In Vitro Degradation of Poly(lactic-co-glycolic acid) Copolymers

 

Biodegradable polymers have become important biomedical materials. In particular linear aliphatic polyester polymers have been found to be very useful in biomedical applications due to their easy processability, good mechanical strength and excellent degradation properties. Polyglycolic acid (PGA), polylactic acid (PLA) and their random block copolymers poly(lactic-co-glycolic) acid (PLGA) are polyester polymers and are used mainly in degradable and absorbable sutures, implants, artificial skin graft and drug release systems. The main advantage of such synthetic biocompatible polymers is that degradation occurs via simple hydrolysis of the ester backbone in aqueous solution and that the degradation products can ultimately be metabolized or eliminated by the body.

 

Reaction of hydrolysis of an ester.

 

In drug delivery systems, the rate of drug release is known to be linked to the rate of degradation of the polymer. Consequently the dynamics of degradation needs to be controlled and tailored to the specific application. Several factors can influence the rate of degradation of PLGA including chemical architecture, structure, morphology, processing conditions and degradation media.

This project aims to address the influence of such factors by investigating their effect on thermodynamic properties and microstructures of PLGA with the aim of understanding, controlling and optimising scaffold morphology for drug delivery.

The degradation studies are performed at body temperature (37C) on solvent-cast films of controlled thickness and shape in different media including phosphate buffer solution, simulated body fluid and distilled water. Analysis techniques used to follow the degradation dynamics include potentiometry, optical microscopy (for example see figure below), gravimetry, gel permeation chromatography (GPC), differential scanning calorimetry (DSC) as well as infrared and Raman spectroscopy. The combination of these different techniques allows us to characterise and understand the in vitro degradation of the copolymers.

 

           

Optical micrographs for PLGA films degraded in 20 mL PBS at 37 C at different time points as indicated. The scale bar represents 5 mm.

 

Publications:

The impact of chemical composition on the degradation kinetics of poly(lactic-co-glycolic) acid copolymers cast films in phosphate buffer solution E. Vey, C. Roger, L. Meeham, J. Booth, M. Claybourn, A.F. Miller, A. Saiani; Polymer Degradation and Stability, 97, 358-365 (2012)

Degradation kinetics of poly(lactic-co-glycolic) acid block copolymer cast films in phosphate buffer solution as revealed by infrared and Raman spectroscopies; E. Vey, C. Roger, J. Booth, M. Claybourn, A.F. Miller, A. Saiani; Polymer Degradation and Stability, 96, 1882-1889 (2011)

Degradation mechanism of poly(lactic-co-glycolic) acid block copolymer cast films in sulphate buffer solution; E. Vey, C. Roger, L. Meeham, J. Booth, M. Claybourn, A.F. Miller, A. Saiani; Polymer Degradation and Stability, 93, 1869-1876 (2008)

In vitro degradation of poly(lactic-co-glycolic acid) random copolymers; E. Vey, A.F. Miller, M. Claybourn, A. Saiani; Macromolecular Symposia, 251, 81-87 (2007)

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