Nanobubbles Research Articles

Preparation of biocompatible nanobubbles carrying quercetin and their inhibitory effects on non-small-cell lung carcinoma

Non-small-cell lung carcinoma (NSCLC), major lung cancer is currently considered one of the leading causes of mortality and has become a progressively serious global public health burden. However, the conventional drug delivery approaches were unable to efficiently inhibit the proliferation and metastasis of lung cancer cells. Exploiting Nanobubbles (NBs) as a novel drug delivery system has recently a research hotspot mainly due to their outstanding characteristics such as small size, biosafety and competent drug-transporting ability. The present study aimed to establish a novel biocompatible approach for Nanobubble constructions by the water-in-oil method and loading quercetin inside the obtained micelles. Dextran coating was used for more stability of NBs and the effectiveness of drug delivery to A549 NSCLC and HeLa cells was evaluated. Ultrasound waves were used to stimulate the Nano bubble to release the drug. The approximate size of NBs was 0.149 nm that reach by dynamic light scattering dominantly with a spherical shape visualized by TEM. Excellent drug-loading capacity and ultrasound-mediated release of quercetin were confirmed by a UV spectrophotometer with an absorption of about 1.6. NBs efficiently inhibited the proliferation of NSCLC cells in a concentration-dependent manner as well as the capability to achieve ultrasound enhancement. This experiment showed that obtained NBs effectively delivered quercetin into lung cancer cells promoted by ultrasound irradiation. In conclusion, proposed biocompatible quercetin-loaded NBs are suitable for ultrasound-targeted drug delivery and are thus a promising strategy for their noninvasive clinical application.

Effects of Nanobubbles in Dermal Delivery of Drugs and Cosmetics

Dermal delivery, which delivers drugs and cosmetics through the skin, has attracted significant attention due to its non-invasive and simple administration compared with oral or injectable administration. However, delivery of the ingredients through the skin barrier is difficult because the primary function of the skin is to protect the human body by preventing the invasion of contaminants. Although various techniques have been developed to overcome skin barriers, chemical toxicity, complicated processes, and expensive equipment still remain as obstacles. Moreover, green chemistry, which minimizes or eliminates the use of toxic chemicals, is required in the cosmetic industry. Thus, the development of a new method for dermal delivery is required. In this study, we provide a new method for dermal delivery using nanobubbles (NBs). NBs generated in oil improve the delivery effect of the active ingredients through the high Brownian motion and charge-balancing effect. Franz cell experiments and depigmentation experiments using the B16F10 melanoma cells were conducted to confirm the enhanced delivery effects. The system using NBs will contribute to the advancement of the dermal delivery of drugs and cosmetics.

Production of Reactive Oxygen Species via Nanobubble Water Improves Radish Seed Water Absorption and the Expression of Aquaporin Genes.

Nanobubbles (NBs) stimulate seed germination; however, the mechanism of the promotion effect of NBs remains unclear. The impact of NBs on seed water absorption was investigated; we subsequently studied the genes associated with the response of radish seeds to NB water and used RNA sequencing to generate their expression profiles, especially those of aquaporin genes. NB water significantly promoted germination. The times at which 50% of the germinating seeds achieved germination (T50) for the submerged radish seeds in NB and control water were 11.6 and 17.4 h, respectively. NB water-germinated radish seeds showed a water uptake rate coefficient that was 15% higher than that of those germinated in control water. Through GO enrichment and cluster analyses, it was evident that NB water significantly increased the level of expression of the genes associated with the following activities: oxidoreductase, peroxidase, and antioxidant. Our results demonstrated that NB water increases the water uptake rate of radish seeds via two mechanisms. The NB water-produced exogenous hydroxyl radical (•OH) increases the seed coat's water permeability and enhances cell wall loosening, and NB water increases the aquaporin gene expression level of radish seeds.

Pharmacokinetic modeling of PSMA-targeted nanobubbles for quantification of extravasation and binding in mice models of prostate cancer.

