Effects of ozone nano-bubble water on periodontopathic bacteria and oral cells - in vitro studies

Radical generation and bactericidal activity of nanobubbles produced by ultrasonic irradiation of carbonated water

Our previous study showed that nanobubbles (NBs) encapsulating CO2 gas have bactericidal activity due to reactive oxygen species (ROS) (Yamaguchi et al., 2020). Here, we report that bulk NBs encapsulating CO2 can be efficiently generated by ultrasonically irradiating carbonated water using a piezoelectric transducer with a frequency of 1.7 MHz. The generated NBs were less than 100 nm in size and had a lifetime of 500 h. Furthermore, generation of ROS in the NB suspension was investigated using electron spin resonance spectroscopy and fluorescence spectrometry. The main ROS was found to be the hydroxyl radical, which is consistent with our previous observations. The bactericidal activity lasted for at least one week. Furthermore, a mist generated by atomizing the NB suspension with ultrasonic waves was confirmed to have the same bactericidal activity as the suspension itself. We believe that the strong, persistent bactericidal activity and radical generation phenomenon are unique to NBs produced by ultrasonic irradiation of carbonated water. We propose that entrapped CO2 molecules strongly interact with water at the NB interface to weaken the interface, and high-pressure CO2 gas erupts from this weakened interface to generate ROS with bactericidal activity.

Nanoshell Formation at the Electrically Charged Gas-Water Interface of Collapsing Microbubbles: Insights from Atomic Force Microscopy Imaging

AFM imaging has revealed intriguing features when bulk nanobubbles were deposited on a positively charged substrate. Numerous spherical objects, each less than 20 nm in diameter, were observed on the substrate. These objects were adorned with noticeable, tiny protrusions, each measuring a few nanometers. These findings suggest the presence of solid shells contributing to the stability of the gas bodies. Furthermore, electrically charged microbubbles appear to play a critical role in the formation of these solid shells. The collapse of microbubbles in an electrolyte aqueous solution containing iron ions leads to a condensing ionic cloud, creating conditions necessary for solid nucleation at the interface. At the end of the collapsing process, concurrent multinucleation may result in the deposition of solid material on the interface, forming solid shells with specific structures on the surfaces. This study illuminates the phenomenon of electrically charged gas-water interfaces during microbubble collapse and highlights the generation of stabilized nanoshells in aqueous solutions without the need for chemical stabilizers.

Investigating the effects of ultrafine bubbles on bacterial growth

Several previous studies have considered ultrafine bubbles as a potential research target because their properties can be applied in many different research areas. In particular, the interaction between UFBs and microorganisms has always been one of the aspects that receives much attention due to the high difficulty in controlling a living system. The properties of UFBs, as mobile air-water interfaces, are greatly determined by their gas cores which play a critical role in regulating microbial growth. This study aims to investigate the effects of ultrafine bubbles on bacterial growth. Two well-studied organisms were chosen as models - Escherichia coli and Staphylococcus aureus. Their growing behavior was examined based on the growth rate, phenotype and biomass. Three types of Luria-Bertani cultures were tested, including a standard culture containing distilled water, an air ultrafine bubble culture, and a hydrogen ultrafine bubble culture. The UFBs were generated via ultrasonic cavitation and stabilized by 50 μM SDS, which was proven to have negligible effects on bacterial growth. By comparing among the three cultivation conditions, the bacterial growth rates were observed to be the highest in exposure to HUFBs. The results also signified that UFBs had an enhancement on cell proliferation. On the other hand, while proposing an increase in cell density, bacteria cultured in HUFB media have their sizes decreased uniformly and significantly (p-value < 0.05). This study confirmed that bacterial growth was promoted by UFBs; and better effects recorded were due to the HUFB present in the culture media. However, the average morphological size of bacteria was in negative correlation with their population size.

Effects of hyperoxia during oxygen nanobubble treatment on innate immunity, growth performance, gill histology, and gut microbiome in Nile tilapia, Oreochromis niloticus

