Bulk manufacture of concentrated oxygen gas-filled microparticles for intravenous oxygen delivery

Advances in nanobubbles for cancer theranostics: Delivery, imaging and therapy

Maximizing treatment efficacy and forecasting patient prognosis in cancer necessitates the strategic use of targeted therapy, coupled with the prompt precise detection of malignant tumors. Theutilizationof gaseous systems as an adaptable platform for creating nanobubbles (NBs) has garnered significant attention as theranostics, which involve combining contrast chemicals typically used for imaging with pharmaceuticals to diagnose and treattumorssynergistically in apersonalizedmanner for each patient. This review specifically examines the utilization of oxygen NBsplatforms as a theranostic weapon in the field of oncology. We thoroughly examine the key factors that impact the effectiveness of NBs preparations and the consequences of these treatment methods. This review extensively examines recent advancements in composition schemes, advanced developments in pre-clinical phases, and other groundbreaking inventions in the area of NBs. Moreover, this review offers a thorough examination of the optimistic future possibilities, addressing prospective methods for improvement and incorporation into widely accepted therapeutic practices. As we explore the ever-changing field of cancer theranostics, the incorporation of oxygen NBs appears as a promising development, providing new opportunities for precision medicine and marking a revolutionary age in cancer research and therapy.

Controlled oxygen delivery to power tissue regeneration

Oxygen plays a crucial role in human embryogenesis, homeostasis, and tissue regeneration. Emerging engineered regenerative solutions call for novel oxygen delivery systems. To become a reality, these systems must consider physiological processes, oxygen release mechanisms and the target application. In this review, we explore the biological relevance of oxygen at both a cellular and tissue level, and the importance of its controlled delivery via engineered biomaterials and devices. Recent advances and upcoming trends in the field are also discussed with a focus on tissue-engineered constructs that could meet metabolic demands to facilitate regeneration.

Nanosome-Mediated Delivery Of Hdac Inhibitors and Oxygen Molecules for the Transcriptional Reactivation of Latent Hiv-Infected Cd4+ T Cells

The treatment of human immunodeficiency virus (HIV) infection is notoriously difficult due to the ability of this virus to remain latent in the host's CD4+ T cells. Histone deacetylases (HDACs) interfere with DNA transcription in HIV-infected hosts, resulting in viral latency. Therefore, HDAC inhibitors can be used to activate viral transcription in latently infected cells, after which the virus can be eliminated through a shock-and-kill strategy. Here, a drug delivery system is developed to effectively deliver HDAC inhibitors to latent HIV-infected cells. Given that the efficacy of HDAC inhibitors is reduced under hypoxic conditions, oxygen-containing nanosomes are used as drug carriers. Oxygen-containing nanosomes can improve the efficiency of chemotherapy by delivering essential oxygen to cells. Additionally, their phospholipid bilayer structure makes them uniquely well-suited for drug delivery. In this study, a novel drug delivery system is developed by taking advantage of the oxygen carriers in these oxygen nanosomes, incorporating a multi-drug strategy consisting of HDAC inhibitors and PKA activators, and introducing CXCR4 binding peptides to specifically target CD4+ T cells. Oxygen nanosomes with enhanced targeting capability through the introduction of the CXCR4 binding peptide mitigate drug toxicity and slow down drug release. The observed changes in the expression of p24, a capsid protein of HIV, indirectly confirm that the proposed drug delivery system can effectively induce transcriptional reactivation of HIV in latent HIV-infected cells.

Oxygen therapy alternatives in COVID-19: From classical to nanomedicine

Around 10-15% of COVID-19 patients affected by the Delta and the Omicron variants exhibit acute respiratory insufficiency and require intensive care unit admission to receive advanced respiratory support. However, the current ventilation methods display several limitations, including lung injury, dysphagia, respiratory muscle atrophy, and hemorrhage. Furthermore, most of the ventilatory techniques currently offered require highly trained professionals and oxygen cylinders, which may attain short supply owing to the high demand and misuse. Therefore, the search for new alternatives for oxygen therapeutics has become extremely important for maintaining gas exchange in patients affected by COVID-19. This review highlights and suggest new alternatives based on micro and nanostructures capable of supplying oxygen and/or enabling hematosis during moderate or acute COVID-19 cases.

