Micro and Nanoplastics
Plastics have become essential resources for human daily lives due to their lightweight, versatility, and low cost, playing a fundamental role in several sectors, including transport, health, energy, and food. Despite these benefits, improper disposal of plastic waste has significant environmental impacts1. About 10 million tons of plastic waste end up in the ocean annually, raising environmental concerns about marine ecosystem pollution, mainly due to the generation of long-lasting chemical debris2–4. Plastics can be further degraded by abrasion and ultraviolet light into particles shorter than 5 mm, known as microplastics (MPs), or even smaller particles less than 100 nanometers, called nanoplastics (NPs)5,6. MPs can cause significant harm when ingested by small organisms, as they accumulate within the food chain, leading to the contamination of other animals and the surrounding environment7.
Before reaching our homes, drinking water undergoes treatment at wastewater plants which can partially remove MPs and other contaminants. However, significant amounts of these microparticles and most of the nanoparticles still escape the filtration process, resulting in the release of hundreds to thousands of particles per cubic meter of effluent8. This inefficiency in water treatment arises from the lack of standardized protocols for identifying, assessing, and quantifying micro/nanoplastics (MNPs) in freshwater ecosystems. Additionally, the absence of commercial filters designed to effectively remove these tiny contaminants from water adds to the challenge9. MNPs, along with toxic chemical additives found in plastic products, pose a serious threat to human health, potentially leading to inflammation, cellular damage, and endocrine disruption10. Learn more about the problem here.
How our Eco-Filter Works
Our filter is based on plastic-binding proteins (PBPs). As a proof of concept, we evaluated the plastic-binding efficiency of BaCBM211, a protein known to bind PET, PUR, and Nylon-6, which was originally used by the Kyoto team in 2019. We then utilized an open-source pipeline we developed, now available on our wiki, to create an improved PBP, BARBIE1. This pipeline enables other researchers to quickly design pollutant-binding proteins tailored to their specific needs. BARBIE1 has demonstrated superior effectiveness in affinity tests compared to the original BaCBM2.
To support our engineered proteins, the PBPs are fusioned to a spidroin matrix. This configuration ensures that even the smallest nanoplastics passing through conventional filtration systems are captured by our PBPs, thereby preventing harm to humans.
How the Biosensor Works
The sensor is positioned at both the water inlet and outlet to ensure the filter's efficiency and to monitor plastic concentration. It utilizes a newly developed microplastic sensor that relies on electrochemical impedance spectroscopy (EIS) and square wave voltammetry (SWV) measurements to accurately determine the concentration and size of microplastics12. It is important to note that the conventional sensor by Colson & Michel12 often struggles to detect very small microplastics and nanoplastics. Our biological component addresses this issue: by using PBPs to bind even to the smallest nanoplastic particles, we are able to enhance the electrochemical signal, thus improving the sensor's efficiency and selectivity.
Through our bioengineered BARBIE proteins, connected in the spider silk matrix and powered by our microplastic sensor, our team has developed a new device capable of removing even the tiniest microplastic particles from one of the most precious resources we all rely on: the drinking water.
References
1 Directorate-General for Research and Innovation (European Commission) et al. A Circular Economy for Plastics: Insights from Research and Innovation to Inform Policy and Funding Decisions. (Publications Office of the European Union, 2019).
2 Foundation, E. M. The new plastics economy: rethinking the future of plastics & catalysing action. (2016).
3 Böll, F. H. Atlas do plástico: Fatos e números sobre o mundo dos polímeros sintéticos. vol. 17 (2020).
4 Schmidt, C., Krauth, T. & Wagner, S. Export of Plastic Debris by Rivers into the Sea. Environ. Sci. Technol. 51, 12246–12253 (2017).
5 Arthur, C., Baker, J. E. & Bamford, H. A. Proceedings of the International Research Workshop on the Occurrence, Effects, and Fate of Microplastic Marine Debris, September 9-11, 2008, University of Washington Tacoma, Tacoma, WA, USA.
6 Yu, Z., Wang, J.-J., Liu, L.-Y., Li, Z. & Zeng, E. Y. Drinking Boiled Tap Water Reduces Human Intake of Nanoplastics and Microplastics. Environ. Sci. Technol. Lett. 11, 273–279 (2024).
7 Kosuth, M., Mason, S. A. & Wattenberg, E. V. Anthropogenic contamination of tap water, beer, and sea salt. PLOS ONE 13, e0194970 (2018).
8 Pivokonsky, M. et al. Occurrence of microplastics in raw and treated drinking water. Sci Total Environ 643, 1644–1651 (2018).
9 Upadhyay, S. et al. Microplastics in freshwater: Unveiling sources, fate, and removal strategies. Groundwater for Sustainable Development 26, 101185 (2024).
10 Mohapatra, P., Shubhadarshinee, L., Jali, B. R., Barick, A. K. & Mohapatra, P. Comparative Analysis of the Toxicity of Micro- and Nanoplastics along with Nanoparticles on the Ecosystem. in Toxic Effects of Micro- and Nanoplastics 399–414 (John Wiley & Sons, Ltd, 2024). doi:10.1002/9781394238163.ch18.
11 Weber, J. et al. Interaction of carbohydrate-binding modules with poly(ethylene terephthalate). Appl Microbiol Biotechnol 103, 4801–4812 (2019).
12 Colson, B. C. & Michel, A. P. M. Flow-Through Quantification of Microplastics Using Impedance Spectroscopy. ACS Sens. 6, 238–244 (2021).