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Encapsulation of T4 bacteriophage in electrospun biopolymers Korehei, Reza


Packaging foods with antibacterial electrospun fibrous mats, in particular the incorporation of bacteria specific viruses such as bacteriophages may address concerns triggered by recent waves of bacterial food contamination. To this end several methods for incorporating or encapsulating T4 bacteriophage into electrospun fibres were investigated. The incorporation of T4 bacteriophage using simple suspension electrospinning lead to major losses in T4 bacteriophage activity, with more than five-orders of magnitude decrease in activity being observed. Improved T4 bacteriophage viability was obtained using two newly developed electrospinning processes, emulsion and coaxial electrospinning. In emulsion electrospinning, T4 bacteriophage was pre-encapsulated in an alginate reservoir via an emulsification process and subsequently electrospun into fibres. The emulsion electrospun fibres exhibited only two-orders of magnitude decrease in T4 bacteriophage activity. By contrast, complete T4 bacteriophage activity was maintained when coaxial electrospinning was employed. In the coaxial electrospinning process, a core/shell fibre structure was formed where the T4 bacteriophage was allocated to the fibre core, protected by the outer polymer shell. Depending on the polymer system used the rate of T4 bacteriophage release from the coaxial electrospun fibres varied. When hydrophilic poly(ethylene oxide) (PEO) was used as the polymer shell layer, immediate release of T4 bacteriophage was observed upon exposure to buffer. Increasing the PEO molecular weight increased the electrospun fibre diameter and viscosity of the releasing medium, which resulted in relatively slower T4 bacteriophage release pro-files. Similarly, the blending of cellulose diacetate (CDA) with PEO dramatically decreased the release behaviour. Depending on the PEO/CDA ratio, post-release electrospun fibre morphology varied from discontinuous fibres to minimally swollen fibres, consistent with the release profiles. In the PEO fibres the mechanism of T4 bacteriophage release is likely through solvent activa-tion/polymer dissolution, while in the PEO/CDA blends a more diffusion control mechanism likely prevails. The Encapsulation of T4 bacteriophage within the electrospun fibres also improved T4 bacteriophage storability; full T4 bacteriophage activity was maintained for more than a month at +4 °C, as compared to only hours for non-encapsulated phage. These results are significant in the context of controlling and preventing bacterial infections in perishable foods during refrigerated storage.

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