Micro and Nanoplastic Filtering

Discussions about the remediation of micro and nanoplastics have been increasingly frequent, as these pollutants pose a significant threat to both aquatic ecosystems and human health¹. Microplastics (MPs), defined as particles smaller than 5 mm, and nanoplastics (NPs), which are even smaller, can originate from the degradation of larger plastic debris or from direct sources such as personal care products and industrial processes. Once released into the environment, they can persist for decades, accumulating in waterways and entering the food chain through aquatic organisms. This accumulation not only affects wildlife but also introduces toxic substances to humans through the consumption of contaminated water and food sources.

Highlighting the danger and the community's concern about this type of contamination¹, researchers and environmental advocates have increasingly called for effective methods to detect, capture, and remove these pollutants. Existing water treatment methods often fall short when it comes to capturing the smallest particles, emphasizing the urgent need for new technologies capable of addressing this challenge, see more in Understanding the Problem section.

Known MNPs Removal Methods

In order to develop an effective and consistent method for the removal of micro and nanoplastics (MNPs), it is essential to first understand the current methods reported in the literature, along with their strengths and limitations². As the global awareness of plastic pollution increases, so too does the urgency for developing technologies capable of addressing this challenge. Consequently, numerous reviews have been published, exploring the range of techniques available for MNP remediation.

In this section, we will describe some of the most well-known methods, highlighting their advantages and shortcomings. This overview will serve as a foundation for introducing our team's proposed solution: the B.A.R.B.I.E. filter, which seeks to combine the best features of existing technologies while overcoming their limitations.

As shown in Figure 1, a wide variety of MNP remediation methods exist, each with its own approach and applicability. The CNPEM.Brazil team aimed to select a method that would be not only efficient but also accessible to the general population, ensuring that it could be easily implemented in household water filtration systems.

Adsorption methods, coagulation-flocculation-sedimentation, advanced oxidative processes (AOPs), and membrane filtration are among the most common techniques for MNP removal, each with its own advantages and limitations.

Each of these methods has been explored to some extent in the context of large-scale water treatment or industrial applications, but their integration into household filtration systems presents unique challenges. For a technology to be viable in home filters, it must be efficient, cost-effective, and safe for continuous use by consumers. Furthermore, it should not rely on extreme conditions, such as high temperatures or the use of harmful chemicals, which could pose risks during regular operation. By examining the pros and cons of these established methods, we can better understand which approach offers the best balance of performance and practicality.

In Table 1, we summarize these methods, providing an overview of their applicability and the challenges they present when considering their integration into a household filtration system.

Table 1: Overview of MNP Removal Methods

Method	Advantages	Disadvantages
Physical Adsorption	Low cost, simple implementation	Requires low temperatures; less effective at very small particle sizes
Chemical Adsorption	Effective for a wide range of contaminants	Requires high temperatures, difficult to implement in household filters due to chemical reactions
Coagulation-Flocculation-Sedimentation	Effective in large-scale treatment plants	Time-consuming, involves chemical reagents that may be harmful if not fully removed
Advanced Oxidative Processes (AOPs)	Potential for highly efficient contaminant removal, ongoing research	Expensive, generates waste, relies on complex chemical reactions
Membrane Filtration	Widely used in home filters, eco-friendly, allows for MNP separation	May require advanced membranes for smaller NPs

Given these characteristics, membrane filtration methods stand out as the most viable option for integration with our technology. They are already present in the vast majority of home water filters around the world and offer an eco-friendly way to separate MNPs. This type of system also provides a straightforward method for incorporating the engineered protein developed by our team, as the B.A.R.B.I.E project combines membrane filtration techniques with bioremediation.

Biofiltering and B.A.R.B.I.E. Filter Conceptualization

The idea for the B.A.R.B.I.E. filter originated from the knowledge of the engineered protein Barbie1's interaction with plastics. Given this protein's ability to bind to plastic particles, our team decided to use it as a bioactive layer within the filter, capable of capturing even the smallest plastic particles. To achieve this, we needed a suitable substrate to support this interaction. We chose protein nanofibers due to their potential as biofilters. The combination of nanofibers and the Barbie1 protein would create an effective barrier, capable of trapping plastic particles through protein-plastic affinity.

With the goal of reaching as many people as possible with our solution, the CNPEM-Brazil team focused on developing a membrane filter incorporating these plastic-binding proteins (PBPs), supported on protein nanofibers. The development of filters based on protein nanofiber hydrogels has already been reported in the literature³, and our team aimed to implement this biological component in widely available filter models.

