Nanobubble Water Research Articles

The effects of exposure to O2- and HOCl-nanobubble water on human salivary microbiota

Nanobubbles of gas remain dissolved in water for longer periods than ordinary bubbles, and exhibit unique physicochemical and biological properties. As a result, nanobubble water (NBW) is finding widespread use many applications, such as cleaning in the industry and purification of lake water. The ozone NBW (O3-NBW), in particular, has been used in clinical dentistry; however, it has several disadvantages, including the instability of ozone, which is spontaneously converted to molecular oxygen (O3 to O2), and its broad range of antibacterial activity, which can disrupt the oral microbiota. Therefore, the use of NBW in dental medicine requires greater evaluation. Here, we examined the effects of oxygen and hypochlorite NBW (O2-NBW and HOCl-NBW, respectively) on the microbiota in human saliva in 16 male patients (35–75 years old; median: 53.5 years) using multiple assays, including next generation sequencing analysis. 16S rRNA gene sequencing revealed no significant changes in both alpha-diversity and beta-diversity. Principal Coordinate Analysis (PCoA) revealed two subclusters in both unweighted and weighted UniFrac distances. Overall, the results revealed that HOCl-NBW exposure of saliva may lead to inhibition or delay in oral biofilm formation while maintaining the balance of the oral microbiome. These results can lead to the development of a novel type of mouthrinse for prevention of oral infectious diseases.

Nanobubbles in vase water inhibit transpiration and prolong the vase life of cut chrysanthemum flowers.

Nanobubble (NB) water has been shown to promote the growth of several types of plants and animals, but the mechanism underlying this promoting effect remains unclear. The present study evaluated the mechanism by which NBs maintain the freshness of cut flowers by keeping cut chrysanthemum (Chrysanthemum morifolium Ramat.) flowers at the bud stage in vase water containing air NBs. The condition of petals and leaves was assessed to determine the vase life of these cut flowers. The NB treatment delayed bud opening and petal senescence of the inflorescences. Water absorption and transpiration by cut flower stems were lower in NB water than in distilled water (DW). Furthermore, when all the leaves were removed from the cut flower stems, no significant difference in vase life was observed between NB water and DW. These findings indicate that the inhibition of transpiration from leaves prolonged the vase life of NB-treated cut chrysanthemum flowers. In the early stage of the treatment, NB treatment significantly reduced transpiration without closing stomata, suggesting that the reduction in transpiration observed in the NB-treated plants might be due to the suppression of cuticular transpiration, defined as water loss through the epidermis. Surface tension, one of the important driving forces of water movement in plants, was not affected by the presence of NBs in water. To our knowledge, this is the first report to show that transpiration from leaves is inhibited by NB treatment.

Air nanobubble water improves plant uptake and tolerance toward cadmium in phytoremediation

Heavy metal contamination continues to be a persistent environmental problem. To address this issue, this study evaluated the impact of air nanobubbles (NBs) in water on the uptake of heavy metals by Alternanthera philoxeroides (A. philoxeroides), a common aquatic plant in China known for its rapid growth, strong vitality, and high capacity for heavy metal remediation. This study found that diluted air NBs (25% concentration) boosted cadmium uptake of A. philoxeroides by 17.39%. They also enhanced plant growth (25–50%) and photosynthetic pigments (10–20%) even at low cadmium levels (0.1 mM). Furthermore, the incorporation of 25% air NBs has been demonstrated to significantly amplify the performance of key antioxidant enzymes, such as superoxide dismutase and catalase, alongside heightened levels of crucial antioxidants such as malondialdehyde. This heightened activity of antioxidant defenses offers a compelling explanation for the potential amelioration of cadmium toxicity and concurrent enhancements in overall plant growth rates. Notably, a comprehensive analysis utilizing the excitation emission matrix–parallel factor analysis (EEM-PARAFAC) technique has revealed alterations in the composition of rhizosphere dissolved organic matter due to the presence of NBs. This ncomposition change of the rhizosphere dissolved organic mattermposition has subsequently exerted an influence on plant complexation processes and the subsequent uptake of cadmium. This study demonstrates that the strategic implementation of air NBs in water systems holds the potential to significantly enhance the plant's ability to detoxify cadmium and improve the uptake of heavy metals during phytoremediation processes.

