Oxygen Microbubbles Research Articles

Mechanism of OH radical production from ozone bubbles in water after stopping cavitation.

It has been experimentally reported that OH radicals are produced from ozone microbubbles even after stopping cavitation. Microbubbles are mostly produced using acoustic or hydrodynamic cavitation. In the present paper, numerical simulations of chemical reactions inside an ozone bubble and an oxygen bubble are performed during and after acoustic cavitation in order to study the mechanism of OH radical production. The results have indicated that less than one molecule of OH radicals is produced from a dissolving ozone bubble after stopping cavitation when local pH near the bubble wall is <8. On the other hand, more than 108 or 106 molecules of H2O2 are produced inside an ozone or oxygen microbubble, respectively, in water during acoustic cavitation per violent collapse. It suggests that OH radicals are possibly produced by the chemical reaction of H2O2 with O3 in the liquid phase even after stopping cavitation. Furthermore, in strongly acidic conditions (pH < 5), the reaction of H2O2 with O3 in the liquid phase is relatively slow, and OH production considerably continues after stopping cavitation. This may be the reason for the enhanced OH signals in strongly acidic conditions observed experimentally after stopping cavitation.

Oxygen Microbubble Generator Enabled by Tunable Catalytic Microtubes.

Rolled-up catalytic Ti/Cr/Pt microtubes, consisting of inorganic nanomembranes integrated on-chip, are used to generate oxygen microbubbles in solutions of hydrogen peroxide. Oxygen bubble parameters (frequency, radius and volumetric flow rate) are optimized at different concentrations of hydrogen peroxide and common dish soap. Increasing the aspect ratio of the microtube (e.g., tube length/diameter) leads to the formation of smaller bubbles, but at higher frequencies. Longer tubes produce less total oxygen volume in comparison to shorter tubes. We attribute this observation to the specific dynamic behaviours of bubbles in tubes.

Hydrogel micromotors with catalyst-containing liquid core and shell

Methacrylic anhydride-derived hydrogel microcapsules have unique properties, including reversibly tunable permeation, purification, and separation of dissolved molecular species. Endowing these dynamic encapsulant systems with autonomous motion will significantly enhance their efficiency and applicability. Here, hydrogel micromotors are realized using complex water-in-oil-in-water double emulsion drops and oil-in-water emulsion drops from glass capillary microfluidics and subsequent photopolymerization. Three hydrogel micromotor strategies are explored: microcapsules with thin shells and liquid cores with dispersed catalytic Pt nanoparticles, as well as water-cored microcapsules and homogeneous microparticles selectively coated with Ti/Pt catalytic layers. Autonomous motion of hydrogel particles and capsules is realized in hydrogen peroxide solutions, where generated oxygen microbubbles propel the dynamically responsive micromotors. The micromotors are balanced by weight, buoyancy, lateral capillary forces and show specific autonomous behaviours that significantly extend short range dynamic responses of hydrogels. Drop-based microfluidics represent a paradigm shift in the integration of multifunctional subsystems and high-throughput design of chemical micromachines in reasonable quantities towards their desired biomedical, environmental and flow/diffusion microreactor applications.

Preserving the Integrity of Surfactant-Stabilized Microbubble Membranes for Localized Oxygen Delivery.

Ultrasound contrast agents consist of stabilized microbubbles. We are developing a surfactant-stabilized microbubble platform with a shell composed of Span 60 (Sorbitan monostearate) and an emulsifying agent, water-soluble vitamin E (α-tocopheryl poly(ethylene glycol) succinate, abbreviated as TPGS), named SE61. The microbubbles act both as an imaging agent and a vehicle for delivering oxygen to hypoxic areas in tumors. For clinical use, it is important that a platform be stable under storage at room temperature. To accomplish this, a majority of biologicals are prepared as freeze-dried powders, which also eliminates the necessity of a cold chain. The interfaces among the surfactants, gas, and liquids are subject to disruption in both the freezing and drying phases. Using thermocouples to monitor temperature profiles, differential scanning calorimetry to determine the phase transitions, and acoustic properties to gauge the degree of microbubble disruption, the effects of the freezing rate and the addition of different concentrations of lyoprotectants were determined. Slower cooling rates achieved by freezing the samples in a -20 °C bath were found to be reproducible and produce contrast agents with acceptable acoustical properties. The ionic strength of the solutions and the concentration of the lyoprotectant determined the glass-transition temperature (Tg') of the frozen sample, which determines at what temperature samples can be dried without collapse. Crucially, we found that the shelf stability of surfactant-shelled oxygen microbubbles can be enhanced by increasing the lyoprotectant (glucose) concentration from 1.8 to 5.0% (w/v), which prevents the melt temperature (Tm) of the TPGS phase from rising above room temperature. The increase in glucose concentration results in a lowering of Tm of the emulsifying agent, preventing a phase change in the liquid-crystalline phase and allowing for more stable bubbles. We believe that preventing this phase change is necessary to producing stabilized freeze-dried microbubbles.