A microfluidic device for real-time on-demand intravenous oxygen delivery

The treatment of hypoxemia that is refractory to the current standard of care is time-sensitive and requires skilled caregivers and use of specialized equipment (e.g., extracorporeal membrane oxygenation). Most patients experiencing refractory hypoxemia will suffer organ dysfunction, and death is common in this cohort. Here, we describe a new strategy to stabilize and support patients using a microfluidic device that administers oxygen gas directly to the bloodstream in real time and on demand using a process that we call sequential shear-induced bubble breakup. If successful, the described technology may help to avoid or decrease the incidence of ventilator-related lung injury from refractory hypoxemia.

Oxygen is picked up in the lungs, carried by the blood, and delivered to tissues where it serves as the terminal electron acceptor during oxidative phosphorylation. During health, oxygen is available in abundance; however, COVID-19 and many other forms of critical illness can damage the lungs and compromise systemic oxygen delivery. Cells that are very active cannot tolerate deficiencies in energy production that result from oxygen deprivation. Hypoxemia that lasts even a few minutes can turn a healthy person into a neurologically devastated patient for life, and when refractory it is often lethal. In this paper, we develop a way to administer oxygen gas to a patient through an intravenous line, replacing or supplementing the function of injured lungs. Here, we show that by coinfusing oxygen gas and a liquid solution through a series of sequential nozzles of decreasing size we are able to create bubbles of oxygen that are smaller than a single red blood cell on demand and in real time. These bubbles are coated with a “membrane” similar to that in every other cell in the body, which 1) prevents them from merging with other bubbles to create larger ones, 2) provides a path for oxygen to diffuse out and into the blood, and 3) minimizes the likelihood of material-related toxicities. Importantly, these devices allow us to control the dosage of oxygen delivered and the volume of fluid administered, both of which are critical parameters in the management of critically ill patients.

Review of Oxygenation with Nanobubbles: Possible Treatment for Hypoxic COVID-19 Patients

The coronavirus disease (COVID-19) pandemic, which has spread around the world, caused the death of many affected patients, partly because of the lack of oxygen arising from impaired respiration or blood circulation. Thus, maintaining an appropriate level of oxygen in the patients' blood by devising alternatives to ventilator systems is a top priority goal for clinicians. The present review highlights the ever-increasing application of nanobubbles (NBs), miniature gaseous vesicles, for the oxygenation of hypoxic patients. Oxygen-containing NBs can exert a range of beneficial physiologic and pharmacologic effects that include tissue oxygenation, as well as tissue repair mechanisms, antiinflammatory properties, and antibacterial activity. In this review, we provide a comprehensive survey of the application of oxygen-containing NBs, with a primary focus on the development of intravenous platforms. The multimodal functions of oxygen-carrying NBs, including antimicrobial, antiinflammatory, drug carrying, and the promotion of wound healing are discussed, including the benefits and challenges of using NBs as a treatment for patients with acute hypoxemic respiratory failure, particularly due to COVID-19.

Theranostic nanobubbles towards smart nanomedicines

Targeted therapy and early accurate detection of malignant lesions are essential for the effectiveness of treatment and prognosis in cancer patients. The development of gaseous system as a versatile platform for the fabricated nanobubbles, has attracted much interest in improving the efficacy of ultrasound therapeutic, diagnostic, and theranostic platforms. Nano-sized bubble, as an ultrasound contrast agent, with spherical gas-filled structures exhibited contrast enhancement capability due to their inherent EPR effect. Additionally, nanobubbles exhibited good stability with extended retention time in the blood stream. The current review summarized various nanobubbles and discussed about the crucial parameters affecting the stability of ultrafine bubbles. Furthermore, therapeutic and theranostic gaseous systems for fighting against cancer were described.