Molecular hydrogen-based irrigation extends strawberry shelf life by improving the synthesis of cell wall components in fruit

Strawberries (Fragaria × ananassa Duch.) are highly perishable due to their soft texture, and easily decay during transportation and storage. Our previous report showed that molecular hydrogen-based irrigation in the form of hydrogen nanobubble water (HNW) could obviously improve flavor and consumer preferences of strawberry fruit at the harvesting stage. This study further investigated whether this approach could influence the shelf life of strawberry. During storage for 15 d at 4 ℃, HNW delayed the degradation in the quality of strawberry fruit, evaluated by alteration in sensory attributes (including aroma, luster, color, shape, and general evaluation), weight loss, contents of vitamin C, soluble sugar, and titratable acidity, and sugar/acid ratio. The higher levels of lignin, cellulose, and hemicellulose were observed. Compared to conventional surface water (control) irrigation, the firmness of fruit was increased by HNW irrigation at the harvest stage, and progressively maintained during the storage period. Molecular evidence revealed that before the harvesting period, the transcripts of cinnamyl CoA reductase (CCR) and cinnamyl alcohol dehydrogenase (CAD), as well as cellulose synthase 1/4/6 (CesF1/4/6), the representative genes for the synthesis of lignin, cellulose, and hemicellulose, were induced by HNW irrigation. These changes were positively matched with the increased lignin, cellulose, and hemicellulose contents at the harvesting period. Overall, the extended shelf life of strawberries achieved by molecular hydrogen-based irrigation might be due to the improvement in lignin, cellulose, and hemicellulose accumulation. Therefore, this study demonstrated the effectiveness of HNW irrigation for retarding the decay of harvested strawberries.

Hydrogen Nanobubble Water: A Good Assistant for Improving the Water Environment and Agricultural Production.

Hydrogen nanobubble water (HNW) is an emerging technique in the field of environment and agriculture that is attracting more attention due to its eminent characteristic. HNW exhibits a higher solution stagnation rate with a longer existence in water than molecular hydrogen, which ensures its practical usage. In this Viewpoint, the properties and applications of HNW are discussed. HNW, acting as an antioxidant, effectively eliminates reactive oxygen species and counteracts Cu and Cd stress; HNW also increases crop growth, enhances crops quality, and improves transportation and storage processes. On the basis of the advantages of HNW, we recommend focusing on the potential functions of HNW and broadening its wider applications in environment and agriculture.

The Effect of Nanobubble Water Containing Cordyceps Extract and Withaferin A on Free Fatty Acid-Induced Lipid Accumulation in HepG2 Cells.

Cordyceps extract and withaferin A (Wi-A) are natural compounds that have therapeutic effects on non-alcoholic fatty liver disease (NAFLD). However, their efficacy is limited and a long treatment duration is usually required. To enhance their efficiency, the synergistic effects of nanobubble water (NBW) derived from nitrogen, hydrogen, and oxygen gases were investigated. Results showed that the physical properties of all three NBWs, including nanobubble density (108 particles/mL) and zeta potential (below -22 mV), were stable during 48 h of storage. Hydrogen and nitrogen NBWs did not reduce, but instead promoted, free fatty acid-induced lipid accumulation in HepG2 cells. In contrast, oxygen NBW synergistically enhanced the effects of cordyceps extract and Wi-A. The lipid content decreased by 29% and 33% in the oxygen NBW + cordyceps extract and oxygen NBW + Wi-A groups, respectively, compared to reductions of 22% and 16% by aqueous extracts without NB. This study found that NBW may enhance the lipid-reducing effects of natural compounds, such as cordyceps extract and withaferin A, in hepatic cells. Further studies in animal experiments are needed to determine whether NBW has a potential application in NAFLD.

Oxygen nanobubble water affects wound healing of fibroblast WI-38 cells.