PH-Responsive Oxygen Nanobubbles for Spontaneous Oxygen Delivery in Hypoxic Tumors.

Tumor hypoxia is a significant factor leading to the resistance of tumors to treatment, especially for photodynamic therapy and radiotherapy where oxygen is needed to kill cancer cells. Oxygen delivery agents such as oxygen-saturated perfluorocarbon nanoemulsions and lipid oxygen microbubbles have been employed to supply oxygen to hypoxic tumors with ultrasound activation. Such oxygen delivery systems are still associated with several drawbacks, including premature oxygen release and the dependence of external stimuli. To address these limitations, we developed oxygen nanobubbles that were enclosed by the acetalated dextran polymer shells for spontaneous oxygeneration in response to a minor pH drop in the tumor microenvironment. The acetalated dextran polymer shell serves as a robust barrier against gas dissolution in the circulating blood to retain the majority of the oxygen payload, and its pH-responsive property enables an abrupt burst release of oxygen in the mild acidic tumor microenvironment. The acetalated dextran oxygen nanobubbles exhibited excellent stability and biocompatibility. In vitro and in vivo experiments were conducted to investigate the pH-responsive oxygen release. The external stimuli-free supply of oxygen by the acetalated dextran oxygen nanobubbles was evaluated on CNE2 tumor-bearing mice, and the intratumoral oxygen level increased by 6-fold after the administration of the oxygen nanobubbles, manifesting that our pH-responsive oxygen nanobubbles hold great potential as a potent oxygen delivery agent to overcome the hypoxia-induced resistance.

Tubular catalytic micromotors in transition from unidirectional bubble sequences to more complex bidirectional motion

The generation of oxygen microbubbles in catalytic microtubes has attracted tremendous attention towards the exploration of unidirectional and overloaded bubble ejection regimes, leading to simple and more complex motions of micromotors. While it is widely believed that a bubble's frequency in a unidirectional regime (i.e., a bubble ejected from a single tubular opening) is random, this study shall demonstrate that periodic oxygen bubble frequencies and sequences can be experimentally controlled using various concentrations of hydrogen peroxide fuel and surfactants. When released from a substrate, unidirectional micromotors self-propel in straight, circular, and helical trajectories, leading to a class of well-predictable or simple micromachines. Under overloaded conditions, micromotors generate bubbles at both tubular openings, which influence the trajectories of micromotor motion strongly. A one-dimensional reaction-diffusion equation is formulated to explain the possible mechanisms of mass transport in microtubes and the transition from the unidirectional to the overloaded regime of micromotors.

Normalization of Tumor Vasculature by Oxygen Microbubbles with Ultrasound.

