh_terms: D000464:Alginates / Q000737:chemistry*; D020723:Glucuronic Acid / Q000737:chemistry*; D006603:Hexuronic Acids / Q000737:chemistry*; D010777:Photochemistry; D012212:Rheology; D012256:Riboflavin / Q000737:chemistry*; D012996:Solutions
chemical_list: D000464:Alginates; D006603:Hexuronic Acids; D012996:Solutions; D020723:Glucuronic Acid; D012256:Riboflavin