Development of biosensors for detection of SARS-CoV-2 virus by Triplex Enhanced Nucleic Acid Detection Assay (TENADA).

SARS-CoV-2, a positive-strand RNA virus has caused devastating effects. The standard method for COVID diagnosis is based on polymerase chain reaction (PCR). The method needs expensive reagents and equipment and well-trained personnel and takes a few hours to be completed. The search for faster solutions has led to the development of immunological assays based on antibodies that recognize the viral proteins that are faster and do not require any special equipment. Here we explore an innovative analytical approach based on the sandwich oligonucleotide hybridization which can be adapted to several biosensing devices. PolyPurine Reverse Hoogsteen hairpins (PPRHs) oligonucleotides that form high affinity triplexes with the polypyrimidine target sequences are used for the efficient capture of the viral genome. Then, a second labelled oligonucleotide is used to detect the formation of a trimolecular complex in a similar way than antigen tests do. The limit of detection is around 0.01 nM (a few femtomoles) without the use of any amplification steps. The Triplex Enhanced Nucleic Acid Detection Assay (TENADA) can be readily adapted for the detection of any pathogen requiring only the knowledge of the pathogen genome sequence.