CAST scientist Masashi Serizawa recently published a manuscript in which he investigated a novel size-exclusion chromatography hyphenated with mass spectrometry and ultraviolet (SEC-MS/UV) method to characterize poly lactide-co-glycolide (PLGA), and also co-authored work on the use of enzymes for polyester polymer degradation.
· SEC-MS characterization of PLGA:
Size-exclusion chromatography (SEC) hyphenated with MS is valuable for microstructure analysis. While SEC-UV/RI determines molecular weight distribution (MWD), SEC-MS is used for chemical composition distribution (CCD) and functionality-type distribution (FTD). However, previous applications of SEC-MS have failed to address the risk of polymer fragmentation during the analysis process. It is crucial to establish whether SEC-MS methods can be applied to biodegradable polymers and to recognize if fragmentation processes occurred during the SEC separation or during the ESI-MS process.
This study addresses fragmentation in PLGA analysis by optimizing SEC-MS conditions. We demonstrate that cesium iodide (CsI) minimizes fragmentation during electrospray ionization (ESI-MS), simplifying spectra and enabling differentiation of PLGA isomers. This facilitates accurate determination of CCD and FTD, even revealing “blockiness” when coupled with selective degradation.
Figure 1: schematic illustration of in-source fragmentation in SEC-MS, depending on ionization agents
The study is supported by the COAST/TKI-Chemistry POLY-SEQU-ENCHY project between the UvA and Corbion and is funded by Mitsubishi Chemical Corporation. This work was recently published in the Journal of the American Society for Mass Spectrometry and can be accessed freely at the link below:
https://doi.org/10.1021/jasms.4c00447
· Insights in the selectivity of enzymes for polyester co-polymer degradation
Another example of the SEC-MS/UV polymer application conducted by our group is the structural analysis of aromatic/aliphatic polyesters. To understand the polymer chain structure of aromatic/aliphatic polyesters, Eman et al. successfully developed a two novel thermostable cutinase that primarily degrade aliphatic ester bonds. These enzymes maintain activity at elevated temperatures of up to 90 °C thanks to enzyme engineering.
For both enzymes, higher hydrolysis rates were observed for aliphatic compared to aromatic homo-polyesters. SEC-MS analysis revealed that the hydrolysis of aliphatic/aromatic co-polyesters occurred at the aliphatic monomers, significantly reducing the molecular weight and changing the end-group composition. These results underline the importance of co-polymer composition in the biodegradation of co-polymer systems and demonstrate the applicability of enzymes for the analytical characterization of synthetic polymers by selectively reducing their molecular weight.
Figure 2: Results of SEC-MS/UV analysis of a copolymer containing aromatic/aliphatic polyesters,
comparing between before and after enzymatic degradation (The degradations were
performed at 71°C, using thermostable cutinase)
This research was funded by Topconsortium voor Kennis en Innovatie (TKI) Chemie, deployment project PPS-programma toeslag 2019 (CHEMIE.PGT.2020.020). This work was recently published in the Chemistry – A European Journal and can be accessed at the link below:
https://doi.org/10.1002/chem.202403879