Oxygen nanobubble (NB-O2) technology has been introduced to the aquaculture industry in recent years. This treatment usually results in a tremendously high level of dissolved oxygen (DO) in the water. However, little is known about the possible negative effects of hyperoxia due to NB-O2 treatment (hyper-NB-O2) on farmed fish. Here, we investigated i) the effect of short-term hyper-NB-O2 exposure (single treatment) on the innate immunity in Nile tilapia, Oreochromis niloticus, and ii) the effect of long-term hyper-NB-O2 exposure (26-day treatments) on survival, growth performance, gill histology, and gut microbiome in Nile tilapia. A single treatment with NB-O2 for 10 min in 50 L of water resulted in 24.2 ± 0.04 mg/L DO (approximately 2-3 × 107 nanoscale oxygen bubbles/mL). This treatment did not result in differences in expression of several immune-related genes (e.g., TNF-α, LYZ and HPS70) in various tissues (e.g., gill, head kidney, and spleen) compared to the non-treated control. Over a 26-day period of exposure, no significant differences were observed in survival and growth performance of the fish, but minor histological changes were occasionally noted on the gills. Analysis of the gut microbiome revealed a significant increase in the genera Bosea, Exiguobacterium, Hyphomicrobium, and Singulisphaera in the group receiving NB-O2. Moreover, no signs of "gas bubble disease" were observed in the fish throughout the duration of the experiment. Overall, these results suggest that both short- and long-term hyper-NB-O2 exposure appears to be benign and has no obvious adverse effects on fish.

Novel intrathoracic irrigation using ultrafine ozone bubbles in a rat empyema model

Dissolved ozone is generally used for sanitization, but it has not been used for thoracic cavity sanitization because of its short half-life (< 20 min) and possible toxicity. We developed a novel solution containing ultrafine ozone bubbles (ozone-UFB) with a fivefold longer half-life than non-UFB ozone. Using an in vitro model, Staphylococcus aureus colonies were counted after exposure to ozone-UFB or non-UFB ozone at the same ozone concentration (0.4 mg/L). The colony count was significantly lower in the ozone-UFB group than in the non-UFB ozone group (p = 0.034). The effect of repeated pleural irrigation using ozone-UFB and saline was compared in a rat empyema model of S. aureus infection. The bacterial count in the pleural effusion was decreased by at least fivefold following intrathoracic lavage with ozone-UFB (3 mg/L). To examine the safety of ozone-UFB for intrathoracic use, ozone-UFB with a higher ozone concentration (10 mg/L) was injected into the thoracic cavities of normal rats. The treatment did not result in any specific pleural damage or elevated serum interleukin-6 concentrations. The findings highlighted the efficacy and safety of ozone-UFB for intrathoracic sanitization, but further studies are needed to determine the optimal therapeutic ozone concentration with appropriate safety margins.

Nanobubbles: a promising efficient tool for therapeutic delivery of antibacterial agents for the Staphylococcus aureus infections

The current research is focused to address the implementation of nanobubbles technology to antibacterial agents against Staphylococcus aureus infections. Nanobubbles technology is a novel, latest research employed in many medical fields including drug discovery. In this present work, supramolecular nanoliquid formulation of potential antiseptic agent chloroxylenol-based Dettol and its enhanced antibacterial activity, biocompatibility assessment was studied. Nanobubble technology was adopted to prepare nanoformulation (NB-D) using a household hand mixer under thermostatically controlled conditions. A high-stability nanoformulation with high potential antibacterial activity against human pathogenic strains of Pseudomonas aeruginosa and Staphylococcus aureus was produced by the nanobubbles created in the antiseptic solution. The overall vitality of both strains was significantly reduced in all dose tests on NB-D treatment as a result of the antibacterial activity as assessed by the well-diffusion assay, turbidometric microdilution assay, biofilm inhibition assay, and total count reduction assay. Biocompatibility of the NB-D formulation was studied by the determination of cytotoxicity against HaCaT-human keratinocytes and hemocytes. NB-D treatment did not induce any notable cytotoxic effect on HaCaT cells by showing none of the changes in cell morphology and architecture. No toxic effect on the hematocytes was observed in NB-D treatment. The enhanced antibacterial activity and best biocompatibility of NB-D result shows that the nanobubble technology could be used as an effective strategy for the formulation of antiseptics or disinfectants against high health risk infectious organisms. The novelty of the work is the formation of supramolecular nanoformulation on antiseptic agent which promised the results enhanced than the raw antiseptic agent.

Nonsurgical Periodontal Treatment Options and Their Impact on Subgingival Microbiota

BACKGROUND

Different periodontal treatment methods (quadrant-wise debridement, scaling and root planing (Q-SRP), full-mouth scaling (FMS), full-mouth disinfection (FMD), and FMD with adjuvant erythritol air-polishing (FMDAP)) were applied in periodontitis patients (stage III/IV). The study objective (substudy of ClinicalTrials.gov Identifier: NCT03509233) was to compare the impact of treatments on subgingival colonization.

METHODS

Forty patients were randomized to the treatment groups. Periodontal parameters and subgingival colonization were evaluated at baseline and 3 and 6 months after treatment.