This study investigated the usefulness of oxygen nanobubble water (O2NBW) for wound repair by analyzing its effect on the wound-healing process in human lung fibroblasts (WI-38 cells). The WI-38 cells were treated with 0%, 50%, and 100% O2NBW. The cell viability, reactive oxygen species (ROS) production, and wound healing following treatment were determined to elucidate the effects of O2NBW. Our findings revealed that O2NBW had no cytotoxic effects on WI-38 cells, but instead increased cell numbers. The production of ROS was inhibited in the presence of O2NBW. Further, O2NBW induced migration and wound closure in WI-38 cells. In addition, the mRNA expression levels of antioxidant enzymes and wound-healing-related genes were evaluated. The results demonstrated that O2NBW enhanced the expression levels of all representative genes. In conclusion, our findings suggest that O2NBW could affect ROS production and wound healing in WI-38 cells and genes associated with the antioxidant system and wound healing.

Two-step anaerobic digestion of rice straw with nanobubble water

Lignocellulose usually requires pretreatment to improve biogas production. To enhance lignocellulose biodegradability and improve anaerobic digestion (AD) efficiency, different types (N2, CO2, and O2) of nanobubble water (NW) were applied in this study as soaking agent and AD accelerant to increase the biogas yield of rice straw. The results showed that the cumulative methane yields of treating with NW in two-step AD increased by 11.0%–21.4% compared with untreated straw. The maximum cumulative methane yield was 313.9±1.7 mL/gVS in straw treated with CO2-NW as soaking agent and AD accelerant (PCO2-MCO2). The application of CO2-NW and O2-NW as AD accelerants increased bacterial diversity and relative abundance of Methanosaeta. This study suggested that using NW could enhance soaking pretreatment and methane production of rice straw in two-step AD; however, combined treatment with inoculum and NW or microbubble water in the pretreatment needs to compare in future.

Bioinspired nanobubble water channel membranes for ultrafast osmosis desalination

Biological water channels (BWCs) and artificial water channels (AWCs) exhibit standout water-to-ion selectivity. However, difficult membrane integration threatened their desalination application. Inspired by biological cell membranes, an ultrafast osmosis desalination membrane is fabricated with air nanobubbles adhered on fluorinated carbon nanotubes (ANBs-FCNTs) interlayer sandwiched between polyacrylonitrile (PAN) nanofiber layers. Water transport through nanobubble water channel is accelerated by nanobubble gating for selective transport and nanobubble-lubricated water channels for low friction, which was confirmed by varying combination modes of forward osmosis (FO) and membrane distillation (MD). Superior salt rejection is achieved by efficient nanobubble gating, resulting from the combined action by size screening, fast surface slip, electrostatic shielding and sufficient adsorption of ANBs-FCNTs interlayer. In nanofluidic diode membrane concatenation model, multistep capillary force provides enhanced water flux, whereas multi-staged concatenation layers offer more barrier gating for the ion's diffusion, thus resulting in higher permselectivity. The bioinspired nanobubble membranes can achieve high water flux (479.8 L m−2 h−1), high rejection (>95%) to solutes and low reverse salt flux (0.686 g m−2 h−1) under robust and continuous cross flow operation, which outperformed the state-of-the-art forward osmosis membranes. The electrospinning and deposition technique allows for scalable membrane preparation for desalination, resources and energy production.

How nano-bubble water and nano-silica affect the air-voids characteristics and freeze-thaw resistance of air-entrained cementitious materials at low atmospheric pressure?

With more infrastructures being built in plateau regions, low atmospheric pressure is put forward as a new factor affecting the mechanical properties and durability of cementitious materials, but its influence is inconclusive, and the failure of freeze-thaw has not been effectively solved. This research explored the influences of both nano-bubble water (NBW) and nano-silica (NS) on air-voids characteristics and freeze-thaw resistance of cementitious materials formed and cured at different air pressure (0.4P, 0.7P, P; P=1atm); and investigated the effects and its mechanisms of low air pressure on performances of cementitious materials. The air-voids structure analyser, SEM, XRD and TG-DSC were employed to evaluate the microstructure and cement hydration of hardened cement paste samples. Results show that low-pressure samples have abnormal air-void parameters and poor bubble stability, which lead to a decrease in freeze-thaw resistance. It is proved that both NBW and NS can improve the freeze-thaw resistance and mechanical strength of samples at low atmospheric pressure by accelerating cement hydration, enhancing bubble stability, and optimizing air-voids parameters. The mechanisms of low pressure, NBW and NS on properties of cementitious materials are expounded. This research proposes new perspectives for improving the durability of air-entrained cementitious materials in plateau and enables us to further comprehend the effects and principles of low air pressure on performances of cementitious materials.