Tumor microenvironment influences the efficacy of anti-cancer therapies. The dysfunctional tumor vasculature limits the efficiency of oxygenation and drug delivery to reduce treatment outcome. A concept of tumor vascular normalization (VN), which inhibits angiogenesis to improve vessel maturity, blood perfusion, and oxygenation, has been demonstrated under the anti-angiogenic therapy. The efficiency of drug delivery and penetration is increased by enhancing perfusion and reducing interstitial fluid pressure during the time window of VN. However, anti-angiogenic agents only induce transient VN and then prune vessels to aggravate tumor hypoxia. To repair tumor vessels without altering vessel density, we proposed to induce tumor VN by local oxygen release via oxygen microbubbles with ultrasound. With tumor perfusion enhancement under ultrasound contrast imaging tracing, the time window of VN was defined as 2-8 days after a single oxygen microbubble treatment. The enhanced tumor oxygenation after oxygen microbubble treatment inhibited hypoxia inducible factor-1 alpha (HIF-1α)/vascular endothelial growth factor (VEGF) pathway to improve the morphology and function of tumor vasculature. The pericyte coverage and Hoechst penetration of tumor vessels increased without any changes to the vessel density. Finally, the intratumoral accumulation of anti-cancer drug doxorubicin could be increased 3-4 folds during tumor VN. These findings demonstrate that regulating tumor oxygenation by oxygen microbubbles could normalize dysfunctional vessels to enhance vascular maturity, blood perfusion, and drug penetration. Furthermore, ultrasound perfusion imaging provides a simple and non-invasive way to detect the VN time window, which increases the feasibility of VN in clinical cancer applications.

Lipid-Polymer Bilaminar Oxygen Nanobubbles for Enhanced Photodynamic Therapy of Cancer

Hypoxia in solid tumors may be a hindrance to effective treatments of tumors in achieving their therapeutic potential, especially for photodynamic therapy (PDT) which requires oxygen as the supplement substrate. Oxygen delivery using perfluorocarbon emulsions or lipid oxygen microbubbles has been developed as the agents to supply endogenous oxygen to fuel singlet oxygen generation in PDT. However, such methods suffer from premature oxygen release and storage issues. To address these limitations, we designed lipid-polymer bilaminar oxygen nanobubbles with chlorin e6 (Ce6) conjugated to the polymer shell as a novel oxygen self-supplement agent for PDT. The resultant nanobubbles possessed excellent stability to reduce the risk of premature oxygen release and were stored as freeze-dried powders to avoid shelf storage issues. In vitro and in vivo experimental results demonstrated that the nanobubbles exhibited much higher cellular uptake rates and tumor targeting efficiency compared to free Ce6. Using the oxygen nanobubbles for PDT, a significant enhancement of therapeutic efficacy and survival rates was achieved on a C6 glioma-bearing mice model with no noticeable side effects, owing to the greatly enhanced singlet oxygen generation powered by oxygen encapsulated nanobubbles.

Progress in Ultrasonic Cleaning Research

Physical cleaning based on underwater ultrasound is widely used in industry and its cleaning efficiency is known, from recent studies, to be augmented by promoting the mechanical activity of cavitation bubbles. As a side effect, ultrasound cleaning may give rise to material damage from violent collapse of cavitation bubbles. Traditionally, degassed water is favored as cleaning solution in order to reduce the probability of having cavitation (and the resulting erosion); however, there is no chance to promote cleaning efficiency with this approach. In this review, we introduce our recent effort toward the development of an erosion-free ultrasonic cleaning technique using aerated water. Under dissolved gas supersaturation in aerated water, bubbles can be created easily with low-intensity ultrasound and the resulting bubble dynamics are expected to be mild enough to avoid erosive collapse. To demonstrate this conjecture, we run a series of ultrasound cleaning tests with glass samples on which submicron SiO2 particles are spin-coated; we use a transparent cleaning bath for visualization of acoustic phenomena by a high-speed camera. Dissolved oxygen (DO) supersaturation in water (aerated by oxygen microbubbles) and ultrasound frequency (at 28 kHz or 200 kHz) are varied as parameters, while the input power to drive the ultrasound transducer is fixed and the ultrasound amplitude at the pressure antinode is set at Pe=1.0 atm (root-mean-square value) for the case of degassed water. Particle removal efficiency (PRE) is defined based on image analysis of light scattering from the residual particles (i.e., the so-called Haze method). We see that there exists an optimal DO supersaturation to maximize the PRE. We also see that the PRE is higher in the case of lower frequency (28 kHz), for its cavitation inception threshold is reduced and the number of activated bubbles is thus increased.

Efficacy of using oxygen microbubble device for facultative anaerobe removal.

