Material-binding peptides empowering MP/NPs enrichment, detection, and quantification

The widespread production and application of synthetic polymers has resulted in an annual global output of over 400 million metric tons. While their desirable properties support modern infrastructure and products, the transition toward a circular polymer economy is expected to dramatically increase the release of micro- and nanoplastics into the environment. These particles originate from various sources, including textiles, packaging, and tire abrasion, and have become pervasive across ecosystems, such as air, water, food, beverages, and even human tissues. The lack of standardized methods, particularly for particles smaller than 5 mm, remains a key regulatory and scientific barrier, as acknowledged by the European Commission. To address this, the primary objective of this doctoral thesis was to develop enrichment and analytical methods using material-binding peptides for the reliable detection and quantification of MP/NPs in environmental water samples and human tissues. In the first part of the work, an enrichment platform called MagNanoTrap was developed. It is based on a custom-engineered bifunctional peptide (LCI-DZ-MBP1) that functionalizes Fe₃O₄ superparamagnetic nanoparticles. The LCI domain binds iron oxide beads, while MBP1 targets common plastic types such as polypropylene, polyethylene, polystyrene, and polyethylene terephthalate. This platform achieved an adsorption capacity of 3.95 ± 0.14 g/g for 500 nm polystyrene nanoparticles. In combination with pyrolysis–gas chromatography/mass spectrometry, the method enabled detection down to 0.061 µg of PS from only 1 L of water using 16 mg of coated SPIONs. The system proved effective across seven environmental water types, including river, lake, sea, and wastewater, for detecting a broad range of polymer types. In the second part, a dual-functional biohybrid catalyst system was developed, named Hooked for Decay, for simultaneous micro- and nanoplastics capture and degradation. This system combines a Grubbs-Hoveyda catalyst with a peptide variant (LCI_F16C) immobilized on iron oxide beads. It forms a hydrophobic polynorbornene coating via ring-opening metathesis polymerization, allowing rapid capture of various hydrophobic nanoplastics such as polypropylene, polyethylene, polystyrene, poly(ethylene terephthalate), poly(methyl methacrylate), and styrene-butadiene rubber. The system demonstrated a high adsorption capacity (5.53 ± 0.29 g/g for polystyrene nanoplastics) and a 99% recovery rate for styrene-butadiene rubber nanoplastics. Moreover, the embedded catalyst retained its ethenolysis activity, achieving a 6.5% degradation of styrene-butadiene rubber, validating the potential of combined capture and degradation. In the final part of this work, micro- and nanoplastics were successfully detected and quantified in 139 human kidney tissue samples using pyrolysis–gas chromatography/mass spectrometry. Eight different types of polymers were identified and quantified. Visualization of MP/NPs in kidney tissue was achieved using a fluorescently labeled peptide (“plastibody”). Importantly, an inverse correlation between MP/NP content and estimated glomerular filtration rate was observed, suggesting a possible link between particle accumulation and declining kidney function. In summary, this thesis presents significant advances in the enrichment, detection, quantification, and biological assessment of micro- and nanoplastics. Two peptide-based nanotechnologies were developed: MagNanoTrap, which facilitates the efficient capture, identification, and quantification of nanoplastics in environmental water samples; and Hooked for Decay, which not only captures hydrophobic nanoplastics but also enables partial degradation of styrene-butadiene rubber nanoparticles. Furthermore, this work provides evidence of micro- and nanoplastic accumulation in kidneys and its potential association with impaired kidney function. Together, these findings contribute to the development of next-generation tools for environmental monitoring and public health assessment in the context of plastic pollution.