title: Phosphated crosslinked guar for colon-specific drug delivery. I. Preparation and physicochemical characterization.
abstract: Guar gum (GG) was crosslinked with increasing amounts of trisodium trimetaphosophate (STMP) to reduce its swelling properties for use as a vehicle in oral delivery formulations, especially drug delivery systems aimed at localizing drugs in the distal portions of the small bowel. Swelling of GG in artificial gastrointestinal fluids was reduced from 100 to 120-fold (native GG) to 10-35-fold depending on the amount of crosslinker used, showing a bell-shape dependency. As a result of the crosslinking procedure GG lost its non-ionic nature and became negatively charged. This was demonstrated by methylene blue (MB) adsorption studies and swelling studies in sodium chloride solutions with increasing concentrations in which the hydrogels' network collapsed. The adsorption of MB was also used to characterize the degree of the GG crosslinking, from which the effective network density was calculated. In addition, effective network density was calculated from elasticity measurements. Both measurements showed that the crosslinking density (but not swelling) of the new products was linearly dependent on the amount of STMP used in the reaction.
authors.affiliation: The Hebrew University of Jerusalem, Faculty of Medicine, School of Pharmacy, P.O. Box 12065, Jerusalem, Israel.
authors.forename: I
authors.initials: I
authors.lastname: Gliko-Kabir
authors.forename: B
authors.initials: B
authors.lastname: Yagen
authors.forename: A
authors.initials: A
authors.lastname: Penhasi
authors.forename: A
authors.initials: A
authors.lastname: Rubinstein
mesh_terms: D000327:Adsorption; D002240:Carbohydrate Sequence; D003106:Colon / Q000378:metabolism*; D003432:Cross-Linking Reagents / Q000737:chemistry*; D016503:Drug Delivery Systems; D004548:Elasticity; D005685:Galactans / Q000008:administration & dosage / Q000138:chemical synthesis* / Q000493:pharmacokinetics; D020100:Hydrogels / Q000008:administration & dosage / Q000138:chemical synthesis / Q000737:chemistry; D008351:Mannans / Q000008:administration & dosage / Q000138:chemical synthesis* / Q000493:pharmacokinetics; D008751:Methylene Blue / Q000737:chemistry; D008969:Molecular Sequence Data; D009928:Organ Specificity; D009994:Osmolar Concentration; D014677:Pharmaceutical Vehicles / Q000008:administration & dosage / Q000138:chemical synthesis* / Q000493:pharmacokinetics; D053149:Plant Gums; D011122:Polyphosphates / Q000008:administration & dosage / Q000138:chemical synthesis* / Q000493:pharmacokinetics; D012965:Sodium Chloride / Q000737:chemistry; D012996:Solutions
chemical_list: D003432:Cross-Linking Reagents; D005685:Galactans; D020100:Hydrogels; D008351:Mannans; D014677:Pharmaceutical Vehicles; D053149:Plant Gums; D011122:Polyphosphates; D012996:Solutions; D012965:Sodium Chloride; C007894:guar gum; C009293:trimetaphosphoric acid; D008751:Methylene Blue