By integrating these cutting-edge materials into a household-friendly design, our team sought to create a highly efficient, yet accessible, filtration system, ensuring that the solution can be implemented in standard water filters, making it practical for everyday use.

In addition to the bioactive layer, we aimed to use a filter design that was both cost-effective and widely available. The goal was to ensure that the entire filtration system could be easily adopted in household settings without complex modifications. To this end, we considered the most common filtration designs, activated carbon and reverse osmosis.

The selection of an activated carbon filter was based on its wide availability and simplicity of use in most household water filtration systems. To further evaluate the viability of using activated carbon as the base for our B.A.R.B.I.E. filter, we compared it with reverse osmosis filtration. The comparison highlights the practicality, cost, and complexity of both options. In Table 2, we summarize the key characteristics of each method.

Table 2: Comparison Between Activated Carbon Filters and Reverse Osmosis

	Activated Carbon Filter	Reverse Osmosis
Price	Affordable (~U$11.00)	Expensive (~U$110.00)
Frequency in households	Common in the majority of household filtration systems	Rare, mainly used in specialized, high-end filtration units
Complexity	Extremely simple to use and replace	Complex setup, often integrated into larger systems
Maintenance	Easy to replace filters	Difficult maintenance, often requiring professional help
Viability for B.A.R.B.I.E	Adaptable for incorporating the bioactive BARBIE layer	Potentially adaptable

Prototype

With the basic concept defined, the next step was to develop a prototype based on the type of filter assessed as most viable. Since the B.A.R.B.I.E. filter would be designed for use in common household water filters, we proceeded with the development of an initial prototype. To achieve this, we modeled the filter in 3D using Autodesk INVENTOR software.

The design incorporated a layered structure with the Barbie1 protein+Nanofiber system being the main component in one layer, while the additional layers would resemble those found in conventional household filters. These layers were intended to work together to enhance the capture of micro and nanoplastics, see more in Layers section. Figure 2 shows the first prototype of the B.A.R.B.I.E filter, developed primarily to provide a visual representation of the initial concept [hyperlink to the layers section].

It is important to note that conventional household water filters are not typically organized into vertical layers like the prototype shown here. However, this layered design was intentionally adopted in our prototype to serve as a hypothetical framework, allowing us to visualize the potential positioning of the bioactive layer within the filter. By starting with this conceptual model, we aimed to facilitate the development of ideas on how to incorporate the Barbie1+Nanofiber system into existing filtration systems. This structure provides flexibility, enabling us to experiment with different configurations and determine the most effective placement of our bioactive layer for optimal MNPs capture.

B.A.R.B.I.E. Filter Technical Specifications

In this section, we will explore the structure of these layers in more detail, highlighting where bioactive components such as the Barbie1 protein are incorporated. We will also provide an overview of the materials selected for the filter.

The B.A.R.B.I.E filter was designed with a balance of functionality, practicality, and sustainability, ensuring that it could be easily integrated into conventional household water filtration systems. The core principle behind the design was to create a filter that removes micro and nanoplastics efficiently, and also remains affordable and accessible for widespread use. For this reason, we adhered to strict guidelines when selecting materials, ensuring they are compatible with those commonly found in existing water filters. This alignment with established filtration systems allows for a smoother adoption process, as it leverages materials that have already undergone rigorous quality and safety assessments in the market.

In this section, we will explore the technical aspects of the B.A.R.B.I.E filter in greater detail. We will first delve into the layers that make up the filter, providing a breakdown of each layer's function and how they work together to remove contaminants from the water. This will be followed by an explanation of where the bioactive components, such as the Barbie1 protein, are integrated into the filtration system. Lastly, we will provide an overview of the materials selected for the filter, detailing their sustainability, safety, and role in maintaining the overall efficiency of the filtration process.

Layers

The B.A.R.B.I.E. filter follows a design similar to that of conventional activated carbon filters, as shown in the prototype in Figure 2. It contains multiple layers, each serving a specific role in the filtration process. The first layer, made of meltblown polypropylene, acts as a physical barrier, trapping larger particles such as sediment and debris.

Below this layer is the activated carbon, which plays a crucial role in adsorbing chemical contaminants such as chlorine, pesticides, and organic compounds. Activated carbon is highly effective due to its large surface area and porous structure, which trap these molecules and improve water quality.

