They develop a device that detects COVID-19 in saliva using light

Spanish research has managed to develop a device that uses light to detect COVID-19 in saliva samples in less than 30 minutes.

The low-cost, portable and non-invasive device can detect very low concentrations of SARS-CoV-2 with a sensitivity of 91.2% and a specificity of 90%, values ​​similar to those of a PCR, and offers a response almost as as fast as the antigen test.

According to scientists from the Institute of Photonic Sciences (ICFO) in the Spanish city of Barcelona and the AIDS Research Institute (IrsiCaixa), who have published their study in the journal Biomedical Optical Express, this new diagnostic test using light is cheaper and just as precise as a PCR and does not require specialized personnel and equipment.

Given the importance since the beginning of the pandemic of detecting infected people to control the spread of the virus, IrsiCaixa decided to look for an alternative to PCR tests and Rapid Antigen Tests (TAR) that would combine the advantages and strengths of both tests and to detect SARS-CoV-2 infection from saliva samples, which are easier to obtain and cause less discomfort to the patient.

They then contacted an ICFO team specialized in the development of biosensors to find a solution to the problem of diagnostic tests and develop a new device that could detect SARS-CoV-2 from saliva samples, in order to avoid sampling. nasal and at the same time obtain precise results in a short interval of time, as fast as ART.

Thus, they developed a flow virometer, a device that uses light to detect the concentration of the virus in a liquid that flows through a small tube, called a microfluidic channel.

According to ICFRO, the device uses “a couple of saliva drops and fluorescent light markers. When saliva samples are collected from patients, we put them in a solution containing fluorescent antibodies. If there are viral particles in the saliva sample, the fluorescent antibodies adhere to the virus.”

Saliva samples are then introduced into the sensor and passed through a microfluidic channel under the light of a laser, which illuminates the sample and, if it contains viral particles, emits a signal thanks to the fluorescent marker.

In less than a minute, the reader transmits the detected peaks of the signal to a graph and alerts that the sample is positive.

The ICFO research team carried out a blind test with 54 saliva samples and managed to confirm 31 of 34 positive cases with only three false negatives.

In addition, it managed to measure 3,834 viral copies per milliliter, about three orders of magnitude below those obtained with ART.

This means that this device is capable of detecting the presence of the virus at very low concentration levels in a solution.

The ICFO assures that the new device “is very versatile” and could be adapted to detect other viruses, such as seasonal coronaviruses or the flu, or even microorganisms present in the water, such as legionella or E. coli, “with a response time faster than the usual analyzes from cultures”.

With a single device it is possible to do about 2,000 tests per day. In addition, the components of the mechanism are of low cost and are available on the market, which allows the device to be manufactured on a large scale.

“This technique could also help reduce the volume of waste generated by the plastic wrappers of the materials with which PCR and antigen tests are carried out,” add the researchers, who see their invention as very suitable for diagnostics and control of the spread of the virus in developing countries where there is limited access to vaccines and fragile health systems.