The Development of New Nanocomposite Polytetrafluoroethylene/Fe2O3 NPs to Prevent Bacterial Contamination in Meat Industry

Abstract

The bacterial contamination of cutting boards and other equipment in the meat processing industry is one of the key reasons for reducing the shelf life and consumer properties of products. There are two ways to solve this problem. The first option is to create coatings with increased strength in order to prevent the formation of micro damages that are favorable for bacterial growth. The second possibility is to create materials with antimicrobial properties. The use of polytetrafluoroethylene (PTFE) coatings with the addition of metal oxide nanoparticles will allow to the achieving of both strength and bacteriostatic effects at the same time. In the present study, a new coating based on PTFE and Fe₂O₃ nanoparticles was developed. Fe₂O₃ nanoparticles were synthesized by laser ablation in water and transferred into acetone using the developed procedures. An acetone-based colloidal solution was mixed with a PTFE-based varnish. Composites with concentrations of Fe₂O₃ nanoparticles from 0.001-0.1% were synthesized. We studied the effect of the obtained material on the generation of ROS (hydrogen peroxide and hydroxyl radicals), 8-oxoguanine, and long-lived active forms of proteins. It was found that PTFE did not affect the generation of all the studied compounds, and the addition of Fe₂O₃ nanoparticles increased the generation of H₂O₂ and hydroxyl radicals by up to 6 and 7 times, respectively. The generation of 8-oxoguanine and long-lived reactive protein species in the presence of PTFE/Fe₂O₃ NPs at 0.1% increased by 2 and 3 times, respectively. The bacteriostatic and cytotoxic effects of the developed material were studied. PTFE with the addition of Fe₂O₃ nanoparticles, at a concentration of 0.001% or more, inhibited the growth of E. coli by 2-5 times compared to the control or PTFE without NPs. At the same time, PTFE, even with the addition of 0.1% Fe₂O₃ nanoparticles, did not significantly impact the survival of eukaryotic cells. It was assumed that the resulting composite material could be used to cover cutting boards and other polymeric surfaces in the meat processing industry.

Keywords: Teflon; antibacterial activity; cytotoxicity; fluoroplast; food industry; iron oxide nanoparticles; reactive oxygen species.

Figure 1

Physical characteristics of Fe₂O₃ NPs: (a) size distribution histogram; (b) ζ-potential distribution histogram; (c) UV–visible absorbance spectrum; (d) TEM image (scale bar—1 μm).

Figure 2

Example of applying a PTFE-based coating to a damaged surface of a fluoroplast before (left) and after (right) coating (a); AFM images of composite material surface: (b) 3D reconstruction of PTFE without NPs; (c) result of analysis of PTFE selected area (shown as a diagonal line in the figure) without NPs surface; (d) 3D reconstruction of PTFE/0.1% Fe₂O₃ NPs; (e) result of analysis of PTFE/0.1% Fe₂O₃ NPs surface. The results of the analysis in panels (c) and (e) are presented in the form of profiles and a table with data on the depth of the asperities in the sample.

Figure 3

The results of the analysis of the obtained materials by MIM method: (a) PTFE without the addition of nanoparticles; (b) PTFE with the addition of 0.001% Fe₂O₃ nanoparticles; (c) PTFE with the addition of 0.01% Fe₂O₃ nanoparticles; (d) PTFE with the addition of 0.1% Fe₂O₃ nanoparticles. The images are presented as 3D reconstructions, where the abscissa and ordinate axes correspond to the real distance in μm. The Oz axis displays the phase difference in nm (the larger the phase difference, the higher the value on the Oz axis). Coloring is a pseudo-color. The initial data on the spatial distribution of the phase difference in the analyzed sample, used to construct 3D reconstructions, are shown in the lower left corners of each panel.

Figure 3

The results of the analysis of the obtained materials by MIM method: (a) PTFE without the addition of nanoparticles; (b) PTFE with the addition of 0.001% Fe₂O₃ nanoparticles; (c) PTFE with the addition of 0.01% Fe₂O₃ nanoparticles; (d) PTFE with the addition of 0.1% Fe₂O₃ nanoparticles. The images are presented as 3D reconstructions, where the abscissa and ordinate axes correspond to the real distance in μm. The Oz axis displays the phase difference in nm (the larger the phase difference, the higher the value on the Oz axis). Coloring is a pseudo-color. The initial data on the spatial distribution of the phase difference in the analyzed sample, used to construct 3D reconstructions, are shown in the lower left corners of each panel.

Figure 4

Effect of PTFE/Fe₂O₃ NPs on generation of free radicals: (a) hydrogen peroxide (2 h, 40 °C); (b) OH radials (2 h, 80 °C). Data are presented as means ± standard errors. *—p < 0.05 vs. control, Mann–Whitney test (n = 3).

Figure 5

Effect of PTFE/Fe₂O₃ NPs on generation of free radicals: (a) LRPS (2 h, 40 °C); (b) 8-oxoguanine (8-oxoGua) in DNA in vitro (2 h, 45 °C). Data are presented as means ± standard errors. *—p < 0.05 vs. control, Mann–Whitney test (n = 3).

Figure 6

Examination of antibacterial activity of composite PTFE/Fe₂O₃ NPs against E. coli. Data are presented as means ± standard errors. *—p < 0.05 vs. control, Mann–Whitney test (n = 3).

Figure 7

Examples of fluorescent microscopy images of cells during cytotoxicity study: (a) Hoechst (blue stain) image of cells on PTFE; (b) Hoechst image of cells on PTFE + 0.1% Fe₂O₃ NPs; (c) PI (red stain) of cells on PTFE; (d) PI of cells on PTFE + 0.1% Fe₂O₃ NPs; (e) merged image of cells on PTFE; (f) merged image of cells on PTFE + 0.1% Fe₂O₃ NPs. Scale bar is 30 μm. Magnification ×200, image resolution 1024 × 1024 pxl².

Figure 7

Examples of fluorescent microscopy images of cells during cytotoxicity study: (a) Hoechst (blue stain) image of cells on PTFE; (b) Hoechst image of cells on PTFE + 0.1% Fe₂O₃ NPs; (c) PI (red stain) of cells on PTFE; (d) PI of cells on PTFE + 0.1% Fe₂O₃ NPs; (e) merged image of cells on PTFE; (f) merged image of cells on PTFE + 0.1% Fe₂O₃ NPs. Scale bar is 30 μm. Magnification ×200, image resolution 1024 × 1024 pxl².

Figure 8

Cytotoxicity of composite PTFE/Fe₂O₃ NPs: (a) percentage of non-viable cells, where the amount of all analyzed cells was taken as 100%; (b) average nuclei size of cells. Data are presented as means ± standard errors. *—p < 0.05, Mann–Whitney test (n = 3).