RESULTS

Positive changes in clinical parameters were recorded in every treatment group during the 3-month follow-up period, but did not always continue. In three groups, specific bacteria decreased after 3 months; however, this was associated with a renewed increase after 6 months (FMS: Porphyromonas gingivalis; FMD: Eubacterium nodatum, Prevotella dentalis; and FMDAP: uncultured Prevotella sp.).

CONCLUSIONS

The benefit of all clinical treatments measured after 3 months was associated with a decrease in pathogenic bacteria in the FMS, FMD, and FMDAP groups. However, after 6 months, we observed further improvement or some stagnation in clinical outcomes accompanied by deterioration of the microbiological profile. Investigating the subgingival microbiota might help appraise successful periodontal treatment and implement individualized therapy.

Ozone ultrafine bubble water inhibits the early formation of Candida albicans biofilms

This study aimed to investigate the effect of ozone ultrafine bubble water (OUFBW) on the formation and growth of Candida albicans (C. albicans) biofilms and surface properties of denture base resins. OUFBWs were prepared under concentrations of 6 (OUFBW6), 9 (OUFBW9), and 11 ppm (OUFBW11). Phosphate buffered saline and ozone-free electrolyte aqueous solutions (OFEAS) were used as controls. Acrylic resin discs were made according to manufacturer instructions, and C. albicans was initially cultured on the discs for 1.5 h. A colony forming unit (CFU) assay was performed by soaking the discs in OUFBW for 5 min after forming a 24-h C. albicans biofilm. The discs after initial attachment for 1.5 h were immersed in OUFBW and then cultured for 0, 3, and 5 h. CFUs were subsequently evaluated at each time point. Moreover, a viability assay, scanning electron microscopy (SEM), Alamar Blue assay, and quantitative real-time polymerase chain reaction (qRT-PCR) test were performed. To investigate the long-term effects of OUFBW on acrylic resin surface properties, Vickers hardness (VH) and surface roughness (Ra) were measured. We found that OUFBW9 and OUFBW11 significantly degraded the formed 24-h biofilm. The time point CFU assay showed that C. albicans biofilm formation was significantly inhibited due to OUFBW11 exposure. Interestingly, fluorescence microscopy revealed that almost living cells were observed in all groups. In SEM images, the OUFBW group had lesser number of fungi and the amount of non-three-dimensional biofilm than the control group. In the Alamar Blue assay, OUFBW11 was found to suppress Candida metabolic function. The qRT-PCR test showed that OUFBW down-regulated ALS1 and ALS3 expression regarding cell-cell, cell-material adhesion, and biofilm formation. Additionally, VH and Ra were not significantly different between the two groups. Overall, our data suggest that OUFBW suppressed C. albicans growth and biofilm formation on polymethyl methacrylate without impairing surface properties.

The neutralizing effect of mouth rinsing with alkaline electrolyzed water on different regions of the oral cavity acidified by acidic beverages

PURPOSE

Acids contained in foods and drinks are involved in the initiation and progression of dental erosion which causes tooth wear. The authors evaluated the neutralizing activity of alkaline electrolyzed water (AEW) in vitro and in vivo.

METHODS

The neutralizing ability of AEW against eight beverages was investigated in vitro. Furthermore, in an in vivo study, the effect of mouth rinsing with AEW on the pH of the oral cavity acidified with acidic beverages was examined. Following mouth rinsing, the oral pH was measured using a pH meter with a micro pH-sensor at the cervical surface of the mandibular teeth and the surface of soft tissues.

RESULTS

Regarding the neutralizing ability, the higher the pH of the AEW, the lower the volume required for neutralization of the tooth surface. Changes in the pH by mouth rinsing with AEW and purified tap water (PTW) were analyzed. The degree of increase of pH with AEW was greater than with PTW at almost all sites.

CONCLUSION

These results suggest that AEW has the potential to prevent the initiation and progression of dental erosion. Mouth rinsing with AEW could be a simple and effective way to prevent the initiation and progression of dental erosion and dental caries.

