Gold-Polyoxoborates Nanocomposite Prohibits Adsorption of Bacteriophages on Inner Surfaces of Polypropylene Labware and Protects Samples from Bacterial and Yeast Infections

Abstract

Bacteriophages (phages) are a specific type of viruses that infect bacteria. Because of growing antibiotic resistance among bacterial strains, phage-based therapies are becoming more and more attractive. The critical problem is the storage of bacteriophages. Recently, it was found that bacteriophages might adsorb on the surfaces of plastic containers, effectively decreasing the titer of phage suspensions. Here, we showed that a BOA nanocomposite (gold nanoparticles embedded in polyoxoborate matrix) deposited onto the inner walls of the containers stabilizes phage suspensions against uncontrolled adsorption and titer decrease. Additionally, BOA provides antibacterial and antifungal protection. The application of BOA assures safe and sterile means for the storage of bacteriophages.

Keywords: antibacterial; antifungal; bacteriophages; nanocomposite; nanoparticles; surface coatings.

Figure 1

(A) DLS measurements show the hydrodynamic diameter of the initial AuNPs equal to 4.5 ± 1 nm. (B) UV-Vis measurement of the initial AuNPs. (C) EDX spectrum of BOA deposited onto the polypropylene surface, proving gold presence within the coating. SEM pictures of (D) pristine polypropylene vial used in the study; (E) pristine vial after 24 h incubation with M13 phages. Visible fiber-like features are virions. (F) The inner surface of the vial after single deposition of BOA, and (G) triple deposition of BOA. The inset in (C) shows the same surface as the main picture in (C), but without an additional thin layer of gold-sputtered to facilitate SEM observations. Scale bars correspond to 500 nm.

Figure 2

Comparison of the number of bacteriophages presented as a percent of concentration at 0 h. The initial concentrations were (A) 3.75 × 10³ ± 3.74 × 10² PFU/mL for MS2, (B) 5.08 × 10³ ± 1.60 × 10² PFU/mL for M13, and (C) 6.60 × 10⁵ ± 5.01 × 10⁴ PFU/mL for T4. The visible decrease was visible in pristine vials in M13 and MS2 but not in T4. BOA showed the statistically significant protection against the phage titer decrease in the case of M13 and MS2 and did not show any adverse effect on T4 suspensions (*** p < 0.001).

Figure 3

Comparison of growth-rate of (A) Escherichia coli BL21 (DE3) (initial concentration of 1.78 × 10³ ± 2.38 × 10² CFU/mL), (B) Staphylococcus aureus WT (initial concentration of 1.53 × 10⁴ ± 3.28 × 10³ CFU/mL), and (C) Saccharomyces cerevisiae WT (initial concentration of 8.25 × 10⁴ ± 1.84 × 10⁴ CFU/mL) in pristine vials and BOA-modified vials. In all cases, BOA caused a decrease in the number of viable cells compared to pristine vials (* p < 0.05; ** p < 0.01; *** p < 0.001).