Contrast-enhanced ultrasound (CEUS) by injection of microbubbles (MBs) has shown promise as a cost-effective imaging modality for prostate cancer (PCa) detection. More recently, nanobubbles (NBs) have been proposed as novel ultrasound contrast agents. Unlike MBs, which are intravascular ultrasound contrast agents, the smaller diameter of NBs allows them to cross the vessel wall and target specific receptors on cancer cells such as the prostate-specific membrane antigen (PSMA). It has been demonstrated that PSMA-targeted NBs can bind to the receptors of PCa cells and show a prolonged retention effect in dual-tumor mice models. However, the analysis of the prolonged retention effect has so far been limited to qualitative or semi-quantitative approaches. This work introduces two pharmacokinetics models for quantitative analysis of time-intensity curves (TICs) obtained from the CEUS loops. The first model is based on describing the vascular input by the modified local density random walk (mLDRW) model and independently interprets TICs from each tumor lesion. Differently, the second model is based on the reference-tissue model, previously proposed in the context of nuclear imaging, and describes the binding kinetics of an indicator in a target tissue by using a reference tissue where binding does not occur. Our results show that four estimated parameters, β, , , for the mLDRW-input model, and γ for the reference-based model, were significantly different (p-value <0.05) between free NBs and PSMA-NBs. These parameters estimated by the two models demonstrate different behaviors between PSMA-targeted and free NBs. These promising results encourage further quantitative analysis of targeted NBs for improved cancer diagnostics and characterization.

Targeted Nanobubbles of PD-L1 mAb Combined with Doxorubicin as a Synergistic Tumor Repressor in Hepatocarcinoma.

PurposeUltrasound nanobubbles (NBs) can kill tumor cells, mediated by their effects of cavitation and acoustic perforation through ultrasound, while as novel drug carriers, biomaterial-modified NBs release drugs at a target region. In this work, the ultrasound NBs bridged by biotin-streptavidin were prepared simultaneously to be loaded with both programmed death ligand 1 monoclonal antibody (PD-L1 mAb) and doxorubicin (DOX), which are immune checkpoint inhibitors (ICIs) and chemotherapeutic agents, to synergize immunotherapy and chemotherapy combined with sonodynamic therapy (SDT).MethodsThe PD-L1 mAb/DOX NBs, using bridging affinity biotin (BRAB) technology as a bridge, were prepared by thin-film hydration and mechanical oscillation for the targeted delivery of biotinylated PD-L1 mAb and DOX. Characterization and pharmacokinetic studies of PD-L1 mAb/DOX NBs were performed in vitro and in vivo. The antitumor effect of ultrasound-mediated PD-L1 mAb/DOX-NBs was studied in the subcutaneously transplanted tumor of the H22 hepatoma model, and the mechanism of synergistic tumor repression was investigated.ResultsThe data of in vitro targeting experiments, contrast-enhanced ultrasound imaging (CEUS), in vivo imaging of the small animals imaging system (IVIS), and frozen sections showed that PD-L1 mAb/DOX-NBs have well-targeted aggregation in the tumor. By observing tumor inhibition rate, tissue cell apoptosis, and apoptosis-related gene and protein expression, the PD-L1 mAb/DOX-NBs group showed the best immunotherapy effects, and its tumor volume and mass inhibition rates were about 69.64% and 75.97%, respectively (P < 0.01). Therefore, blocking the PD-1/PD-L1 pathway could improve immune cells’ tumor-killing ability. Antitumor immune cytokines were further enhanced when combined with DOX-induced tumor cell apoptosis and immunogenic cell death (ICD).ConclusionIn summary, ultrasound-mediated PD-L1 mAb/DOX-NBs showed significant synergistic antitumor effects, providing a potential combined immunotherapy strategy for HCC.

Flotation of suspended solid by introducing coagulant and fine bubbles in the mobile wastewater treatment plant

Turbidity is an essential process variable in water treatment processes for clean water. This study reports the development of a mobile mini wastewater treatment plant (WTTP) intended to provide clean water in flooding incidents, where access to clean water is demanding. The mobile mini-WTTP employed with a fine bubbles generator aims to provide micro and nano bubbles with longer residence in the water expected to promote an effective flotation process. The system was evaluated in removing suspended solid capability to reduce total suspended solids (TSS) or water turbidity. The system consists of a mesh trap, chemical flocculation, dissolved air flotation chamber, and activated carbon–zeolite as a mineral filter. The system was tested on the suspended solid from homogenized clay resulted from a turbid tap water effluent with adjusted turbidity up to 500 FNU on the storage tank. Alum solution with a dosage of 200 mg/L was used as a coagulant agent. In the flotation process was introduced a fine bubbles generator with a pressurized mechanism. The effluent was pumped from a storage tank into a treatment plant with a flow rate of 200 L/h, and the samples were obtained after the separation from the corresponding sub-system at the condition of steady state of water flow. A digital water quality measurement was operated to evaluate the effluent after the separation process. The results show that the separation of turbidity up to 98% was obtained at the end of the processing system. The successful flotation of the suspended solid due to the zeta potential turn to zero up on the addition of flocculants lead to effective fine bubbles flotation. Finally, clean water was achieved in the performance test of mobile mini WTTP utilized with fine bubbles.

