Qualitative evaluation of antiviral properties of materials (packaging and surfaces of different types)

The antiviral activity with respect to SARS-CoV-2 is evaluated using a viral suspension of a known titer. The materials, tested in triplicate, are placed in contact with the viral suspension for an incubation period of three hours. The viral suspension is then used to inoculate VERO E6 cells.

After 48 hours, the antiviral titer is measured by Real-Time PCR testing (40 cycles): T48h is the value after 48 hours; T0h is the value immediately after inoculation.

The antiviral activity is calculated according to the following formula:

ΔCt= Ct48h – Ct0h


Ct: threshold cycle, the number of the amplification cycle which first yields a signal of successful amplification.

Ct48h= Ct of the virus 48 h after the infection/treatment

Ct0h= Ct of the virus 0 h after the infection/treatment

This procedure provides for internal controls:

  • Control of the viral suspension: the titer of the viral suspension is inoculated directly onto the VERO E6 cells in order to assess the quality of the starting inoculum.
  • Control to exclude the presence of cytotoxic substances in the analyzed material: This test is performed to ensure that there are no cytotoxic substances in the analyzed material that might compromise the viability of the VERO cells. To do this, the culture medium (virus-free) in which the viral suspension is prepared is inoculated on the material in triplicate, just as for the viral suspension. We then proceed as per protocol.

Interpreting the RESULTS

If Δct < 0, the material has no antiviral activity

If Δct ≥ 0, viral replication was inhibited by the material


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