A Robust Oxygen Microbubble Radiosensitizer for Iodine-125 Brachytherapy

Iodine-125 (125I) brachytherapy, a promising form of radiotherapy, is increasingly applied in the clinical treatment of a wide range of solid tumors. However, the extremely hypoxic microenvironment in solid tumors can cause hypoxia-induced radioresistance to 125I brachytherapy, resulting in therapeutic inefficacy. In this study, the aim is to sensitize hypoxic areas in solid tumors using ultrasound-activated oxygen microbubbles for 125I brachytherapy. A modified emulsion freeze-drying method is developed to prepare microbubbles that can be lyophilized for storage and easily reconstituted in situ before administration. The filling gas of the microbubbles is modified by the addition of sulfur hexafluoride to oxygen such that the obtained O2/SF6 microbubbles (OS MBs) achieve a much longer half-life (>3×) than that of oxygen microbubbles. The OS MBs are tested in nasopharyngeal carcinoma (CNE2) tumor-bearing mice and oxygen delivery by the OS MBs induced by ultrasound irradiation relieve hypoxia instantly. The post-treatment results of brachytherapy combined with the ultrasound-triggered OS MBs show a greatly improved therapeutic efficacy compared with brachytherapy alone, illustrating ultrasound-mediated oxygen delivery with the developed OS MBs as a promising strategy to improve the therapeutic outcome of 125I brachytherapy in hypoxic tumors.

Hyperbaric polymer microcapsules for tunable oxygen delivery

Over the past decade, there have been many attempts to engineer systems capable of delivering oxygen to overcome the effects of both systemic and local hypoxia that occurs as a result of traumatic injury, cell transplantation, or tumor growth, among many others. Despite progress in this field, which has led to a new class of oxygen-generating biomaterials, most reported techniques lack the tunability necessary for independent control over the oxygen flux (volume per unit time) and the duration of delivery, both of which are key parameters for overcoming tissue hypoxia of varying etiologies. Here, we show that these critical parameters can be effectively manipulated using hyperbarically-loaded polymeric microcapsules (PMC). PMCs are micron-sized particles with hollow cores and polymeric shells. We show that oxygen delivery through PMCs is dependent on its permeability through the polymeric shell, the shell thickness, and the pressure gradient across the shell. We also demonstrate that incorporating an intermediate oil layer between the polymeric shell and the gas core prevents rapid outgassing by effectively lowering the resultant pressure gradient across the polymeric membrane following depressurization.

Is Structured Exercise Performed with Supplemental Oxygen a Promising Method of Personalized Medicine in the Therapy of Chronic Diseases?

Aim: This systematic review aimed to explore the literature to identify in which types of chronic diseases exercise with supplemental oxygen has previously been utilized and whether this type of personalized therapy leads to superior effects in physical fitness and well-being. Methods: Databases (PubMed/MEDLINE, CINHAL, EMBASE, Web of knowledge and Cochrane Library) were searched in accordance with PRISMA. Eligibility criteria included adult patients diagnosed with any type of chronic diseases engaging in supervised exercise training with supplemental oxygen compared to normoxia. A random-effects model was used to pool effect sizes by standardized mean differences (SMD). Results: Out of the identified 4038 studies, 12 articles were eligible. Eleven studies were conducted in chronic obstructive pulmonary disease (COPD), while one study included coronary artery disease (CAD) patients. No statistical differences were observed for markers of physical fitness and patient-reported outcomes on well-being between the two training conditions (SMD −0.10; 95% CI −0.27, 0.08; p = 0.26). Conclusions: We found that chronic exercise with supplemental oxygen has mainly been utilized for COPD patients. Moreover, no superior long-term adaptations on physical fitness, functional capacity or patient-reported well-being were found, questioning the role of this method as a personalized medicine approach. Prospero registration: CRD42018104649.