Anti-HER2 scFv-nCytc-Modified Lipid-Encapsulated Oxygen Nanobubbles Prepared with Bulk Nanobubble Water for Inducing Apoptosis and Improving Photodynamic Therapy.

Bulk nanobubbles fascinate scientists because of their stability over long periods of time and their ability to carry gases, leading to numerous potential applications. Considering the hypoxic tumor microenvironment and the advantages of bulk nanobubbles, lipid-encapsulated oxygen nanobubbles are prepared from free bulk oxygen nanobubbles in this study. The obtained carrier is then modified with a protein fused with the single-chain antibody of human epidermal growth factor receptor 2 (anti-HER2 scFv) and tandem-repeat cytochrome c (anti-HER2 scFv-nCytc) to enhance tumor targeting and induce tumor apoptosis. Copper phthalocyanine is used as the photosensitizer to demonstrate how the oxygen in the nanobubbles affects the efficiency of photodynamic therapy(PDT). The combination of anti-HER2 scFv-nCytc and PDT synergistically improves the therapeutic effect and alleviates hypoxia in tumors in vivo while causing little inflammatory response. Based on the findings, bulk nanobubble water shows promise in the targeted delivery of oxygen and can be combined with antibody therapy to enhance the efficiency of PDT.

Supplementation of CO2-nanobubble water to enhance the methane production from anaerobic digestion of corn straw

Nanobubble water (NBW) could improve methane production from anaerobic digestion (AD) of corn straw without secondary contamination. In this study, the effect of carbon dioxide nanobubble water (CO2-NBW) volumes (0%, 25%, 50%, 75%, 100%) on methane production from corn straw was investigated. The results showed that addition of CO2-NBW could improve methane production and promote substrate degradation in AD process. The highest cumulative methane production of 132.16 mL g−1VSadded was obtained in the 100% CO2-NBW added reactor, which was 17% higher than that in the control group. Additionally, the addition of CO2-NBW could mitigate the sharp decrease in pH by acting as a buffer. CO2-NBW could also enhance microorganism activity throughout the AD process. The electron transport system (ETS) activity was increased by 23%, while the β-glucosidase, dehydrogenase (DHA), and coenzyme F420 activities were increased by 15%, 23%, and 11%, respectively, at optimum addition of CO2-NBW. Meanwhile, addition of CO2-NBW accelerated the production and consumption of reducing sugar and volatile fatty acids (VFAs), promoting the reduction rates of TS (Total solid) and VS (Volatile solid).

Use of nanobubble water bioaugmented anaerobically digested sludge for high-efficacy energy production from high-solids anaerobic digestion of corn straw

An increasing attention has been paid to the secure and sustainable management of agricultural wastes, especially lignocellulosic biomass. Nanobubble water (NBW) contains 106–108 bubbles/mL with diameter <1000 nm. Although previous studies have examined the enhancement effects of NBW on methane production from organic solid wastes, the NBW-based anaerobic digestion (AD) system is still restrained from practical application due to the large increase in AD reactor volume, generation of wastewater, and increase in energy consumption as well. In this study, NBW bioaugmentation of anaerobically digested sludge for the first time was performed for high-solids AD of corn straw. Results show that cellulase, xylanases and lignin peroxidase activities were increased by 2–55% during the NBW bioaugmentation process. Significant enrichment of hydrolytic/acidogenic bacteria and methanogenic archaea were noticed in the NBW bioaugmented sludge. This study clearly demonstrated 47% increase in methane production from high-solids AD of corn straw when O2-NBW bioaugmented sludge was applied, achieving a net energy gain of 5138 MJ/t-volatile solids of corn straw with an energy recovery of 34%. The NBW-based high-solids AD system can provide a novel and sustainable management solution for renewable energy production from agricultural wastes, targeting the reduction of environmental pollution and energy crisis.