Micro and nano bubbles promoted biofilm formation with strengthen of COD and TN removal synchronously in a blackened and odorous water.

Blackening and odorization of rivers (BOR) distributed widely in urban cities with high density of human beings. Amounts of pollution control methods have been developed for treatment of these contaminated rivers. Among them, artificial aeration is an effective method for BOR treatment. As a novel developed aeration approach, Micro and nano bubbles (MNBs) takes advances of high specific surface area, high oxygen transfer, long retain time and interface effect. Thus, MNBs aeration was used in an anoxic-oxic (AO) process with traditional activated sludge methods to treat water of BOR in this study. A special designed reactor was made to allow both MNBs and macro bubbles aeration of which mode could be altered easily. The results revealed that MNBs improved removal of COD, NH4+-N and TN distinctly in water of BOR. MNBs provided high dissolved oxygen and promoted the transformation from floc sludge to biofilm. Significant difference between the microbial community of MNBs and macro bubbles sludges was revealed by 16S rRNA amplicon sequencing. Function predictions of MNBs and macro bubbles sludges indicated MNBs enhanced nitrification and aerobic ammonia oxidation without negative impact on denitrification. Moreover, biofilm formed bacteria were enriched by MNBs aeration. This study demonstrated MNBs would be a great potential for the combination of activated sludge and biofilm to treat BOR.

Influence of operating parameters on nanobubble-assisted flotation of graphite

Although many studies have focused on processing of lithium-ion batteries (LiBs), there is a considerable lack of information concerning the application of nanobubbles (NBs) in their floatabilities. To cover this knowledge gap, the current study aims at exploring the effect of key operating parameters on flotation of two types of graphite i.e., lithium-ion batteries’ graphite (LIBG) and natural ore graphite (NOG) in the presence of NBs. For this purpose, the effects of NB solution ratio, impeller speed, air flow rate, as well as dosage and type of collector and frother on recovery of graphite were investigated in the presence and absence of NBs. Three frothers (i.e., methyl isobutyl carbinol (MIBC), terpenic oil, and 2-octanol), and three collectors (i.e., n-dodecane, kerosene and diesel oil) were employed for comparison purposes using an XFG micro-flotation unit. The hydrodynamic cavitation and dynamic light scattering (DLS) methods were utilized to produce and characterize ultrafine bubbles, respectively. The DLS results confirmed the bubble size distribution ranged between 180 and 400 nm. The maximum recovery of graphite particles (ca. 98%) was obtained for the LIBG particles, at an impeller speed of 1000 rpm, air flow rate of 0.4 L/min, using 2-octanol as a frother, and n-dodecane as a collector. Further, the influential order of the frothers was found as 2-octanol > terpenic oil > MIBC. According to the flotation results, the presence of NBs increased the LIBG flotation recovery and its kinetic rate by 15% and 33%, respectively.

Nanoparticle-based Olaparib delivery enhances its effect, and improves drug sensitivity to cisplatin in triple negative breast cancer

PurposeUltrasound-mediated nanobubbles destruction (UTND) technology could enhance drug transport efficiency and increase the local drug concentration. We structured a novel Olaparib-loaded nanobubbles (Ola-NBs). Then investigated its ability to inhibit triple negative breast cancer (TNBC) cell growth in vitro. Additionally, we observed the change of cisplatin sensitivity before and after Olaparib treatment. MethodsThe Ola-NBs were prepared using extrusion and thin-film hydration combination methods. Cell viability was checked by CCK-8 assay, and calculated the 50% inhibition concentration (IC50) of Olaparib and cisplatin. Next, Jc-1 staining was used to observe mitochondrial membrane depolarization, and an apoptosis assay was applied to assess the apoptosis in different groups. Finally, a Western blot assay was used to evaluate the inhibition effect of Olaparib on TNBC at the molecular level. ResultsOla-NBs were prepared successfully. The zeta potential was −0.617 ± 0.197 mV, and the average diameter was 473.52 ± 17.33 nm. The IC50 of Olaparib had not significant difference in TNBC cells. However, the IC95 was higher in cisplatin-resistant MDA-MB-231 cells (MDA-MB-231/CDDP). The cell viability decreased following Olaparib treatment and was more obvious in the Ola-NBs group (P < 0.05). In addition, the IC50 of cisplatin was lower in the post-Olaparib treatment group. Jc-1 results revealed that the mitochondrial membrane decreased more strongly in the Ola-NBs and combination therapy groups. And the results of Jc-1 corroborated the apoptosis assay results. Moreover, Bax protein expression level increased, while Bcl-2 protein expression decreased in the treatment groups. ConclusionOlaparib not only inhibited TNBC cell growth, but it also improved the sensitivity of cisplatin in TNBC cells. And nanobubbles (NBs) might be an effective supporter, because it can enhance the drug efficacy under ultrasound irradiation.

