Scientists have developed the first photo-electrochemical aptasensor that detects the SARS-CoV-2 virus in a saliva sample. This sensor, which uses aptamers (a type of artificial antibody), is more sensitive that antigen-based sensors and detects the virus more quickly and cheaply than PCR tests. The new devices can be incorporated into portable diagnostic systems and are easy to use.
The new aptasensor has a wide range of sensitivity to different virus concentrations. It is thus capable of detecting concentrations below 0.5 nanomolars (nM), typical in patients who have not yet developed COVID symptoms, as well as working at higher concentrations (up to 32 nM), so it could provide clinical practices with an extra tool for monitoring the progress of infection in patients.
It would be used in a similar way to current antigen sensors: a sample of the patient’s saliva is dissolved in a buffer solution and then placed on to the sensor’s surface. The measurement would be available in a few minutes.
The device uses a surface that contains graphitic carbon nitride-cadmium sulphide quantum dots (C3N4-CdS) with photoactive properties. It is on this surface that a specific receptor is immobilised in such a way that, in the presence of the target molecule, it binds to the bioreceptor, thereby reducing the current generation associated with the presence of light. On this particular sensor, the bioreceptor used is an aptamer that is capable of interacting with the receptor-binding domain (RBD) of the SARS-CoV-2 virus.