Polypropylene-Rendered Antiviral by Three-Dimensionally Surface-Grafted Poly(N-benzyl-4-vinylpyridinium bromide)

To inhibit viral infection, it is necessary for the surface of polypropylene (PP), a polymer of significant industrial relevance, to possess biocidal properties. However, due to its low surface energy, PP weakly interacts with other organic molecules. The biocidal effects of quaternary ammonium compounds (QACs) have inspired the development of nonwoven PP fibers with surface-bound quaternary ammonium (QA). Despite this advancement, there is limited knowledge regarding the durability of these coatings against scratching and abrasion. It is hypothesized that the durability could be improved if the thickness of the coating layer were controlled and increased. We herein functionalized PP with three-dimensionally surface-grafted poly(N-benzyl-4-vinylpyridinium bromide) (PBVP) by a simple and rapid method involving graft polymerization and benzylation and examined the influence of different factors on the antiviral effect of the resulting plastic by using a plaque assay. The thickness of the PBVP coating, surface roughness, and amount of QACs, which jointly determine biocidal activity, could be controlled by adjusting the duration and intensity of the ultraviolet irradiation used for grafting. The best-performing sample reduced the viral infection titer of an enveloped model virus (bacteriophage ϕ6) by approximately 5 orders of magnitude after 60 min of contact and retained its antiviral activity after surface polishing-simulated scratching and abrasion, which indicated the localization of QACs across the coating interior. Our method may expand the scope of application to resin plates as well as fibers of PP. Given that the developed approach is not limited to PP and may be applied to other low-surface-energy olefinic polymers such as polyethylene and polybutene, our work paves the way for the fabrication of a wide range of biocidal surfaces for use in diverse environments, helping to prevent viral infection.


Figure S2 .
Figure S2.FT-IR spectra of PVP-grafted PP prepared by varying the UV irradiation time from 0.5 to 30 min.Peaks derived from PP (2955, 2915, and 2871 cm -1 ) 1 are shown as black dashed lines.The inner portion of the gray frame is enlarged and shown in Figure 2a.

Figure S3 .
Figure S3.FT-IR spectra of PBVP-grafted PP prepared by varying benzylation times from 0.5 to 5 h.The absorption peak at 3400 cm −1 (purple dashed line) is caused by adsorbed water present in both PVP-and PBVP-grafted PP.Peaks derived from PP (2955, 2915, and 2871 cm -1 ) are shown as black dashed lines.The inner portion of the gray frame is enlarged and shown in Figure 2b.

Figure S7 .
Figure S7.Electro-osmosis profiles of (a) NC, (b) T-1, (c) T-3, and (d) T-10.The apparent electrophoretic mobility of the monitored particles was measured at seven different points in the cell's depth direction.Each electro-osmosis profile was used to determine the velocity of the electro-osmotic flow at the solid interface and derive the zeta potential of the flat surface.

Figure S8 .
Figure S8.Schematic cross-sectional view of PBVP-coated PP.Coating thickness (d) refers to the thickness of the PBVP coating layer, and total thickness is the thickness of the entire specimen.

Figure S9 .
Figure S9.(a) 2D image of the boundary between the non-coated and PBVP-coated areas of T-3.The red line shows the line scan position.(b) Surface topography of the area line-scanned in (a).The horizontal axis displays the x-coordinate, while the vertical axis displays the height.The flat orange line indicates the non-coated area, while the pink line shows the unevenness in the coated area.The difference in height between these two lines was used to calculate d.(c) 2D image of T-1.(d) Surface topography of the area line-scanned in (c).The d value of T-1could not be calculated because the border between coated and noncoated areas could not be detected.

Figure S10 .
Figure S10.(a) Cross-sectional SEM image of PBVP-coated PP.(b) EDX spectra of areas enclosed by (b) red and (c) yellow lines.

Figure S11 .
Figure S11.FT-IR spectra after the (a) heat and (b) moisture treatments of T-10 for 60 and 133 h and after immersion in (c) water and (d) 70% ethanol for 15 h and 1 week.Red and black dotted lines indicate pyridinium salt (1635 cm −1 ) and PP (1375 cm −1 ) peaks, respectively.

Figure S13 .
Figure S13.Plate of plaque assay with bacteriophage φ6 in contact with (a) NC and (b) T-10 for 60 min.

Figure S14 .
Figure S14.Reverse transcription-quantitative polymerase chain reaction (RT-qPCR) analysis for bacteriophage φ6 S_1 gene.All examinations were performed in triplicate and independently.The results are presented as the corresponding means ± SDs.RT-qPCR was performed using Taqman fast Virus 1-step master Mix (Thermo Fisher Scientific, Waltham, MA) using QuantStudio 3 (Thermo Fisher Scientific, Waltham, MA) and the following set of primers/probes.Forward primer, 5'-TGGCGGCGGTCAAGAGC -3';

Figure S16 .
Figure S16.(a) Schematic cross-sectional view of PBVP-coated PP before and after polishing.The thickness of the entire specimen (total thickness) was measured with a digital micrometer before and after polishing, and the difference due to polishing (decreased total thickness) is shown in Figure 8a.The thickness of four NC samples were measured, and the mean was used as the substrate thickness.Coating thickness (d) was calculated by subtracting substrate thickness from total thickness.(b) Residual coating thicknesses of T-1, T-3, and T-10 determined from the coating thicknesses calculated before and after polishing in (a).Four pieces were polished for each sample, and the results were expressed as the corresponding means ± SDs.

Figure S18 .
Figure S18.Water contact angles (WCAs) of 2 µL water droplets on polished T-1, T-3, and T-10.Data represent the means and SDs from five different spots on the same sample.