Hemoglobin-based Oxygen Carriers: Current State-of-the-art and Novel Molecules

In blood, the primary role of red blood cells (RBCs) is to transport oxygen via highly regulated mechanisms involving hemoglobin (Hb). Hb is a tetrameric porphyrin protein comprising of two α- and two β-polypeptide chains, each containing an iron-containing heme group capable of binding one oxygen molecule. In military as well as civilian traumatic exsanguinating hemorrhage, rapid loss of RBCs can lead to suboptimal tissue oxygenation and subsequent morbidity and mortality. In such cases, transfusion of whole blood or RBCs can significantly improve survival. However, blood products including RBCs present issues of limited availability and portability, need for type matching, pathogenic contamination risks, and short shelf-life, causing substantial logistical barriers to their prehospital use in austere battlefield and remote civilian conditions. While robust research is being directed to resolve these issues, parallel research efforts have emerged toward bioengineering of semisynthetic and synthetic surrogates of RBCs, using various cross-linked, polymeric, and encapsulated forms of Hb. These Hb-based oxygen carriers (HBOCs) can potentially provide therapeutic oxygenation when blood or RBCs are not available. Several of these HBOCs have undergone rigorous preclinical and clinical evaluation, but have not yet received clinical approval in the USA for human use. While these designs are being optimized for clinical translations, several new HBOC designs and molecules have been reported in recent years, with unique properties. The current article will provide a comprehensive review of such HBOC designs, including current state-of-the-art and novel molecules in development, along with a critical discussion of successes and challenges in this field.

Biogenic nanobubbles for effective oxygen delivery and enhanced photodynamic therapy of cancer

Tumor hypoxia is believed to be a factor limiting successful outcomes of oxygen-consuming cancer therapy, thereby reducing patient survival. A key strategy to overcome tumor hypoxia is to increase the prevalence of oxygen at the tumor site. Oxygen-containing microbubbles/nanobubbles have been developed to supply oxygen and enhance the effects of therapies such as radiotherapy and photodynamic therapy. However, the application of these bubbles is constrained by their poor stability, requiring major workarounds to increase their half-lives. In this study, we explore the potential of biogenic gas vesicles (GVs) as a new kind of oxygen carrier to alleviate tumor hypoxia. GVs, which are naturally formed, gas-filled, protein-shelled compartments, were modified on the surface of their protein shells by a layer of liposome. A substantial improvement of oxygen concentration was observed in hypoxic solution, in hypoxic cells, as well as in subcutaneous tumors when lipid-GVs(O₂) were added/tail-injected. Significant enhancement of tumor cell apoptosis and necrosis was also observed during photodynamic therapy (PDT) in the presence of lipid-GVs(O₂) both in vitro and in vivo. Lipid-GVs(O₂) alone induced no obvious change in cell viability in vitro or any apparent pathological abnormalities after mice were tail-injected with them. In all, lipid-GVs exhibited promising performance for intravenous gas delivery, enhanced PDT efficacy and low toxicity, a quality that may be applied to alleviate hypoxia in cancers, as well as hypoxia-related clinical treatments. STATEMENT OF SIGNIFICANCE: The development of stable oxygen-filled micro/nanobubbles capable of delivering oxygen to tumor sites is a major hurdle to enhancing the efficacy of cancer therapy. Currently, micro/nanobubbles are limited by their instability when oxygen is encapsulated, creating a large pressure gradient and surface tension. To improve stability, we modified the surfaces of GVs, a biogenic stable nanoscale hollow structure, as a new class of oxygen carriers. Lipid-coated GVs were found to be stable in solution and effective O₂ carriers. This will overcome the limitations of coalescence, short circulation time of synthetic bubbles during application. Our surface-modified GVs demonstrated low toxicity in vitro cell in vivo, while also being able to overcome hypoxia-associated therapy resistance when combined with photodynamic therapy.

