Ozone ultrafine bubble water exhibits bactericidal activity against pathogenic bacteria in the oral cavity and upper airway and disinfects contaminated healthcare equipment.

Ozone is strong oxidizing agent that is applied in aqueous form for sanitation. However, ozonated water is unstable and has a short half-life. Ultrafine bubble technology is promising to overcome these issues. Ultrafine bubble is nanoscale bubble and can exist in water for a considerable duration of time. This study aims to investigate the application of ozone ultrafine bubble water (OUFBW) as a disinfectant. We produced an OUFBW generator which generates OUFBW containing 4-6 ppm of ozone. Thereafter, we examined the bactericidal activity of the OUFBW against various pathogenic bacteria in oral cavity and upper airway, including antibiotic-susceptible and antibiotic-resistant Streptococcus pneumoniae, Pseudomonas aeruginosa, Streptococcus mutans, Streptococcus sobrinus, Fusobacterium nucleatum, Prevotella intermedia, and Porphyromonas gingivalis. Exposure of planktonic culture of these bacterial species to OUFBW reduced viable bacteria by > 99% within 30s. Additionally, OUFBW exerted bactericidal activity against S. pneumoniae and P. aeruginosa adhered to toothbrush and gauze, respectively. We also observed disruption of bacterial cell wall of S. pneumoniae exposed to OUFBW by transmission electron microscope. Additionally, OUFB did not show any significant cytotoxicity toward the human gingival epithelial cell line Ca9-22. These results suggest that OUFBW exhibits bactericidal activity against broad spectrum of bacteria and has low toxicity towards human cells.

Continuous organic synthesis in water around micro-orifices after flows.

Water flows through micro-orifices are important because they occur in various fields, such as biology, medical science, chemistry, and engineering. We have reported in previous work that organic matter was generated in micro-orifices after water flowed through the orifice, and we proposed that the organic matter was synthesized from nonorganic materials, including CO2 and N2 dissolved in water from air, and water via the action of hydroxyl radicals produced by the flow through the micro-orifice. In the present study, we examined whether organic materials are produced in the water outside of the orifices in addition to that in the orifice. We used the decrease in water volume to measure the organic synthesis because water should be consumed during the synthesis, and thus the decrease in water volume should reflect the organic synthesis. We let ultrapure water containing dissolved air flow through a micro-orifice as a pre-flow, we stopped the flow, and then we measured the volume of water enclosed in the mount in which the micro-orifice was set over more than 100 h. The volume of water decreased gradually and substantially over time. We used Raman and infrared spectroscopy to analyze the residue obtained by evaporating the water present around the orifice. The residue contained organic matter, including carotenoids, amides, esters, and sugars, which were similar to those found in the membranes generated in the orifice in our previous paper, suggesting that the organic matter was synthesized in a wide region of water around the orifice as well as in the orifice. These results may be relevant to the origins of life and biology, and may lead to the development of a technology for reducing CO2 in air, as well as applications in many scientific and engineering fields.

Organic compounds generated after the flow of water through micro-orifices: Were they synthesized?

Micro-fluid mechanics is an important area of research in modern fluid mechanics because of its many potential industrial and biological applications. However, the field is not fully understood yet. In previous work, when passing ultrapure water (UPW) in which air was dissolved (UPW*) through micro-orifices, we found that the flow velocity decreased and stopped over time, and membranes were frequently formed in the orifice when the flow stopped. The membrane came from the dissolved air in UPW*, and membrane formation was closely related to electric charges generated in orifices by the flow. In the present paper, we clarified the components of the membrane and suggested a mechanism for membrane formation. We examined the effect of contaminants on the membrane formation and confirmed our previous results. We identified the chemical components of the membrane and those present in the UPW* itself by using an electron probe microanalyzer and found that the proportion of each element differed between the membrane and UPW*. Raman and infrared (IR) spectroscopy showed that the membrane consisted of organic substances such as carotenoids, amides, esters, and sugars. We irradiated UPW* with ultraviolet light to cut organic chains that may be left in UPW* as contaminants. We found a similar membrane and organic compounds as in nonirradiated UPW*. Furthermore, although the UPW that was kept from contact with air after it was supplied from the UPW maker (UPW0) and bubbled with Ar gas (UPW0 bubbled with Ar) formed no membrane, the UPW0 bubbled with CO2 formed thin membranes, and Raman and IR analysis showed that this membrane contained carboxylic acid salts, carotenoids, or a mixture of both. We found that electric grounding of the orifice reduces the probability of membrane formation and that the jets issuing from an aperture bear negative charges, and we assumed that the micro-orifices possess positive charges generated by flows. Consequently, we suggest that organic compounds are synthesized from nonorganic matter in air or CO2 dissolved in water by the action of hydroxyl radicals generated by flows through micro-orifices.