Effects of mechano-hydrolysis on PLGA composition and its degradation products

Poly(lactic-co-glycolic acid) (PLGA) is a widely used copolymer in the medical industry for tissue implants and drug-delivery systems. In vivo, these polymer matrices are subjected to concurrent fluid sorption, hydrolytic degradation, thermolysis, and mechanical loading. While extensive studies on how PLGA degrades via hydrolysis and thermolysis have been conducted, there is very limited information on how mechanical loading affects the degradation process and byproducts, and, more specifically, how the copolymer's composition itself might change during this process. In this study, Fourier-transform infrared (FTIR) spectroscopy was employed to track the evolution of functional groups, degradation products, and lactide-to-glycolide ratio at the specimen surface subjected to static mechanical load during hydrolytic degradation of PLGA 85/15 at human body temperature (37°C). These spectral results were further connected with one of our previous studies to correlate the polymer’s thermal properties, water uptake, and molecular weight. Analysis of the degradation products, namely carbonyl and carboxyl/carboxylate bands, revealed that static loading promotes earlier diffusion and neutralization of carboxylic end groups, thereby delaying the accumulation of carboxylate ions and the onset of autocatalytic degradation relative to non-loaded samples, which exhibited earlier carboxylate formation, pronounced swelling, stronger autocatalytic degradation, and eventual structural collapse. FTIR peak-fitting of the methyl and methylene bending vibrational modes further demonstrated an overall increase in the relative lactide content at the surface of both loaded and non-loaded PLGA 85/15 samples undergoing hydrolysis at 37ºC.