Stability of Oxygen Nanobubbles under Freshwater Conditions

The use of nanobubbles (NBs) has gained significant attention in various applications (e.g., aeration in biological water treatment, water disinfection, membrane defouling, and ground water and sediment remediation) in recent decades because of their superior characteristics such as the improved mass transfer at the gas-liquid interfaces, their lifetime up to a couple of weeks, the formation of reactive oxygen species (ROS) with high oxidative potential. However, there is a lack of information about the effect of various factors on the stability of NBs for a long storage period under freshwater conditions. In this study, a comprehensive investigation was conducted to systematically examine the stability of oxygen NBs in water under various conditions which are closely related to a typical freshwater or the drinking water treatment. The oxygen NB stability in water was evaluated by monitoring the change in the bubble concentrations, size distribution, average diameter, and zeta potential for 60 days of storage time under different pH, hardness, ionic strength, natural organic matter (NOM), chlorine, and temperature conditions. In addition, the formation of hydroxyl radical (•OH) was investigated using disodium terephthalate which form fluorescent adducts with •OH in the presence of oxygen NBs. Among the parameters investigated, the impacts of cations, low pH, and high SUVA₂₅₄ NOM on the stability of oxygen NBs were more significant than other conditions. The half-lives of oxygen NBs under various conditions follow the order Ca²⁺ < Na⁺ < pH 3 < high SUVA₂₅₄ NOM < pH 5 < 30 °C. Oxygen NBs were more stable in softwater than hardwater. Oxygen NBs were relatively stable for 3 days regardless of pH. For a longer storage period, oxygen NBs disappeared faster at pH 3 than at high pH. High SUVA₂₅₄ NOM destabilized NBs more than low SUVA₂₅₄ NOM, indicating the impact of hydrophobicity on the NB stability. The temperature effect on the NB stability was negligible for a short storage time, while higher temperature destabilized oxygen NBs for a longer storage time. One of the main disappearance pathway of oxygen NBs in water was found to be coalescing, rising, and leaving the container, which would be promoted greatly by cations, low pH and NOM with high aromaticity. The formation of hydroxyl radical in NB solutions was detected at pH 3 by a florescent probe molecule. When oxygen NBs are released in water bodies, high calcium, high SUVA₂₅₄ NOM, and low pH would significantly reduce the availability of NBs and their residence time in freshwater.

The Effect Ultrasound and Surfactants on Nanobubbles Efficacy against Listeria innocua and Escherichia coli O157:H7, in Cell Suspension and on Fresh Produce Surfaces

Removing foodborne pathogens from food surfaces and inactivating them in wash water are critical steps for reducing the number of foodborne illnesses. In this study we evaluated the impact of surfactants on enhancing nanobubbles' efficacy on Escherichia coli O157:H7, and Listeria innocua removal from spinach leaves. We evaluated the synergistic impact of nanobubbles and ultrasound on these two pathogens inactivation in the cell suspension. The results indicated that nanobubbles or ultrasound alone could not significantly reduce bacteria in cell suspension after 15 min. However, a combination of nanobubbles and ultrasonication caused more than 6 log cfu/mL reduction after 15 min, and 7 log cfu/mL reduction after 10 min of L. innocua and E. coli, respectively. Nanobubbles also enhanced bacterial removal from spinach surface in combination with ultrasonication. Nanobubbles with ultrasound removed more than 2 and 4 log cfu/cm² of L. innocua and E. coli, respectively, while ultrasound alone caused 0.5 and 1 log cfu/cm² of L. innocua and E. coli reduction, respectively. No reduction was observed in the solutions with PBS and nanobubbles. Adding food-grade surfactants (0.1% Sodium dodecyl sulfate-SDS, and 0.1% Tween 20), did not significantly enhance nanobubbles efficacy on bacterial removal from spinach surface.

Nanobubbles activate anaerobic growth and metabolism of Pseudomonas aeruginosa

The effect of nanobubbles on anaerobic growth and metabolism of Pseudomonas aeruginosa was investigated. P. aeruginosa grew earlier in the culture medium containing nanobubbles and the bacterial cell concentration in that culture medium was increased a few times higher compared to the medium without nanobubbles under anaerobic condition. Both gas and protein, which are the metabolites of P. aeruginosa, were remarkably produced in the culture medium containing nanobubbles whereas those metabolites were little detected in the medium without nanobubbles, indicating nanobubbles activated anaerobic growth and metabolism of P. aeruginosa. The carbon dioxide nanobubbles came to be positively charged by adsorbing cations and delivered ferrous ions, one of the trace essential elements for bacterial growth, to the microbial cells, which activated the growth and metabolism of P. aeruginosa. The oxygen nanobubbles activated the activities of P. aeruginosa as an oxygen source.