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.

Proliferative effects of nanobubbles on fibroblasts

In recent years, the potential of nanobubbles (NBs) for biological activation has been actively investigated. In this study, we investigated the proliferative effects of nitrogen NBs (N-NBs) on fibroblast cells using cell assays with image analysis and flow cytometry. A high concentration of N-NBs (more than 4 × 108 NBs/mL) was generated in Dulbecco’s modified Eagle’s medium (DMEM) using a gas–liquid mixing method. In image analysis, the cells were counted and compared, which showed an 11% increase in cell number in the culture medium with N-NBs. However, in two further cell cytometry analyses, the effect of nanobubbles on cell division was found to be insignificant (approximately 2%); as there is insufficient evidence that N-NB is involved in cell division mechanism, further studies are needed to determine whether NB affects other cellular mechanisms such as apoptosis. This study presents the first successful attempt of directly generating and quantifying N-NBs in a culture medium for cell culture. The findings suggest that the N-NBs in the culture medium can potentially facilitate cell proliferation.

Drug delivery system based on nanobubbles

AbstractUltrasound (US) medical technology is widely used due to its advantages of safety, speed, and low cost. With the rapid development of biomedical nanotechnology, micro/nanobubbles, as US contrast agents, are not only valuable in US imaging diagnosis but also show broad application prospects in drug delivery. Nanobubbles (NBs) have more advantages as drug delivery systems (DDSs) due to their smaller size and longer circulation time compared with microbubbles. In this review, the fundamentals of NBs, including classification, stability mechanism, and preparation methods are summarized. Then, the strategies of a DDS based on NBs, including direct delivery, codelivery, target delivery, and stimuli‐responsive delivery are reviewed and discussed. The three main applications of NBs‐based DDSs, namely tumor theranostics, brain drug delivery, and vascular disease theranostics were highlighted. The challenges and future directions of the NBs‐based DDSs are also considered and discussed.

Oxygen Nanobubbles for Lake Restoration—Where Are We at? A Review of a New-Generation Approach to Managing Lake Eutrophication

Nutrient enrichment of lakes from anthropogenic activities is a significant and increasing issue globally, impairing the health, biodiversity and service provisioning from lakes, with impacts on cultural, recreational, economic and aesthetic values. Internal nutrient loads from lakebed sediment releases are a primary cause of lake eutrophication and have necessitated geoengineering methods to mitigate releases and speed up recovery from eutrophication. Our objective in this review was to evaluate the use of oxygen nanobubbles as a geoengineering technology to remediate low oxygen conditions at the lake sediment/water interface, as a precursor to alleviating eutrophication linked to high internal nutrient loads. Oxygen nanobubbles (NBs) are bubbles &lt; 1000 nm formed at the interface of solid surfaces and aqueous solutions. These bubbles have higher density than water, persist for longer and facilitate greater oxygen solubility than larger bubbles. Methods have been developed to enable NB formation at the surface of carrier materials, which are then used in conjunction with modified local soils (MLSs), to ‘floc, lock and oxygenate’ to strip nutrients from the water column, locking them in lakebed sediments and oxygenating the sediments to prevent re-release of nutrients. Most studies of NBs for lake restoration have thus far only demonstrated their potential for this purpose, using short-term, small-scale core incubations conducted mainly in laboratory settings. Work is required to (1) address scalability, including procurement and cost, (2) extend laboratory incubation studies to large outdoor enclosures and pond/lake trials, (3) examine longevity of the effects in the natural environment, including potential for MLSs to smother benthos and/or have toxic effects, and (4) extend to a range of lake environments and MLS types. Legal, cultural and social acceptance of the technology is another prerequisite of applications in the natural environment and requires individualised analysis. Until these issues are addressed in a systematic way that addresses scalability and recommends suitable carrier materials and MLSs, NBs may continue to remain largely untried as a geoengineering method to address lake eutrophication.

