Tackling microbial adhesion to surfaces by adding mesoporous SiO2 nanoparticles to nanocomposite based on PVDF-HFP and PVP polymers

Increasing microbial resistance, many foods recall due to microbiological contamination, significant increase in nosocomial infections and deaths are the reasons for the development of highly efficient antimicrobial polymer nanocomposites with a particularly circular and simultaneous mechanism of action. In this study, the influence of different weight fractions of the individual components of polymer nanocomposites PVDF-HFP/PVP/SiO 2 consisting of PVDF-HFP (poly(vinylidene fluoride-co-hexafluoropropylene)) and PVP (polyvinylpyrrolidone) with the addition of mesoporous SiO 2 nanoparticles on the surface (topography, roughness, hardness, wettability, charge), on thermal and mechanical behavior was investigated. The polymer nanocomposite with 50 wt. % PVDF-HFP and 40 wt. % PVP has a microstructured, positively charged, rough surface that reduced the adhesion of bacteria Staphylococcus aureus and Escherichia coli over 99 % in 24 h. However, the polymer nanocomposite with 70 wt. % PVDF-HFP and 20 wt. % PVP (with the same amount of SiO 2 nanoparticles, 10 wt. %) without the microstructured surface reduced the number of S. aureus adhered cells only by 85.8 %, but still twice as much as the pure polymer blend. All polymer nanocomposites were stable up to 175 °C, but thermal stability decreased slightly with a higher mass fraction of PVP polymer. The polymer nanocomposite with 70 wt.% PVDF-HFP and 20 wt. % PVP exhibited the highest degree of crystallinity, while crystallinity was absent when 30 wt. % or more PVP was added. In the polymer nanocomposite with microstructure surface, the presence of the strongest antifouling mechanisms of action was found at the dissolution dynamics (lowest pH and highest conductivity). The results showed that mechanisms of action are initially related to the formation of silicic acid, then to its protonation process and finally to the hydrolysis reaction of the PVP polymer, which leads to the formation of ammonium salts and carboxylic acid. This study shows the importance of the different ratio of polymers in the polymer blend that the improvement of antimicrobial and antifouling activity was achieved at the same filler concentration, especially due to the viscoelastic phase separation pattern on the surface morphology.