Questioning ZnO, Ag, and Ag/ZnO nanoparticles as antimicrobial agents for textiles: Do they guarantee total protection against bacteria and SARS-CoV-2?

Abstract

Coronavirus Disease 2019 (COVID-19) occasioned global economic and health systems collapse. Also, it raised several concerns about using conventional cotton fabrics for manufacturing personal protective equipment without the antimicrobial capacity to inactivate viruses, such as Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) and its variants. Therefore, developing antimicrobial cotton fibers is crucial to avoid new global pandemics or the transmission of dangerous pathogens that remain on surfaces for long periods, especially in hospitals and medical clinics. Herein, we developed antimicrobial cotton fabrics with Ag, ZnO, and Ag/ZnO nanoparticles and evaluated their bactericidal activity against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus), photocatalytic activity, and antiviral activity against Delta SARS-CoV-2. Although the antimicrobial fabrics are effective against these bacteria, they only reduce part of the SARS-CoV-2 virions during the first 15 min of direct contact via damage only to biological structures on the viral surface particle while the viral RNA remains intact.

Keywords: Antimicrobial; Multifunctional textiles; SARS-CoV-2; Silver; ZnO.

Graphical abstract

Fig. 1

(a) The hydrodynamic diameter of the AgNPs, ZnO-NPs, and Ag/ZnO-NPs. Color map for the (b) direct optical bandgap (E_g^d) and (c) indirect optical bandgap (E_gⁱ) of the ZnO-NPs, and Ag/ZnO-NPs after the sonochemical procedure. Adjust error (R²) higher than 0.96 or the polynomial surface fitting.

Fig. 2

SEM images of the CF before and after surface modification with different concentrations of Ag, ZnO, and Ag/ZnO nanoparticles.

Fig. 3

Color map for the inhibition zone diameter determined from the bacterial plaque assay against E. coli (a) and S. aureus (b). (c) Photodegradation efficiency of the CF coated with AgNPs, ZnO-NPs, and Ag/ZnO-NPs. (d) Rate constant (k), (e) kinetics profile, and (f) trapping experiment data of the photocatalytic degradation of methylene blue (MB) by the coated CF under blue light irradiation (450 nm). Adjust error (R²) higher than 0.94 or the polynomial surface fitting. Turkey's test indicates that the ZnO and Ag content significantly influences photodegradation efficiency from trapping experiment data with p < 0.0001, using a 95% reliability level. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)

Fig. 4

(a) Antiviral activity of the CF coated with AgNPs, ZnO-NPs, and Ag/ZnO-NPs against SARS-CoV-2 after 5, 10, and 15 min of cotton-virus exposition. Amplified RNA and Ct values determined by RT-qPCR for SARS-CoV-2 using the N1 (b) and N2 (c) gene targets. Mean and standard deviation are shown and only statistically significant differences (* p < 0.05) are marked on graphs.