Patients with serious gingivitis or periodontal diseases suffer from receding gums. Brushing teeth with a toothbrush may result in bleeding gums and new wounds, which increases the difficulty of removing facultative anaerobes from gum pockets, to decrease the damage inflicted on gums, this study proposed a cleaning device that can generate and emit oxygen microbubbles for eliminating facultative anaerobes in the mouth cavity. In this study, the authors conducted simulations with a denture to investigate the efficacy of using this method to remove facultative anaerobes. In this research for the optimal device design, several variables were manipulated including rotation speeds of the bubble generator, different nozzle diameters, and different numbers of nozzle holes. The results revealed that the device is effective in removing facultative anaerobes; moreover, of all design variables, the number of nozzle holes was the factor having the largest effect on anaerobe removal, as it influenced the flow volume and oxygen content of the discharge: the greater the number of nozzles, the greater the flow volume, oxygen content, and efficacy of anaerobe removal.

Oxygen microbubbles improve radiotherapy tumor control in a rat fibrosarcoma model - A preliminary study.

Cancer affects 39.6% of Americans at some point during their lifetime. Solid tumor microenvironments are characterized by a disorganized, leaky vasculature that promotes regions of low oxygenation (hypoxia). Tumor hypoxia is a key predictor of poor treatment outcome for all radiotherapy (RT), chemotherapy and surgery procedures, and is a hallmark of metastatic potential. In particular, the radiation therapy dose needed to achieve the same tumor control probability in hypoxic tissue as in normoxic tissue can be up to 3 times higher. Even very small tumors (<2–3 mm3) comprise 10–30% of hypoxic regions in the form of chronic and/or transient hypoxia fluctuating over the course of seconds to days. We investigate the potential of recently developed lipid-stabilized oxygen microbubbles (OMBs) to improve the therapeutic ratio of RT. OMBs, but not nitrogen microbubbles (NMBs), are shown to significantly increase dissolved oxygen content when added to water in vitro and increase tumor oxygen levels in vivo in a rat fibrosarcoma model. Tumor control is significantly improved with OMB but not NMB intra-tumoral injections immediately prior to RT treatment and effect size is shown to depend on initial tumor volume on RT treatment day, as expected.

Sensitization of Hypoxic Tumors to Radiation Therapy Using Ultrasound-Sensitive Oxygen Microbubbles

Much of the volume of solid tumors typically exists in a chronically hypoxic microenvironment that has been shown to result in both chemotherapy and radiation therapy resistance. The purpose of this study was to use localized microbubble delivery to overcome hypoxia prior to therapy. In this study, surfactant-shelled oxygen microbubbles were fabricated and injected intravenously to locally elevate tumor oxygen levels when triggered by noninvasive ultrasound in mice with human breast cancer tumors. Changes in oxygen and sensitivity to radiation therapy were then measured. In this work, we show that oxygen-filled microbubbles successfully and consistently increase breast tumor oxygenation levels in a murine model by 20mmHg, significantly more than control injections of saline solution or untriggered oxygen microbubbles (P<.001). Using photoacoustic imaging, we also show that oxygen delivery is independent of hemoglobin transport, enabling oxygen delivery to avascular regions of the tumor. Finally, we show that overcoming hypoxia by this method immediately prior to radiation therapy nearly triples radiosensitivity. This improvementin radiosensitivity results in roughly 30days of improved tumor control, providing statistically significant improvements in tumor growth and animal survival (P<.03). Our findings demonstrate the potential advantages of ultrasound-triggered oxygen delivery to solid tumors and warrant future efforts into clinical translation of the microbubble platform.

