Perfluorocarbon nanodroplets can reoxygenate hypoxic tumors in vivo without carbogen breathing

Development of Perfluoro Decalin/Fluorinated Polyimide Core-Shell Microparticles via SPG Membrane Emulsification Using Methyl Perfluoropropyl Ether Cosolvent

Red blood cell-inspired perfluorocarbon-encapsulated core-shell particles have been developed for biomedical applications. Although the use of perfluorodecalin (FDC) is expected for core-shell particles owing to its high oxygen solubility, the low solubility of FDC in any organic solvent, owing to its fluorous properties, prevents its use in core-shell particles. In this study, a new cosolvent system composed of dichloromethane (DCM) and heptafluoropropyl methyl ether (HFPME) was found to dissolve both FDC and fluorinated polyimide (FPI) based on a systematic study using a phase diagram, achieving a homogeneous disperse phase for emulsification composed of oxygen-permeable FPI and oxygen-soluble FDC. Using this novel cosolvent system and Shirasu porous glass (SPG) membrane emulsification, FDC-encapsulated FPI shell microparticles were successfully prepared for the first time. In addition to oxygenation, demonstrated using hypoxia-responsive HeLa cells, the fabricated core-shell microparticles exhibited monodispersity, excellent stability, biocompatibility, and oxygen capacity.

Perfluorocarbons in Research and Clinical Practice: A Narrative Review

Perfluorocarbons (PFCs) are organic liquids derived from hydrocarbons in which some of the hydrogen atoms have been replaced by fluorine atoms. They are chemically and biologically inert substances with a good safety profile. They are stable at room temperature, easy to store, and immiscible in water. Perfluorocarbons have been studied in biomedical research since 1960 for their unique properties as oxygen carriers. In particular, PFCs have been used for liquid ventilation in unusual environments such as deep-sea diving and simulations of zero gravity, and more recently for drug delivery and diagnostic imaging. Additionally, when delivered as emulsions, PFCs have been used as red blood cell substitutes. This narrative review will discuss the multifaceted utilization of PFCs in therapeutics, diagnostics, and research. We will specifically emphasize the potential role of PFCs as red blood cell substitutes, as airway mechanotransducers during artificial placenta procedures, as a means to improve donor organ perfusion during the ex vivo assessment, and as an adjunct in cancer therapies because of their ability to reduce local tissue hypoxia.

Leveraging hypoxia in triple-negative breast cancer as a promising treatment strategy

Current treatment strategies for triple-negative breast cancer (TNBC) are based upon conventional chemotherapy, immunotherapy, or a combination of both. The treatment regimen for chemotherapy is often a combination of two or more drugs, either dose dense or low dose for synergy. Anthracyclines, alkylating agents, antimicrotubule agents, and antimetabolites for early-stage TNBC; and antimetabolites, non-taxane microtubule inhibitors, and cross-linker platinums for late-stage TNBC are usually administered in the clinical setting. Newer options for patients with advanced TNBC, such as poly (ADP-ribose) polymerase (PARP) inhibitors and immune checkpoint inhibitors, have recently emerged for cases where surgery is not a viable option and the disease has metastasized. This review outlines the current trends in hypoxia-inspired treatment strategies for TNBC with a focus on clinical trials.

Acoustomechanically activatable liposomes for ultrasonic drug uncaging

Ultrasound-activatable drug-loaded nanocarriers enable noninvasive and spatiotemporally-precise on-demand drug delivery throughout the body. However, most systems for ultrasonic drug uncaging utilize cavitation or heating as the drug release mechanism and often incorporate relatively exotic excipients into the formulation that together limit the drug-loading potential, stability, and clinical translatability and applicability of these systems. Here we describe an alternate strategy for the design of such systems in which the acoustic impedance and osmolarity of the internal liquid phase of a drug-loaded particle is tuned to maximize ultrasound-induced drug release. No gas phase, cavitation, or medium heating is necessary for the drug release mechanism. Instead, a non-cavitation-based mechanical response to ultrasound mediates the drug release. Importantly, this strategy can be implemented with relatively common pharmaceutical excipients, as we demonstrate here by implementing this mechanism with the inclusion of a few percent sucrose into the internal buffer of a liposome. Further, the ultrasound protocols sufficient for in vivo drug uncaging with this system are achievable with current clinical therapeutic ultrasound systems and with intensities that are within FDA and society guidelines for safe transcranial ultrasound application. Finally, this current implementation of this mechanism should be versatile and effective for the loading and uncaging of any therapeutic that may be loaded into a liposome, as we demonstrate for four different drugs in vitro, and two in vivo. These acoustomechanically activatable liposomes formulated with common pharmaceutical excipients promise a system with high clinical translational potential for ultrasonic drug uncaging of myriad drugs of clinical interest.

