Strategies to Encapsulate the Staphylococcus aureus Bacteriophage phiIPLA-RODI

Abstract

The antimicrobial properties of bacteriophages make them suitable food biopreservatives. However, such applications require the development of strategies that ensure stability of the phage particles during food processing. In this study, we assess the protective effect of encapsulation of the Staphylococcus aureus bacteriophage phiIPLA-RODI in three kinds of nanovesicles (niosomes, liposomes, and transfersomes). All these systems allowed the successful encapsulation of phage phiIPLA-RODI with an efficiency ranged between 62% and 98%, regardless of the concentration of components (like phospholipids and surfactants) used for vesicle formation. Only niosomes containing 30 mg/mL of surfactants exhibited a slightly lower percentage of encapsulation. Regarding particle size distribution, the values determined for niosomes, liposomes, and transfersomes were 0.82 ± 0.09 µm, 1.66 ± 0.21 µm, and 0.55 ± 0.06 µm, respectively. Importantly, bacteriophage infectivity was maintained during storage for 6 months at 4 °C for all three types of nanovesicles, with the exception of liposomes containing a low concentration of components. In addition, we observed that niosomes partially protected the phage particles from low pH. Thus, while free phiIPLA-RODI was not detectable after 60 min of incubation at pH 4.5, titer of phage encapsulated in niosomes decreased only 2 log units. Overall, our results show that encapsulation represents an appropriate procedure to improve stability and, consequently, antimicrobial efficacy of phages for application in the food processing industry.

Keywords: Staphylococcus aureus; bacteriophages; encapsulation; liposomes; niosomes; transfersomes.

Figure 1

Stability (log₁₀ PFU/mL) of bacteriophage phiIPLA-RODI encapsulated in different types of nanovesicles and in SM buffer (control), after storage at 4 °C: (A) niosomes, (B) liposomes and (C) transfersomes. Phage titer was determined after encapsulation (black bars) and also after storage for 2 months (dark grey bars), 4 months (light grey bars) and 6 months (white bars). (F): non encapsulated or free phage; (E): encapsulated phage. Numbers (30, 50 or 70) indicates the concentration of components expressed in mg/mL. Bars represent mean ± standard deviation of three biological replicates. Different letters indicate differences in stability (p < 0.05; ANOVA and SNK post-hoc comparison).