Porous engineered prussian blue-based antibacterial film with boosting photothermal and oxidase-like activities for long-term citrus preservation

Controlling microbial growth through antibacterial packaging is pivotal in preventing food spoilage and extending shelf life. In this study, we developed a multi-functional synergistic sterilization film based on the interaction between photothermal and oxidase-like activities. The essence of this system resides in the meticulous porous engineering of performance-upgraded Prussian blue (PPB) nanocubes and their sophisticated incorporation into chitosan (CS) matrices, culminating in the formation of CS/PPB composite films. The mildly acidic environment provided by CS facilitated the oxidase-like activity, allowing the CS/PPB film to exhibit both self-activated oxidase-like properties and photothermal performance attributed to the PPB. By matching these grafted activities of PPB and the inherent antimicrobial properties of CS film, the CS/PPB film demonstrated potent antibacterial activity, achieving sterilization rates of 99.82 % for E. coli and 99.83 % for S. aureus, while also enabling rapid heating within 2 min for effective low-temperature sterilization at 51.9 °C, with safe and non-toxic characteristics. The incorporation of PPB also markedly augmented the physicochemical attributes of the CS film. Consequently, the CS/PPB film significantly extended the shelf life of citrus from 9 to 24 days with minimal impact on fruit quality. These advantageous attributes underscore the substantial potential of the CS/PPB film for advanced microbial control applications in fruit preservation.