Molecular beacons aptamers were tested for the detection of the SARS-Cov-2 virus protein S. The interest for the direct detection of protein S lies in the fact that the assay can be performed in 1 single step, with no sample preparation required. Moreover, targeting the protein S could possibly enable the detection and identification of diverse variants (i.e. modified protein S). From the very beginning of the project, a patent attorney was consulted about the patentability of the beacon aptamers. While it became clear that the general idea of beacon aptamer was already published and therefore not patentable, some more narrow aspect, such as specific sequence, ratio of nucleotides in loop to stem of the beacon configuration were possibly patentable. However, more research was needed to identify these.
To this end, aptamers for SARS-COV-2 protein S were selected, adapted to a beacon configuration and tested for protein S detection. The read-out techniques that were tested were all based on fluorescence detection: we tested bulk fluorescence using a fluorescence plate reader and substrate bound assay. Among the molecular beacon aptamers that were tested, one in particular showed a capacity to detect protein S at the nM level, which can be of interest, despite the fact that this limit of detection is 2 orders of magnitude lower than the LOD of current antigen tests available commercially, which are designed to detect the SARS-Cov-2 protein N. The interest lies in the direct detection of protein S, not requiring virus lysis and possibly opening up for variant specific detection. However, at the same time, a publication showed this very same aptamer adapted as beacon (
https://doi.org/10.1021/acssensors.1c01222(opens in new window)).
