Document Detail


pH and osmotic pressure inside biodegradable microspheres during erosion.
MedLine Citation:
PMID:  10397604     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
PURPOSE: To measure changes in pH as well as osmotic pressure in aqueous pores and cavities inside biodegradable microspheres made from polymers such as poly(D,L-lactic acid) (PLA) and poly(D,L-lactic acid -co- glycolic acid) (PLGA). METHODS: The internal osmotic pressure inside eroding PLA microspheres was analyzed with differential scanning calorimetry (DSC) in a temperature range of 10 to--25 degrees C. The osmotic pressure was calculated from the melting peaks of the aqueous phase using purity analysis. For pH determination, PLGA microspheres were loaded with a pH-sensitive spin probe which allowed the determination of pH by electron paramagnetic resonance (EPR). RESULTS: The osmotic pressure in PLA microspheres increased to 600 mOsm within four days and decreased to 400 mOsm after two weeks. The pH in PLGA microspheres in this study was < or =4.7. Basic drugs such as gentamicin free base or buffering additives led to a pH increase. In no case, however, did the internal pH exceed a value of 6 within 13 hours. CONCLUSIONS: DSC and EPR are useful techniques to characterize the chemical microenvironment inside eroding microspheres. This data in combination with detailed information on peptide and protein stability could allow in the future to predict the stability of such compounds within degradable polymers.
Authors:
A Brunner; K Mäder; A Göpferich
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Pharmaceutical research     Volume:  16     ISSN:  0724-8741     ISO Abbreviation:  Pharm. Res.     Publication Date:  1999 Jun 
Date Detail:
Created Date:  1999-08-18     Completed Date:  1999-08-18     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  8406521     Medline TA:  Pharm Res     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  847-53     Citation Subset:  IM    
Affiliation:
Aventis Research & Technologies, Industriepark Hoechst, Frankfurt am Main, Germany.
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MeSH Terms
Descriptor/Qualifier:
Algorithms
Biodegradation, Environmental
Hydrogen-Ion Concentration
Lactic Acid / chemistry*,  metabolism
Microspheres*
Models, Chemical
Osmotic Pressure
Polyglycolic Acid / chemistry*,  metabolism
Polymers / chemistry*,  metabolism
Chemical
Reg. No./Substance:
0/Polymers; 0/polylactic acid-polyglycolic acid copolymer; 26009-03-0/Polyglycolic Acid; 26100-51-6/poly(lactic acid); 50-21-5/Lactic Acid

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine


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