Labeling of PET and PP nanoplastic test materials with non-leachable π-conjugated fluorescent polymers

Micro- and nanoplastic (MNP) particles are widely present in nature, mainly due to the extensive overuse of single-use plastics combined with poor waste management. Despite the diversity in the environment, many experimental studies still rely almost exclusively on polystyrene as a model plastic test material, while other environmentally relevant polymers remain underrepresented. In addition, labeled MNP test materials suitable for biological studies are still limited. In this study, nanosized polyethylene terephthalate (PET) and polypropylene (PP) particles were produced using a co-precipitation approach with the fluorescent π-conjugated polymer, poly(9,9-dioctylfluorene-alt-benzothiadiazole) (F8BT) at low (0.8 % w/w) and high (3–5 % w/w) F8BT content. Fluorescently labeled MNPs (75–85 % dye internalization) could be produced with > 85 % of the particles in the submicron size range. Co-precipitation of F8BT with PET produced a subset of spindle-shaped particles, while F8BT-labeled PP particles were primarily spherical. The fluorescence limit of detection of the F8BT labeled PET and PP was ~0.2 µg/mL for both systems. The strong fluorescence enabled measurements of cell uptake using an innovative exposure system, the FlowCube, which overcomes dosimetry issues with buoyant particles. This work provides an innovative approach to producing fluorescently labeled PET and PP nanoplastic test materials for environmental and biological studies.