Optoplasmonic sensor for rapid milk testing

Pests can enter the milk through udder infection. They bring chemicals such as antibiotics and pesticides through feed or through insufficient control to cause contamination. In order to prevent contaminated milk from entering the food chain, controls are carried out throughout the production process and throughout the supply chain. But these standard tests are associated with high costs and time. EU Milk Project – Multiplex Plasmonic Contamination Sensor for Milk Based on PLasmon Milk – Twelve Partners from Seven Countries Find Milk Contamination Solution Much Cheaper and Faster: New Optoplasmonic Sensor Should Be Used as an Early Warning System control before milk enters the tank. In about five minutes you should analyze them with a single measurement on a total of six ingredients. The sensor is functionalized with specific antibodies for different parameters of milk safety and quality and enables automatic on-site quantitative analysis in dairy farms.

The complete system consists of a reusable microfluidic chip, organic light transistors (OLETs) or diodes (OLEDs), organic photodetectors (OPDs) as sensors, nanostructured plasmonic lattices, and specific antibodies. Fraunhofer Institute for Organic Electronics, Electron Beam and Plasma Technology FEP develops an organic photodetector, the Fraunhofer Institute for Electronic Nanosystems, an ENAS microfluidic chip. OLET and photonic grids are being developed by CNR-ISMN in Bologna, together with the Italian company Plasmore Srl in Pavia.

"The peculiarity of our chip is that you can reuse it. This is achieved by the target molecules using the regeneration buffer of the immobilized antibodies so that they can be reused for new detection," says Andreas Morschhauser, a scientist at Fraunhofer ENAS. The chip is designed for a hundred measurements. Six parameters or pollutants and proteins can be analyzed with each measurement. To this end, Morschhauser and his colleagues develop a microfluidic system in the form of a replaceable, automated and miniaturized cartridge. In addition to the milk information obtained, the measured parameters also make it possible to draw conclusions about the health of each individual cow, and farmers receive a wealth of information on their condition. For example, infections can be recognized early and treated quickly. Early treatment can contribute to the prudent use of antibiotics and therefore to their reduction.

"The transistor creates light that falls on the antibody-covered grid. These are specific to the relevant constituents. If the milk is now spilled over the antibodies, the target molecules bind to them. As a result, the refractive index changes near the grid, resulting in a change in light reflection. "Reflected light falls on a photodetector, which measures the minimum change in the refractive index," says Michael Törker, a Fraunhofer FEP scientist. The basic effect of plasmon surface resonance occurs on specially structured nanotubes. The effect allows for fast and very sensitive measurements.

The biosensor should be used at various points along the value chain: both as a laboratory device and directly integrated into milking parlors. However, the system is not only suitable for checking the quality of milk. With the help of an optoplasmon sensor, other liquids such as beer or water could be analyzed in the future. For this purpose, only the adaptation of the immobilized capture molecules and the required reaction buffer is required. Only gripper molecules must be replaced and adapted for this purpose.

Fh.-FEP / JOL

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