Electroflotation of Escherichia coli Improves Detection Rates by Loop-Mediated Isothermal Amplification

Abstract. The power of portable molecular diagnostic systems for detection of pathogenic microorganisms in food and environmental samples is largely limited by small assay volumes (typically 1 to 5 µL), making direct detection of trace contamination (i.e., &amp;lt;104 CFU mL-1) unreliable. To improve detection limits for pathogens dispersed on an ecological scale, we developed a portable point-of-care (POC) sample preparation system using electroflotation (EF) to recover small quantities of these organisms from samples of hundreds of milliliters. Electrolysis reactions, supported on platinum-coated titanium electrodes, generate hydrogen and oxygen microbubbles that impel and displace suspended cells into a recovered concentrate. Samples were prepared by inoculating 380 mL of sterilized phosphate buffer (0.1 M, pH 6.6) with stock culture of ATCC 25922 to final concentrations ranging from 102 to 104 CFU mL-1. Samples were subjected to 10, 15, and 20 min durations of EF treatment under high and low turbulence conditions. We used a loop-mediated amplification (LAMP) assay with primers targeting a single-copy gene (glycerate kinase) in generic to evaluate the effects of EF treatment on concentration and recovery of detectable cell material. LAMP failed to detect in all untreated (control) samples at concentrations below 104 CFU mL-1 but was able to detect in 102 CFU mL-1 samples subjected to various conditions of EF treatment. Two-way ANOVA showed significant differences in detection rates between EF treatment durations for both high (p = 0.0019) and low turbulence (p = 0.002). Dunnett’s multiple comparison tests identified five process conditions resulting in significant (p &amp;lt; 0.05) differences in detection between treatments and the control. Keywords: Biotechnology, Electrolysis, Food pathogens, Microbubbles, Molecular diagnostics, Pathogen detection, POC sample preparation.

Aeration of water with oxygen microbubbles and its purging effect

In this paper, we apply aeration with oxygen microbubbles to tap water; the intent is to quantitatively evaluate whether nitrogen gas originally dissolved in the water under the atmosphere is purged by the aeration with oxygen microbubbles. Oxygen microbubbles are continuously injected into the circulation system of tap water open to the atmosphere. While the concentration of dissolved oxygen (DO) can be detected by a commercial DO meter, that of dissolved nitrogen (DN) is unavailable. To detect the DN level, we observe the growth of millimetre-sized gas bubbles nucleated at glass surfaces in contact with the aerated water and compare it with the multi-species theory of Epstein and Plesset where the (unknown) DN concentration is treated as a fitting parameter. In the theory, we solve binary diffusion of each gas species (oxygen or nitrogen) in the water independently, under the assumption that the dissolved gases are sufficiently dilute. Comparisons between the experiment and the theory suggest that the DN in the water is effectively purged by the oxygen aeration. The supplemental experiment of aeration with nitrogen microbubbles is also documented to show that the DO can be effectively purged as well.

Hemodynamic Effects of Lipid-Based Oxygen Microbubbles via Rapid Intravenous Injection in Rodents.

Low oxygen levels, or hypoxemia, is a common cause of morbidity and mortality in critically ill patients. Hypoxemia is typically addressed by increasing the fraction of inspired oxygen, the use of mechanical ventilation, or more invasive measures. Recently, the injection of oxygen gas directly into the bloodstream by packaging it within lipid-based oxygen microbubbles (LOMs) has been explored. The purpose of this work is to examine the acute hemodynamic effects of intravenous injections of LOMs. LOMs composed of 1,2-distearoyl-sn-glycero-3-phosphocoline and cholesterol were manufactured using a process of shear homogenization under an oxygen headspace. A 5mL aliquot of either PlasmaLyte A, or low (37%) or high (55%) concentration LOMs (n=10 per group) was injected over a 1min period into Sprague Dawley rats instrumented for measurement of cardiac index and pulmonary (PVR) and systemic (SVR) vascular resistance during a 60min observation period. Hemodynamics were compared between groups by linear mixed modeling. Approximately 1011 LOMs with mean diameter 3.77±1.19μm were injected over the 1min period. Relative to controls, rodents treated with high concentration LOMs exhibited a higher pulmonary artery pressure (20±0.4mmHg vs 18±0.4mmHg, P<0.001) and higher PVR (0.31±0.01 vs 0.23±0.01mmHg/mL*min*kg, P<0.001. Despite a stable cardiac index (62.2±3.5 vs 62.3±3.4mL/min*kg, P<0.001), mean arterial blood pressure decreased significantly in LOM-treated animals (46±2 vs 60±2mmHg, P<0.001) due to a decrease in SVR. Injections with aged LOM emulsions (>48h since manufacture) resulted in a higher incidence of hemodynamic collapse during the observation period (P=0.02). LOMs may be injected in quantities sufficient to deliver clinically meaningful volumes of oxygen but cause significant decrements in blood pressure and elevations in PVR.

