The anti SARS-CoV-2 activity of nanofibrous filter materials activated with metal clusters.

Nanofibrous filter materials were prepared by electrospinning a solution of 28 wt% poly(vinylidene fluoride) in N,N-dimethylacetamide with and without the addition of 2 wt% AgNO3, Cu(NO3)2·2.5H2O or ZnCl2. X-ray diffraction, scanning electron microscopy with energy dispersive X-ray spectroscopy, inductively coupled plasma mass spectroscopy, thermogravimetric analysis, contact angle measurement, nitrogen sorption, and mercury intrusion porosimetry methods were used for the characterization of physical structure as well as the chemical composition of the electrospun materials. Particle filtration efficiency and antiviral activity against the SARS-CoV-2 alpha variant were tested in order to estimate the suitability of the prepared electrospun filter materials for application as indoor air filtration systems with virucidal properties. All filter materials prepared with salts demonstrated very high particle filtration efficiency (≥98.0%). The best antiviral activity was demonstrated by a material containing Cu(NO3)2·2.5H2O in the spinning solution, which displayed the decrease in the number of infectious virions by three orders of magnitude after a contact time of 12 h. Materials with the addition of AgNO3 and ZnCl2 decreased the number of infectious virions after the same contact time by only ∼8 and ∼11 times, respectively.

Zebrafish embryos to study BSL-3 viruses and antiviral molecules

Emerging viruses are currently a burden with the recent SARS-CoV-2 pandemic resulting in more than 6 million death worldwide. Other viruses such as Arboviruses, transmitted by mosquitoes, can also emerge easily and represent a threat for humans and animals. These viruses are often RNA enveloped viruses and require to be studied in a BSL-3 (Bio-Safety- Laboratory of level 3 security), underlying the need to develop simple and rapid antiviral screenings. In recent years, the zebrafish has become a powerful tool in the biomedical sector to study viral infection and immunity. The optical transparency of the zebrafish embryo offers a major advantage for real time imaging of the infection process, and study hostpathogen interactions at subcellular levels in living systems using fluorescently labelled pathogens. While zebrafish embryos have been shown to be a successful vertebrate model to study a large panel of human disease, this model has been very little explored to study BSL-3 pathogen infection and propagation. This project was created to develop the zebrafish infection model for emerging BSL-3 viruses, and evolve towards high-content screening methods for antiviral molecules. Thanks to the setup of a microinjection system under a laminar flow hood in the BSL-3, we were able to inject in zebrafish embryos several emerging viruses, including the Chikungunya virus (CHIKV), Dengue virus (DENV) and SARS-CoV-2. Using fluorescently tagged viruses, infection was monitored in real time in vivo and confirmed with classical virology methods (RT-qPCR, plaque assays, TCID50). We then tested several nucleoside analogues described for their antiviral activity in vitro for these different viruses and we were able to validate the antiviral effect of some of these molecules in infected embryos. Altogether, our zebrafish infection model will provide us a better understanding of in vivo infection and propagation of these emergent BSL-3 viruses, and will be used as an intermediate model between in vitro antiviral screens and in vivo screens in mammals.

Preparation of nanofibrous materials activated with metal clusters for active and long-lasting air filters

Nanowire poly(vinylidene fluoride) (PVDF) polymer membranes activated with Ag and Zn nanoclusters were prepared using the electrospinning method. The structure of membranes was varied by using different polymer concentrations in N,N-dimethylacetamide, electric field strength, and concentration of AgNO3 and ZnCl2 in an electrospinning solution. Materials synthesised were analysed by nitrogen sorption and mercury intrusion porosimetry, X-ray diffraction, scanning electron microscopy with energy dispersive X-ray spectroscopy, thermogravimetry, inductively coupled plasma mass spectroscopy, particle filtration efficiency, and pressure drop methods. The concentration of Ag and Zn nanoclusters in PVDF membranes was established and the influence on nanofibers activity has been discussed. The hydrophobicity of membranes was tested using the wetting (contact) angle measurement method. The human influenza A virus (IAV) A/WSN/1933 (H1N1) strain was used to evaluate the virucidal activity of filtration materials. The virucidal activity increased with Ag nanoclusters concentration in fibres. The most hydrophilic nanofibers with Zn nanoclusters showed very high and practically concentration independent virucidal activity that was two orders of magnitude higher compared to materials activated with Ag nanoclusters.