Investigation of mechanism and effectiveness of metal nanoparticles in self-sterilizing packaging

Microbial contaminants intimidate food safety and shelf-life. Metal nanoparticles (NPs) have become a leading area of interest and research in barrier packaging materials that ensure food safety. Traits such as small size, high surface-to-volume ratio and multi-functionality make them ideal materials for producing self-sterilizing packaging. Numerous metal NPs have proven to fight against a wide range of pathogenic microbes through various methods. Further, metal NPs exhibit more biocompatibility than metal ions. This study investigates the role and the mechanism of action of the various NPs in selfsterilizing packaging. AgNPs, TiO2NPs, MgONPs, ZnONPs, AuNPs, FeONPs, Cu-based NPs and SnO2NPs have been explored for their biocidal action in self-sterilizing surfaces and food packaging applications in this work. The size, shape, surface structure, surface reactivity and other environmental factors (like pH) influence the biocidal properties of these metal NPs. From the literature survey, it was inferred that it was necessary for the metal NPs to be smaller than 50 nm in size to exhibit effective biocidal action against pathogenic microbes. The mechanisms followed by the metal NPs against bacteria and fungi include disturbing the cell wall, the metabolic process by inducing reactive oxygen species (ROS) and/or the DNA synthesis mechanism. It was inferred that AgNPs, MgNPs and ZnONPs are some of the NPs that have a significant share in self-sterilizing surfaces. Being expensive, the works of literature on AuNPs and their application in this subject are very few. This paper aims to study the biocidal behaviour and rank the effectiveness of these metal NPs to act as ideal materials for self-sterilising packaging.