The impact of monomer sequence and stereochemistry on the swelling and erosion of biodegradable poly(lactic-co-glycolic acid) matrices

Abstract

Monomer sequence is demonstrated to be a primary factor in determining the hydrolytic degradation profile of poly(lactic-co-glycolic acid)s (PLGAs). Although many approaches have been used to tune the degradation of PLGAs, little effort has been expended in exploring the sequence-control strategy exploited by nature in biopolymers. Cylindrical matrices and films prepared from a series of sequenced and random PLGAs were subjected to hydrolysis in a pH 7.4 buffer at 37 °C. Swelling ranged from 107% for the random racemic PLGA with a 50:50 ratio of lactic (L) to glycolic (G) units to 6% for the sequenced alternating copolymer poly LG. Erosion followed an inverse trend with the random 50:50 PLGA showing an erosion half-life of 3-4 weeks while poly LG required ca. >10 weeks. Stereosequence was found to play a large role in determining swelling and erosion; stereopure analogs swelled less and were slower to lose mass. Molecular weight loss followed similar trends and increases in dispersity correlated with the onset of significant swelling. The relative proportion of rapidly cleavable G-G linkages relative to G-L/L-G (moderate) and L-L (slow) correlates strongly with the degree of swelling observed and the rate of erosion. The dramatic sequence-dependent variation in swelling, in the absence of a parallel hydrophilicity trend, suggest that osmotic pressure, driven by the differential accumulation of degradation products, plays an important role.

Soybean Lecithin‐Mediated Nanoporous PLGA Microspheres with Highly Entrapped and Controlled Released BMP‐2 as a Stem Cell Platform

“…PLGA is one of the most applied polymers for preparing microsphere systems in the field of medical applications . Its degradation kinetics can be adjusted by changing monomer sequence and stereochemistry . Phospholipids are small amphipathic molecules and are the main components of cell membranes .…”

Precision Aliphatic Polyesters via Segmer Assembly Polymerization

“…The result reveals that a more gradual burst release is achieved by employing microparticles composed of sequenced PLGAs. Pioneered by this group, biomedical applications of microparticles and matrices composed of sequence-engineered PLGAs are currently under exploration [ 106 , 107 ]. Nevertheless, it is noteworthy that transesterification was occasionally observed during polymerization, thus disrupting microstructural periodicity.…”

Assessment of Chemical and Mechanical Properties of Polymers Aiming to Replace the Stainless Steel in Distillation Column

“…Posteriorly, the samples returned to the autoclaves and to the oven during 30 days of testing, after this period, weight and area were measured once again. The purpose of measuring the weight and area was to detect the degree of swelling, which was done through equation 1 20 , and the increase of area in contact with ethanol. (1) Where W wet is the mass (g) of the wet material and W dry is the mass (g) of the dry material, that is, before the contact with the liquid.…”