Bactericidal Activity of Bulk Nanobubbles through Active Oxygen Species Generation

We investigated the bactericidal activity of bulk nanobubbles (NBs) using E. coli, a model bacterium. Bulk NBs were produced by forcing gas through a porous alumina membrane with an ordered arrangement of nanoscale straight holes in contact with water. NBs with different gas contents, including CO2, O2, and N2, were generated and evaluated for their bactericidal effects. The survival rate of E. coli was significantly reduced in a suspension of CO2-containing NB (CO2-NB water). The N2-NB water demonstrated a small amount of bactericidal behavior, but its impact was not as significant as that of CO2-NB water. When E. coli was retained in O2-NB water, the survival rate was even higher than that in pure water (PW). We investigated the generation of reactive oxygen species (ROS) in NB suspensions by electron spin resonance spectroscopy. The main ROS generated in the NB water were hydroxyl radicals and OH·, and the production of ROS was the strongest in CO2-NB water, which was consistent with the results of the bactericidal effect measurements. We assumed that NB mediated by ROS would exhibit bactericidal behavior and proposed a kinetic model to explain the retention time variation of the survival rate. The results calculated based on the proposed model matched closely with the experimental results.

Ozone nanobubble modulates the innate defense system of Nile tilapia (Oreochromis niloticus) against Streptococcus agalactiae

Ozone nanobubble (NB-O₃) is a promising technology for improving dissolved oxygen and reducing bacterial concentration in aquaculture systems. Here, we investigated the effects of NB-O₃ on the innate immunity of fish by monitoring the expression levels of nonspecific immune-related genes (IL-1β, IL-2β, TNF-α), heat-shock protein genes (HSP70, HSP90-α), and a bacteriolytic enzyme, C-type lysozyme, gene (LYZ) post-treatment with this technology. Following exposure to NB-O₃, the different tissues of Nile tilapia (Oreochromis niloticus) were collected over time for quantitative real-time PCR (qPCR) analysis. The expression of all the genes evaluated in the gills, the head kidney, and the spleen of the NB-O₃ treated group was significantly up-regulated compared to that in the untreated control group. The expression levels were the highest (approx. 2 to 4-fold) at 15 min and 3 h post-exposure and then decreased from 6 to 24 h. These findings suggested that NB-O₃ could switch on the innate immunity genes of Nile tilapia. Thus, we hypothesized that the NB-O₃-immune-activated fish would respond more effectively to subsequent bacterial infections, thereby improving survivability compared to that of untreated fish. To test this hypothesis, 3 h post NB-O₃ exposed fish and unexposed fish were challenged with a lethal dose of Streptococcus agalactiae. Interestingly, the survival rate of the NB-O₃ group was significantly higher than that of the non-treated controls, with a relative percent survival (RPS) of 60-70%. Together, these findings indicate, for the first time, that NB-O₃ may trigger the nonspecific defense system of the fish, thereby improving fish survivability during subsequent bacterial infections. This research identified another potential benefit of NB-O₃ in aquaculture for preventing infectious bacterial diseases.

Free-Radical Generation from Bulk Nanobubbles in Aqueous Electrolyte Solutions: ESR Spin-Trap Observation of Microbubble-Treated Water

Microbubbles are very fine bubbles that shrink and collapse underwater within several minutes, leading to the generation of free radicals. Electron spin resonance spectroscopy (ESR) confirmed the generation of hydroxyl radicals under strongly acidic conditions. The drastic environmental change caused by the collapse of the microbubbles may trigger radical generation via the dispersion of the elevated chemical potential that had accumulated around the gas-water interface. The present study also confirmed the generation of ESR signals from the microbubble-treated waters even after several months had elapsed following the dispersion of the microbubbles. Bulk nanobubbles were expected to be the source of the spin-adducts of hydroxyl radicals. Such microbubble stabilization and conversion might be caused by the formation of solid microbubble shells generated by iron ions in the condensed ionic cloud around the microbubble. Therefore, the addition of a strong acid might cause drastic changes in the environment and destroy the stabilized condition. This would restart the collapsing process, leading to hydroxyl radical generation.

In vitro three-dimensional organotypic culture models of the oral mucosa

Three-dimensional, organotypic models of the oral mucosa have been developed to study a wide variety of phenomena occurring in the oral cavity. Although a number of models have been developed in academic research labs, only a few models have been commercialized. Models from academic groups offer a broader range of phenotypes while the commercial models are more focused on the oral and gingival mucosa. The commercialized models are manufactured under highly controlled conditions and meet the requirements of quality standards, which leads to high levels of reproducibility. These in vitro models have been used to evaluate the irritancy of oral care products such as toothpastes, mouthwashes, and mucoadhesives. The effects of cigarette smoke on oral cavity tissues have been studied and compared to those of e-cigarettes. Oral tissue models have facilitated investigation of the mechanisms of oral mucositis and oral candidiasis and have been used to examine transbuccal drug delivery rates and the absorption of nanoparticles. Infection studies have investigated the effects of HIV-1 along with the effects of commensal and pathogenic bacteria. More recently, a differentiated oral tissue model has been shown to express the ACE2 receptor, which is known to be important for the receptor-mediated entry of the SARS-CoV-2 coronavirus into human cells and tissues. Hence, oral mucosal models may find application in determining whether viral infection of the oral mucosa is possible and whether such infection has implications vis-a-vis the current COVID-19 pandemic. As is apparent, these models are used in a broad variety of applications and often offer advantages versus animal models in terms of reproducibility, avoiding species extrapolation, and the ethical concerns related to human and animal experimentation. The goals of this paper are to review commercially available models of the human buccal and gingival mucosa and highlight their use to gain a better understanding of a broad range of phenomena affecting tissues in the oral cavity.

