Optimization of a nanotechnology based antimicrobial platform for food safety applications using Engineered Water Nanostructures (EWNS)

Abstract

A chemical free, nanotechnology-based, antimicrobial platform using Engineered Water Nanostructures (EWNS) was recently developed. EWNS have high surface charge, are loaded with reactive oxygen species (ROS), and can interact-with, and inactivate an array of microorganisms, including foodborne pathogens. Here, it was demonstrated that their properties during synthesis can be fine tuned and optimized to further enhance their antimicrobial potential. A lab based EWNS platform was developed to enable fine-tuning of EWNS properties by modifying synthesis parameters. Characterization of EWNS properties (charge, size and ROS content) was performed using state-of-the art analytical methods. Further their microbial inactivation potential was evaluated with food related microorganisms such as Escherichia coli, Salmonella enterica, Listeria innocua, Mycobacterium parafortuitum, and Saccharomyces cerevisiae inoculated onto the surface of organic grape tomatoes. The results presented here indicate that EWNS properties can be fine-tuned during synthesis resulting in a multifold increase of the inactivation efficacy. More specifically, the surface charge quadrupled and the ROS content increased. Microbial removal rates were microorganism dependent and ranged between 1.0 to 3.8 logs after 45 mins of exposure to an EWNS aerosol dose of 40,000 #/cm(3).

Figure 1. The EWNS synthesis principles.

(a) Electrospray occurs when a high voltage is applied between a capillary containing the liquid and the counter electrode. (b) The application of the high voltage results into two distinct phenomena: (i) the electrospray of the water and (ii) generation of reactive oxygen species (ions) that are trapped in the EWNS. (c) The unique structure of EWNS. (d) EWNS due to their nanoscale nature are highly mobile and can interact with airborne pathogens.

Figure 2. The experimental setup.

(a) The Engineered Water Nano-Structures (EWNS) Generation System. (b) Cross section of the sampler and the electrospray device, showing the most important parameters. (c) The experimental setup that was used for the bacteria inactivation.

Figure 3. The physicochemical characterization of the EWNS.

(a–c) The size distribution as measured with the AFM. (d–f) The surface charge characterization. (g) The ROS characterization with the EPR.

Figure 4. The deposition of the EWNS in the EPES.

Figure 5. Inactivation of bacteria on tomato surface in EPES with the optimized EWNS.

The data presented are normalized to the control.

Figure 6. The electron microscopy imaging of the control and exposed bacteria revealing the damage to the membrane.