Perfluorocarbons: A perspective of theranostic applications and challenges

Perfluorocarbon (PFC) are biocompatible compounds, chemically and biologically inert, and lacks toxicity as oxygen carriers. PFCs nanoemulsions and nanoparticles (NPs) are highly used in diagnostic imaging and enable novel imaging technology in clinical imaging modalities to notice and image pathological and physiological alterations. Therapeutics with PFCs such as the innovative approach to preventing thrombus formation, PFC nanodroplets utilized in ultrasonic medication delivery in arthritis, or PFC-based NPs such as Perfluortributylamine (PFTBA), Pentafluorophenyl (PFP), Perfluorohexan (PFH), Perfluorooctyl bromide (PFOB), and others, recently become renowned for oxygenating tumors and enhancing the effects of anticancer treatments as oxygen carriers for tumor hypoxia. In this review, we will discuss the recent advancements that have been made in PFC's applications in theranostic (therapeutics and diagnostics) as well as assess the benefits and drawbacks of these applications.

Effect of Anesthetic Carrier Gas on In Vivo Circulation Times of Intravenously Administered Phospholipid Oxygen Microbubbles in Rats

OBJECTIVE

For the treatment of tumor hypoxia, microbubbles comprising oxygen as a majority component of the gas core with a stabilizing shell may be used to deliver and release oxygen locally at the tumor site through ultrasound destruction. Previous work has revealed differences in circulation half-life in vivo for perfluorocarbon-filled microbubbles, typically used as ultrasound imaging contrast agents, as a function of anesthetic carrier gas. These differences in circulation time in vivo were likely due to gas diffusion as a function of anesthetic carrier gas, among other variables. This work has motivated studies to evaluate the effect of anesthetic carrier gas on oxygen microbubble circulation dynamics.

METHODS

Circulation time for oxygen microbubbles was derived from ultrasound image intensity obtained during longitudinal kidney imaging. Studies were constructed for rats anesthetized on inhaled isoflurane with either pure oxygen or medical air as the anesthetic carrier gas.

RESULTS

Results indicated that oxygen microbubbles were highly visible via contrast-specific imaging. Marked signal enhancement and duration differences were observed between animals breathing air and oxygen. Perhaps counterintuitively, oxygen microbubbles disappeared from circulation significantly faster when the animals were breathing pure oxygen compared with medical air. This may be explained by nitrogen counterdiffusion from blood into the bubble, effectively changing the gas composition of the core, as has been observed in perfluorocarbon core microbubbles.

CONCLUSION

Our findings suggest that the apparent longevity and persistence of oxygen microbubbles in circulation may not be reflective of oxygen delivery when the animal is anesthetized breathing air.

Recent Advances in Nanoplatform Construction Strategy for Alleviating Tumor Hypoxia

Hypoxia is a typical feature of most solid tumors and has important effects on tumor cells' proliferation, invasion, and metastasis. This is the key factor that leads to poor efficacy of different kinds of therapy including chemotherapy, radiotherapy, photodynamic therapy, etc. In recent years, the construction of hypoxia-relieving functional nanoplatforms through nanotechnology has become a new strategy to reverse the current situation of tumor microenvironment hypoxia and improve the effectiveness of tumor treatment. Here, the main strategies and recent progress in constructing nanoplatforms are focused on to directly carry oxygen, generate oxygen in situ, inhibit mitochondrial respiration, and enhance blood perfusion to alleviate tumor hypoxia. The advantages and disadvantages of these nanoplatforms are compared. Meanwhile, nanoplatforms based on organic and inorganic substances are also summarized and classified. Through the comprehensive overview, it is hoped that the summary of these nanoplatforms for alleviating hypoxia could provide new enlightenment and prospects for the construction of nanomaterials in this field.

Towards an In Vitro 3D Model for Photosynthetic Cancer Treatment: A Study of Microalgae and Tumor Cell Interactions

As hypoxic tumors show resistance to several clinical treatments, photosynthetic microorganisms have been recently suggested as a promising safe alternative for oxygenating the tumor microenvironment. The relationship between organisms and the effect microalgae have on tumors is still largely unknown, evidencing the need for a simple yet representative model for studying photosynthetic tumor oxygenation in a reproducible manner. Here, we present a 3D photosynthetic tumor model composed of human melanoma cells and the microalgae Chlamydomonas reinhardtii, both seeded into a collagen scaffold, which allows for the simultaneous study of both cell types. This work focuses on the biocompatibility and cellular interactions of the two cell types, as well as the study of photosynthetic oxygenation of the tumor cells. It is shown that both cell types are biocompatible with one another at cell culture conditions and that a 10:1 ratio of microalgae to cells meets the metabolic requirement of the tumor cells, producing over twice the required amount of oxygen. This 3D tumor model provides an easy-to-use in vitro resource for analyzing the effects of photosynthetically produced oxygen on a tumor microenvironment, thus opening various potential research avenues.

