Portable Instrument Combines Fluorescence Reader and Microfluidic Chip for Detection of SARS-CoV-2 in Saliva

A portable, low-cost instrument combines a fluorescence reader and microfluidic chip to enable fast, sensitive detection of COVID-19 in saliva samples.

Researchers from the Institute of Photonic Sciences (ICFO Castelldefels, Spain) and IrsiCaixa AIDS Research Institute (Badalona, Spain) have demonstrated a new low-cost portable instrument that manipulates light and fluid for fast and reliable detection of SARS-CoV-2 in saliva samples. Although still in the research stage, the new device could offer a higher sensitivity than today’s COVID-19 rapid antigen tests while also being faster and more cost-effective than PCR tests.

The new instrument, which the researchers call a flow virometry reader, is based on a modification of flow cytometry, a laser-based technique that uses fluorescence to count or analyze cells. Rather than counting cells, the new device detects light emission from fluorescent antibodies that bind to specific viral particles. It can offer quantitative results in less than 30 minutes using an instrument that is about the size of a shoebox. Also, non-specialist users can easily operate the device, and testing can be carried out anywhere since no specialized laboratory is required. To run a test, a saliva sample is introduced in a solution that contains fluorescent antibodies that will attach to SARS-CoV-2 particles. The sample is then processed by the flow virometry reader, which uses a single microfluidic channel to pass the sample through a laser illumination and detection setup. If viral particles are present in the solution, they change the sample’s fluorescence in a detectable way, providing information that can be used to calculate the viral concentration.

The researchers calibrated the new instrument by determining its detection limits using a set of prepared saliva samples containing a known amount of virus. They then evaluated the performance of the system for detecting SARS-CoV-2 in clinical samples. For this, they conducted a blind test of frozen saliva samples from more than 50 COVID-19 positive and uninfected individuals. The instrument reliably detected 31 out of 34 COVID-19 positive patient samples and 18 out of 20 SARS-CoV-2 negative samples, which had been previously analyzed using PCR testing.

While the proposed technology has the potential to replace or complement PCR tests, more experiments are necessary to clinically assess the similarity of the two methods. The researchers are now working to develop an integrated flow virometry reader for simultaneous SARS-CoV-2 antigen and antibody analysis. Such a testing device could identify active infections as well as provide information on the immune response to a previous infection or vaccination. This will allow fast checking of vaccine efficiency and help to determine whether additional vaccination boosters are needed. Before moving into the commercialization phase, the researchers will perform a series of additional tests to increase the statistics and the specificity of the device.

“Our instrument, which requires just a few drops of saliva, would be useful for mass screening in settings such as restaurants, schools, offices, theatres and cinemas,” said researcher Alfredo Ongaro from ICFO. “What’s more, the technology can be easily adapted to detect markers for other pathogens, including those that may be involved in future outbreaks.”

Related Links:
ICFO 
IrsiCaixa AIDS Research Institute