The interaction between hypericin and supported lipid bilayers mimicking coronavirus envelopes.

Biological membranes are one of the most important self-assembled structures in nature. They provide many functional and protective features for cells and have a fundamental role in enveloped virus infectivity. The targeting of the viral envelope is an emerging strategy in the development of broad-spectrum antivirals, also based on photosensitizers (PS). PS are molecules that trigger the production of singlet oxygen upon photo-excitation. Singlet oxygen is a strong oxidant capable of damaging biomolecules, such as phospholipids. For a few decades, PS have been employed in a therapy called Photodynamic Therapy (PDT) mostly against cancer cells, but also against bacteria and viruses. We focused on hypericin (Hyp), a photosensitizer that was found to inactivate enveloped viruses, including SARS-CoV-2, not only upon photo-excitation, but also in dark conditions. To study the effects of hypericin on a viral envelope we used supported lipid bilayers, an excellent model system for membranes, with a lipid mixture to mimic the viral envelope. By performing AFM microscopy and AFM-STED correlative nanoscopy (Hyp is fluorescent), we reported a noticeable effect of Hyp at various concentrations.