Organic chemistry

Polymer chemistry

Lactic acid

Glycolic acid

Bacteria

Nuclear magnetic resonance spectroscopy

Stereochemistry

Biology

Hydrolysis

Nuclear chemistry

Chemistry

In vitro

PLGA

Biodegradable polymer

Polymer

Genetics

Biochemistry

Drug Delivery and Translational Research

Poly(lactic-co-glycolic acid) (PLGA) is among the most common of biodegradable polymers studied in various biomedical applications such as drug delivery and tissue engineering. To facilitate the understanding of the often overlooked impact of PLGA microstructure on important factors affecting PLGA performance, we measured four key parameters of 17 commonly used commercial PLGA polymers (Expansorb®, Resomer®, Purasorb®, Lactel®, and Wako®) by NMR spectroscopy. 1HNMR and 13CNMR spectra were used to determine lactic to glycolic ratio (L/G ratio), polymer end-capping, glycolic blockiness (Rc), and average glycolic and lactic block lengths (LG and LL). In PLGAs with a labeled L/G ratio of 50/50 and acid end-capping, the actual lactic content slightly decreased as molecular weight increased in both Expansorb® and Resomer®. Whether or not acid- or ester-, termination of these PLGAs was confirmed to be consistent with their brand labels. Moreover, in the ester end-capped 75/25 L/G ratio group, the blockiness value (Rc) of Resomer® RG 756S (Rc: 1.7) was highest in its group; whereas for the 50/50 acid end-capped group, Expansorb® DLG 50-2A (Rc: 1.9) displayed notably higher values than their counterparts. Expansorb® 50-2E (LL: 2.5, LG: 2.6) and Resomer® RG 502 (LL: 2.6, LG: 2.5) showed the lowest block lengths, suggesting they may undergo a steadier hydrolytic process compared to random, heterogeneously distributed PLGA. Graphical abstract

Characterization of commercial PLGAs by NMR spectroscopy