Effective delivery of mycophenolic acid by oxygen nanobubbles for modulating immunosuppression

Immunosuppressive drugs are crucial for preventing acute graft rejection or autoimmune diseases. They are generally small molecules that require suitable drug carriers for ensuring stability, bioavailability, and longer half-life. Mycophenolic acid (MPA) is an extensively studied immunosuppressive drug. However, it requires suitable carriers for overcoming clinical limitations. Currently, lipid-shelled micro- and nanobubbles are being thoroughly investigated for diagnostic and therapeutic applications, as they possess essential properties, such as injectability, smaller size, gaseous core, high surface area, higher drug payload, and enhanced cellular penetration. Phospholipids are biocompatible and biodegradable molecules, and can be functionalized according to specific requirements.

Methods: In this study, we synthesized oxygen nanobubbles (ONBs) and loaded the hydrophobic MPA within the ONBs to generate ONB/MPA. Peripheral blood mononuclear cells (PBMCs) were treated with ONB/MPA to determine the suppression of immune response by measuring cytokine release. In vivo murine experiments were performed to evaluate the effectiveness of ONB/MPA in the presence of inflammatory stimulants.

Results: Our results suggest that ONBs successfully delivered MPA and reduced the release of cytokines, thereby controlling inflammation and significantly increasing the survival rate of animals.

Conclusion: This method can be potentially used for implantation and for treating autoimmune diseases, wherein immunosuppression is desired.

Anti-Tumor Drug-Loaded Oxygen Nanobubbles for the Degradation of HIF-1α and the Upregulation of Reactive Oxygen Species in Tumor Cells

Hypoxia is a key concern during the treatment of tumors, and hypoxia-inducible factor 1 alpha (HIF-1α) has been associated with increased tumor resistance to therapeutic modalities. In this study, doxorubicin-loaded oxygen nanobubbles (Dox/ONBs) were synthesized, and the effectiveness of drug delivery to MDA-MB-231 breast cancer and HeLa cells was evaluated. Dox/ONBs were characterized using optical and fluorescence microscopy, and size measurements were performed through nanoparticle tracking analysis (NTA). The working mechanism of Dox was evaluated using reactive oxygen species (ROS) assays, and cellular penetration was assessed with confocal microscopy. Hypoxic conditions were established to assess the effect of Dox/ONBs under hypoxic conditions compared with normoxic conditions. Our results indicate that Dox/ONBs are effective for drug delivery, enhancing oxygen levels, and ROS generation in tumor-derived cell lines.

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.

Evaluation of antitumor effect of oxygen nanobubble water on breast cancer-bearing BALB/c mice

Hypoxia is a condition of low oxygen level which poses a common feature of most cancers. In the current study, we investigated effect of water containing oxygen nanobubble (ONB) on tumor growth in breast cancer 4T1-bearing mice during 14-day treatment period. Tumor-bearing mice were randomly divided into three groups (six mice per group), including the ONB group drinking water containing ONB, the air nanobubble (ANB) group drinking water containing ANB, and control group drinking normal water. Tumor weight and size were measured in 2-day interval during 14-day treatment. mRNA expression of p53, vascular endothelial growth factor (VEGF), hypoxia-inducible factor (HIF), and cyclin D/Cdk2 genes were measured in the treated and control mice. After 8, 12, and 14 days of treatment, tumor size in ONB group was significantly decreased by 40.5%, 32.8%, and 28%, respectively, when compared with the control group. In addition, ANB group showed a significant reduction in tumor burden as well. The messenger RNA (mRNA) level of p53 in tumor cells of ONB and ANB group was found to be 36-fold (P = 0.0001) and 33-fold (P = 0.0001) higher than that in the control group, respectively. There was a ninefold increase in mRNA expression of VEGF gene in tumor cells of ANB mice than that in control mice; however, there was no significant changes in ONB group. Expression of HIF gene was significantly lower in tumor cells of ONB and ANB group than in the control group. It is concluded that drinking ONB water has potential to inhibit tumor growth, however more preclinical and proof-of-concept studies are needed to confirm its safety and therapeutic effect.

