Application of cationic polymer micelles for the dispersal of bacterial biofilms

Abstract

Contamination of surfaces in hospitals and food industry by bacterial biofilms is a serious health risk. Of concern is their resistance to routine antibacterials and disinfectants. This requires the development of novel approaches to biofilm detachment. The study evaluates the effectiveness of cationic polymer micelles (CPMs) against pre-formed biofilms. CPMs based on different polycations were used. The hydrodynamic radius of the particles ranged from 16 to 360 nm. Biofilms of Escherichia coli 420, Pseudomonas aeruginosa PAO1, Staphylococcus aureus 29213 and Bacillus subtilis 168 were cultivated for 24 h then the pre-formed biofilms were treated with the CPMs for 2, 4 or 6 h. Biofilm biomass was evaluated by the crystal violet assay, and live/dead fluorescence test was applied for bacterial viability. The ability of CPMs to interact with pre-formed biofilms of the model strains was evaluated. We observed that the most effective CPMs were those based on poly(2-(dimethylamino)ethyl methacrylate) copolymers which reduced the biofilm biomass three- to four-fold compared with the treatment of the biofilm with water. Significantly reduced vitality of the bacteria in the biofilms was registered by the live/dead stain. The results indicate the applicability of the CPMs for disinfection of biofilm-contaminated surfaces and the treatment of wounds.

Keywords: Bacterial biofilm dispersal; Cationic polymer micelles.

Figure 1

Hydrodynamic radius (A) and ζ‐potential (B) of the cationic polymer micelles prepared at concentration of 1 mg/mL. Inset, electron micrograph of MKPa4, scale bar = 0.5 μm.

Figure 2

Effect of the treatment with the cationic polymer micelles suspensions on the pre‐formed biofilms of (A) E. coli 420, (B) P. aeruginosa PAO1, (C) B. subtilis 168 and (D) S. aureus 29213. Biofilms were developed for 24 h in M63 medium and then treated for 2, 4, or 6 h with the CPMs. Controls: “O h” represents the amount of the pre‐formed 24‐h biofilm at hour “0” i.e., before the application of the CPMs; C(H₂O) represents parallel samples treated with distilled sterile H₂O. Each bar represents the average of 6 replicates and the SD.

Figure 3

Fluorescence microscopy estimation of the vitality of bacterial cells within biofilms of E. coli 420, Live/Dead staining. Biofilms were cultivated on cover slides for 24 h followed by 4 h incubation in H₂O (A, B) or 1 mg/mL MKPa4 (C, D). A, C ‐ images combining the red and green signal; B, D ‐ the corresponding areas, with the red signal only, indicating only the bacteria with altered cell envelope integrity colored by PI. Scale bar = 30 μm.