title: Factors affecting the degradation rate of poly(lactide-co-glycolide) microspheres in vivo and in vitro.
abstract: The purpose of this work was to study the degradation of poly(lactide-co-glycolide) (PLG) microspheres in vivo and in vitro. Degradation rate constants were determined by measuring the polymer molecular weight as a function of time by gel-permeation chromatography. The effects of PLG chemistry and the effects of encapsulating the sparingly soluble salt zinc carbonate and the protein recombinant human growth hormone (rhGH) on the degradation rate were assessed. It was found that in vivo degradation was faster than in vitro degradation. In addition, different types of PLGs were found to degrade at different rates depending on the chemistry of the polymer end group and, to a lesser extent, the molecular weight. Finally, zinc carbonate was found to retard the degradation of some PLGs. These degradation studies have proved valuable in the design of sustained release microsphere products.
authors.affiliation: Alkermes Inc., Cambridge, MA 02139, USA. mark_tracy@alkermes.com
authors.forename: M A
authors.initials: MA
authors.lastname: Tracy
authors.forename: K L
authors.initials: KL
authors.lastname: Ward
authors.forename: L
authors.initials: L
authors.lastname: Firouzabadian
authors.forename: Y
authors.initials: Y
authors.lastname: Wang
authors.forename: N
authors.initials: N
authors.lastname: Dong
authors.forename: R
authors.initials: R
authors.lastname: Qian
authors.forename: Y
authors.initials: Y
authors.lastname: Zhang
mesh_terms: D000818:Animals; D001672:Biocompatible Materials / Q000737:chemistry / Q000378:metabolism; D001673:Biodegradation, Environmental / Q000187:drug effects; D002254:Carbonates / Q000494:pharmacology; D004337:Drug Carriers; D006801:Humans; D066298:In Vitro Techniques; D019344:Lactic Acid / Q000737:chemistry / Q000378:metabolism; D008297:Male; D008422:Materials Testing; D008863:Microspheres; D008970:Molecular Weight; D011100:Polyglycolic Acid / Q000737:chemistry / Q000378:metabolism; D000077182:Polylactic Acid-Polyglycolic Acid Copolymer; D011108:Polymers / Q000737:chemistry / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D017967:Zinc Compounds / Q000494:pharmacology
chemical_list: D001672:Biocompatible Materials; D002254:Carbonates; D004337:Drug Carriers; D011108:Polymers; D017967:Zinc Compounds; D000077182:Polylactic Acid-Polyglycolic Acid Copolymer; D011100:Polyglycolic Acid; D019344:Lactic Acid; C036650:zinc carbonate