Evaluation of biocidal properties of biodegradable nanofiber filters and their use in face masks.

Due to the recent coronavirus-2019 pandemic, several studies have emerged looking for new materials, especially with biocidal characteristics. Thus, the present research investigates the antibacterial properties of biodegradable cellulose acetate (CA) / cetylpyridinium bromide (CPB) electrospun nanofibers, their aerosol filtration, and the possible use as a filter media of surgical face masks. Then, samples of these nanofibers were produced over a nonwoven substrate, using different volumes of polymeric solution during the electrospinning process. The evaluation of the antibacterial properties of the nanofibers was performed for Escherichia coli and Staphylococcus aureus using quantitative methods. The aerosol filtration performance was evaluated in these samples for NaCl nanoparticles (from 7-300 nm) and with 8 mL min-1 of air flow rate. The results show that the single use of the surfactant has antibacterial properties from a concentration of 39 µg mL-1 of solution. The nanofibers presented a reduction of 100% for both bacteria. Air filtration tests showed 126.03 and 207.73 Pa cm-² of pressure drops and 63 and 77% of aerosol filtration efficiency (FE) for samples with 0.13 and 0.15 mL, respectively. Regarding the nanofiber produced with 0.35 mL, the value obtained was 115.13 ± 33.64 Pa cm-2 and 3.15% of particle penetration. These breathability values are higher than those required for the surgical face mask standard, indicating that improvements in the porosity and thickness are necessary to meet the Brazilian requirements. However, the nanofibers could be applied as filter media for indoor air conditioning systems due to their FE and biocidal properties.

Antimicrobial Properties of Composites of Chitosan-Silver Doped Zeolites.

The antimicrobial functionality of composites constituted by chitosan with silver-doped zeolites was developed and characterized. A composite with chitosan particles and silver-doped zeolites was synthesized using an ionic gelation process with sodium tripolyphosphate. The chitosan silver-doped zeolites composite obtained presented sizes up to 5 µm, while the silver-doped zeolites had an average size between 0.5 µm and 3.3 µm. The synthesized chitosan silver-doped zeolites composites, as well as the silver-doped zeolites and the chitosan dissolution, were characterized through X-ray diffraction, Fourier Transform Infrared spectroscopy and scanning electron microscopy. The electro kinetic behaviour of chitosan, silver-doped zeolites and chitosan silver-doped zeolites composite was evaluated under different pH conditions. The antimicrobial activity of the composites was evaluated in terms of minimum inhibitory concentrations and minimum lethal concentrations and the results suggest that the chitosan silver-doped zeolites composites show antimicrobial activity against gram-negative and gram-positive bacteria, Escherichia coli and Staphylococcus aureus, respectively and against Candida albicans. The results here presented support the potential application of the composite of chitosan with silver-doped zeolites in the functionalization of textiles with antimicrobial properties.