Fine ceramics (advanced ceramics, advanced technical ceramics) — Determination of antiviral activity of semiconducting photocatalytic materials under indoor lighting environment - Test method using bacteriophague Q-beta (ISO 18071: 2016).
Test not accredited in our laboratory.
The ISO 18071: 2016 standard establishes a test method to determine the antiviral activity of ceramics or other products with active photocatalytic materials under interior lighting, both integrated and arranged in films on the surface, by quantifying the reduction of bacteriophage Q-beta infectivity after exposure to indoor artificial light. This test is intended for the analysis of interior illuminated photocatalytic semiconductor materials used in construction materials, in the form of a flat sheet, board, or plate, excluding analysis of porous, granular, or porous photocatalytic materials, and fabrics or textiles.
In the test described by ISO 18071, bacteriophage Q-beta is used as the surrogate virus for Influenza viruses. The test sample with the photocatalytic material under interior illumination is inoculated with a suspension of bacteriophage Q-beta of known titer and exposed to an artificial interior light source (100-3000 lx) for a set period of time (2-8 hours). After exposure to light, the bacteriophage titer in the pieces is determined by counting plaque forming units (PFU). For this, the bacteriophage is recovered by washing the pieces and the resulting washing solutions are mixed with suspensions of Escherichia coli bacteria sensitive to bacteriophage Q-beta. The mixtures of the test solutions and the receptor bacteria are plated on agar plates and incubated to obtain the counts of the plaque forming units. The bacteriophage titer (UFP) obtained from the pieces with photocatalytic antiviral material exposed to light is compared with the titer obtained from the control samples (not treated with the photocatalytic material) exposed to light, and with that of the samples and treated and not treated with photocatalytic material kept in the dark for the same period of time, and the value of the photocatalytic antiviral activity under interior lighting with exposure to interior light (ΔV) is calculated. The ISO 18071: 2016 standard does not establish any reduction criteria to affirm that a product does or does not show photocatalytic antiviral activity under interior lighting, but only allows assigning a value of antiviral activity or reduction when comparing the bacteriophage titers obtained from the pieces treated with the photocatalytic test material subjected to illumination, with those of the untreated subject to illumination and those kept in the dark (treated and untreated). In case the test sample includes non-photocatalytic antiviral materials under interior lighting, the value of antiviral activity can also be calculated without active photocatalysis under interior lighting (RV).
Square pieces of the test product of 50 ± 2 mm x 50 ± 2 mm, and the thickness of which should not exceed 10 mm, are used in this test. Both parts treated with the photocatalytic material under interior lighting and control parts with the same characteristics are used, but without the photocatalytic treatment. The number of test pieces is 15 per test (9 pieces untreated and 6 pieces treated with the photocatalytic material under interior lighting). The pieces are destined in the following groups: 3 units without photocatalytic material to quantify the titer of the inoculum control; 3 units with photocatalytic material and another 3 units without photocatalytic material to keep in the same test chamber without exposure to ultraviolet light; and 3 units with photocatalytic material and another 3 units without photocatalytic material to keep in the same test chamber with exposure to interior light. However, it is always recommended to send twice the number of pieces needed (30 pieces: 18 without photocatalytic treatment and 12 with photocatalytic treatment), in case we had to repeat any step of the procedure.
The customer, according to the circumstances where the test product is intended to be used, must choose the test conditions. The standard recommends performing the test with an illuminance of 1000 lx ± 50 lx, but indicates that it can be adjusted between 100 lx ± 5 lx and 3000 lx ± 150 lx, to take into account the actual conditions of use of the material. In addition, the ultraviolet light blocking condition must be selected: condition A implies blocking wavelengths <400 nm, while condition B implies blocking wavelengths <380 nm. The customer must also indicate the artificial lighting time required. The exposure time to artificial light recommended by the standard is 4 hours, but it is allowed to adapt the test time between 2 and 8 hours to adapt the test to the actual use of the product to be analyzed.