The start of the pandemic covid-19 It represented a turning point in the field of medicine. The situation chained a multitude of studies aimed at finding solutions to contain the advance of the coronavirus. Some were looking for, on the one hand, vaccines to mitigate the effects and control the spread of the disease, and on the other, diagnostic techniques that could be accessible to the world.
At first, the PCR tests they were one of the few techniques that provided accurate results, but it has turned out to be an expensive technique that requires specialized personnel and equipment to perform. Due to the increasing demand for diagnostic tests, the antigen test rapid became a faster and cheaper alternative, but less reliable as it was less sensitive than PCR.
A new low-cost, portable, easy-to-use and non-invasive device is presented that uses light to perform diagnostic tests for covid-19 in saliva samples in less than 30 minutes
–
–
In a new study published in the journal Biomedical Optical ExpressICFO and IrsiCaixa researchers have developed a new device capable of detecting SARS-CoV-2 in saliva samples quickly and reliably.
The team has managed to place the detection limit of sensor below that of antigen tests. By carrying out a blind test with more than 50 patients, they managed to obtain a sensitivity of 91.2% and a specificity of 90%.
The IrsiCaixa researchers and co-authors of the work, Marisa Rodriguez and Jorge Carrillopoint out: “we saw that we had to find an alternative to PCR tests and antigen tests that combined the advantages and strengths of both tests, and that also detected SARS-COV-2 infection from saliva samples, since they are easier to obtain and cause less discomfort to the patient”.
With this idea in mind, they contacted the ICFO team specialized in the development of biosensors, led by Professor ICREA Valerio Pruneri and where he also works Alfredo Ongaro, who recalls that it was about “developing a device that could detect SARS-COV-2 from saliva samples, thus avoiding nasal sampling and at the same time obtaining accurate results in a short time interval, so fast like that of antigen tests. Delivers results in less than 30 minutes.
A flux virometer
The team developed a flux virometer (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 the ICFO researcher, Rubaiya Hussain, “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”.
The sensor can detect very low concentrations of SARS-CoV-2 with a sensitivity of 91.2% and a specificity of 90%, similar to PCR, but as fast as the antigen test
–
–
Once this is done, the saliva samples are introduced into the sensor and passed through a “microfluidic channel under the light from a laser –explains the researcher–. The laser illuminates the sample and, if it contains viral particles, a signal is emitted thanks to the fluorescent marker. In less than a minute, the reader transmits the detected peaks of the signal to a graph and the system is alerted that the sample is positive”.
The ICFO team carried out a blind test of 54 samples provided by IrsiCaixa. The analysis confirmed 31 cases out of a total of 34 positives with only 3 false negatives. In addition, they were able to measure 3834 viral copies per milliliter, about three orders of magnitude below those obtained with rapid antigen tests. This means that this device is capable of detecting the presence of the virus at very low concentration levels in a solution.
To be used anywhere
The ICFO researcher and also co-author of the work, Ewelina Wajs, points out that “our device is very versatile. By selecting the appropriate antibodies, this technology could be adapted for the detection of other virusessuch as seasonal coronaviruses or the flu virus, or even microorganisms present in bodies of water, such as Legionella O E. coliwith a faster response time than that of analyzes usually carried out from cultures”.
With a single device, 2,000 tests can be performed per day, it could be adapted to detect other microorganisms and used for mass screening in public places without the need for specialized personnel
–
–
The authors of the study emphasize that with a single device it is possible to perform 2000 tests per day. In addition, they recall that the components of the device are inexpensive and available on the market, which allows the device to be manufactured on a large scale. In addition, this technique could also help reduce the volume of waste generated by the plastic packaging of the materials with which the PCR and antigen tests are carried out.
Finally, and due to its low cost and simplicity of its use, the new sensor could be a solution for the processes of diagnosis and control of the spread of the virus in Developing countrieswhere there is limited access to vaccines and fragile health systems.
The fact that this device does not have to be strictly used and manipulated by qualified personnel and in a specialized laboratory would facilitate its use in tests of mass screening in public placessuch as restaurants, schools, offices, theaters and cinemas.
Reference:
Rubaiya Hussain et al. “A small form factor flow virometer for SARS-CoV-2”. Biomedical Optical Express2022.
Study carried out by ICFO researchers Rubaiya Hussain, Alfredo E. Ongaro, Ewelina Wajs, led by ICREA professor at ICFO Valerio Pruneri, in collaboration with IrsiCaixa researchers Maria L. Rodriguez De La Concepción, Eva Riveira-Muñoz, Ester Ballana, Julià Blanco, Ruth Toledo, Anna Chamorro, Marta Massanella, Lourdes Mateu, Eulalia Grau, Bonaventura Clotet, supervised by Jorge Carrillo.
–
–
Source: ICFO / IrsiCaixa
Rights: Creative Commons.
–