Perfluorocarbon nanodroplet size, acoustic vaporization, and inertial cavitation affected by lipid shell composition in vitro

Perfluorocarbon nanodroplets (PFCnDs) are ultrasound contrast agents that phase-transition from liquid nanodroplets to gas microbubbles when activated by laser irradiation or insonated with an ultrasound pulse. The dynamics of PFCnDs can vary drastically depending on the nanodroplet composition, including the lipid shell properties. In this paper, we investigate the effect of varying the ratio of PEGylated to non-PEGylated phospholipids in the outer shell of PFCnDs on the acoustic nanodroplet vaporization (liquid to gas phase transition) and inertial cavitation (rapid collapse of the vaporized nanodroplets) dynamics in vitro when insonated with focused ultrasound. Nanodroplets with a high concentration of PEGylated lipids had larger diameters and exhibited greater variance in size distribution compared to nanodroplets with lower proportions of PEGylated lipids in the lipid shell. PFCnDs with a lipid shell composed of 50:50 PEGylated to non-PEGylated lipids yielded the highest B-mode image intensity and duration, as well as the greatest pressure difference between acoustic droplet vaporization onset and inertial cavitation onset. We demonstrate that slight changes in lipid shell composition of PFCnDs can significantly impact droplet phase transitioning and inertial cavitation dynamics. These findings can help guide researchers to fabricate PFCnDs with optimized compositions for their specific applications.

Recent Strategies to Address Hypoxic Tumor Environments in Photodynamic Therapy

Photodynamic therapy (PDT) has become a promising method of cancer treatment due to its unique properties, such as noninvasiveness and low toxicity. The efficacy of PDT is, however, significantly reduced by the hypoxia tumor environments, because PDT involves the generation of reactive oxygen species (ROS), which requires the great consumption of oxygen. Moreover, the consumption of oxygen caused by PDT would further exacerbate the hypoxia condition, which leads to angiogenesis, invasion of tumors to other parts, and metastasis. Therefore, many research studies have been conducted to design nanoplatforms that can alleviate tumor hypoxia and enhance PDT. Herein, the recent progress on strategies for overcoming tumor hypoxia is reviewed, including the direct transport of oxygen to the tumor site by O₂ carriers, the in situ generation of oxygen by decomposition of oxygen-containing compounds, reduced O₂ consumption, as well as the regulation of tumor microenvironments. Limitations and future perspectives of these technologies to improve PDT are also discussed.

Perfluorocarbon Nanodroplets as Potential Nanocarriers for Brain Delivery Assisted by Focused Ultrasound-Mediated Blood–Brain Barrier Disruption

The management of brain diseases remains a challenge, particularly because of the difficulty for drugs to cross the blood–brain barrier. Among strategies developed to improve drug delivery, nano-sized emulsions (i.e., nanoemulsions), employed as nanocarriers, have been described. Moreover, focused ultrasound-mediated blood–brain barrier disruption using microbubbles is an attractive method to overcome this barrier, showing promising results in clinical trials. Therefore, nanoemulsions combined with this technology represent a real opportunity to bypass the constraints imposed by the blood–brain barrier and improve the treatment of brain diseases. In this work, a stable freeze-dried emulsion of perfluorooctyl bromide nanodroplets stabilized with home-made fluorinated surfactants able to carry hydrophobic agents is developed. This formulation is biocompatible and droplets composing the emulsion are internalized in multiple cell lines. After intravenous administration in mice, droplets are eliminated from the bloodstream in 24 h (blood half-life (t_1/2) = 3.11 h) and no long-term toxicity is expected since they are completely excreted from mice’ bodies after 72 h. In addition, intracerebral accumulation of tagged droplets is safely and significantly increased after focused ultrasound-mediated blood–brain barrier disruption. Thus, the proposed nanoemulsion appears as a promising nanocarrier for a successful focused ultrasound-mediated brain delivery of hydrophobic agents.

Photoacoustic nanodroplets for oxygen enhanced photodynamic therapy of cancer

Photodynamic therapy (PDT) is a well-known cancer therapy that utilizes light to excite a photosensitizer and generate cytotoxic reactive oxygen species (ROS). The efficacy of PDT primarily depends on the photosensitizer and oxygen concentration in the tumor. Hypoxia in solid tumors promotes treatment resistance, resulting in poor PDT outcomes. Hence, there is a need to combat hypoxia while delivering sufficient photosensitizer to the tumor for ROS generation. Here we showcase our unique theranostic perfluorocarbon nanodroplets as a triple agent carrier for oxygen, photosensitizer, and indocyanine green that enables light triggered spatiotemporal delivery of oxygen to the tumors. We evaluated the characteristics of the nanodroplets and validated their ability to deliver oxygen via photoacoustic monitoring of blood oxygen saturation and subsequent PDT efficacy in a murine subcutaneous tumor model. The imaging results were validated with an oxygen sensing probe, which showed a 9.1 fold increase in oxygen content inside the tumor, following systemic administration of the nanodroplets. These results were also confirmed with immunofluorescence. In vivo studies showed that nanodroplets held higher rates of treatment efficacy than a clinically available benzoporphyrin derivative formulation. Histological analysis showed higher necrotic area within the tumor with perfluoropentane nanodroplets. Overall, the photoacoustic nanodroplets can significantly enhance image-guided PDT and has demonstrated substantial potential as a valid theranostic option for patient-specific photodynamic therapy-based treatments.

