A novel method for bacteria inactivation using Engineered Water Nanostructures

Georgios Pyrgiotakis, James McDevitt, Toshiyuki Yamauchi Joe Brain and Philip Demokritou

The burden of infectious disease worldwide, related to contamination via contact with contaminated surfaces (fomites) and inhalation, is a growing issue. Apart from hospitals, the problem has also become a growing liability at places where food is prepared and handled. Herein a novel nanotechnology based method for microbial disinfection that utilizes the formation of unique Engineered Water Nanostructures (EWNS) generated via the electrospraying of water is presented. Electropsray is a method widely, used to generate aerosols . The objectives of this work are twofold: 1) showcase the proof of concept that these EWNS can be potentially used for the inactivation of pathogens from both surfaces and in the air; 2) Characterize the physico-chemical and morphological properties of EWNS and understand their formation and transport mechamisms. Bacteria Inactivation on surfaces: The inactivation of bacteria on surfaces by the EWNS was assessed both quantitatively and qualitatively. Different types of bacteria were used in order to cover a wide range of potential applications including Serratia Marcescens (gram-negative), Staphylococcus Aureus (gram-positive) and Bacillus Atrophaeus (spore forming). For the Serratia Marcescens the results showed that there is more than a 2-log10 reduction in 90 minutess of exposure. Similarly, the results for Staphylococcus Aureus showed nearly an 1-log10 reduction for same dose. The spore forming bacteria although exposed to the EWNS for 24 hours were not affected. Air disinfection: Serratia Marcescens was aerosolized in an environmental chamber and mixed with a controlled concentration EWNS aerosol. The potential of the EWNS to inactivate bacteria in the air was evaluated using a culture system approach under steady state and decay scenarios. The bioaerosol experimets showed the ability of EWNS to deactivate in a dose dependent matter, the suspended in the air Serratia Marcescens bacteria, by achieving 50% reduction at steady state and complete removal at 45 min under the decay scenario. EWNS synthesis and properties: The synthesis process and the properties of the generated EWNS, including size distribution, charge and reactive oxygen species were assessed. The size and particle charge were measure using atomic force microscopy (AFM)and an electrometer, respectively. Our results show that the EWNS have a size of approximately 25 nm, which is stable over time (hours), and carry an average charge of 10 electrons per particle. EPR was utilized to characterize the present of chemical species and showed that the EWNS are loaded with primarily with OH• radicals and secondary with O2•.