Farnesol and Selected Nanoparticles (Silver, Gold, Copper, and Zinc Oxide) as Effective Agents Against Biofilms Formed by Pathogenic Microorganisms

Abstract

Purpose

Biofilms, which are created by most microorganisms, are known for their widely developed drug resistance, even more than planktonic forms of microorganisms. The aim of the study was to assess the effectiveness of agents composed of farnesol and nanoparticles (silver, gold, copper, and zinc oxide) in the degradation of biofilms produced by pathogenic microorganisms.

Methods

Escherichia coli, Enterococcus faecalis, Staphylococcus aureus, Pseudomonas aeruginosa, and Candida albicans were used to create the biofilm structure. Colloidal suspensions of silver, gold, copper, and zinc oxide (Ag, Au, Cu, ZnO) with the addition of farnesol (F) were used as the treatment factor. The size distribution of those composites was analyzed, their zeta potential was measured, and their structure was visualized by transmission electron microscopy. The viability of the microorganism strains was assessed by an XTT assay, the ability to form biofilms was analyzed by confocal microscopy, and the changes in biofilm structure were evaluated by scanning electron microscopy. The general toxicity toward the HFFF2 cell line was determined by a neutral red assay and a human inflammation antibody array.

Results

The link between the two components (farnesol and nanoparticles) caused mutual stability of both components. Planktonic forms of the microorganisms were the most sensitive when exposed to AgF and CuF; however, the biofilm structure of all microorganism strains was the most disrupted (both inhibition of formation and changes within the structure) after AgF treatment. Composites were not toxic toward the HFFF2 cell line, although the expression of several cytokines was higher than in the not-treated group.

Conclusion

The in vitro studies demonstrated antibiofilm properties of composites based on farnesol and nanoparticles. The greatest changes in biofilm structure were triggered by AgF, causing an alteration in the biofilm formation process as well as in the biofilm structure.

Keywords:

• farnesol
• nanocomposites
• nanoparticles
• biofilm structure
• toxicity

Abbreviations

Ag, silver nanoparticles; ATCC, American Type Culture Collection; Au, gold nanoparticles; BHI, brain heart infusion agar; Cu, copper nanoparticles; DLS, dynamic light scattering; DMEM, Dulbecco’s Modified Eagle Medium; eDNA, extracellular DNA; F, farnesol; FBS, fetal bovine serum; LB, Luria-Bertani agar; NR, neutral red; PdI, polydispersity index; PQS, Pseudomonas quinolone signal; ROS, reactive oxygen species; SEM, scanning electron microscopy; TEM, transmission electron microscope; TSA, tryptic soy agar; WHO, World Health Organization; XTT, sodium 3′-[1-[(phenylamino)-carbony]-3,4-tetrazolium]-bis(4-methoxy-6-nitro) benzene-sulfonic acid hydrate; YNB, yeast nitrogen base; ZnO, zinc oxide nanoparticles.

Disclosure

The authors report no conflicts of interest in this work.

Additional information

Funding

The publication was financed by Science development fund of the Warsaw University of Life Sciences – SGGW.