In 2019, a novel strain of coronavirus, SARS-CoV-2, was identified and the use of protective masks became essential. Considering most mask options display a passive-like action against COVID-19, we proposed the incorporation of anti-viral essential oils (EOs) onto nanofibrous mats, to function as inner layers in three-layer masks, and this way actively fight the virus.

Polycaprolactone (PCL) and cellulose acetate (CA) solutions were prepared individually at 14 wt% in chloroform/dimethylformamide (DMF) and 10 wt% in acetone/DMF, respectively, and then combined at 3:1 ratio. Polymeric solutions were processed via eletrospinning at 24.7 kV, 3.2 mL/h and 21 cm. Uniform, beadless nanofibers were obtained. Mats were characterized as mechanically resilient, to endure movements arising from mask handling, and hydrophobic in nature, to repel droplets coming from the exterior. Twenty EOs selected based on their antimicrobial nature were examined for the first time against the Escherichia virus MS2, a mimetic of COVID-19. The most effective were the lemongrass (LO), Niaouli (NO) and eucalyptus (ELO) with a minimum inhibitory concentration (MIC) of 356.0 mg/mL, 365.2 mg/mL and 586.0 mg/mL, respectively. Loading of the nanofibrous mats was accomplished via physisorption using the free -OH groups of the CA as linkers. Mats were loaded with the EOs at MIC concentration for 72 h (saturation) under constant agitation. Presence of the EOs was confirmed along the mats by UV/visible spectroscopy. Kirby-Bauer examinations verified the EOs-loaded mat’s diffusion abilities and antimicrobial effectiveness (formation of halos). Time-kill kinetics reported the elimination of >99% of MS2 virus in 6 h of contact. Data demonstrated the potential of these EOs-loaded PCL/CA nanofibers mats to work as COVID-19 active barriers in protection masks.