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Generation and characterization of secondary nanoplastics and oligomers from PBAT and their toxicity towards the freshwater microalga C. reinhardtii
Summary
This study generated and characterized secondary nanoplastics and oligomers from biodegradable PBAT polymers, examining whether biodegradable plastics produce hazardous nanoscale breakdown products. Biodegradable PBAT was found to generate nanoplastics and oligomers during degradation, raising concern that these materials are not environmentally benign despite their biodegradable classification.
The production of biodegradable plastics has increased in recent years, as they are proposed as a substitute for conventional plastics. The ecotoxicological effects of primary nanoplastics (NPLs) have been extensively studied in the literature. However, little is known about the effects of biodegradable plastics, secondary NPLs, and oligomers generated by their degradation. In this study, we further developed a high-throughput protocol for the obtention of elevated quantities of isolated fractions of secondary NPLs and oligomers from commercial poly (butylene-adipate-co-terephthalate; PBAT), a biodegradable plastic frequently used in agriculture mulching. Secondary PBAT nanoplastics (PBAT-NPLs) and Secondary PBAT oligomers (PBAT-Oligs) were obtained by mechanical breakdown and photooxidation of pristine PBAT microbeads. We have also compared the physicochemical properties and toxicological effects of secondary NPLs and oligomers from photooxidized and non-photoxidized PBAT on the green microalga Chlamydomonas reinhardtii, which serves as an important model organism in freshwater ecosystems due to its role as a primary producer. To characterize the physicochemical properties of secondary PBAT-NPLs and PBAT-Oligs, techniques such as High-pressure liquid chromatography (HPLC), matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) dynamic light scattering (DLS), electrophoretic light scattering (ELS), scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDX), Fourier transform infrared spectroscopy (FTIR), and dry weight measurement were employed. To investigate the effects of the secondary PBAT-NPLs and PBAT-Oligs, C. reinhardtii was exposed to concentrations ranging from 0.01 to 10 mg/L of both materials. The following parameters were assessed: cellular growth, contents of photosynthetic pigments, ROS generation, and membrane potential. Results showed that secondary PBAT-NPLs and PBAT-Oligs can trigger ROS overproduction, and cause membrane depolarization. However, in the short term, no differences between control and treatment groups were shown in cellular growth and photosynthetic pigments after exposure. Taken together, this study aims to unravel the underlying mechanisms governing the potential biological impact of secondary biodegradable NPLs and oligomers. Also see: https://micro2024.sciencesconf.org/557037/document