Researchers have developed a new process to capture even the smallest, potentially potentially harmful plastic particles in the environment and to detect them reliably. Your “optical sieve” consists of an ordinary microscope and a special test strip. There are tiny depressions in which only particles of suitable size are captured. If a particle goes online, the color changes. At the same time, the existence, number and size of the particles can be determined. With this test kit, nanoplasty in the environment could be quickly and easily detected, as well as in blood and tissue samples.
Plastic waste contaminates seas, rivers and beaches worldwide and disintegrates into micro and nanoplasty. These tiny plastic particles are then absorbed through food, breathing air or skin of living things, end up in the food chain and ultimately also in our body. With the blood, they distribute themselves into all organs where they could interfere with the metabolism and make it sick, fear experts. “In contrast to microplastics, smaller nanoplasty can overcome biological barriers-including the blood-brain barrier-and accumulate in the body tissue, which raises profound health concerns about toxic exposure,” says co-author Brad Clarke from the University of Melbourne.
However, the biological effect of the plastic particles has only been researched. Because how much plastic is in nature and tissue of organisms is difficult to measure, especially in nanoplasty. Because these particles cannot be recognized with the naked eye and only partially detectable with common methods of detection. With these methods, these methods often remain unclear which type of plastic it is, how big the particles are and how many particles are present in the examined sample. This requires complex other analyzes, for example with electron microscopes. So far, there has been a lack of fast and reliable detection procedures for nanoplasty.
“Sieb” captures plastic in tiny depressions
Researchers led by first author Dominik Ludescher from the University of Stuttgart have now developed a new process that can be used to better detect such extremely small plastic particles. They built a kind of “optical sieve” that captures nanoplasty. It consists of a special test strip on which the color changes when such particles tie it. This color envelope is then visible under the light microscope. The process is based on tiny depressions, so -called mie voids, in a semiconductor material. “Our new optical sieve is an arrangement of tiny cavities of different sizes in a gallium arsenide microchip,” says co-author Lukas Wesemann from the University of Melbourne.
When light falls on the small depressions, it is distracted and reflected differently depending on the diameter and depth of the holes. There is a characteristic color that can be seen under an optical microscope. However, if a plastic particle falls from a liquid sample – such as sea water – into one of these depressions, its color changes. “This allows us to determine whether the depressions are filled or empty.” Ludes explains. “If a particle is too big, it does not fit into the recess and is simply washed away during the cleaning process. If a particle is too small, it remains difficult to adhere to the recess and is also washed away when cleaning.” Also dirt and sand hardly stick and are largely rinsed off.
The size and depth of the holes in the material can be specifically adjusted that they capture particles with a diameter between 200 and 1000 nanometers. If the sieve is provided with depressions of different sizes, only one particle with a suitable size collects in each hole. In this way, the test strips can be made in such a way that the number and size of the particles in the holes can be determined from the color, the team explains. The color envelope not only reveals whether and how many particles are in the test, but also how big they are.
Analysis of plastic in waters, blood and body tissue
The new measurement technology offers some advantages: “Compared to conventional, widespread methods such as rasterelectron microscopy, the new procedure is much cheaper, does not require a specialist personnel for operation and reduces the necessary time for a detailed analysis,” explains senior author Mario Hentschel from the University of Stuttgart. “The technology has the potential to serve as a mobile test strip, which could then provide statements about the content of nanoplasty in waters or floors on site.” Accordingly, the new test procedure could be used in the future to analyze environmental samples on plastic pollution – which would close a large gap in knowledge.
“But blood or tissue could also be examined for nanoplasty particles with our new process,” explains co-author Harald Giessen from the University of Stuttgart. This would help to understand the spread and effect of the plastics in our body. For this, the team now wants to further optimize its test strip and bring it onto the market in a practical form. Among other things, the researchers want to carry out experiments with nanoplastic particles that are not spherical. They also want to examine whether the procedure can also be distinguished from which plastic the particles consist of.
Source: Dominik Ludescher (University of Stuttgart) et al.; Nature Photonics, DOI: 10.1038/S41566-025-01733-X