Biological Utility of Fluorinated Compounds: from Materials Design to Molecular Imaging, Therapeutics and Environmental Remediation

The applications of fluorinated molecules in bioengineering and nanotechnology are expanding rapidly with the controlled introduction of fluorine being broadly studied due to the unique properties of C-F bonds. This review will focus on the design and utility of C-F containing materials in imaging, therapeutics, and environmental applications with a central theme being the importance of controlling fluorine-fluorine interactions and understanding how such interactions impact biological behavior. Low natural abundance of fluorine is shown to provide sensitivity and background advantages for imaging and detection of a variety of diseases with ¹⁹F magnetic resonance imaging, ¹⁸F positron emission tomography and ultrasound discussed as illustrative examples. The presence of C-F bonds can also be used to tailor membrane permeability and pharmacokinetic properties of drugs and delivery agents for enhanced cell uptake and therapeutics. A key message of this review is that while the promise of C-F containing materials is significant, a subset of highly fluorinated compounds such as per- and polyfluoroalkyl substances (PFAS), have been identified as posing a potential risk to human health. The unique properties of the C-F bond and the significant potential for fluorine-fluorine interactions in PFAS structures necessitate the development of new strategies for facile and efficient environmental removal and remediation. Recent progress in the development of fluorine-containing compounds as molecular imaging and therapeutic agents will be reviewed and their design features contrasted with environmental and health risks for PFAS systems. Finally, present challenges and future directions in the exploitation of the biological aspects of fluorinated systems will be described.

Tracking the heat-triggered phase change of polydopamine-shelled, perfluorocarbon emulsion droplets into microbubbles using neutron scattering

Perfluorocarbon emulsion droplets are hybrid colloidal materials with vast applications, ranging from imaging to drug delivery, due to their controllable phase transition into microbubbles via heat application or acoustic droplet vapourisation. The current work highlights the application of small- and ultra-small-angle neutron scattering (SANS and USANS), in combination with contrast variation techniques, in observing the in situ phase transition of polydopamine-shelled, perfluorocarbon (PDA/PFC) emulsion droplets with controlled polydispersity into microbubbles upon heating. We correlate these measurements with optical and transmission electron microscopy imaging, dynamic light scattering, and thermogravimetric analysis to characterise these emulsions, and observe their phase transition into microbubbles. Results show that the phase transition of PDA/PFC droplets with perfluorohexane (PFH), perfluoropentane (PFP), and PFH-PFP mixtures occur at temperatures that are around 30-40 °C higher than the boiling points of pure liquid PFCs, and this is influenced by the specific PFC compositions (perfluorohexane, perfluoropentane, and mixtures of these PFCs). Analysis and model fitting of neutron scattering data allowed us to monitor droplet size distributions at different temperatures, giving valuable insights into the transformation of these polydisperse, emulsion droplet systems.

Phototherapy and multimodal imaging of cancers based on perfluorocarbon nanomaterials

Phototherapy, such as photodynamic therapy (PDT) and photothermal therapy (PTT), possesses unique characteristics of non-invasiveness and minimal side effects in cancer treatment, compared with conventional therapies. However, the ubiquitous tumor hypoxia microenvironments could severely reduce the efficacy of oxygen-consuming phototherapies. Perfluorocarbon (PFC) nanomaterials have shown great practical value in carrying and transporting oxygen, which makes them promising agents to overcome tumor hypoxia and extend reactive oxygen species (ROS) lifetime to improve the efficacy of phototherapy. In this review, we summarize the latest advances in PFC-based PDT and PTT, and combined multimodal imaging technologies in various cancer types, aiming to facilitate their application-oriented clinical translation in the future.

Functional ultrasound-triggered phase-shift perfluorocarbon nanodroplets for cancer therapy

In recent years, because of their unique properties, the use of perfluorocarbon nanodroplets (PFC NDs) in ultrasound-mediated tumor theranostics has attracted increasing interest. PFC is one of the most stable organic compounds with high hydrophobicity. Phase-shift PFC NDs can be transformed into highly echogenic microbubbles for ultrasound and photoacoustic imaging by ultrasound and laser light. In addition, in the process of acoustic droplet vaporization, PFC NDs with cavitation nuclei can be combined with a variety of ultrasound technologies to produce cavitation effects for tumor ablation, antivascular therapy and release of therapeutic agents loaded in nanodroplets. Moreover, they can also be used to overcome tumor hypoxia by virtue of high oxygen solubility. In this review, first the preparation and stabilization of PFC NDs are summarized and then the issues and outlook are discussed. More importantly, multifunctional platforms based on PFC NDs for cancer diagnostics, therapy and theranostics are reviewed in detail.

