An improved method to generate secondary nanoplastics and oligomers: application in ecotoxicology

• Published in: Environmental science. Nano 2025
• Main Authors: Gómez-Kong, Silvia, Tamayo-Belda, Miguel, Pulido-Reyes, Gerardo, Edo, Carlos, Verdú, Irene, Leganés, Francisco, Rosal, Roberto, González-Pleiter, Miguel, Fernández-Piñas, Francisca
• Format: Article
• Language: English
• ISSN: 2051-8153; 2051-8161
• DOI: 10.1039/D4EN00866A

Recent studies have highlighted the ecotoxicological effects of conventional primary nanoplastics (NPLs); however, the impacts of secondary NPLs and oligomers (Olig), especially those derived from biodegradable plastics, formed through fragmentation and natural degradation processes ( e.g. , photooxidation) remain underexplored. This gap is partly due to challenges in producing sufficient quantities for toxicity testing. An improved method to generate non-photooxidized (NP) and photooxidized (P) secondary NPLs and Olig from polybutylene adipate co -terephthalate (PBAT), a biodegradable plastic commonly used in agriculture mulching, which involves the mechanical breakdown of PBAT-microbeads with or without prior photooxidation is presented. PBAT was irradiated at ∼9.34 kW m −2 (approximately 120 times the solar irradiance) for 96 h, irradiation that corresponds to ∼16 months of average sunlight in the Iberian Peninsula (7.7 kWh m −2 per day). The toxicological effects on Chlamydomonas reinhardtii , a model green microalga of primary producers in freshwater ecosystems, were also assessed. The protocol yielded 0.199 mg of secondary NP-PBAT-NPLs and 10.275 mg of NP-PBAT-Olig per gram of PBAT-microbeads. PBAT-NPLs presented irregular spherical morphologies and hydrodynamic sizes ranging from 56.71 to 69.86 nm. HPLC and MALDI-TOF analysis identified linear and cyclic Olig, ranging from dimers to 19 repeated-units Olig. PBAT-NPLs and PBAT-Olig exhibited negative surface charges, suggesting colloidal stability in water. While PBAT-NPLs and PBAT-Olig did not inhibit algal growth in the short term, they induced reactive oxygen species overproduction at the environmentally relevant concentration of 0.01 mg L −1 and caused membrane depolarization, impaired photosynthesis and lipid peroxidation at 10 mg L −1 . Non-photooxidized PBAT-NPLs exhibited the highest toxicity, followed by photooxidized PBAT-NPLs and both non-photooxidized and photooxidized PBAT-Olig. This study provides an efficient method for producing reference secondary NPLs and Olig and underscores the potential risks of PBAT towards primary producers in freshwater ecosystems.