A nano-carrier platform for the targeted delivery of nature-inspired antimicrobials using Engineered Water Nanostructures for food safety applications

Abstract

Despite the progress in the area of food safety, foodborne diseases still represent a massive challenge to the public health systems worldwide, mainly due to the substantial inefficiencies across the farm-to-fork continuum. Here, we report the development of a nano-carrier platform, for the targeted and precise delivery of antimicrobials for the inactivation of microorganisms on surfaces using Engineered Water Nanostructures (EWNS). An aqueous suspension of an active ingredient (AI) was used to synthesize iEWNS, with the 'i' denoting the AI used in their synthesis, using a combined electrospray and ionization process. The iEWNS possess unique, active-ingredient-dependent physicochemical properties: i) they are engineered to have a tunable size in the nanoscale; ii) they have excessive electric surface charge, and iii) they contain both the reactive oxygen species (ROS) formed due to the ionization of deionized (DI) water, and the AI used in their synthesis. Their charge can be used in combination with an electric field to target them onto a surface of interest. In this approach, a number of nature-inspired antimicrobials, such as H₂O₂, lysozyme, citric acid, and their combination, were used to synthesize a variety of iEWNS-based nano-sanitizers. It was demonstrated through foodborne-pathogen-inactivation experiments that due to the targeted and precise delivery, and synergistic effects of AI and ROS incorporated in the iEWNS structure, a pico- to nanogram-level dose of the AI delivered to the surface using this nano-carrier platform is capable of achieving 5-log reductions in minutes of exposure time. This aerosol-based, yet 'dry' intervention approach using iEWNS nano-carrier platform offers advantages over current 'wet' techniques that are prevalent commercially, which require grams of the AI to achieve similar inactivation, leading to increased chemical risks and chemical waste byproducts. Such a targeted nano-carrier approach has the potential to revolutionize the delivery of antimicrobials for sterilization in the food industry.

Keywords: Engineered Water Nanostructures; Food Safety; Nano-carrier; Nanotechnology; Nature-inspired antimicrobials.

Figure 1:

Synthesis and targeted delivery concept of iEWNS. (a) The active ingredient is added in DI water to result in an aqueous solution. (b) The solution is transferred to the iEWNS emitter using an air compressor. The applied voltage between the capillary and grounded electrode results in the combined electrospray ionization process that produces the iEWNS nanoparticles. (c) The synthesized iEWNS have nanoscale size and high electric charges. They also contain both the AI molecules and the ROS produced during the ionization process. (d) The targeted delivery of these particles to the surface of interest is performed utilizing the electric field and their inherent electric charges.

Figure 2:

Bacterial inactivation inoculation experiments. The stainless steel coupons inoculated with pathogen were placed under each emitter (centered) and exposed to iEWNS nanoparticles as a function of time. Inactivation results were derived as a function of exposure time for each iEWNS tested in the study. Non-exposed pathogen-inoculated SS coupons were used as controls.

Figure 3:

Antimicrobial efficacy of various iEWNS developed and tested: (a) Inactivation of E. coli produced by various iEWNS (please note that the h1EWNS and L0.1EWNS lines and data points overlap); (b) Inactivation produced by h1EWNS against L. innocua; Note: The initial pathogen inoculum concentration was 10⁶ cfu. Experiments were performed in triplicate. Error bars represent the standard deviation of the measured value.

Figure 4:

Transmission electron microscopy images of E. coli exposed with various iEWNS nano-sanitizers: (a) control (non-exposed), (b) h1EWNS, (c) c1EWNS, (d) c1h1EWNS, (e) L0.1EWNS.

Figure 5:

Required delivered iEWNS and AI dose to produce 3-log reductions in the case of E. coli. Note that the EWNS contain no added AI. The only activity is due to the generated ROS in the aqueous phase.