A new method measures in real time unique molecules from nanoliter of blood

Scientists from the University of Groningen, led by Giovanni Maglia, associate professor of chemical biology, have developed a nanoporous system that can simultaneously measure different metabolites in a variety of biological fluids, all within seconds. The electrical output signal easily integrates into electronic devices for home diagnosis. The results were published in Nature Communications.

Measuring many metabolites or drugs in the body is complicated and time consuming, and real-time monitoring is usually impossible. Ionic currents flowing through individual nanopores appear as a promising alternative to standard biochemical analysis. Nanopores are already integrated into portable devices to determine DNA sequences. "But it's basically impossible to use these nanopores to specifically identify small molecules in a complex biological sample," says Maglia.

Transducer

A year ago, Maglia demonstrated how to use nanopores to identify "fingerprints" of proteins and peptides, and even to distinguish polypeptides that differ from an amino acid. Now he has adapted this system to identify small molecules in biological fluids. To do this, he used a larger cylindrical nanopore to which he added substrate binding proteins. "Bacteria make hundreds of proteins to bind to substrates to transport them into cells, these proteins have specificities that have evolved over billions of years."

Maglia adapts the binding proteins inside the nanopore. If a protein then binds to its substrate, it changes conformation. This, in turn, modifies the current flowing through the pore. "We use the binding protein as an electrical transducer to detect the individual molecules of the substrate," says Maglia. The pores can be incorporated into a standard device that simultaneously analyzes the current of hundreds of individual pores. To this end, scientists work with Oxford Nanopores, the world leader in this type of technology.

Blood, sweat and urine

By adding two different substrate binding proteins, specific to glucose and the amino acid asparagine, Maglia was able to get a reading for both from a fraction of a single drop of blood. less than a minute. "Real-time glucose sensors are available, but asparagine analysis normally takes several days," he said. The Maglia method works with blood, sweat, urine or other body fluid, without the need for sample preparation. The substrate binding proteins are on one side of the membrane and the sample on the other. "The pores are very narrow, mixing only occurs in the nanopore, which allows the system to run continuously," he says.

The challenge now is to identify appropriate binding proteins for more substrates, including drugs. Maglia's group has found ten until now. "But they have to be set to work with the pore, and for the moment we do not really understand the mechanism, so finding the right proteins is a matter of trial and error," he said. Maglia is looking for opportunities to create a company that will provide these binding proteins. "If we could create a system with proteins specific to hundreds of different metabolites, we would have created a truly disruptive new technology for medical diagnosis."

Explore further:
Major progress in the detection of peptides and proteins by nanopores

More information:
Nicole Stéphanie Galenkamp et al, Direct electrical quantification of glucose and asparagine from body fluids using nanopores, Nature Communications (2018). DOI: 10.1038 / s41467-018-06534-1

Gang Huang et al. Electro-osmotic capture and ionic discrimination of peptide and protein biomarkers using FraC nanopores, Nature Communications (2017). DOI: 10.1038 / s41467-017-01006-4