Therapeutic oxygen delivery by perfluorocarbon-based colloids

After the protocol-related indecisive clinical trial of Oxygent, a perfluorooctylbromide/phospholipid nanoemulsion, in cardiac surgery, that often unduly assigned the observed untoward effects to the product, the development of perfluorocarbon (PFC)-based O₂ nanoemulsions ("blood substitutes") has come to a low. Yet, significant further demonstrations of PFC O₂-delivery efficacy have continuously been reported, such as relief of hypoxia after myocardial infarction or stroke; protection of vital organs during surgery; potentiation of O₂-dependent cancer therapies, including radio-, photodynamic-, chemo- and immunotherapies; regeneration of damaged nerve, bone or cartilage; preservation of organ grafts destined for transplantation; and control of gas supply in tissue engineering and biotechnological productions. PFC colloids capable of augmenting O₂ delivery include primarily injectable PFC nanoemulsions, microbubbles and phase-shift nanoemulsions. Careful selection of PFC and other colloid components is critical. The basics of O₂ delivery by PFC nanoemulsions will be briefly reminded. Improved knowledge of O₂ delivery mechanisms has been acquired. Advanced, size-adjustable O₂-delivering nanoemulsions have been designed that have extended room-temperature shelf-stability. Alternate O₂ delivery options are being investigated that rely on injectable PFC-stabilized microbubbles or phase-shift PFC nanoemulsions. The latter combine prolonged circulation in the vasculature, capacity for penetrating tumor tissues, and acute responsiveness to ultrasound and other external stimuli. Progress in microbubble and phase-shift emulsion engineering, control of phase-shift activation (vaporization), understanding and control of bubble/ultrasound/tissue interactions is discussed. Control of the phase-shift event and of microbubble size require utmost attention. Further PFC-based colloidal systems, including polymeric micelles, PFC-loaded organic or inorganic nanoparticles and scaffolds, have been devised that also carry substantial amounts of O₂. Local, on-demand O₂ delivery can be triggered by external stimuli, including focused ultrasound irradiation or tumor microenvironment. PFC colloid functionalization and targeting can help adjust their properties for specific indications, augment their efficacy, improve safety profiles, and expand the range of their indications. Many new medical and biotechnological applications involving fluorinated colloids are being assessed, including in the clinic. Further uses of PFC-based colloidal nanotherapeutics will be briefly mentioned that concern contrast diagnostic imaging, including molecular imaging and immune cell tracking; controlled delivery of therapeutic energy, as for noninvasive surgical ablation and sonothrombolysis; and delivery of drugs and genes, including across the blood-brain barrier. Even when the fluorinated colloids investigated are designed for other purposes than O₂ supply, they will inevitably also carry and deliver a certain amount of O₂, and may thus be considered for O₂ delivery or co-delivery applications. Conversely, O₂-carrying PFC nanoemulsions possess by nature a unique aptitude for ¹⁹F MR imaging, and hence, cell tracking, while PFC-stabilized microbubbles are ideal resonators for ultrasound contrast imaging and can undergo precise manipulation and on-demand destruction by ultrasound waves, thereby opening multiple theranostic opportunities.

Strategies of Alleviating Tumor Hypoxia and Enhancing Tumor Therapeutic Effect by Macromolecular Nanomaterials

Hypoxia as one of the most prominent features in tumors, has presented negative effects on tumor therapies including photodynamic therapy, radiotherapy, and chemotherapies, leading to the tumor regeneration and metastasis. Recently, nanomedicines have been proposed to handle the hypoxia dilemma. Some nanomedicines alleviated hypoxia to enhance the therapeutic effect, others used hypoxia-sensitive substances to treat tumor. Among them, macromolecular nanomaterials-based nanomedicine has attracted increased research interest. However, the complicated tumor microenvironment disturbs the practical application of macromolecular nanomaterials to deal with hypoxia. This review highlights the influence of hypoxia on tumor therapy and some new strategies of using macromolecular nanomaterials to overcome hypoxia for effective tumor therapy.

