Triple-target stimuli-responsive anti-COVID-19 face mask with physiological virus-inactivating agents

Conventional face masks to prevent SARS-CoV-2 transmission are mostly based on a passive filtration principle. Ideally, anti-COVID-19 masks should protect the carrier not only by size exclusion of virus aerosol particles, but also be able to capture and destroy or inactivate the virus. Here we present the proof-of-concept of a filter mat for such a mask, which actively attracts aerosol droplets and kills the virus. The electrospun mats are made of polycaprolactone (PCL) a hydrophilic, functionalizable and biodegradable polyester, into which inorganic polyphosphate (polyP) a physiological biocompatible, biodegradable and antivirally active polymer (chain length, ∼40 P_i units) has been integrated. A soluble Na-polyP as well as amorphous calcium polyP nanoparticles (Ca-polyP-NP) have been used. In this composition, the polyP component of the polyP-PCL mats is stable in aqueous protein-free environment, but capable of transforming into a gel-like coacervate upon contact with divalent cations and protein like mucin present in (virus containing) aerosol droplets. In addition, the Ca-polyP-NP are used as a carrier of tretinoin (all-trans retinoic acid) which blocks the function of the SARS-CoV-2 envelope (E) protein, an ion channel forming viroporin. The properties of this novel mask filter mats are as follows: First, to attract and to trap virus-like particles during the polyP coacervate formation induced in situ by aerosol droplets on the spun PCL fibers, as shown here by using SARS-CoV-2 mimicking fluorescent nanoparticles. Second, after disintegration the NP by the aerosol-mucus constituents, to release polyP that binds to and abolishes the function of the receptor binding domain of the viral spike protein. Third, to destroy the virus by releasing tretinoin, as shown by the disruption of virus-mimicking liposomes with the integrated recombinant viral viroporin. It is proposed that these properties, which are inducible (stimuli responsive), will allow the design of antiviral masks that are smart.