Study on the multiscale properties of cement-based materials containing nano-bubble water

In this work, the effects of nanobubble water (NBW) on the durability, rheology, macromechanics, and microscopic properties of cement-based materials were investigated. NBW did not significantly improve the fluidity and compressive strength of the concrete with strength grades below C25; however, it did significantly improve the fluidity and inhibit the slump loss of concrete with strength grades above C30, while the compressive strengths of the samples at different ages increased to varying degrees. NBW could also improve the durability of the concrete (sulfate resistance, carbonation resistance, and single-side freeze-thaw resistance) to varying degrees. The hydration temperature test, XRD, TGA/DTG, and MIP results indicated that NBW promoted the hydration reaction process and the generation of hydration products such as CSH colloids and CH crystals, which could effectively improve the internal structure of the cement paste, thereby further affecting the macroscopic properties. The mechanism of NBW was such that the high potential adsorption force on the surface of the fine bubbles increased the number of ion nucleation sites in the suspension, which was beneficial for increasing the effective hydration products of the cement in the early stage.

Molecular Hydrogen: The Postharvest Use in Fruits, Vegetables and the Floriculture Industry

Molecular hydrogen (H2) has been found to have significant effects in a range of organisms, from plants to humans. In the biomedical arena it has been found to have positive effects for neurodegenerative disease and even for treatment of COVID-19. In plants H2 has been found to improve seed germination, foliar growth, and crops: effects being most pronounced under stress conditions. It has also been found that treatment with H2 can improve the postharvest preservation of fruits, vegetables and flowers. Therefore, H2-based treatments may be useful for the storage and transport of food products. H2 can be delivered in a range of manners, from the use of the gas to creating H2-enriched solutions, such as hydrogen-rich water (HRW) or hydrogen nanobubble water (HNW). The exact action of H2 at a biochemical level has yet to be established. Despite this, H2 appears to be safe. Treatments of food with H2 would leave no harmful residues, and H2 itself is safe to use, as exemplified by its biomedical use. With H2 production and transport being developed for other industries, H2 is likely to become cheaper and its use for postharvest maintenance of food may be beneficial to explore further.

Molecular Hydrogen Improves Rice Storage Quality via Alleviating Lipid Deterioration and Maintaining Nutritional Values.

Improvement of the storage quality of rice is a critical challenge for the scientific community. This study assesses the effects of the irrigation with hydrogen nanobubble water (HNW) on the storage quality of rice (Oryza sativa ‘Huruan1212’). Compared with ditch water control, after one year of storage at 25 °C and 70% RH, the HNW-irrigated rice had higher contents of essential amino acids, especially lysine. Importantly, the generation of off-flavors in the stored rice was significantly decreased, which was confirmed by the lower levels of volatile substances, including pentanal, hexanal, heptanal, octanal, 1-octen-3-ol, and 2-heptanone. The subsequent results showed that the HNW-irrigated rice not only retained lower levels of free fatty acid values, but also had increased antioxidant capacity and decreased lipoxygenase activity and transcripts, thus resulting in decreased lipid peroxidation. This study opens a new window for the practical application of HNW irrigation in the production and subsequent storage of crops.

Enhanced Removal of Free Radicals by Aqueous Hydrogen Nanobubbles and Their Role in Oxidative Stress.

Elevated levels of reactive oxygen radicals caused by environmental stress are the key triggers of inflammation, aging, and disease; thus, it is critical to develop novel reactive oxygen radical scavenging methods with high efficiency and low toxicity. As a result of their selective reactive oxygen radical removal, hydrogen molecules are strong candidates, but their application is limited by the small hydrogen supply and short duration of action. In this study, we for the first time combined nanobubble (NB) technology and hydrogen water to remove reactive oxygen species (ROS) using copper ions as a representative environmental pollutant and Tetrahymena thermophila as a model organism. Hydrogen NBs displayed a remarkable capability of removing H2O2 and O2•- at molar ratios of 8:1 and 240:1, respectively, which were unable to be removed by dissolved hydrogen molecules only. During the oxidative defense phase, hydrogen NB water either directly removed ROS or increased the activity and relative expression of glutathione peroxidase (GSH-Px). During the oxidative inhibition phase, hydrogen NB water exerted antioxidant effects mainly by increasing the activities of superoxide dismutase and GSH-Px as well as the expression of the corresponding genes. Our results provide an important theoretical support for the wide application of hydrogen NBs in empowering the antioxidant defense system.

Cement Composites with Graphene Nanoplatelets and Recycled Milled Carbon Fibers Dispersed in Air Nanobubble Water.

