Nh2 2co

HCoV-OC43 (ATCC VR-1558) was grown in HCT-8 cells in RPMI 1640 with 5% FBS and 1% penicillin-streptomycin (7 days, 33°C, 5% CO₂). HCoV-229E (ATCC VR-740) was grown in MRC-5 fibroblast cells in DMEM with 5% FBS and 1% penicillin-streptomycin (4 days, 33°C, 5% CO₂). Virus stocks were obtained by harvesting the medium from infected cells and centrifuging at 3,000 × g for 4 min to remove cell debris.
For laundering experiments, HCoV-OC43 was concentrated using polyethylene glycol (PEG) precipitation. A 4× PEG solution (40% PEG 8000, 1.2 M sodium chloride, and 1× phosphate-buffered saline; Sigma-Aldrich, Gillingham, UK) was added to the virus stock and incubated at 4°C overnight before centrifuging at 3,000 × g for 40 min. The resulting pellet was resuspended at 10× concentration in either DMEM or artificial saliva.
Artificial saliva was prepared according to ASTM E2721-16 (37 ), comprising 1.54 mM KH₂PO₄ (Sigma-Aldrich), 2.46 mM K₂HPO₄ (Fisher Scientific, Loughborough, UK), 0.04 mg/liter MgCl₂·7H₂O (Fisher Scientific), 0.11 g/liter NH₄Cl (Sigma-Aldrich), 0.12 g/liter (NH₂)₂CO (Sigma-Aldrich), 0.13 g/liter CaCl₂ (Sigma-Aldrich), 0.19 g/liter KSCN (Sigma-Aldrich), 0.42 g/liter NaHCO₃ (Fisher Scientific), 0.88 g/liter NaCl (Fisher Scientific), 1.04 g/liter KCl (SLS, Wilford, UK), and 3 g/liter mucin (Sigma-Aldrich) at pH 7.
Virus stocks were stored at −80°C prior to use.

Cellulose acetate (CA; average acetyl content of 39.7 wt%, average MW~50,000 (GPC) (Sigma Aldrich, Burlington, MA, USA) has been used as a polymer component for membrane preparation. The N, N-dimethylformamide (DMF) purity of 99% (Sigma Aldrich, Burlington, MA, USA) has been used as a solvent during polymer blending. Laboratory synthesized Zinc oxide (ZnO) has been employed as a membrane additive. A Glycerol (Honeywell, Morristown, NJ, USA) solution was also used in membrane washing operations. For the synthesis of nanostructured zinc nitrate hexahydrate Zn(NO₃)₂·6H₂O (Lach-Ner, Tovární, Neratovice), urea >99% purity (NH2)2CO (Sigma Aldrich, Burlington, MA, USA), zinc acetate dihydrate >99% purity Zn(CH₃COO)₂·2H₂O (Sigma Aldrich, Burlington, MA, USA), hexamethylenetetramine >99% purity (HMTA)C₆H₁₂N₄ (Merck, New York, NY, USA), PEI, sodium citrate dihydrate >99% purity C₆H₅Na₃O₇·2H₂O (Merck, New York, NY, USA) has been used. Methylene Blue was supplied by local manufacturers who use it for their day-to-day applications. The main components of UV source light were used from a mechanical solar simulator model no. 21117 (Newport, CA, USA).