Surface Composition and Preparation Method for Oxygen Nanobubbles for Drug Delivery and Ultrasound Imaging Applications

Phospholipids have been widely investigated for the preparation of liposomes, and micro and nanobubbles. They comprise biocompatible and biodegradable molecules and offer simple preparation with a variety of functions in diagnostic and therapeutic applications. Phospholipids require emulsifiers and surfactants to assemble in the form of bubbles. These surfactants determine the size, zeta potential, and other characteristics of particles. Polyethylene glycol (PEG) and its various derivatives have been employed by researchers to synthesize micro and nanobubbles. The stability of phospholipid-shelled nanobubbles has been reported by various researchers owing to the reduction of surface tension by surfactants in the shell. Nanobubbles have been employed to deliver oxygen to tissues and hypoxic cells. In this study, we investigated the effects of different ratios of phospholipids to PEG on the size, distribution, and characterization of oxygen nanobubbles (ONBs). ONBs were synthesized using a sonication technique. We analyzed and compared the sizes, numbers of generated particles, and zeta potentials of different compositions of ONBs using dynamic light scattering and nanoparticle tracking analysis. Then, we employed these oxygen nanobubbles to enhance the cellular microenvironment and cell viability. ONBs were also investigated for ultrasound imaging.

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.

Oxygen-Carrying Micro/Nanobubbles: Composition, Synthesis Techniques and Potential Prospects in Photo-Triggered Theranostics

Microbubbles and nanobubbles (MNBs) can be prepared using various shells, such as phospholipids, polymers, proteins, and surfactants. MNBs contain gas cores due to which they are echogenic and can be used as contrast agents for ultrasonic and photoacoustic imaging. These bubbles can be engineered in various sizes as vehicles for gas and drug delivery applications with novel properties and flexible structures. Hypoxic areas in tumors develop owing to an imbalance of oxygen supply and demand. In tumors, hypoxic regions have shown more resistance to chemotherapy, radiotherapy, and photodynamic therapies. The efficacy of photodynamic therapy depends on the effective accumulation of photosensitizer drug in tumors and the availability of oxygen in the tumor to generate reactive oxygen species. MNBs have been shown to reverse hypoxic conditions, degradation of hypoxia inducible factor 1α protein, and increase tissue oxygen levels. This review summarizes the synthesis methods and shell compositions of micro/nanobubbles and methods deployed for oxygen delivery. Methods of functionalization of MNBs, their ability to deliver oxygen and drugs, incorporation of photosensitizers and potential application of photo-triggered theranostics, have also been discussed.

Engineering oxygen nanobubbles for the effective reversal of hypoxia

Hypoxia, which results from an inadequate supply of oxygen, is a major cause of concern in cancer therapy as it is associated with a reduction in the effectiveness of chemotherapy and radiotherapy in cancer treatment. Overexpression and stabilization of hypoxia-inducible factor 1α (HIF-1α) protein in tumours, due to hypoxia, results in poor prognosis and increased patient mortality. To increase oxygen tension in hypoxic areas, micro- and nanobubbles have been investigated by various researchers. In the present research, lipid-shelled oxygen nanobubbles (ONBs) were synthesized through a sonication method to reverse hypoxic conditions created in a custom-made hypoxic chamber. Release of oxygen gas from ONBs in deoxygenated water was evaluated by measuring dissolved oxygen. Hypoxic conditions were evaluated by performing in vitro experiments on MDA-MB231 breast cancer cells through the expression of HIF-1α and the fluorescence of image-iT™ hypoxia reagent. The results indicated the degradation of HIF-1α after the introduction of ONBs. We propose that ONBs are successful in reversing hypoxia, downregulating HIF-1α, and improving cellular conditions, leading to further medical applications.