Multifunctional nanoparticles as theranostic agents for therapy and imaging of breast cancer

Over the last decade, there has been significant developments in nanotechnology, in particular for combined imaging and therapeutic applications (theranostics). The core or shell of nanoemulsions (NEs) can be loaded with various therapeutic agents, including drugs with low solubility for effective treatment, or various imaging agents for specific imaging modalities (e.g., MRI, fluorescence). In this work, perfluorohexane (PFH) NEs were synthesized for theranostic applications and were coupled to silica coated gold nanoparticles (scAuNPs) to increase the generation of PFH bubbles upon laser induced vaporization (i.e., optical droplet vaporization). The localized heat generated from the absorption properties of these nanoparticles (used to provide photoacoustic signals) can also be used to treat cancer without significantly damaging nearby healthy tissues. The theranostic potential of these PFH-NEs for contrast imaging of tumors and as a drug-delivery vehicle for therapeutic purposes were demonstrated for both in vitro and in vivo systems using a combination of photoacoustic, ultrasound and fluorescence imaging modalities. The ability of PFH-NEs to couple with scAuNPs, attach to the membranes of cancer cells and internalize within cancer cells, are encouraging for targeted chemotherapeutic applications for directly inducing cancer cell death via vaporization in clinical settings.

Nanovectorization of Prostate Cancer Treatment Strategies: A New Approach to Improved Outcomes

Prostate cancer (PC) is the most frequent male cancer in the Western world. Progression to Castration Resistant Prostate Cancer (CRPC) is a known consequence of androgen withdrawal therapy, making CRPC an end-stage disease. Combination of cytotoxic drugs and hormonal therapy/or genotherapy is a recognized modality for the treatment of advanced PC. However, this strategy is limited by poor bio-accessibility of the chemotherapy to tumor sites, resulting in an increased rate of collateral toxicity and incidence of multidrug resistance (MDR). Nanovectorization of these strategies has evolved to an effective approach to efficacious therapeutic outcomes. It offers the possibility to consolidate their antitumor activity through enhanced specific and less toxic active or passive targeting mechanisms, as well as enabling diagnostic imaging through theranostics. While studies on nanomedicine are common in other cancer types, only a few have focused on prostate cancer. This review provides an in-depth knowledge of the principles of nanotherapeutics and nanotheranostics, and how the application of this rapidly evolving technology can clinically impact CRPC treatment. With particular reference to respective nanovectors, we draw clinical and preclinical evidence, demonstrating the potentials and prospects of homing nanovectorization into CRPC treatment strategies.

Phenotyping placental oxygenation in Lgals1 deficient mice using 19F MRI

Placental hypoperfusion and hypoxia are key drivers in complications during fetal development such as fetal growth restriction and preeclampsia. In order to study the mechanisms of disease in mouse models, the development of quantitative biomarkers of placental hypoxia is a prerequisite. The goal of this exploratory study was to establish a technique to noninvasively characterize placental partial pressure of oxygen (PO2) in vivo in the Lgals1 (lectin, galactoside-binding, soluble, 1) deficient mouse model of preeclampsia using fluorine magnetic resonance imaging. We hypothesized a decrease in placental oxygenation in knockout mice. Wildtype and knockout animals received fluorescently labeled perfluoro-5-crown-15-ether nanoemulsion i.v. on day E14-15 during pregnancy. Placental PO2 was assessed via calibrated 19F MRI saturation recovery T1 mapping. A gas challenge with varying levels of oxygen in breathing air (30%, 60% and 100% O2) was used to validate that changes in oxygenation can be detected in freely breathing, anesthetized animals. At the end of the experiment, fluorophore-coupled lectin was injected i.v. to label the vasculature for histology. Differences in PO2 between breathing conditions and genotype were statistically analyzed with linear mixed-effects modeling. As expected, a significant increase in PO2 with increasing oxygen in breathing air was found. PO2 in Lgals1 knockout animals was decreased but this effect was only present at 30% oxygen in breathing air, not at 60% and 100%. Histological examinations showed crossing of the perfluorocarbon nanoemulsion to the fetal blood pool but the dominating contribution of 19F MR signal is estimated at > 70% from maternal plasma based on volume fraction measurements of previous studies. These results show for the first time that 19F MRI can characterize oxygenation in mouse models of placental malfunction.

Laser activatable perfluorocarbon bubbles for imaging and therapy through enhanced absorption from coupled silica coated gold nanoparticles

Nanoparticles have extensively been used for cancer therapy and imaging (i.e., theranostics) using various imaging modalities. Due to their physical and chemical properties (e.g., absorption, fluorescence, and magnetic properties) they have been used for image guided therapy for cancer treatment monitoring. There are various limitations that make many theranostic agents unable to be used for the extended periods of time required for enhancing theranostic capabilities. Some of these are due to inherent characteristics (e.g., change and/or breakdown of structure) present upon continuous irradiation and others are due to environmental (i.e., physiological) conditions that can lead to physical instability (i.e., in terms of size) affecting the amount of particles that can accumulate at the target site and the overall contrast that can be achieved. In this study, perfluorohexane (PFH) nanoemulsions (NEs) were synthesized with silica coated gold nanoparticles (PFH-NEs-scAuNPs) in order to give both stable and enhanced signals for cancer imaging by increasing vaporization of the emulsions into bubbles through the process of optical droplet vaporization (ODV). The resulting perfluorohexane bubbles could be imaged using nonlinear ultrasound (NL US) which significantly increases the signal to noise ratio due to the nonlinear scattering properties of oscillating bubbles. The NL US signals from PFH bubbles were found to be more stable compared to conventional bubbles used for contrast imaging. In addition, the vaporization of PFH NEs into bubbles was shown to cause significant cancer cell death reflecting the theranostic capabilities of the formed PFH bubbles. Since cell death is initiated with laser excitation of PFH-NEs-scAuNPs, these nanoparticles can specifically target cancer cells once they have accumulated at the tumor region. Due to the type of theranostic agent and imaging modality used, the PFH-NEs-scAuNPs can be used to provide higher specificity compared to other agents for locating the tumor region by minimizing tissue specific signals while at the same time being used to treat cancer.

