New Electrochemical COVID-19 Test Uses Pencil Lead to Deliver 100% Accurate Results from Saliva Samples

A new electrochemical test that uses electrodes made from graphite – the same material found in pencil lead – can address the challenges of cost, time and accuracy associated with current COVID-19 tests.

Developed by researchers at the University of Pennsylvania (Philadelphia, PA, USA), these electrodes reduce the cost to USD 1.50 per test and require only 6.5 minutes to deliver 100% accurate results from saliva samples and up to 88% accuracy in nasal samples. The new test named LEAD (Low-cost Electrochemical Advanced Diagnostic) uses the same concept as RAPID (Real-time Accurate Portable Impedimetric Detection prototype 1.0), a COVID-19 testing kit which uses screen-printed electrodes, but with less expensive materials. The current test reduces costs from USD 4.67 per test (RAPID) to USD 1.50 per test (LEAD) just by changing the building material of the electrodes.

The researchers have explained the step-by-step preparation of the graphite electrodes of LEAD and given an example of the data output showing how a saliva or nasal sample is diagnosed through electrochemical signals. The electrodes are first immersed in a glutaraldehyde solution to allow the surface of the electrode to bind to modified gold nanoparticles which facilitate molecular bonds between the electrode and SARS-CoV-2 proteins in the patient’s sample. The electrodes are then immersed in a reactive intermediary solution which immobilizes the electrode from further chemical reactions. Finally, the electrodes are immersed in Bovine Serum Albumin, a protein which blocks all remaining reaction sites on the electrode, in order to avoid binding to anything other than COVID viral proteins in the patient’s sample, resulting in false positives. The sample comes into contact with the electrodes, and if positive, the COVID-19 spike protein, SARS-CoV-2, binds to the electrode. This binding to the electrode in a positive sample inhibits the electrochemical signal that is emitted, resulting in a weaker peak than a negative sample. Peaks are compared between a negative control sample and the patient’s sample for diagnosis.

LEAD’s functionalization and sample diagnosis take less than a few hours and can be made for a fraction of some of the most inexpensive tests on the market. LEAD’s cost and time efficiency may help it become one of, if not the first, electrochemical COVID-19 tests on the market in the near future and its fundamental process of sample detection could keep it on the market indefinitely. While COVID-19 is the top priority, the tests can also detect other transmissible diseases, keeping this research relevant in the future.

“Both RAPID and LEAD work on the same principle of electrochemistry,” said the test developer César de la Fuente, Presidential Assistant Professor in Bioengineering, Microbiology and Psychiatry with a secondary appointment in Chemical and Biomolecular Engineering. “However, LEAD is easier to assemble, it can be used by anyone and the materials are cheaper and more accessible than those of RAPID. This is important because we are using an abundant material, graphite, the same graphite used in pencils, to build the electrode to make testing more accessible to lower-income communities.”

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