Emerging nanomaterials for dental treatments

The emergence of nanomaterials for dental treatments is encouraged by the nanotopography of the tooth structure, together with the promising benefits of nanomedicine. The use of nanoparticles in dentistry, also termed as 'nanodentistry', has manifested in applications for remineralisation, antimicrobial activity, local anaesthesia, anti-inflammation, osteoconductivity and stem cell differentiation. Besides the applications on dental tissues, nanoparticles have been used to enhance the mechanical properties of dental composites, improving their bonding and anchorage and reducing friction. The small particle size allows for enhanced permeation into deeper lesions, and reduction in porosities of dental composites for higher mechanical strength. The large surface area to volume ratio allows for enhanced bioactivity such as bonding and integration, and more intense action towards microorganisms. Controlled release of encapsulated bioactive molecules such as drugs and growth factors enables them to be delivered more precisely, with site-targeted delivery for localised treatments. These properties have benefitted across multiple fields within dentistry, including periodontology and endodontics and reengineering of dental prosthetics and braces. This review summarises the current literature on the emerging field of nanomaterials for dental treatments.

Impact of gas micro-nano-bubbles on the efficacy of commonly used antimicrobials in the food industry

AIM

To study the impact of incorporating micro-nano-bubbles (MNBs) in commonly used food antimicrobials (AMs) against Escherichia coli O157:H7 (EC) and Listeria monocytogenes (LM).

METHODS AND RESULTS

Air, carbon dioxide (CO₂ ) and nitrogen (N₂ ) were used to incorporate MNBs in city water. AM solution (with or without MNBs) of 9 ml was individually taken into sterile test tubes and mixed with 1 ml of inoculum grown in brain heart infusion (BHI) broth to get the net AM concentrations of 28·4 ppm peracetic acid (PAA), 200 ppm chlorine (Cl₂ ), 5·4% citric acid (CA) and 4·5% lactic acid (LA). After treatment time of 1·5 and 3·0 min, 1 ml of sample was neutralized using Dey-Engley neutralizing broth and plated on BHI agar. For EC, Cl₂ -CO₂ solutions resulted in significantly greater log reductions (5·2 logs) compared to that of Cl₂ solutions without MNBs (3·8 logs). For LM, PAA-CO₂ solutions resulted in significantly greater log reductions (4·4 logs) compared to that of PAA solutions without MNBs (1·7 logs).

CONCLUSIONS

This study demonstrated that the efficacy of Cl₂ and PAA AM solutions could be increased by incorporating CO₂ -MNBs against EC and LM in microbiological growth medium.

SIGNIFICANCE AND IMPACT OF THE STUDY

Incorporation of CO₂ -MNBs in AM solutions could increase the efficacy of AMs against pathogens on/in food matrices, which should be tested in future research.

Inactivation of Aeromonas hydrophila and Vibrio parahaemolyticus by Curcumin-Mediated Photosensitization and Nanobubble-Ultrasonication Approaches

The antimicrobial efficacy of novel photodynamic inactivation and nanobubble technologies was evaluated against Vibrio parahaemolyticus and Aeromonas hydrophila as two important aquatic microbial pathogens. Photodynamic inactivation results showed that LED (470 nm) and UV-A (400 nm)-activated curcumin caused a complete reduction in V. parahaemolyticus at 4 and 22 °C, and a greater than 2 log cfu/mL reduction in A. hydrophila, which was curcumin concentration-dependent (p < 0.05). Furthermore, the photodynamic approach caused a greater than 6 log cfu/mL V. parahaemolyticus reduction and more than 4 log cfu/mL of A. hydrophila reduction in aquaponic water samples (p < 0.05). Our results with the nanobubble technology showed that the nanobubbles alone did not significantly reduce bacteria (p > 0.05). However, a greater than 6 log cfu/mL A. hydrophila reduction and a greater than 3 log cfu/mL of V. parahaemolyticus reduction were achieved when nanobubble technology was combined with ultrasound (p < 0.05). The findings described in this study illustrate the potential of applying photodynamic inactivation and nanobubble-ultrasound antimicrobial approaches as alternative novel methods for inactivating fish and shellfish pathogens.