Biomimetic nanobubbles for triple-negative breast cancer targeted ultrasound molecular imaging

Triple-negative breast cancer (TNBC) is a highly heterogeneous breast cancer subtype with poor prognosis. Although anatomical imaging figures prominently for breast lesion screening, TNBC is often misdiagnosed, thus hindering early medical care. Ultrasound (US) molecular imaging using nanobubbles (NBs) capable of targeting tumor cells holds great promise for improved diagnosis and therapy. However, the lack of conventional biomarkers in TNBC impairs the development of current targeted agents. Here, we exploited the homotypic recognition of cancer cells to synthesize the first NBs based on TNBC cancer cell membrane (i.e., NBCCM) as a targeted diagnostic agent. We developed a microfluidic technology to synthesize NBCCM based on the self-assembly property of cell membranes in aqueous solutions. In vitro, optimal NBCCM had a hydrodynamic diameter of 683 ± 162 nm, showed long-lasting US contrast enhancements and homotypic affinity. In vivo, we demonstrated that NBCCM showed increased extravasation and retention in a TNBC mouse model compared to non-targeted NBs by US molecular imaging. Peak intensities and areas under the curves from time-intensity plots showed a significantly enhanced signal from NBCCM compared to non-targeted NBs (2.1-fold, P = 0.004, and, 3.6-fold, P = 0.0009, respectively). Immunofluorescence analysis further validated the presence of NBCCM in the tumor microenvironment. Circumventing the challenge for universal cancer biomarker identification, our approach could enable TNBC targeting regardless of tumor tissue heterogeneity, thus improving diagnosis and potentially gene/drug targeted delivery. Ultimately, our approach could be used to image many cancer types using biomimetic NBs prepared from their respective cancer cell membranes.

Exploring chitosan-shelled nanobubbles to improve HER2 + immunotherapy via dendritic cell targeting

Immunotherapy is a valuable approach to cancer treatment as it is able to activate the immune system. However, the curative methods currently in clinical practice, including immune checkpoint inhibitors, present some limitations. Dendritic cell vaccination has been investigated as an immunotherapeutic strategy, and nanotechnology-based delivery systems have emerged as powerful tools for improving immunotherapy and vaccine development. A number of nanodelivery systems have therefore been proposed to promote cancer immunotherapy. This work aims to design a novel immunotherapy nanoplatform for the treatment of HER2 + breast cancer, and specially tailored chitosan-shelled nanobubbles (NBs) have been developed for the delivery of a DNA vaccine. The NBs have been functionalized with anti-CD1a antibodies to target dendritic cells (DCs). The NB formulations possess dimensions of approximately 300 nm and positive surface charge, and also show good physical stability up to 6 months under storage at 4 °C. In vitro characterization has confirmed that these NBs are capable of loading DNA with good encapsulation efficiency (82%). The antiCD1a-functionalized NBs are designed to target DCs, and demonstrated the ability to induce DC activation in both human and mouse cell models, and also elicited a specific immune response that was capable of slowing tumor growth in mice in vivo. These findings are the proof of concept that loading a tumor vaccine into DC-targeted chitosan nanobubbles may become an attractive nanotechnology approach for the future immunotherapeutic treatment of cancer.Graphical abstract

FN3 linked nanobubbles as a targeted contrast agent for US imaging of cancer-associated human PD-L1.

PD-L1 (programmed death-ligand 1) targeted therapies may be useful for several cancers. The use of non-invasive diagnostic and prognostic molecular imaging platforms could improve clinical assessment of PD-L1 tumor status during these therapies. Contrast enhanced ultrasound molecular imaging (CE-USMI) techniques may offer versatile and cost-effective ways to detect and quantify the expression levels of cellular targets in vivo. However, conventional use of microbubbles as a blood pool contrast agent for CE-USMI is limited to accessing intravascular biomarkers rather than reflecting the tumor molecular status. Using a microfluidic based reconstruction process we therefore developed ultra-stable nanobubbles (NBs) as a contrast agent for molecular imaging of vascular and extravascular cell surface markers. We then functionalized these NBs by covalently linking to nanobody (FN3hPD-L1) targeting human (h)PD-L1 to measure the expression of human PD-L1 in the tumor microenvironment (TME) in vivo. We showed the specific binding of hPD-L1 targeted NBs in cell culture, and in xenografted mouse models of hPD-L1 expressing CT26 tumors. CE-USMI of hPD-L1 in the TME in vivo showed ~3-fold increase in contrast signal compared to non-targeted NBs. Overall, in vivo use of CE-USMI with hPD-L1 targeted NBs has the potential for clinical translation and imaging of human cancers during immunotherapy, and for prognostic evaluation of patient response to PD-L1 targeted immunotherapy.

