Quantitative HPLC–mass spectrometry analysis shows the drastic impact of the composition of aqueous and biochemical media on the release of soluble hydrolysis products from submicron polycaprolactone

Abstract

Accumulation of micro- and nanoplastics in the environment is a major concern, and biodegradable polymers are receiving growing interest as an alternative to more stable material. It remains yet to identify the degradation products of biodegradable plastics. In the present work, we studied polycaprolactone (PCL), a polymer used in a growing number of packaging and medical applications. We gathered quantitative data on the release of soluble oligomers from submicrometric PCL particles (100–1000 μm in diameter) throughout their degradation. This was made possible by the synthesis of well-characterized PCL oligomers, which were then used for the development of HPLC-mass spectrometry methods. The assay was first applied to degradation studies performed in aqueous media, in relationship to environmental degradation. We observed an influence of temperature and salinity, and obtained specific information on the mechanism of release of PCL hydrolysis products at the sub-micrometric scale. The same approach was then applied to study PCL degradation in cell culture media used in toxicity studies. Oligomers arising from the hydrolysis of PCL particles were released in both the presence and the absence of cells. The size distribution under these conditions was shifted to shorter oligomers than in water. This observation, supported by experiments on synthetic PCL oligomers, pointed to a significant contribution of fetal calf serum used as an additive in cell culture medium. The bulk of these results show that hydrolysis of submicrometric PCL particles and the subsequent production of oligomers is an efficient process that is strongly modulated by the degradation medium.