Immobilization/incorporation methods of bacteriophages into polymeric films: Technological challenges & perspectives

Bacteriophage(phage)-based interventions have been considered for environmental and biomedical applications as well as during food processing, representing a promising alternative when multidrug-resistant bacteria are found. Although liquid and semi-solid formulations are easier to prepare as few unit operations are required, stability issues or short-term effects have led to the prioritization of solid formulations. Polymeric films have gained prominence as a strict control of phage release or improved phage stability can be achieved. During film preparation, phages are deposited onto a pre-ready solid support or incorporated in a film-forming solution. Advantages and disadvantages of each preparation method as well as the impact of different processing conditions (temperature, pH, ionic strength and agitation) on phage viability/stability are discussed in detail in this review. High viral titer broadens the spectrum of materials and film preparation methods that can be considered. The orientation of some phages during immobilization into solid supports, in turn, has proven to be a key aspect for phage infectivity, particularly for tailed phages. The points raised in this review are certainly an important direction for future technological developments in this field, contributing to the development of films with longer-lasting action.