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New Technique to Improve the Detection of Biomolecules

Biomolecules have to be monitored in a fast, simple, and sensitive way in clinical diagnostics. Most often, clinicians track antibodies because these tiny proteins adhere to antigens or foreign substances that are faced on a daily basis.

Schematic drawing of the sensor device using the aptamer-modified CNT-TFT (Credit: Ryota Negishi)

However, the majority of biomolecules have complex charge properties, and the sensor response from traditional carbon nanotube systems can be unpredictable. Recently, a group of researchers in Japan showed the workings of these systems and recommended changes to considerably enhance the detection of biomolecules. The results of the study have been reported in AIP Publishing’s Journal of Applied Physics.  

The researchers showed a novel method through which biomolecules with inhomogeneous charge distributions can be detected, measured, and analyzed by altering the solution in which the biomolecule is monitored. They utilized used carbon nanotube thin film transistors, or CNT-TFTs, to find out the exact amount of a specific biomolecule in a specimen.

Immune antibody receptors known as aptamers are used by CNT-TFT biosensors for detecting the net electric charge of the part of the molecule of interest. After investigators detect a molecule, an antibody is allowed to adhere to it in solution. That antibody subsequently links to an aptamer on a thin film of carbon nanotubes which changes the connection into an electrical signal for sensor detection. With this improved sensor response, scientists can map out the uneven charge distributions of a molecule by determining the Debye length, or the distance between the molecule and a point charge.

The researchers discovered that they had to observe the way these charges are distributed close to the surface of a molecule to infer the complex behavior in the sensor signal. “Despite being the same target molecule, the polarities of the sensor response are completely different from positive or negative,” stated the paper’s author Ryota Negishi.

We achieved the improvement of dynamic range by using low concentration of buffer solution,” Negishi stated. “As a result, we clarified the mechanism of complicated sensor response which has not been clarified in previous reports.”

A molecule’s Debye length can be affected by many different features of an experiment and therefore, these outcomes show potential for further controlling sensors and altering their dynamic range.

Negishi and his colleagues are now hoping to find a means to apply their findings in more real-life situations. “For practical application, it is essential to develop a sensing technology that can be detected under high concentration conditions close to blood.”

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