title: The potential of a microencapsulated urease-zeolite oral sorbent for the removal of urea in uremia.
abstract: Although successful in reducing urea levels, the use of oral microcapsules containing a urease-silica adduct and a zirconium phosphate ion exchanger result in a number of problems, including a negative calcium balance. In this study, it is demonstrated that the use of microcapsules containing a urease-zeolite preparation may be a potential route to urea removal. The use of zeolite ion exchangers, and zeolite W in particular, can alleviate the problems encountered with zirconium phosphate. Unlike zirconium phosphate, zeolite W is nonselective toward calcium ions and is stable at the high pH found in the intestinal tract. Zeolite W, when present in the sodium form, has a high ammonium capacity of 3.6 mEq NH4+/g zeolite under simulated intestinal conditions; its reactivity to ammonium is also higher. The application of enzyme envelopes to zeolite particles is a novel immobilization procedure that does not involve the use of colloidal silica and can reduce the amount of ingested material by as much as 25%. The current in vitro study shows that cellulose acetate butyrate microcapsules, containing a urease-zeolite preparation, remove up to 80% of urea in less than 1 hour. These microcapsules can be dried and retain activity when sealed in a jar at 4 degrees C.
authors.affiliation: Artificial Cells and Organs Research Centre, McGill University, Montreal, Quebec, Canada.
authors.forename: M V
authors.initials: MV
authors.lastname: Cattaneo
authors.forename: T M
authors.initials: TM
authors.lastname: Chang
mesh_terms: D000538:Aluminum Silicates / Q000737:chemistry*; D000641:Ammonia; D002214:Capsules; D003432:Cross-Linking Reagents / Q000737:chemistry; D004355:Drug Stability; D006801:Humans; D007474:Ion Exchange; D008954:Models, Biological; D010316:Particle Size; D016060:Sorption Detoxification; D014508:Urea / Q000032:analysis*; D014510:Urease / Q000737:chemistry*; D014511:Uremia / Q000628:therapy*; D017641:Zeolites
chemical_list: D000538:Aluminum Silicates; D002214:Capsules; D003432:Cross-Linking Reagents; D017641:Zeolites; D000641:Ammonia; D014508:Urea; D014510:Urease