A one-step method for generating antimicrobial nanofibre meshes via coaxial electrospinning

Abstract

Respiratory diseases, including influenza, infectious pneumonia, and severe acute respiratory syndrome (SARS), are a leading cause of morbidity and mortality worldwide. The recent COVID-19 pandemic claimed over 6.9 million lives globally. With the possibility of future pandemics, the creation of affordable antimicrobial meshes for protective gear, such as facemasks, is essential. Electrospinning has been a focus for much of this research, but most approaches are complex and expensive, often wasting raw materials by distributing antiviral agents throughout the mesh despite the fact they can only be active if at the fibre surface. Here, we report a low cost and efficient one-step method to produce nanofibre meshes with antimicrobial activity, including against SARS-CoV-2. Cetrimonium bromide (CTAB) was deposited directly onto the surface of polycaprolactone (PCL) fibres by coaxial electrospinning. The CTAB-coated samples have denser meshes with finer nanofibres than non-coated PCL fibres (mean diameter: ∼300 nm versus ∼900 nm, with mean pore size: ∼300 nm versus > 600 nm). The formulations have > 90% coating efficiency and exhibit a burst release of CTAB upon coming into contact with aqueous media. The CTAB-coated materials have strong antibacterial activity against Staphylococcus aureus (ca. 100%) and Pseudomonas aeruginosa (96.5 ± 4.1%) bacteria, as well as potent antiviral activity with over 99.9% efficacy against both respiratory syncytial virus and SARS-CoV-2. The CTAB-coated nanofibre mesh thus has great potential to form a mask material for preventing both bacterial and viral respiratory infections.

Fig. 1. The concept of the antimicrobial nanofibre mesh generated in this study. CTAB-coated PCL nanofibres (CidalMesh) are fabricated using coaxial electrospinning. The mesh is designed to have a theoretical average pore size of approximately 300 nm, facilitating efficient physical interception of respiratory pathogens. The CTAB coating is hypothesised to demonstrate rapid and potent antibacterial and antiviral activity against common respiratory pathogens, including S. aureus, P. aeruginosa, RSV, and SARS-CoV-2. Created with BioRender.com.

Fig. 2. Microscopy data. (a) SEM images (magnification: 8000×); (b) fibre diameter size distribution; (c) pore size distribution; (d) TEM images (magnification: S0 – 13 500×; S25, S50, S75 – 17 500×; S100 – 24 500×).

Fig. 3. Water contact angle data. (a) Photographs acquired with high-speed camera showing the change in shape of water droplets on the fibre formulations over 20 seconds; (b) graph showing the change in contact angle with time.

Fig. 4. Characterising data on the formulations. (a) FTIR spectra; (b) XRD patterns; (c) DSC data.

Fig. 5. CTAB release (%) from the electrospun formulations over 48 h, with an inset showing the release profile for the first 4 hours. Data are given from three independent experiments as mean ± S.D.

Fig. 6. Antibacterial effects of S0–S100 on S. aureus and P. aeruginosa as quantified by (a) agar diffusion and (b) colony-counting. Single factor ANOVA with post hoc Tukey's test. Statistical significance: *** (α = 0.01, p-value ≤ 0.001). ND = not detected.

Fig. 7. Viral activity of the formulations against (a) RSV and (b) SARS-CoV-2. Single factor ANOVA with post hoc Tukey's test. Statistical significance: ** (α = 0.01, p-value ≤ 0.01), *** (α = 0.01, p-value ≤ 0.001).