How can functionalized nanomaterials be engineered to selectively bind or degrade microplastics in biological or aquatic systems without introducing new toxicological concerns?
The growing burden of nano- and microplastics (NMPs) in biological tissues and aquatic systems is a pressing environmental and health concern. Engineered nanomaterials (ENMs) like metal oxides, sulfides, carbon-based materials (e.g., graphene oxide), and polymer-based nanostructures offer potential as scavengers, sensors, or degraders of these pollutants. However, many challenges remain in designing nanomaterials that are both selective and safe for use in complex biological or ecological environments.
Gamini
Here we are concerned on developing functionalized Nanomaterials selectively bind and destroy nano- and micro-plastics. This requires several strategic approaches.
1. The materials used should be biocompatible and non-toxic. They should not have ecotoxicity. Natural materials such as Chitosan, poly(lactic acid) (PLA), PLGA are suitable polymeric materials. Non-toxic such as titanium dioxide (TiO2), ZnO (NnO), iron oxide (Fe2O3), etc can be used as photocatalytic materials to make composites with above polymers. Use of green synthesis strategies may avoid toxic chemical usage. Natural materials such as plant extracts containing reducing agents, some microbes such as bacteria and fungi can be used for nanoparticle synthesis. Reactive oxygen species generation by the electron-hole pairs formed by light excited semiconductor nanomaterials can be minimized by surface coating with the polymers. That will also help stabilize these Nanomaterials in suspension. When the target nano or microplastic particles are in the body of living organisms at locations where shining with UV or visible radiation is not possible, other mechanisms of destruction such as physical destruction by star-shaped nanoparticles with sharp nano-blades can be used.
2. Selective binding of nano or microplastics to the catalytic material or composite requires careful investigations of interactions between target materials and catalysts. That depend mainly on the chemical nature of the materials. If the plastics are hydrophobic then we will have to functionalise the semiconductor nano particles with hydrophobic coatings or shells. For that purpose graphite, expanded graphite and graphene, carbon nanotubes etc. can be used. However, if the plastics have polar functional groups such as ammonium groups then the polymer with carboxylic acid groups such as PLA is useful since the two can chemically react forming ester linkages and thereby bind the nano or microplastics selectively on the composite material. Also pi-pi interactions and H-bonding etc can be employed to interact and bind nano or microplastic particles on the surface of the functionalized catalysis containing extended pi conjugation such as that is present in graphene.
Enzymes can be used instead of inorganic semiconductor nano particles or else enzymes such as PETase, cutinase or laccase that have the proven microplastic degradation ability can be coated on nanoparticle surfaces for selective destruction of relevant micro or nanoplastics. Some bacteria and fungi are known to destroy microplastics and nanoplastics. It is important to make sure that degraded products are further biodegrade eventually to carbon dioxide and water to eliminate the formation of toxic degraded products.
3. Iron oxide nano particles have magnetic properties. This can be used to remove micro or nano particles present in body via magnetic removal when the plastics are bound to magnetic nanoparticles such as magnetite.
4. Testing of bio toxicity and chemical toxicity is essential to make sure non-toxicity of the catalysts and degraded products.
1. The materials used should be biocompatible and non-toxic. They should not have ecotoxicity. Natural materials such as Chitosan, poly(lactic acid) (PLA), PLGA are suitable polymeric materials. Non-toxic such as titanium dioxide (TiO2), ZnO (NnO), iron oxide (Fe2O3), etc can be used as photocatalytic materials to make composites with above polymers. Use of green synthesis strategies may avoid toxic chemical usage. Natural materials such as plant extracts containing reducing agents, some microbes such as bacteria and fungi can be used for nanoparticle synthesis. Reactive oxygen species generation by the electron-hole pairs formed by light excited semiconductor nanomaterials can be minimized by surface coating with the polymers. That will also help stabilize these Nanomaterials in suspension. When the target nano or microplastic particles are in the body of living organisms at locations where shining with UV or visible radiation is not possible, other mechanisms of destruction such as physical destruction by star-shaped nanoparticles with sharp nano-blades can be used.
2. Selective binding of nano or microplastics to the catalytic material or composite requires careful investigations of interactions between target materials and catalysts. That depend mainly on the chemical nature of the materials. If the plastics are hydrophobic then we will have to functionalise the semiconductor nano particles with hydrophobic coatings or shells. For that purpose graphite, expanded graphite and graphene, carbon nanotubes etc. can be used. However, if the plastics have polar functional groups such as ammonium groups then the polymer with carboxylic acid groups such as PLA is useful since the two can chemically react forming ester linkages and thereby bind the nano or microplastics selectively on the composite material. Also pi-pi interactions and H-bonding etc can be employed to interact and bind nano or microplastic particles on the surface of the functionalized catalysis containing extended pi conjugation such as that is present in graphene.
Enzymes can be used instead of inorganic semiconductor nano particles or else enzymes such as PETase, cutinase or laccase that have the proven microplastic degradation ability can be coated on nanoparticle surfaces for selective destruction of relevant micro or nanoplastics. Some bacteria and fungi are known to destroy microplastics and nanoplastics. It is important to make sure that degraded products are further biodegrade eventually to carbon dioxide and water to eliminate the formation of toxic degraded products.
3. Iron oxide nano particles have magnetic properties. This can be used to remove micro or nano particles present in body via magnetic removal when the plastics are bound to magnetic nanoparticles such as magnetite.
4. Testing of bio toxicity and chemical toxicity is essential to make sure non-toxicity of the catalysts and degraded products.
Dr. VVK
Adsorption Methods: Due to the large surface area, porous activated carbon and biochar with surface functional groups (e.g., -OH, -COOH) offer a low-cost solution for microplastic bindings.
Degradation Methods: In degradation methods metal oxides play a very vital role in breaking down the microplastics upon light irradiation.
Plasmonic photocatalysis: Combining noble metal nanoparticles (Ag, Au) with photocatalytic systems enhances light absorption and degradation efficiency. Nanofiber membranes modified with surface groups (e.g., -OH, -COOH) can be used to filter microplastics.