Improved methane production from corn straw using anaerobically digested sludge pre-augmented by nanobubble water

Nanobubble water (NBW) has been proven to efficiently improve methane production from organic solid wastes. However, the increase in reactor volume due to addition of NBW hinders its practical applications. In this study, anaerobically digested sludge was first pre-augmented by N₂-NBW and O₂-NBW using corn straw as sole substrate for methane production with electron transfer activity being monitored. 20%, 33% and 38% of cellulose and 29%, 35% and 35% of hemicellulose were reduced respectively from the control, N₂-NBW and O₂-NBW pre-augmented sludge reactors. N₂-NBW and O₂-NBW pre-augmented sludge reactors achieved methane yields of 127 and 142 mL/g-VS, about 10% and 22% higher than that from the control. Results show that use of NBW pre-augmented anaerobically digested sludge as inoculum can remarkably enhance methane yield from corn straw, providing a novel concept for NBW-based anaerobic digestion system with no increase of reactor volume and construction cost in practice.

Palmoplantar pustulosis treated with oral rinse using ozone nanobubble water: A case series

Neither the etiology nor a reliable treatment for palmoplantar pustulosis has been clearly established. Ozone nanobubble (ONB) water, which is treated with nanosized ozone gas particles and has strong antimicrobial activity, has attracted attention as a future therapeutic option for palmoplantar pustulosis. Oral rinsing, particularly in the periodontal areas, with 10 to 20 mL ONB water for a couple of minutes per night, was prescribed to seven palmoplantar pustulosis patients, comprising five female and two male patients, for 6 months. Skin lesions were observed to be completely cured within a treatment period of approximately 3 to 4 months in six patients; the exception case was the one suspected of having pyorrhea. Rinsing the periodontal area with ONB water resulted in very effective suppression of skin lesions and showed promise as a new treatment method for palmoplantar pustulosis, which suggested the involvement of oral bacteria.

Effects of ozone nano-bubble water on mucositis induced by cancer chemotherapy

No effective, reliable treatment for stomatitis associated with cancer therapy has been established. This study focused on the its effectiveness of ozone nano-bubble water (ONBW) for the treatment of chemotherapy-induced stomatitis. Oral mucositis was induced in 14-week-old male Sprague-Dawley rats (N = 21). The animals were randomly divided into 3 groups: 7 without treatment (control); 7 treated with physiological salt solution (saline); and 7 treated with ONBW. Animals were weighed on Days 7, 9, 11, and 16. Stomatitis grade evaluation and bacterial count measurements were performed before rinsing in all animals 3, 5, and 10 days after acetic acid irritation (Days 9, 11, and 17 respectively). Weight loss after stomatitis creation was observed in all groups, with significant differences between the control and ONBW groups and between the saline and ONBW groups on Day 16. The stomatitis grade did not worsen during the experimental period in any group, with the lowest grades in the ONBW group on Days 11 and 16. Significant differences were identified between the control and ONBW groups and between the saline and ONBW groups on Days 11 and 16. Oral bacterial counts tended to decrease over time in all three groups, with the greatest decrease in the ONBW group, followed by the saline group. The decrease in the bacterial count was steepest in the ONBW group. Rinsing out the oral cavity with ONBW decreased bacterial counts and encouraged the healing of oral chemotherapy-induced stomatitis. ONBW may be an effective treatment for chemotherapy-induced stomatitis.

Bulk nanobubbles in the mineral and environmental areas: Updating research and applications

