Researchers from the University of Arizona are creating a COVID-19 test that uses a smartphone microscope to analyze saliva samples and deliver test results in 10 minutes.

The new test aims to combine the speed of the existing nasal swab antigen tests with the high accuracy of nasal swab polymerase chain reaction (PCR) tests. To create the test, the team adapted a cheap method originally designed to detect norovirus with a smartphone microscope.

UArizona researchers image a sample using a smartphone microscope. Source: University of Arizona Biosensors LabUArizona researchers image a sample using a smartphone microscope. Source: University of Arizona Biosensors Lab

Traditional norovirus detection methods are expensive, require a large suite of lab equipment and scientific expertise. The new test consists of a smartphone, a simple microscope and a piece of microfluidic paper. The wax-coated paper guides liquid sample to flow through specific channels. Overall, the new test is smaller and cheaper than the traditional methods, costing in total about $45.

With the new method, users introduce antibodies with fluorescent beads to a potentially contaminated water sample. If enough particles of the pathogen are present, several antibodies attach to the pathogen particles. Under a microscope, the pathogen particles show up as clumps of fluorescent beads that the user then counts. The entire process takes about 10 to 15 minutes.

The team says that their method can be improved with a 3D printed housing for the microscope attachment and a microfluidic chip. They hope to one day introduce the adaptive thresholding method, where artificial intelligence (AI) sets the danger threshold and accounts for environmental differences.

The team plans to partner with the University of Arizona testing facilities to fine-tune the method as they adapt it for COVID detection. It will be tested on university student volunteers. The goal is to distribute the device to campus hubs so an average person could test saliva on their own.

A study on the new test was published in Nature Protocols.