title: Polylactones 57. Biodegradable networks based on A-B-A triblock segments containing poly(ethylene glycol)s-syntheses and drug release properties.
abstract: Condensation of Bu(2)Sn(OMe)(2) with poly(ethylene glycol)s yielded macrocyclic tin alkoxides which were, in turn, used as cyclic initiators for the ring-expansion polymerization of epsilon-caprolactone, D,L-lactide, or trimethylene carbonate. The resulting cyclic triblock copolymers were in situ cross-linked with trimesoyl chloride. The lengths of the A-B-A triblock segments were varied via the monomer-initiator ratio (M/I) or via the lengths of the poly(ethylene glycol)s. After extraction with CH(2)Cl(2), the isolated networks were characterized by (1)H NMR spectroscopy, DSC measurements, and swelling experiments. The release of dexamethasone and 5-fluorouracil from two triblock networks was studied in physiological buffer solutions at 37 degrees C over a period of several weeks. A strong initial burst was found in all cases. Only a weak initial burst and a more continuous release was observed when networks of random L-lactide/epsilon-caprolactone copolymers were studied under the same conditions.
authors.affiliation: Institut für Technische und Makromolekulare Chemie, Bundesstr. 45, D-20146 Hamburg, Germany.
authors.forename: Hans R
authors.initials: HR
authors.lastname: Kricheldorf
authors.forename: Björn
authors.initials: B
authors.lastname: Fechner
authors.forename: Ariella
authors.initials: A
authors.lastname: Shikanov
authors.forename: Abraham
authors.initials: A
authors.lastname: Domb
mesh_terms: D020341:Absorbable Implants; D002152:Calorimetry, Differential Scanning / Q000379:methods; D003907:Dexamethasone / Q000737:chemistry; D004146:Dioxanes / Q000737:chemistry; D016503:Drug Delivery Systems / Q000379:methods*; D005472:Fluorouracil / Q000737:chemistry; D007783:Lactones / Q000138:chemical synthesis / Q000737:chemistry* / Q000378:metabolism*; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000737:chemistry; D011091:Polyesters / Q000737:chemistry; D011092:Polyethylene Glycols / Q000737:chemistry*; D011108:Polymers / Q000138:chemical synthesis / Q000737:chemistry* / Q000378:metabolism*; D014001:Tin / Q000737:chemistry
chemical_list: D004146:Dioxanes; D007783:Lactones; D009942:Organometallic Compounds; D011091:Polyesters; D011108:Polymers; C016240:polycaprolactone; D011092:Polyethylene Glycols; C443643:trimethylene carbonate; C033616:poly(lactide); D014001:Tin; D003907:Dexamethasone; D005472:Fluorouracil