What the research is about
Have you heard of nanoplastics-plastic particles even smaller than microplastics? Nanoplastics are tiny pieces of plastic less than 1 micrometer in size. One micrometer is just one-thousandth of a millimeter.
Nanoplastics are thought to be widespread in environments such as oceans and rivers, raising concerns about their possible effects on aquatic organisms and human health. But because of their small size, finding out where nanoplastics are present and in what amounts is far from easy. Microplastics, for example, can be examined using optical microscopes and other methods. Nanoplastics, however, are too small to be detected easily using conventional approaches.
A research team led by Associate Professor Mana Toma at Institute of Science Tokyo (Science Tokyo) approached the problem from a different angle. Instead of carefully analyzing samples to search for nanoplastics, they asked: what if we could capture the nanoplastics first?
The researchers focused on a peptide-a short chain of amino acids-that binds to polystyrene, a common type of plastic. They set out to use this peptide to develop a sensor that could detect polystyrene nanoplastics.
Why this matters
The researchers attached the peptide to the surface of a sensor and developed a system that detects changes in reflected light when nanoplastics bind to it. Using this approach, they demonstrated that polystyrene particles just 50 nanometers in diameter could be detected within 20 minutes, without the need for complicated analytical procedures.
The team also used an electron microscope to confirm that nanoplastics had actually attached to the sensor surface. This showed that the sensor was working as intended and that the change in the optical signal was indeed caused by the captured particles.
What’s next
The sensor worked not only in relatively pure laboratory water but also in tests using aquarium and pond water, which contain many other substances. Challenges remain-for example, differences in water quality can affect detection sensitivity. With further improvements, however, the technology could provide a simpler way to investigate nanoplastics in the environment. In the future, it may also be possible to apply the method to more complex samples, including biological materials.
Comment from the researcher
My interest in this research began when I learned about the discovery of a bacterium at a recycling facility in Japan that can break down PET, the plastic widely used in products such as beverage bottles. Many biomolecules in living organisms can recognize and bind to specific molecules, and this bacterium was reported to have an enzyme capable of breaking down PET-an artificial material.
Inspired by this discovery, we wondered whether biomolecules that bind to plastics could be used in a sensor to capture and detect nanoplastics. Because nanoplastics are extremely small, they are difficult to collect and analyze. By using biomolecules to capture them, however, we were able to overcome this challenge and develop a sensor capable of detecting nanoplastics.
(Mana Toma, Associate Professor, Department of Electrical and Electronic Engineering, School of Engineering, Institute of Science Tokyo)
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