Beneath the activated carbon layer is another layer of meltblown polypropylene, further enhancing the filtration by trapping any remaining particles that passed through the previous layers, as shown in Figure 3.

The key innovation of the B.A.R.B.I.E filter lies in the inclusion of an additional bioactive layer, strategically positioned after these filtration layers. This layer incorporates the Barbie1 protein, immobilized on a nanofiber hydrogel matrix. Its purpose is to capture MNPs. The affinity between the protein and plastics enables this layer to trap even the smallest plastic particles, complementing the adsorption properties of the activated carbon.

Together, these layers create a multi-stage filtration system. First, larger particles are captured by the upper meltblown polypropylene layer, followed by the removal of chemical contaminants by the activated carbon. Then, the lower meltblown polypropylene layer traps any remaining particles, and finally, the bioactive layer captures MNPs, ensuring a thorough and effective filtration process.

Where are the bio parts?

The bioactive components of the B.A.R.B.I.E filter are integrated into a dedicated layer within the filtration system, positioned after the second meltblown polypropylene layer. By placing the bioactive layer here, the water has already passed through the initial filtration stages, which remove larger particles and chemical contaminants. This setup allows the proteins to focus specifically on capturing MNPs, which are often missed by conventional filters.

The Barbie1 protein is immobilized on a substrate of spidroin nanofibers, see more in Engineering section, selected for their high surface area and stability. These nanofibers provide robust support for the protein and maximize contact between the water and the bioactive material. The large surface area of the nanofibers enhances the interaction between the Barbie1 protein and plastic particles, ensuring that even the smallest MNPs are efficiently captured.

Materials

The B.A.R.B.I.E. filter was designed with sustainability at its core, using materials that are fully recyclable to ensure responsible disposal after use. Unlike some conventional water filters that focus primarily on efficiency and performance, the B.A.R.B.I.E. filter integrates eco-friendly principles into its design. Many filters on the market today are starting to adopt recyclable or even recycled materials, recognizing the growing environmental concern surrounding plastic waste. However, not all filters prioritize the recyclability of their components, and many still rely on single-use plastic parts that end up contributing to landfill waste.

By selecting recyclable materials for the B.A.R.B.I.E filter we aim to go beyond merely addressing water contamination; we also tackle the issue of plastic pollution generated by the filtration system itself. This holistic approach ensures that the materials used in the filter, from the casing to the filtration components, can be reprocessed and reintroduced into the production cycle, reducing the environmental footprint associated with water purification.

On the biological side, we also took steps to ensure that the use of the Barbie1 protein would not introduce new environmental risks. After capturing the MNPs, we considered potential ways to recycle the protein layer and the plastic particles it binds. The goal is to safely remove and reuse these proteins, as well as the plastic pollutants they capture, to prevent them from becoming a new source of contamination, see more in Recycling sections. By focusing on both the recyclable nature of the filter materials and the regeneration of the bioactive components, we aim to make the B.A.R.B.I.E filter not only effective, but also environmentally responsible.

Maintenance and Infrastructure

Regarding the filter's lifespan, the bioactive layer with Barbie1 protein and spidroin nanofibers is expected to function effectively until it becomes saturated with plastic particles. The lifespan depends directly on water quality and the amount of MNPs present. Practically, users will be notified of the need for filter replacement or regeneration via sensors integrated into the system, which monitor the accumulation of microplastics and indicate when the filter is saturated. These sensors will be connected to an app developed by us.

The filter replacement has been designed to be user-friendly, such as in today’s common water filters, allowing consumers to do it without technical assistance. The saturated part must be easy to detach and replace with a new unit, simplifying maintenance.

The behavior of the B.A.R.B.I.E filter under different environmental conditions has also been carefully studied. The Barbie1 protein and spidroin nanofibers maintain their effectiveness across a wide range of temperatures and pH levels, ensuring that the filter can be used in various water conditions, such as water sources with fluctuating pH or temperature. This adaptability enables the filter to be employed in different geographical regions and systems that treat water from rivers, wells, or lakes. In more extreme situations, such as brackish water or highly polluted sources, adjustments can be made to enhance the filter’s performance.