Development of single nanometer-sized ultrafine oxygen bubbles to overcome the hypoxia-induced resistance to radiation therapy via the suppression of hypoxia-inducible factor‑1α

Radiation therapy can result in severe side-effects, including the development of radiation resistance. The aim of this study was to validate the use of oxygen nanobubble water to overcome resistance to radiation in cancer cell lines via the suppression of the hypoxia-inducible factor 1-α (HIF-1α) subunit. Oxygen nanobubble water was created using a newly developed method to produce nanobubbles in the single-nanometer range with the ΣPM-5 device. The size and concentration of the oxygen nanobubbles in the water was examined using a cryo-transmission electron microscope. The nanobubble size was ranged from 2 to 3 nm, and the concentration of the nanobubbles was calculated at 2×10¹⁸ particles/ml. Cell viability and HIF-1α levels were evaluated in EBC-1 lung cancer and MDA-MB-231 breast cancer cells treated with or without the nanobubble water and radiation under normoxic and hypoxic conditions in vitro. The cancer cells grown in oxygen nanobubble-containing media exhibited a clear suppression of hypoxia-induced HIF-1α expression compared to the cells grown in media made with distilled water. Under hypoxic conditions, the EBC-1 and MDA-MB231 cells displayed resistance to radiation compared to the cells cultured under normoxic cells. The use of oxygen nanobubble medium significantly suppressed the hypoxia-induced resistance to radiation compared to the use of normal medium at 2, 6, 10 and 14 Gy doses. Importantly, the use of nanobubble media did not affect the viability and radiation sensitivity of the cancer cell lines, or the non-cancerous cell line, BEAS-2B, under normoxic conditions. This newly created single-nanometer range oxygen nanobubble water, without any additives, may thus prove to be a promising agent which may be used to overcome the hypoxia-induced resistance of cancer cells to radiation via the suppression of HIF-1α.

Mimicking oxygen delivery and waste removal functions of blood

In addition to immunological and wound healing cell and platelet delivery, ion stasis and nutrient supply, blood delivers oxygen to cells and tissues and removes metabolic wastes. For decades researchers have been trying to develop approaches that mimic these two immediately vital functions of blood. Oxygen is crucial for the long-term survival of tissues and cells in vertebrates. Hypoxia (oxygen deficiency) and even at times anoxia (absence of oxygen) can occur during organ preservation, organ and cell transplantation, wound healing, in tumors and engineering of tissues. Different approaches have been developed to deliver oxygen to tissues and cells, including hyperbaric oxygen therapy (HBOT), normobaric hyperoxia therapy (NBOT), using biochemical reactions and electrolysis, employing liquids with high oxygen solubility, administering hemoglobin, myoglobin and red blood cells (RBCs), introducing oxygen-generating agents, using oxygen-carrying microparticles, persufflation, and peritoneal oxygenation. Metabolic waste accumulation is another issue in biological systems when blood flow is insufficient. Metabolic wastes change the microenvironment of cells and tissues, influence the metabolic activities of cells, and ultimately cause cell death. This review examines advances in blood mimicking systems in the field of biomedical engineering in terms of oxygen delivery and metabolic waste removal.