The individual effect of nano- and micro-carbon-based fillers on the mechanical and the electrical properties of cement paste were experimentally examined in this study. The objective of the study was to separately examine the effects of size and morphology (platelets and fibers) of nano- and micro-reinforcement. Three different sizes of Graphene Nanoplatelets (GNPs), at contents of 0.05% and 0.20% and recycled milled carbon fibers (rCFs), at various dosages from 0.1–2.5% by weight of cement, were incorporated into the cementitious matrix. GNPs and rCFs were dispersed in water with air nanobubbles (NBs), an innovative method that, compared to common practice, does not require the use of chemicals or high ultrasonic energy. Compressive and bending tests were performed on GNPs- and rCFs-composites. The four-wire-method was used to evaluate the effect of the conductive fillers on the electrical resistivity of cement paste. The compressive and flexural strength of all the cementitious composites demonstrated a considerable increase compared to the reference specimens. Improvement of 269.5% and of 169% was observed at the compressive and flexural strength, respectively, at the GNPs–cement composites incorporating the largest lateral size GNPs at a concentration of 0.2% by weight of cement. Moreover, the rCFs–cement composites increased their compressive and flexural strength by 186% and 210%, respectively, compared to the reference specimens. The electrical resistivity of GNPs- and rCFs-composite specimens reduced up to 59% and 48%, respectively, compared to the reference specimens, which proves that the incorporation of GNPs and rCFs can create a conductive network within the cementitious matrix.

Effect of aging time, airflow rate, and nonionic surfactants on the surface tension of bulk nanobubbles water

• Effects of aging time and airflow rate on the surface tension of bulk NB water are investigated. • Effects of airflow rate on the surface tension of bulk NB water is discussed. • The surface tension of bulk NB water is affected by the presence of NBs in the gas–liquid interface. • The surfactant adsorption affected by NBs in the gas–liquid interface determines the surface tension. Nanobubbles have attracted considerable and ever increasing scientific and commercial interest in the past two decades. The main interest focuses on the observation that they are colloidally stable showing various potential applications including flotation, wastewater treatment, cleaning. Here, we report a systematic study studying the surface tension of bulk nanobubbles (BNBs) in water with respect to the aging time and airflow rate. Further, the interfacial tensions of methyl isobutyl carbinol (MIBC) and 2-octanol solutions in the presence and absence of BNBs has been investigated. This study showed that the surface tension of freshly generated nanobubble water is significantly lower than the surface tension of pure water and gradually increase with time until it reaches 70.5 mN/m. Further, a reduction in surface tension and an increase in nanobubbles size were observed when airflow rate was increased. The surface tensions of mixed nanobubbles with methyl isobutyl carbinol (MIBC) was lower than those without nanobubbles, unlike nanobubbles mixed with 2-octanol solutions which led to an increase in the surface tension compared to those without nanobubbles. A possible mechanism for the change in the surface tension in nanobubbles mixed with nonionic surfactant is discussed.

Effects of Ultrafine Single-Nanometer Oxygen Bubbles on Radiation Sensitivity in a Tumor-Bearing Mouse Model.

Radiation therapy against cancer cells often causes radiation resistance via accumulation of hypoxia-inducible factor 1 subunit alpha (HIF-1α) under hypoxic conditions and severe side effects. Radiation sensitizers without side effects are required to overcome hypoxia-induced radiation resistance and decrease radiation-related side effects in patients with refractory cancer. We previously developed oxygen nanobubble water (NBO2 water) and demonstrated that it suppresses hypoxia-induced radiation resistance in cancer cell lines within the single-nanometer range. This study aimed to elucidate whether NBO2 water could act as a radiosensitizer via regulation of HIF-1α in a tumor-bearing mouse model. Six-week-old female BALB/c mice subcutaneously injected with tumor cells received control water or NBO2 water for 28 days, after which biochemical examinations and radiation treatment were performed. Hypoxic tumor regions were detected immunohistochemically. We found that NBO2 water sensitized radiation reactivity in the xenografted tumors. Notably, NBO2 water administration downregulated the accumulation of HIF-1α in xenografted tumors and did not affect the vital organs of healthy mice. The combination of radiation and single-nanometer NBO2 water without severe side effects may be a promising therapeutic option to improve radiation sensitivity in cancer patients without tolerance to invasive treatments.