In mobile health, the next desirable evolution in this discipline is a wearable capable of monitoring the health of a person through the exchange of information via the internet without requiring human intervention.  Nonetheless, crucial steps in the miniaturization of biosensors are needed as is the conversion of a biological signal into an electrical current to enable the direct sampling of bodily fluids. 

Self-powered artificial nanopores

Now, a study from researchers at the University of Groningen develops a nanopore system able to measure different metabolites simultaneously in a variety of biological fluids. This is all achieved in a matter of seconds whilst their nanotechnology system creates an electrical current to power itself.  The team states incorporation of their nanopore technology into portable electronic devices will allow the development of sensitive, continuous, and non-invasive sensors for metabolites in point-of-care and home diagnostics.  The opensource study is published in the journal Nature Communications.

Previous studies show measuring many metabolites or drugs in the body is complicated and time-consuming, rendering real-time monitoring impractical. In contrast, the ionic currents passing through individual nanopores are emerging as a promising alternative to standard biochemical analysis. Consequently, these nanoscale pores are already integrated into many portable devices to determine DNA sequences. 

Presently, however, it is not possible to use these nanopores to specifically identify small molecules in complex biological samples.  The current study demonstrates protein sensors in combination with a nanopore acting as an electrical transducer can accurately quantify metabolites in real-time directly from a nanolitre of blood.

The current study illustrates how the nanopore cytolysin A can be used to monitor the function of two different substrate-binding proteins. The proteins, which are specific to glucose and the amino acid asparagine, were monitored when lodged inside the nanopore. 

Results show the nanopores report the concentration of glucose and asparagine directly from a fraction of a drop of blood, sweat, and other bodily fluids in under a minute.  Data findings show no sample preparation is required and the concentration of the metabolite can be monitored continuously.

Results show as the binding proteins are adapted to fit inside the nanopore when a protein binds to its substrate its conformation changes altering the electrical current passing through the nanopore. 

Analyzing a nanolitre of blood

The lab states they are using the binding protein as an electrical transducer to detect single molecules of the substrate.  They go on to add the nanopores can be incorporated into a standard device with the capability to analyze the current of hundreds of individual pores simultaneously, whilst operating continuously.

The team surmises they have demonstrated that nanopores can produce an ionic current to continuously measure specific molecules in a nanolitre of blood with no sample preparation.  For the future, the researchers state they plan to develop a system with proteins specific to hundreds of different metabolites.

Source: University of Groningen

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