PFH-NEs from PFH-NEs-scAuNPs can vaporize upon laser excitation leading to formation of PFH bubbles that can be used for contrast enhanced US imaging and therapy.

DNA Nanostructures and DNA-Functionalized Nanoparticles for Cancer Theranostics

In the last two decades, DNA has attracted significant attention toward the development of materials at the nanoscale for emerging applications due to the unparalleled versatility and programmability of DNA building blocks. DNA-based artificial nanomaterials can be broadly classified into two categories: DNA nanostructures (DNA-NSs) and DNA-functionalized nanoparticles (DNA-NPs). More importantly, their use in nanotheranostics, a field that combines diagnostics with therapy via drug or gene delivery in an all-in-one platform, has been applied extensively in recent years to provide personalized cancer treatments. Conveniently, the ease of attachment of both imaging and therapeutic moieties to DNA-NSs or DNA-NPs enables high biostability, biocompatibility, and drug loading capabilities, and as a consequence, has markedly catalyzed the rapid growth of this field. This review aims to provide an overview of the recent progress of DNA-NSs and DNA-NPs as theranostic agents, the use of DNA-NSs and DNA-NPs as gene and drug delivery platforms, and a perspective on their clinical translation in the realm of oncology.

Perfluorocarbon-based oxygen carriers: from physics to physiology

Developing biocompatible, synthetic oxygen carriers is a consistently challenging task that researchers have been pursuing for decades. Perfluorocarbons (PFC) are fascinating compounds with a huge capacity to dissolve gases, where the respiratory gases are of special interest for current investigations. Although largely chemically and biologically inert, pure PFCs are not suitable for injection into the vascular system. Extensive research created stable PFC nano-emulsions that avoid (i) fast clearance from the blood and (ii) long organ retention time, which leads to undesired transient side effects. PFC-based oxygen carriers (PFOCs) show a variety of application fields, which are worthwhile to investigate. To understand the difficulties that challenge researchers in creating formulations for clinical applications, this review provides the physical background of PFCs’ properties and then illuminates the reasons for instabilities of PFC emulsions. By linking the unique properties of PFCs and PFOCs to physiology, it elaborates on the response, processing and dysregulation, which the body experiences through intravascular PFOCs. Thereby the reader will receive a scientific and easily comprehensible overview why PFOCs are precious tools for so many diverse application areas from cancer therapeutics to blood substitutes up to organ preservation and diving disease.

Current developments in nanotechnology for improved cancer treatment, focusing on tumor hypoxia

Hypoxia is a common feature of the tumor microenvironment, which is characterized by tissue oxygen deficiency due to an aggressive proliferation of cancer cells. Hypoxia activates hypoxia-inducible factor-dependent signaling, which in turn regulates metabolic reprogramming, immune suppression, resistance to apoptosis, angiogenesis, metastasis, and invasion to secondary sites. In this review, we provide an overview of the use of nanotechnology to harmonize intra-tumoral oxygen or suppress hypoxia-related signaling for an improved efficacy of cancer treatment. The biological background was followed by conducting a literature review on the (1) nanoparticles responsible for enhancing oxygen levels within the tumor, (2) nanoparticles sensitizing hypoxia, (3) nanoparticles suppressing hypoxia-inducing factor, (4) nanoparticles that relieve tumor hypoxia for enhancement of chemotherapy, photodynamic therapy, and immunotherapy, either individually or in combination. Lastly, the heterogeneity of cancer and limitations of nanotechnology are discussed to facilitate translational therapeutic treatment.

Enhanced antitumor efficacy in colon cancer using EGF functionalized PLGA nanoparticles loaded with 5-Fluorouracil and perfluorocarbon

Background

Tumor recurrence and metastasis occur at a high rate in patients with colon cancer. Identification of effective strategies for the treatment of colon cancer is critical. Recently, poly (lactic-co-glycolic acid) (PLGA) has been shown to have potential as a broad therapeutic drug delivery system. We designed a dual-loaded nanoparticle drug delivery system to overcome the limitations of chemotherapeutic drugs used to treat colon cancer.