Bio-inspired nanomedicine strategies for artificial blood components

Blood is a fluid connective tissue where living cells are suspended in noncellular liquid matrix. The cellular components of blood render gas exchange (RBCs), immune surveillance (WBCs) and hemostatic responses (platelets), and the noncellular components (salts, proteins, etc.) provide nutrition to various tissues in the body. Dysfunction and deficiencies in these blood components can lead to significant tissue morbidity and mortality. Consequently, transfusion of whole blood or its components is a clinical mainstay in the management of trauma, surgery, myelosuppression, and congenital blood disorders. However, donor-derived blood products suffer from issues of shortage in supply, need for type matching, high risks of pathogenic contamination, limited portability and shelf-life, and a variety of side-effects. While robust research is being directed to resolve these issues, a parallel clinical interest has developed toward bioengineering of synthetic blood substitutes that can provide blood's functions while circumventing the above problems. Nanotechnology has provided exciting approaches to achieve this, using materials engineering strategies to create synthetic and semi-synthetic RBC substitutes for enabling oxygen transport, platelet substitutes for enabling hemostasis, and WBC substitutes for enabling cell-specific immune response. Some of these approaches have further extended the application of blood cell-inspired synthetic and semi-synthetic constructs for targeted drug delivery and nanomedicine. The current study provides a comprehensive review of the various nanotechnology approaches to design synthetic blood cells, along with a critical discussion of successes and challenges of the current state-of-art in this field. WIREs Nanomed Nanobiotechnol 2017, 9:e1464. doi: 10.1002/wnan.1464 For further resources related to this article, please visit the WIREs website.

Oxygen delivery using engineered microparticles

A continuous supply of oxygen to tissues is vital to life and interruptions in its delivery are poorly tolerated. The treatment of low-blood oxygen tensions requires restoration of functional airways and lungs. Unfortunately, severe oxygen deprivation carries a high mortality rate and can make otherwise-survivable illnesses unsurvivable. Thus, an effective and rapid treatment for hypoxemia would be revolutionary. The i.v. injection of oxygen bubbles has recently emerged as a potential strategy to rapidly raise arterial oxygen tensions. In this report, we describe the fabrication of a polymer-based intravascular oxygen delivery agent. Polymer hollow microparticles (PHMs) are thin-walled, hollow polymer microcapsules with tunable nanoporous shells. We show that PHMs are easily charged with oxygen gas and that they release their oxygen payload only when exposed to desaturated blood. We demonstrate that oxygen release from PHMs is diffusion-controlled, that they deliver approximately five times more oxygen gas than human red blood cells (per gram), and that they are safe and effective when injected in vivo. Finally, we show that PHMs can be stored at room temperature under dry ambient conditions for at least 2 mo without any effect on particle size distribution or gas carrying capacity.

Nanobubbles: a promising efficienft tool for therapeutic delivery

In recent decades ultrasound-guided delivery of drugs loaded on nanocarriers has been the focus of increasing attention to improve therapeutic treatments. Ultrasound has often been used in combination with microbubbles, micron-sized spherical gas-filled structures stabilized by a shell, to amplify the biophysical effects of the ultrasonic field. Nanometer size bubbles are defined nanobubbles. They were designed to obtain more efficient drug delivery systems. Indeed, their small sizes allow extravasation from blood vessels into surrounding tissues and ultrasound-targeted site-specific release with minimal invasiveness. Additionally, nanobubbles might be endowed with improved stability and longer residence time in systemic circulation. This review will describe the physico-chemical properties of nanobubbles, the formulation parameters and the drug loading approaches, besides potential applications as a therapeutic tool.

Manufacture of concentrated, lipid-based oxygen microbubble emulsions by high shear homogenization and serial concentration

Gas-filled microbubbles have been developed as ultrasound contrast and drug delivery agents. Microbubbles can be produced by processing surfactants using sonication, mechanical agitation, microfluidic devices, or homogenization. Recently, lipid-based oxygen microbubbles (LOMs) have been designed to deliver oxygen intravenously during medical emergencies, reversing life-threatening hypoxemia, and preventing subsequent organ injury, cardiac arrest, and death. We present methods for scaled-up production of highly oxygenated microbubbles using a closed-loop high-shear homogenizer. The process can produce 2 L of concentrated LOMs (90% by volume) in 90 min. Resulting bubbles have a mean diameter of ~2 μm, and a rheologic profile consistent with that of blood when diluted to 60 volume %. This technique produces LOMs in high capacity and with high oxygen purity, suggesting that this technique may be useful for translational research labs.