Angiotensin-converting enzyme 2 (ACE2), a host protein with strong binding to the COVID-19 S protein, was used by Pinals and co-workers to build a nanosensor based on non-covalently functionalised SWCNTs.56 Within 90 minutes of being exposed to the COVID-19 S protein, the fluorescence of the nanosensor increases two-fold. This evidence concerns the gene ACE2 and COVID-19.