Small tabletop diagnostic device for Covid-19 saliva samples

A quick, safe and affordable testing and monitoring of corona patients is one of the most powerful tools in the fight against SARS-CoV-2. Therefore, the WHO recommends massive testing to identify infectious people and isolate contagious contact-cases before symptoms develop. The EU increased their capacities for testing from 1.5 million in April 2020 to 6.0 million RT-PCR tests every week in October 2020. Costs of each PCR test can go from 40€ to 190€. Leading to a tremendous amount of costs for governments and citizens. A possible approach for future disease testing comes from a collaboration of Massachusetts Institute of Technology (MIT) and the Harvard University:

They developed a small tabletop diagnostic device, which can detect SARS-CoV-2 and specific variants from saliva samples within one hour. The device combines built-in sample preparation from saliva, room temperature stable reagents, simple visual and no need for additionally laboratory equipment or knowledge. At the same time the device has an accuracy like the gold standard PCR tests. At present the device costs are at 15$, which should decrease to 2-3$ in mass production.

The minimally instrumented SHERLOCK (miSHERLOCK) device can be used at home or in health care centres which do not have access to PCR testing or genetic sequencing of SARS-CoV-2 variants. This Point of Care (POC) testing requires only two operational steps, first is to apply 2 mL of saliva sample to the sample preparation chamber and second is to push the plunger down.

• In the first step the virus particles of the saliva sample are lysed by the preload lysis reagents and the build-in heater, salivary nucleases are inactivated, and the salvia goes through a filter, leaving concentrated and purified RNA on the PES (polyethersulfon) membrane.
• In the second step the PES membrane is transferred to the reaction chamber and the plunger is pushed down, which initialize the specific high sensitivity enzymatic reporter unlocking (SHERLOCK) reaction.

After 55 minutes the visual fluorescence readout through the transilluminator can be identfied with the naked eye. An additional mobile phone app is available to read the signal automatically and for quantifying the results. Test results can also be sent to an online database for real-time distributed disease reporting and strain tracking as required.

The last year showed, that the tracking of new variants of SARS-CoV-2 is essential for the containment of the Corona-Pandemic. But also, for future diseases, a fast and affordable testing device for everyone at home could slow down the outbreak of new diseases significantly. This device would be critical for the underdeveloped countries looking out for low-cost testing alternative to PCR tests as well as to the communities such as low-income families, highly vulnerable essential workers, and minorities.

Quellen: WHO(2020): https://apps.who.int/iris/handle/10665/331509;
ECDC(2020): https://www.ecdc.europa.eu/en/covid-19/data;
SortirParis(2021): https://www.sortiraparis.com/news/coronavirus/articles/253871-covid-how-much-do-pcr-tests-cost-in-eu-countries/lang/en; Main Article: https://news.mit.edu/2021/covid-19-saliva-diagnosis-0806; Main Paper: https://www.science.org/doi/10.1126/sciadv.abh2944