Supersensors

Another biosensor has been created – "fast and hypersensitive"

Roman Ivanov, Computer

The University of New South Wales (Australia) has created a new class of biosensors capable of detecting extremely trace amounts of toxins in liquids in a very short time.

The research report is presented in the journal Angewandte Chemie (Lai et al., The Biochemiresistor: An Ultrasensitive Biosensor for Small Organic Molecules). It follows from it that it took only 40 minutes to detect the antibiotic enrofloxacin in milk – despite the fact that the concentration of the substance, known for its dangerous ability to move further along the food chain, was negligible – 1 nanogram per liter of milk.

In general, a biosensor is a portable analytical device that uses biological molecules to selectively detect a single specific compound in a complex mixture. Small biosensors have long been used on a daily basis – for example, to assess the safety of drinking water, check the blood sugar level of diabetic patients, as well as as a home pregnancy test.

The new biosensor is based on gold–coated magnetic nanoparticles with antibodies bound to their surface with high affinity (binding strength to the antigen) in relation to the analyte chemical of interest to us.

The nanoparticles are dispersed in the solution of the sample taken for analysis, and in the case of the presence of an analyte, some antibodies leave the nanoparticles, connecting with their target. Under the action of the magnet, the nanoparticles line up in a row, forming a kind of "chain" connecting two opposite contacts and reducing the overall resistance of the system. The measured change in resistance is a qualitative (as well as quantitative) characteristic of the presence of analyte in the sample. The higher the content of the detected substance, the more antibodies leave the nanoparticles and the lower the resistance of the system.

The sensor operation scheme. Left: low analyte concentration; the more antibodies the metal particles lined up in a row with a magnet shield, the higher the resistance. Right: analyte concentration is higher; more antibodies have left the nanoparticles.

A significantly higher sensitivity of the sensor in question is achieved due to the fact that the nanoparticles are dispersed throughout the entire volume of the sample: this allows analyzing the maximum possible amount of substance, and not a small part of it covering the surface of the device.

Prepared based on the materials of the University of New South Wales: New type of biosensor is fast, super-sensitive.

Portal "Eternal youth" http://vechnayamolodost.ru30.05.2012