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The influence of pH on the molecular degradation mechanism of PLGA

Published online by Cambridge University Press:  30 October 2018

Rainhard Machatschek ,
Burkhard Schulz  and
Andreas Lendlein
Rainhard Machatschek
Affiliation:
Institute of Biomaterial Science, Helmholtz-Zentrum Geesthacht and Berlin-Brandenburg Center for Regenerative Therapies, Kantstraße 55, 14513 Teltow, Germany
Burkhard Schulz
Affiliation:
Institute of Biomaterial Science, Helmholtz-Zentrum Geesthacht and Berlin-Brandenburg Center for Regenerative Therapies, Kantstraße 55, 14513 Teltow, Germany Institute of Chemistry, University of Potsdam, Karl-Liebknecht-Straße 24-25,14469 Potsdam, Germany
Andreas Lendlein*
Affiliation:
Institute of Biomaterial Science, Helmholtz-Zentrum Geesthacht and Berlin-Brandenburg Center for Regenerative Therapies, Kantstraße 55, 14513 Teltow, Germany Institute of Chemistry, University of Potsdam, Karl-Liebknecht-Straße 24-25,14469 Potsdam, Germany
*
*Correspondence to: Andreas Lendlein, Institute of Biomaterial Science and Berlin-Brandenburg Center for Regenerative Therapies, Helmholtz-Zentrum Geesthacht, Kantstraße 55, 14513 Teltow, Germany. E-Mail: andreas.lendlein@hzg.de
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Abstract

Poly[(rac-lactide)-co-glycolide] (PLGA) is used in medicine to provide mechanical support for healing tissue or as matrix for controlled drug release. The properties of this copolymer depend on the evolution of the molecular weight of the material during degradation, which is determined by the kinetics of the cleavage of hydrolysable bonds. The generally accepted description of the degradation of PLGA is a random fragmentation that is autocatalyzed by the accumulation of acidic fragments inside the bulk material. Since mechanistic studies with lactide oligomers have concluded a chain-end scission mechanism and monolayer degradation experiments with polylactide found no accelerated degradation at lower pH, we hypothesize that the impact of acidic fragments on the molecular degradation kinetics of PLGA is overestimated. By means of the Langmuir monolayer degradation technique, the molecular degradation kinetics of PLGA at different pH could be determined. Protons did not catalyze the degradation of PLGA. The molecular mechanism at neutral pH and low pH is a combination of random and chainend-cut events, while the degradation under strongly alkaline conditions is determined by rapid chainend cuts. We suggest that the degradation of bulk PLGA is not catalyzed by the acidic degradation products. Instead, increased concentration of small fragments leads to accelerated mass loss via fast chain-end cut events. In the future, we aim to substantiate the proposed molecular degradation mechanism of PLGA with interfacial rheology.

Keywords

biomaterialmolecular weightmicroscalepolymer
Type
Articles
Information
MRS Advances , Volume 3 , Issue 63: International Materials Research Congress XXVII , 2018 , pp. 3883 - 3889
Copyright
Copyright © Materials Research Society 2018 

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