Novel sensor could change the face of medical diagnostics

Researchers at the Okinawa Institute of Science and Technology Graduate University (OIST) have created a novel sensor that detects biomolecules more accurately than ever before.

The sensor has been used to show that biomolecules can be successfully sealed within microfluidic devices. Prior to the scientists’ research, it was unknown if biomolecules could survive the harsh process required in the sealing process. The results of their research has profound implications for healthcare diagnostics and open up opportunities for producing pre-packaged microfluidic platform blood or urine testing devices.

Traditionally, metal oxide semiconductor (MOS) sensors are used to detect the binding of biomolecules to a surface by measuring changes in charge. Comprised of a silicon semiconductor layer, a glass insulator layer and a gold metal layer, these sensors are incorporated in an electric circuit with the biomolecule sitting in an electrolyte-filled plastic well on top of the sensor. If you then apply a voltage and measure current, you can work out the charge from the capacitance reading given off. Biomolecules with different charges will give you different capacitance readings, enabling you to quantify the presence of biomolecules.

The novel sensor created by the OIST scientists measures charge using the same technique as conventional sensors but has the additional function of measuring mass. Instead of having a solid gold metal layer, the so-called nano-metal-insulator semiconductor (nMIS) sensor has a layer of tiny gold metal islands. If you shine light on these nanostructures, the surface electrons start oscillating at a specific frequency. When biomolecules are added to these nanoislands, the frequency of these oscillations change proportional to the mass of the biomolecule. Based on this change, you can use this technique to measure the mass of the biomolecule, and confirm whether it survives exposure to ionised gas during encapsulation within the microfluidic platform.

Measuring two fundamental properties of surface chemical reactions on the same device means that researchers can be far more confident that biomolecules have been successfully encapsulated within the microfluidic platform. A measurement of charge or mass alone could be misleading, making it look like biomolecules have bound to a surface when in fact they have not. Having more than one technique in the same device means that you can switch from one mode to the other to see if you have the same result.

This novel nMIS sensor could be used to create microfluidic platforms that test for various diseases. By measuring charge and mass using the nMIS sensor, researchers can ensure that disease-detecting biomolecules are successfully sealed and functional inside the testing device.

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