Enhanced and copper concentration dependent virucidal effect against SARS-CoV-2 of electrospun poly(vinylidene difluoride) filter materials

Virucidal filter materials were prepared by electrospinning a solution of 28 wt% poly(vinylidene difluoride) in N,N-dimethylacetamide without and with the addition of 0.25 wt%, 0.75 wt%, 2.0 wt% or 3.5 wt% Cu(NO3)2·2.5H2O as virucidal agent. The fabricated materials had a uniform and defect free fibrous structure and even distribution of copper nanoclusters. X-ray diffraction analysis showed that during the electrospinning process, Cu(NO3)2·2.5H2O changed into Cu2(NO3)(OH)3. Electrospun filter materials obtained by electrospinning were essentially macroporous. Smaller pores of copper nanoclusters containing materials resulted in higher particle filtration than those without copper nanoclusters. Electrospun filter material fabricated with the addition of 2.0 wt% and 3.5 wt% of Cu(NO3)2·2.5H2O in a spinning solution showed significant virucidal activity, and there was 2.5 ± 0.35 and 3.2 ± 0.30 logarithmic reduction in the concentration of infectious SARS-CoV-2 within 12 h, respectively. The electrospun filter materials were stable as they retained virucidal activity for three months.