They design a chemical antibody sensor to detect the coronavirus in saliva.

Scientists of Carlos III University of Madrid (UC3M) developed the first photoelectrochemical sensor that detects the SARS-Cov-2 virus in a saliva sample. This device, which uses aptamers (a type of chemical antibody), has more sensitivity than those based on antigens and performs detection faster and more cost-effectively than PCR testing.

According to their creators, these new devices can be incorporated into portable diagnostic systems and are easy to use.

The new aptasensor has great sensitivity to different concentrations of the virus, and is capable of detecting concentrations below 0.5 nanomolar, typical in patients who have not yet developed any symptoms of covid-19

The new aptasensor has great sensitivity to different concentrations of the virus and is able to detect concentrations below 0.5 nanomolar (nM), typical of patients who have not yet developed any symptoms of covid-19.

Furthermore, it also acts at higher concentrations (up to 32 nM), which could provide clinical practice with an additional tool to monitor the evolution of the infection in patients.

the use would be very similar to current antigen sensors: a sample of the patient’s saliva would have to be dissolved in a buffer solution and then deposited on the sensor surface. The measurement would be available in a few minutes.

“The advantage over current antigen-based sensors is the increased sensitivity Y specificity of measurements from photoelectrochemical sensors comparable to other more complex ones, such as those based on fluorescence, and simpler, cheaper and faster than those based on PCR”, he highlights. Mahmoud Amouzadeh Tabrizi, from Carlos III University (UCM3) and main author of the research.

The science behind an aptasensor

ONE photoelectrochemical sensor it can be assimilated to a solar cell or to the phenomenon of photosynthesis: in both cases, in the presence of Light (photons), a specific material (or molecule) is capable of generating a electric current (electrons).

The researcher points out that, in his case, they used “a surface containing quantum dots based on graphitic carbon nitride Y cadmium sulfide (C3N4-CdS) with photoactive properties. It is on this surface that, additionally, a specific receptor is immobilized in such a way that, in the presence of the target molecule, it binds to the bioreceptor, reducing, in this case, the generation of current associated with the presence of light. ”.

Furthermore, Tabrizi continues, in this specific sensor, the bioreceptor that has been used is an aptamer capable of interacting with the recipient domain – required (RBD) of the SARS-CoV-2 virus, hence the name photoelectrochemical aptasensor.

The results of this and other work by the group on the detection of SARS-CoV-2 in saliva were recently published in several scientific journals, such as Sensors and Actuators B: Chemical Y Biosensors and Bioelectronics.

A sensible low-cost system

As observed Pablo Acedo, responsible for Sensors and Instrumentation Techniques (SITec) at UC3M, “the idea now is to complement these results with the development of complete biomedical instruments and diagnostics to obtain a highly sensitive and specific, portable and potentially low-cost diagnostic system to use in clinical practice.

“It would be trying to obtain a diagnosis similar to what exists today for reading blood glucose levels in patients with diabetes, for example. Our idea is to also get in touch with companies that may be interested in these projects”, completes the researcher.

One of the critical aspects in the manufacture of this type of electrochemical sensor based on nanomaterials it is the correct characterization of the material’s surface and of the receptor immobilized on the surface.

To do this, the researchers used various techniques and technologies, such as scanning electron microscopy (WITHOUT), microscopic atomic force (AFM) and Fourier transform spectroscopy (FTIR).

“The results obtained with the use of all these techniques allow us to guarantee that both the manufacture of the desired photosensitive nanomaterial and the immobilization of the bioreceptor have been carried out in a satisfactory manner”, concludes Acedo.


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