A paper tape sensor that measures blood sugar through saliva

     There may soon be an alternative to the finger-tingling blood sugar tests that diabetics must endure every day, as scientists from Saudi Arabia have developed a paper tape sensor that measures blood sugar through a patient's saliva. The project was led by King Abdullah University of Science and Technology biologist Sahika Inal, electrical engineer Khaled Salama, and materials scientist Derya Baran.

     They first loaded a commercial ink containing a conductive polymer into an inkjet printer, and then used the ink to print the miniature electrode pattern onto a smooth paper tape. Next, on top of the electrode they printed a layer of an enzyme called glucose oxidase. Finally, they covered the whole thing with a thin film of nafion polymer.

     They first loaded a commercial ink containing a conductive polymer into an inkjet printer, and then used the ink to print the miniature electrode pattern onto a smooth paper tape. Next, on top of the electrode, they printed a layer of an enzyme called glucose oxidase. Finally, they covered the entire object with a polymer film of perfluorosulfonic acid resin (nafion).

     When saliva is transferred to the sensor, glucose in the body fluid reacts with glucose oxidase to produce an electrical signal. This signal is then picked up by an electrode and can also be read by another device - the strength of the signal corresponds to the blood sugar level of the person providing the saliva.

     While saliva contains substances such as ascorbic acid that would normally interfere with conducting polymers, the PFOS film prevents this from happening because it repels the negative charge generated by these compounds. The film also improves the shelf life of the sensor, allowing glucose oxidase to remain active after a month of storage in a sealed bag.

     "Optimization never stops in engineering, so we're trying to make the system more robust to detect other metabolites in biological fluids," said Inal. "We also want to integrate printable, self-powered energy devices into the sensors to give us a friendlier platform that eliminates external batteries or wires."