Coacervate Droplet Sequestration of Heterogeneous Nanoplastics With Elastin-Like Polypeptides

Nanoplastics generated from waste in our ecosystems are becoming increasingly prevalent as bulk plastics exposed to natural factors fragment over time. These incidental nanoplastics span a wide range of physicochemical properties, which makes studying nanoplastic interactions in biological systems difficult. Here, we characterized incidental nanoplastics generated through mechanical abrasion and their interactions with polypeptide coacervate droplets to probe the dominant surface features of the nanoplastics. We used elastin-like polypeptides to create hydrophobic or charged coacervate microenvironments. Using optical microscopy and fluorescence quantification, we observed that nanoplastics made from polyethylene terephthalate (nPET), nylon 6 (nPA), and polystyrene (nPS) exhibited distinct partitioning behavior with more favorable interactions with hydrophobic droplets. This indicated that the hydrophobic polymer backbone was the predominate factor driving interactions despite exposed functional groups, in contrast to findings with model carboxylated latex nanospheres (nPS-COOH). Furthermore, the partitioning of incidental nanoplastics into the hydrophobic droplets was able to capture over 80% of nPET, and after recovery of the protein droplet, was able to cumulatively capture over 70% of the nPET feedstock across multiple cycles. This work explores the nuanced surface characteristics of incidental nanoplastics, expands the application of coacervates as chemical probes, and demonstrates an approach for effective nanoplastic removal.