Determination of water-soluble acid distribution in poly(lactide-co-glycolide).
Determination of the kinetics of water-soluble degradation products inside poly(lactide-co-glycolide) (PLGA) delivery systems during polymer degradation is important to evaluate the polymer microclimate conditions, particularly microclimate pH changes for optimization of encapsulated drug stability. A pre-derivatization high-performance liquid chromatography (HPLC) method was developed for separation and quantification of water-soluble acid impurities and degradation products in PLGA. Thin PLGA films (approximately 200 microm) were incubated in PBS/0.02% Tween 80, pH 7.4, for 6 weeks. Water-soluble monomers and oligomers were obtained from polymer films after repeated CHCl(3)/H(2)O extraction and then derivatized into bromophenacyl esters. With the common chromophore, the esters were separated and quantified by HPLC with increased ultraviolet (UV) sensitivity at 254 nm. The total amount of water-soluble acids in the extract was validated by potentiometric titration with tetrabutyl ammonium hydroxide. During the first 3 weeks of incubation of PLGA 50:50 (inherent viscosity = 0.63 dL/g), the principal water-soluble acids in the polymer were glycolic, lactic, and lactoyllactic acids, and an unknown oligomer. After 4 weeks of incubation, a large fraction of higher molecular weight oligomers was observed. Pre-derivatization HPLC can be used to accurately measure water-soluble acid distribution, and may be invaluable to examine the degradation behavior of PLGAs, including the underlying mechanism of polymer microclimate pH development.
Ding
Amy G
AG
Department of Pharmaceutical Sciences, College of Pharmacy, The University of Michigan, Ann Arbor, MI 48109, USA.
Schwendeman
Steven P
SP
D000143:Acids / Q000032:analysis; D002851:Chromatography, High Pressure Liquid; D004566:Electrodes; D005079:Excipients; D007202:Indicators and Reagents; D019344:Lactic Acid / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D013058:Mass Spectrometry; D008567:Membranes, Artificial; D011100:Polyglycolic Acid / Q000737:chemistry*; D000077182:Polylactic Acid-Polyglycolic Acid Copolymer; D011108:Polymers / Q000737:chemistry*; D011199:Potentiometry; D012015:Reference Standards; D012995:Solubility; D014867:Water
D000143:Acids; D005079:Excipients; D007202:Indicators and Reagents; D008567:Membranes, Artificial; D011108:Polymers; D014867:Water; D000077182:Polylactic Acid-Polyglycolic Acid Copolymer; D011100:Polyglycolic Acid; D019344:Lactic Acid