Social Impact and Accessibility

The accessibility of the B.A.R.B.I.E filter can be one of its most significant advantages. From the outset, the project was designed with social impact in mind, aiming to reach as many people as possible, regardless of their economic background. By using widely available and sustainable materials, the filter remains cost-effective, and its format compatible with current water filters ensures that it can be implemented in homes without the need for expensive infrastructure or equipment.

The B.A.R.B.I.E filter’s easy integration into existing household water filtration systems ensures that it is accessible not only in urban areas but also in rural and underserved communities. Additionally, the incorporation of sensors and the companion app makes it possible for users to monitor the filter's status in real-time, increasing the filter's overall effectiveness and ease of use.

Safety Notes

Laboratorial Safety

Creating a method to control genetically modified bacteria is essential for ensuring environmental safety and ethical responsibility in biotechnology. A kill switch allows for the controlled shutdown of these organisms if they escape their intended environment, preventing ecological disruption, reducing biosecurity risks, and addressing public concerns about biodiversity loss. Without such mechanisms, genetically modified organisms (GMOs) could proliferate uncontrollably, threaten native species, and lead to significant ecological imbalances. Implementing kill switches not only enhances regulatory compliance but also fosters public trust in biotechnological innovations, making it a critical component for the sustainable development of GMOs. To ensure biosafety and proper behavior of the bacteria producing our proteins, we designed a circuit kill switch for biocontainment.

This mechanism will cause the death of the microorganisms in case they leave the production environment. The cells are going to have a constitutive expression of our guide RNA (gRNA) targeting the recA gene. RecA was selected since it is involved in homologous recombination and DNA repair. It has an important role in the repair of double-strand DNA breaks and the restart of stalled replication forks. In our OR logic gate, the promoters are activated by UV light (pUV - BBa_I765001) or temperatures below 18ºC (pCold - BBa_K1949000), allowing, therefore, the transcription of the Cas9 protein and the attachment to the gRNA, originating the double strand break in the DNA sequence and killing the bacteria.

B.A.R.B.I.E. Filter Safety

Given the growing concern about the effects of microplastics on human health, there has been a rising number of academic studies looking into the retention of these microparticles in human tissues and their effect on our biological system. However, there are still several bottlenecks that need to be clarified, such as the minimum amount of microplastics accumulated in tissues to cause notable negative effects and the time needed to reach their toxic potential, as well as defining the main sources of human daily microplastic intake and the fraction that drinking water corresponds to in this list. Therefore, more research will be needed to define, at a global level, the maximum amount of microplastics that can be contained in a given volume of water to be considered safe for human consumption.

This information is crucial when considering legislation to regulate the level of microplastics in drinking water, and without a safe limit value, regulatory agencies cannot efficiently inspect and control the action, like California (USA), which, after the bill was approved in 2018, is still developing methodologies for quantification and detection.

By understanding the safe limit of MNPs in water, we can integrate this value into the design of predictive maintenance models. As the filter approaches its saturation point — when it can no longer efficiently remove MNPs beyond the safe threshold – the user would be notified via the real-time monitoring application to replace the filter , ensuring continuous protection and adherence to safety standards, see more in Model page.

In terms of the security of the usability by household and commercial filtration systems around the world, we have carefully considered the risks, such as the Barbie1 and spidroin proteins being stable under normal filtration conditions, avoiding contamination of the water. To mitigate this, we have simulated the materials under various conditions, in the same way as in the safe limit of MNPs alert, the predictive system would alert users when the filter needs to be replaced by some imperfection in the filter, preventing overuse and potential contamination.

The recycling of saturated filters is another central point of our sustainability strategy. Once the B.A.R.B.I.E filter has reached its saturation point, indicated by the predictive maintenance system, the user will have to replace the filter. In the future, we envision implementing a filter return program where used filters can be sent back to a recycling facility for safe handling and regeneration.

Scalability and Expected Price

To assess the feasibility of the B.A.R.B.I.E. filter project, particularly considering its scalability for large-scale production, we examined several factors including the production of the Barbie1 protein in bioreactors. The production model we follow uses microbial systems with a bioprocessing approach modeled on the Monod growth equation, ensuring that the production of the protein is not only efficient but also cost-effective, see more in Model page.

When considering the financial aspects for end users, the B.A.R.B.I.E filter was designed with long-term advantages in mind. The filter system offers predictive maintenance via real-time monitoring through an integrated application. This allows users to manage and optimize the lifespan of the filter, reducing unnecessary replacements and lowering costs over time. The app provides notifications when the filter needs maintenance or replacement, ensuring the system operates at peak efficiency and preventing overuse or contamination risks.