Effects of O2 Concentration and Precipitates on the Lithium Air Battery

Lithium-air battery attracts great attention because of its high energy density. In this study, we focus on the aqueous lithium–air secondary battery. The aqueous electrolyte realizes cost reduction and ensures the safe use of a battery. However, to realize a more powerful lithium–air battery, it is necessary to clarify and improve the reaction and mass transport phenomena in the cathode [1]. Low solubility of oxygen in aqueous electrolyte limits oxygen transport to the reaction site. Discharge reaction products in cathode electrode cause cell performance degradation. In this study, effect of dissolved oxygen concentration in the electrolyte on cathode performance is investigated. Low energy X-ray CT was employed to observe discharge reaction products in a porous cathode electrode.Figure 1 shows experimental apparatus, which is composed of two main parts: a beaker cell and control section for oxygen concentration in the electrolyte, respectively. The cell is consisted from composite anode, cathode, and reference electrode. The composite anode was water-stable and had a multilayer structure for the aqueous lithium air battery [2]. LATP [Li1+x+yAlxTi2-xSiyP3-y] (Ohara Co., Kanagawa, Japan), which is a water-stable lithium-ion-conducting glass ceramic, was used, along with PEO18LiTFSI [poly (ethylene oxide) with lithium bis (trifluoromethanesulfonyl) imide] as the organic electrolyte. Because the cell resistance was drastically decreased [3], beaker cell was heated in the constant temperature bath to keep the cell temperature at 60°C. For the cathode, SIGRACET® 10AA (SGL Group, USA) was used as the carbon porous layer with no catalyst. Reaction area of anode/cathode was f4 mm. In order to control the dissolved oxygen concentration in electrolyte (1M LiCl aq.), a micro-bubble generator (Nagoya Oshima machinery Co.,Ltd.) was employed. Acceleration of dissolution rate and the overconcentration condition were achieved by generating oxygen micro-bubbles. Normal dissolved oxygen concentration was approximately 6.5 mg/L under 60 °C heating condition. On the other hand, the generator realized high concentration up to 15 mg/L.Figure 2 shows cathodic polarization curves. The cathode performance was improved by using high oxygen concentration electrolyte. However, performance degradation was still caused under high current density condition. When the cathode potential excesses approximately -1.0 V, plot trend of all results changes and shows same plateau. It means that the discharge reaction on the cathode was shifted from oxygen reduction to hydrogen evolution reaction under high current density condition [4].In order to observe precipitate of discharge products in the cathode, low energy X-ray CT and visualization cell as shown in Figure 3. By using closed type cell and aqueous solution (saturated LiOH with 10 M LiCl), experimental condition mimicked less oxygen condition involving precipitation of discharge products. As shown in Figure 4, emergence of bubble and solid precipitate were clearly visualized by low energy X-ray CT. It is considered that emergence of bubble and solid precipitate depended on oxygen concentration. Solid precipitate (Li2O2 [5]) was emerged at the bottom part of cathode where oxygen was able to reach by diffusion. On the other hand, oxygen was not transported efficiently to the top part of cathode, and discharge reaction was shifted. As result, electrolysis of water (H2bubble generation) has occurred.In order to realize higher performance under high current density condition, electrolyte was flowed through the porous cathode. As shown Figure 5, cathode performance was significantly improved. It is considered that oxygen concentration overpotential was reduced by supplying oxygen rich electrolyte. AcknowledgementThis work was supported by JSPS KAKENHI Grant Number 15K13881, 15H02347. Reference[1] K. Shibata, S. Uemura, S. Tsushima, S. Hirai, ECS Trans. 2015, 64(19), pp 39-46.[2] T. Zhang, N. Imanishi, S. Hasegawa, A. Hirano, J. Xie, Y. Takeda, O. Yamamoto, N. Sammes, J. Electrochem. Soc., 2008, 155, A965.[3] T. Zhang, N. Imanishi, A. Hirano, Y. Takeda, and O. Yamamoto, Electrochem. Solid-State Lett., 2011, 14, A45.[4] H. He, W. Niu, N. M. Asl, J. Salim, R. Chen, Y. Kim, Electrochimica Acta, 2012, 67, 87.[5] M.Matsui, A. Wada, Y. Maeda, H. Ohkuma, O. Yamamoto, N. Imanihsi, 224th ECS meeting abstract, 2013, MA2013-02, 411. Figure 1

