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 debris^2–4. 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.

Why B.A.R.B.I.E?

The idea for our project emerged during the Latin America competition iGEM Design League 2023 in which our team was the grand prize winner of the season by developing the first version of the project B.A.R.B.I.E (Bioengineered Approach for Removal of microplastics through Bioremediation and Innovative Electromagnetics). This initial iteration involved a strategy for detecting and removing MPs in water treatment plants using an impedance-based sensor and plastic-binding proteins, respectively.

Our team of scientists identified areas for improvement in tackling microplastic pollution and decided to shift our focus from water treatment plants to water filters. This led to the development of B.A.R.B.I.E 4.0 (Bioengineered Aquatic pollutants Removal and Bio-sensing through Integrated Eco-filter), an innovative solution designed to enhance pollutant removal. This brand new version features an Eco-filter built with a spidroin matrix - the protein found in spider silk - coupled with plastic-binding proteins and an impedance-based biosensor to enhance the efficiency of MPs and NPs detection. The "4.0" in our name signifies both a nod to Industry 4.0, reflecting our integration of advanced technologies, and the four iterative DBTL (Design-Build-Test-Learn) cycles we went through to refine and perfect this strategy.

Throughout the design process, our team realized B.A.R.B.I.E 4.0’s potential goes far beyond MNP removal. By leveraging computational tools to create custom proteins that bind efficiently to specific pollutants, we envisioned B.A.R.B.I.E 4.0 as a platform for broader applications. This includes enabling scientists and students from iGEM teams worldwide to design their own pollutant-specific proteins tailored to various environmental contaminants. Like the versatility of Barbie herself, B.A.R.B.I.E 4.0 is designed to adapt to numerous challenges, offering a flexible and innovative approach to fight pollution. The concept is simple: "Show us the pollutant, and we'll create a protein that binds to it."

Integrated Water Eco-Filter and Biosensor

As our proof-of-concept, we are focusing on addressing MNPs that enter our homes through tap water or by passing through conventional water filters. To tackle this, we developed an innovative approach for household water filters. This filter features a matrix made of spider silk proteins, engineered to bind specifically to MNPs through custom-designed plastic-binding proteins (PBPs). But we had one concern: could this filter capture the tiniest MNPs particles? To address this, our bioinformaticians team conducted molecular dynamics simulations, allowing us to determine the smallest size of particles that this advanced filter can effectively capture.

To ensure the filter’s effectiveness, we integrated the developed biosensor at both the inlet and outlet of the filtration system. These biosensors measure the removal efficiency of MNPs in real-time, providing users with clear feedback on how well the filter reduces their exposure to harmful plastic particles.

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).