The viability of large-scale production of the proteins has been carefully considered. Following the mathematical modeling, we can ensure a consistent and scalable production of these bioactive materials, aiming to make our filter accessible to households and institutions alike.

The B.A.R.B.I.E filter is designed to be adaptable to existing domestic and commercial filtration systems. While the current prototype is optimized for common household filters, future iterations could be developed to fit larger-scale industrial, laboratorial or even municipal water treatment systems. However, these adaptations are part of our future development plans and would require further testing and modifications to accommodate different water treatment infrastructures.

Our project is also mindful of adapting to different economic realities and local regulations around the world. For example, certain regions, such as Europe, have stricter regulations regarding bioproducts, especially those derived from genetically modified organisms (GMOs).

In terms of adapting the B.A.R.B.I.E filter for different water sources, such as rivers, lakes, or wells, we recognize the need for adjustments to accommodate varying water qualities. For water sources with high sediment loads or salinity (e.g., brackish water), the bioactive layer containing the Barbie1 and spidroin protein matrix may need to be augmented with additional pre-filtration stages or modified to handle the unique challenges posed by such conditions. These adaptations will ensure that the filter remains effective even in heavily polluted or sediment-rich environments, making it suitable for use in diverse contexts around the world.

How to Recycle the Proteins?

Another really important part is the development of a solid path to the already used filter components. For the proteins, there are some options based on the studies our team conducted, see more in Circular Dichroism page. The studies revealed that our protein loses part of its secondary structures with the increase of the temperature, decreasing the interaction force between the PBPs and the plastic molecules. This way, we propose a heating treatment to the already used filter, removing most of the ligands bound to the protein.

With the proteins free of ligands, we can think about how to reuse our filter, our filter will have a specific part where the proteins will be deposited. This part will be the most important component in the recycling process, since it will be exchanged for a new one, and the old and saturated one will pass through a treatment to restore the structure of the proteins.

How to Recycle the Captured MNPs?

Although the main focus of the B.A.R.B.I.E filter project is the efficient removal of MNPs from water, it is equally important to consider what happens to these particles once they have been captured. After the MNPs are removed from the saturated filter, they need to be properly disposed of or recycled to avoid further environmental impact.

While recycling the captured MNPs is not the primary objective of our project, we acknowledge that several methods for plastic recycling already exist in the literature. For example, the degradation of plastics using enzymatic or chemical treatments offers potential pathways for dealing with these particles.

In practice, the MNPs could be sent to specialized recycling facilities where they would undergo processes such as chemical recycling, decomposition in smaller molecules, or even biological treatment. Each of these methods has its advantages, depending on the type of plastic and the available technology.

B.A.R.B.I.E App

To facilitate the integration of the B.A.R.B.I.E filter into daily life, we have developed a prototype of a user-friendly mobile application that allows users to monitor their filter's performance and health in real time using Adobe XD. The app, designed with accessibility and simplicity in mind, provides several key functionalities that enhance the experience of using the B.A.R.B.I.E filter, such as:

Home Interface Predictions and Plastic Removal Efficiency Real-Time Sensing Profile and Personalization Product Catalog

Conclusion

The development of the B.A.R.B.I.E filter emerged in response to the urgent need for practical and effective solutions to combat MNPs pollution in drinking water. Through a system that integrates membrane filtration, bioactive components, and sustainable materials, our project offers a viable and scalable solution to this growing environmental challenge.

Our team’s efforts extend beyond the filter itself. By incorporating modern technology, such as real-time monitoring through a companion application, users can easily track the performance of their filters, receive alerts when maintenance or replacements are required, and monitor the amount of plastic being captured, providing a user-friendly interface that makes advanced filtration technology accessible to households globally.

As we look to the future, we remain committed to pushing the boundaries of water filtration technology. Continued research and development allow us to refine the B.A.R.B.I.E filter and explore new possibilities for its application, including expanding to industrial, laboratorial and even municipal water systems. Furthermore, our dedication to sustainability ensures that the filter and its components are not only efficient but also environmentally responsible, minimizing waste through recycling and regeneration processes.

The B.A.R.B.I.E filter stands as a powerful tool in the fight against plastic pollution, and with ongoing development, we believe it has the potential to make a significant impact on environmental sustainability and public health, providing clean and safe drinking water for communities worldwide.

References

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