Design and Development of a Rat Peritoneal Infusion Device for Oxygen Microbubble Bolus Delivery1

Design and Development of a Rat Peritoneal Infusion Device for Oxygen Microbubble Bolus Delivery1

REVITALIZAÇÃO DO RIO TIETÊ: UMA OPÇÃO VIÁVEL

O presente trabalho terá como tema: A revitalização do rio Tietê com a utilização de diversas estratégias. Como já se sabe é um processo muito longo, pois o rio está bastante poluído, também possui um alto custo para seu tratamento, para o Governo. O Tietê sofre a ação de três tipos de poluição: industrial, difusa (lixo das casas), e do esgoto doméstico. O primeiro passo para a despoluição do rio é garantir que nenhum esgoto seja lançado, os principais métodos são: barras de proteção (são grades feitas no encanamento para evitar a entrada do lixo sólido), câmera espiã (para identificar ligações de esgotos clandestinas nas águas pluviais), oxigênio em dose extra ( uma rede de tubos implantada no fundo do rio, que injeta microbolhas de oxigênio, que fazem a sujeira boiar), rebaixamento do leito (evitar enchentes), filtragem limitada e modernização industrial. Percebe-se portanto que é possível tratar qualquer rio, mesmo que o processo de despoluição demore séculos. Entretanto, é fundamental conscientizar a população da importância da preservação de nossos corpos hídricos, uma vez que a mesma só será eficaz após a mudança de atitude da população, das indústrias e de nossos governantes diante desse importante recurso natural.

Effect of microbubble generator operating parameters on oxygen transfer efficiency in water

This study utilized multistage orifice microbubble generator to investigate dissolved oxygen (DO) formation characteristics and to increase its efficiency, by considering saturator pressure, water supply, and gas flow rates as the main operating factors. The effect of changing the parameters was described in terms of dissolution performance using volumetric mass transfer rate, which is very important element for aerator design and scale-up. Pressure values from 1 to 6 atm were taken for the analysis. To improve the oxygen transfer efficiency of the multistage orifice, the internal supply line was controlled to circulate the bubbles water up to 300% cycling. The volumetric mass transfer coefficient was limited below 0.01 per min for air; however, the value varied from 0.10 to 0.13 per min for oxygen at 4.5 L/min flow rate, showing increasing pattern with pressure. The transfer characteristic was doubled, with circulating ratio applied, because circulation could multiply the number of microbubbles. Examining the various operating conditions within the range set for the cost to generate 1 kg of DO, under gas injection velocity of 1.27 m/s, higher liquid pressurization showed lower cost per production in case of oxygen than air. Thus, natural water bottom area environment can be economically improved using oxygen microbubbles, considering the excessive dissolution.

Freeze-thawing at point-of-use to extend shelf stability of lipid-based oxygen microbubbles for intravenous oxygen delivery

Abstract A continuous supply of oxygen gas is critical to sustain life. However, current delivery strategies are dependent on functioning lungs for effective gas delivery. We have recently shown that oxygen gas can be safely administered through intravenous routes when packaged within lipid-based oxygen microbubbles (LOMs). However, the long-term stability of LOMs is poor, which may limit the clinical applicability of this technology. Here, we describe a freeze-thawing strategy to prolong the shelf life of concentrated LOMs. In addition, we examine the effect of various rapid thawing strategies in an attempt to identify an approach that would enable use of this technique in emergent clinical situations. Our results suggest that LOM emulsions stored at −20 °C followed by rapid thawing under warm running water or microwave irradiation exhibit preserved microbubble size distribution and oxygen carrying capacity for at least 30 days. Further investigation into the limits and clinical viability of these techniques are warranted.