Influence of Nanobubble Size Distribution on Ultrasound-Mediated Plasmid DNA and Messenger RNA Gene Delivery.

The use of nanobubbles (NBs) for ultrasound-mediated gene therapy has recently attracted much attention. However, few studies have evaluated the effect of different NB size distribution to the efficiency of gene delivery into cells. In this study, various size of albumin stabilized sub-micron bubbles were examined in an in vitro ultrasound (1 MHz) irradiation setup in the aim to compare and optimize gene transfer efficiency. Results with pDNA showed that gene transfer efficiency in the presence of NB size of 254.7 ± 3.8 nm was 2.5 fold greater than those with 187.3 ± 4.8 nm. Similarly, carrier-free mRNA transfer efficiency increased in the same conditions. It is suggested that NB size greater than 200 nm contributed more to the delivery of genes into the cytoplasm with ultrasound. Although further experiments are needed to understand the underlying mechanism for this phenomenon, the present results offer valuable information in optimizing of NB for future ultrasound-mediate gene therapy.

Confined helium, density dependence of the inelastic electron and photon scattering cross-sections and the optical oscillator strength

The electron and photon excitation of confined and compressed atoms is discussed. It is shown that the optical oscillator strength, the inelastic X-ray and electron impact cross-sections are all density-dependent. Ab-initio electronic structure calculations are presented for the 1 s 2 → 1 s 2 p ( 1 P ) transition in helium, which predict that the amplitudes for the inelastic scattering of electrons, optical absorption and the excitation energy are all significantly increased in bulk condensed phases of pure helium compared to those of an isolated atom. The enhancements increase with atomic density but are very similar for bcc and fcc structured bulk phases of the same density. These enhancements need to be incorporated into the analysis of scanning transmission electron microscope studies of helium nano bubbles embedded in different materials. The excitation energy and cross-section enhancements with increasing density arise from the contraction of the 2 p orbital on entering a condensed phase. For the bulk phases, but not the bubbles, the close agreement between the experimental and computed values of the energy shifts can be well described by a simple relationship.

Extrusion: A New Method for Rapid Formulation of High-Yield, Monodisperse Nanobubbles.

Shell-stabilized gas microbubbles (MB) and nanobubbles (NB) are frequently used for biomedical ultrasound imaging and therapeutic applications. While it is widely recognized that monodisperse bubbles can be more effective in these applications, the efficient formulation of uniform bubbles at high concentrations is difficult to achieve. Here, it is demonstrated that a standard mini-extruder setup, commonly used to make vesicles or liposomes, can be used to quickly and efficiently generate monodisperse NBs with high yield. In this highly reproducible technique, the NBs obtained have an average diameter of 0.16± 0.05µm and concentration of 6.2± 1.8 × 1010 NBs mL-1 compared to 0.32± 0.1µm and 3.2± 0.7 × 1011 mL-1 for NBs made using mechanical agitation. Parameters affecting the extrusion and NB generation process including the temperature, concentration of the lipid solution, and the number of passages through the extruder are also examined. Moreover, it is demonstrated that extruded NBs show a strong acoustic response in vitro and a strong and persistent US signal enhancement under nonlinear contrast enhanced ultrasound imaging in mice. The extrusion process is a new, efficient, and scalable technique that can be used to easily produce high yield smaller monodispersed nanobubbles.

Microbubble and nanobubble-based gas flotation for oily wastewater treatment: a review

Gas flotation for oily wastewater treatment is based on the attachment of gas bubbles to oil droplets to produce lighter aggregates that rise to the wastewater surface. It is a feasible, promising, and effective method for oily wastewater treatment due to its high separation efficiency with no secondary contamination, cost-effectiveness, and simple operation. This review focuses on separating oil from emulsions by gas flotation using microbubbles (MBs) and nanobubbles (NBs), which offer the advantages of small bubble size, large specific surface area, and slow rising velocity. The properties of different types of gas bubbles and their generation methods were discussed. Different gas flotation system designs and operational parameters were summarized for dissolved gas flotation, induced gas flotation, and electrolytic flotation (EF). The review illustrated that oil removal efficiency in MB- and NB-based gas flotation was affected by various factors including initial oil concentration, pH, temperature, flotation time, and oil droplet size.