In the last decade, the research with bulk nanobubbles (ultrafine bubbles with a diameter <1 μm, according to ISO 20480-1:2017) has been rapidly increasing in the academic and industrial environments. Nowadays, there are many applications reported in the literature, with several patents, procedures, and techniques on nanobubbles generation and an evergrowing research and many applications. Yet, most of those publications reporting bulk nanobubbles generation devices, do not bring information on measurements of size distribution or bubbles concentration (if nanobubbles). Further, there is a problem of scale and many of these products are small bench discontinuous rigs difficult to scale up, which might serve small scale purposes, but are not able for treating high flow-rate wastewaters or minerals pulps at industrial scale. These nanometric bubbles present interesting and peculiar properties such as high surface area per volume unit, high stability and longevity, surface charge in water and the ability to aggregate hydrophobic particles. These findings demonstrate their high potential for applications in many technological areas, which occur not only as isolated bubbles but also jointly with micro (~ 1-100 μm diameter) and/or macrobubbles (~100 μm - 2 mm diameter). This paper reviews the evolution of basic research on nanobubbles, the challenges concerning generation and stability and their applications in the mineral (flotation) and environmental areas (treatment of water and wastewaters or remediation of contaminated environments). Herein, because the importance in engineering, as a whole, most of the studies are based on the nanobubbles generated by depressurisation/hydrodynamic cavitation of the air-saturated water in flow constrictors (venturi, needle valves). In the mineral area, they appear to be responsible for increasing the recovery and flotation kinetics of fine (<74 μm) and ultrafine (<13 μm) particles at lower frother and collector dosages. In the environmental area, nanobubbles have been reported to enhance the removal of a variety of pollutants (emulsified oil, colloidal solids, organic/inorganic precipitates, ions) by flotation associated with bigger bubbles. More, the application of isolated nanobubbles on the removal of residual pollutants, such as amine and oil (both as flocs) were reported. Also, the use of ozone and oxygen nanobubbles has been studied for the remediation/decontamination of soil and aquatic ecosystems and for the oxidation of emerging pollutants in water and wastewater treatment. The future of nanobubbles in flotation separation research is highly promising; operating costs of the different forms of nanobubbles generation and bench studies should be validated through pilot and real scale with the continuous injection of these bubbles.

Ozone ultrafine bubble water induces the cellular signaling involved in oxidative stress responses in human periodontal ligament fibroblasts

Periodontitis is a chronic inflammatory disease caused by oral microorganisms in the subgingival biofilm. Stable aqueous ozone ultrafine bubble water (OUFBW) has recently begun to be used as an antiseptic in the treatment of periodontitis. The effectiveness of OUFBW is thought to depend on the bactericidal actions of dissolved ozone exerted via its oxidizing effect. On the other hand, the effects of ozone on the periodontal tissues are largely unknown. In this paper we examined the cellular responses after OUFBW treatment. Human primary periodontal ligament fibroblasts (hPDLFs) or Ca9-22 human gingival epithelial cells were treated with OUFBW or UV-inactivated OUFBW. The production of reactive oxygen species (ROS), the activation of mitogen-activated protein kinase (MAPK) and the nuclear factor-kappa B (NF-κB) activation were analyzed. The transcript profiles of hPDLFs after OUFBW treatment were also analyzed by RNA sequencing (RNA-seq). Our results showed that OUFBW induces oxidative stress by generating ROS, which, in turn, activated the MAPK pathway. OUFBW triggered activation of c-Fos, a major component of the transcription factor activator protein 1 (AP-1), and also nuclear factor erythroid 2 (NF-E2)-related factor 2 (Nrf2), which possessed a high sensitivity to oxidative stress. The results of RNA-seq analysis revealed that the numerous genes involved in oxidative stress responses or MAPK signaling pathway were up-regulated after OUFBW treatment. Investigation of the signaling pathways activated by OUFBW highlights another aspect of the biological roles of OUFBW, in addition to its bactericidal activity, in the treatment of periodontitis.

Effects of nanobubble water on the growth ofLactobacillus acidophilus1028 and its lactic acid production

Nanobubbles (NBs) in the culture medium may offer a new way of accelerating bacterial growth in the lag and logarithmic phases.

Microbicidal Effects of Stored Aqueous Ozone Solution Generated by Nano-bubble Technology

BACKGROUND/AIM

Clinically used disinfectants are often irritating and cause skin problems. Ozone water is unique among disinfectants. It does not damage skin cells and readily decomposes to oxygen without generating harmful residues. On the other hand, it rapidly loses its sanitizing activity. Recently developed nano-bubble ozone water (NBOW) can keep its sanitizing activity much longer. This study aimed to examine the microbicidal effects of NBOW after long-term storage.

MATERIALS AND METHODS

The concentration of ozone in NBOW was examined by measuring the NBOW redox potential. Microbicidal activity was evaluated by colony formation assays, after incubating bacteria with NBOW for set time periods.

RESULTS

NBOW lost its microbicidal activity after 1 year of storage at 4°C. Stocked frozen, NBOW retained appreciable microbicidal activity after 1 year of storage. Mycobacterium smegmatis, one of the most disinfectant-resistant bacteria, was killed within 15 min. NBOW was resistant to freeze-thawing.

CONCLUSION

NBOW that had been stored frozen possessed sufficient microbicidal activity to kill bacteria even after 1 year of storage. Moreover, it was shown that NBOW is freeze-thaw resistant. NBOW possesses desirable features rendering it an attractive alternative disinfectant.