Methods

We developed epidermal growth factor (EGF) functionalized PLGA nanoparticles (NPs) co-loaded with 5-fluorouracil (5Fu) and perfluorocarbon (PFC) (EGF-PLGA@5Fu/PFC) for targeted treatment of colon cancer. CCK-8 assay, Hoechst33342 staining and flow cytometry were performed to investigate the functions of EGF-PLGA@5Fu/PFC NPs in SW620 cells. Beside, animal experiment, histological analysis and immunofluorescence staining were adopted to further confirm the role of EGF-PLGA@5Fu/PFC NPs in vivo.

Results

The findings showed that EGF-PLGA@5Fu /PFC NPs had an average size 200 nm and a 5Fu-loading efficiency of 7.29%. Furthermore, in vitro release was pH-sensitive. Targeted EGF-PLGA@5Fu/PFC NPs exhibited higher cellular uptake than non-targeted NPs into colon cancer cells. In addition, EGF-PLGA@5Fu/PFC NPs suppressed cell viability and induced apoptosis in SW620 cells to a greater extent than non-targeted NPs. In tumor xenografted mice, EGF-PLGA@5Fu/PFC NPs suppressed tumor growth more effectively than 5Fu, PLGA@5Fu or PLGA@5Fu/PFC NPs. Histopathological analysis further demonstrated that EGF-targeted NPs inhibited tumor growth to a greater extent than non-targeted or non-NP treatments. The improved therapeutic outcomes observed in this study were due to relief of tumor hypoxia by transport of oxygen by PFC to the tumors.

Conclusion

We constructed a biocompatible nanodrug delivery system based on functionalized nanoparticles that provided a novel strategy for selective delivery of chemotherapy drugs to tumors.

Nanoparticles-mediated reoxygenation strategy relieves tumor hypoxia for enhanced cancer therapy

Tumor hypoxia is a characteristic hallmark of malignant solid tumors, which remains an essential impediment to many current treatments like chemotherapy, radiotherapy, photodynamic therapy and immunotherapy, thereby leading to poor clinical prognosis after therapy. Rationally, modulating tumor hypoxia can be of great interest to augment the therapeutic efficacy of these treatments. In this review, we focus our discussion on current advances in nanoparticles-mediated tumor reoxygenation strategy for relieving tumor hypoxia to improve the therapeutic efficacy of versatile therapies. These nanoparticles can improve tumor oxygen levels via nanoparticles-mediated oxygen-carrying or oxygen-generating tactics to synergize the effectiveness of many current therapeutic modalities. Based on these considerable summaries and analyses, we propose some feasible perspectives on nanoparticles-based tumor reoxygenations to ameliorate the therapeutic outcomes.

Overcoming hypoxia-induced chemoresistance to cisplatin through tumor oxygenation monitored by optical imaging

Perfluorocarbon nanoparticles have been reported to deliver oxygen to tumors and reduce hypoxia-induced radioresistance, however few studies have been carried out to study its role in reducing hypoxia-induced chemoresistance. The oxygenation effect also varies dramatically between different perfluorocarbon formulations and protocols, and there have been no efficient tools to monitor dynamic changes of tumor oxygenation non-invasively. Our goal was to promote tumor oxygenation using perfluorooctyl bromide (PFOB) nanoemulsion and to assess its role in sensitizing tumors to cisplatin treatment. A novel optical imaging protocol was also created to monitor the dynamic changes of tumor oxygenation in real-time.

Methods: PFOB nanoemulsion with high oxygen-carrying capacity was prepared and administered to tumor-bearing mice intravenously. Tumor oxygenation was monitored using optical imaging with a hypoxia probe injected intratumorally, thus the oxygenation dynamics and best oxygenation protocol were determined. Various treatment groups were studied, and the tumor growth was monitored to evaluate the role of oxygenation in sensitizing tumors to cisplatin treatment.

Results: PFOB nanoemulsion with and without pre-oxygenation along with carbogen breathing resulted in much better tumor oxygenation compared to carbogen breathing alone, while PFOB with air breathing did not show significant increase in tumor oxygenation. Pre-oxygenated PFOB with carbogen breathing produced the most effective oxygenation as early as 5 min post administration. In vitro and in vivo data showed preoxygenated PFOB nanoemulsion with carbogen breathing could increase cisplatin-mediated apoptosis of cancer cells and inhibited tumor growth at a low dose of cisplatin (1 mg/kg) treatment. Furthermore, the treatment did not induce nephrotoxicity.

Conclusions: Preoxygenated PFOB nanoemulsion with carbogen breathing can effectively increase tumor oxygenation, which has a great potential to prevent/overcome hypoxia-induced chemotherapy resistance. In addition, optical imaging with intratumoral injection of the hypoxia probe was an efficient tool to monitor tumor oxygenation dynamics during PFOB administration, providing better understanding on oxygenation effects under different protocols.