Development and Evaluation of Perfluorocarbon Nanobubbles for Apomorphine Delivery

Modifications of Nanobubble Therapy for Cancer Treatment

Cancer development is related to genetic mutations in primary cells, where 5-10% of all cancers are derived from acquired genetic defects, most of which are a consequence of the environment and lifestyle. As it turns out, over half of cancer deaths are due to the generation of drug resistance. The local delivery of chemotherapeutic drugs may reduce their toxicity by increasing their therapeutic dose at targeted sites and by decreasing the plasma levels of circulating drugs. Nanobubbles have attracted much attention as an effective drug distribution system due to their non-invasiveness and targetability. This review aims to present the characteristics of nanobubble systems and their efficacy within the biomedical field with special emphasis on cancer treatment. In vivo and in vitro studies on cancer confirm nanobubbles' ability and good blood capillary perfusion; however, there is a need to define their safety and side effects in clinical trials.

A Systematic Study on Long-acting Nanobubbles: Current Advancement and Prospects on Theranostic Properties

Delivery of diagnostic drugs via nanobubbles (NBs) has shown to be an emerging field of study. Due to their small size, NBs may more easily travel through constricted blood vessels and precisely target certain bodily parts. NB is considered the major treatment for cancer treatment and other diseases which are difficult to diagnose. The field of NBs is dynamic and continues to grow as researchers discover new properties and seek practical applications in various fields. The predominant usage of NBs in novel drug delivery is to enhance the bioavailability, and controlled drug release along with imaging properties NBs are important because they may change interfacial characteristics including surface force, lubrication, and absorption. The quick diffusion of gas into the water was caused by a hypothetical film that was stimulated and punctured by a strong acting force at the gas/water contact of the bubble. In this article, various prominent aspects of NBs have been discussed, along with the long-acting nature, and the theranostical aspect which elucidates the potential marketed drugs along with clinical trial products. The article also covers quality by design aspects, different production techniques that enable method-specific therapeutic applications, increasing the floating time of the bubble, and refining its properties to enhance the prepared NB's quality. NB containing both analysis and curing properties makes it special from other nano-carriers. This work includes all the possible methods of preparing NB, its application, all marketed drugs, and products in clinical trials.

Next-Generation Colloidal Materials for Ultrasound Imaging Applications

Ultrasound has important applications, predominantly in the field of diagnostic imaging. Presently, colloidal systems such as microbubbles, phase-change emulsion droplets and particle systems with acoustic properties and multiresponsiveness are being developed to address typical issues faced when using commercial ultrasound contrast agents, and to extend the utility of such systems to targeted drug delivery and multimodal imaging. Current technologies and increasing research data on the chemistry, physics and materials science of new colloidal systems are also leading to the development of more complex, novel and application-specific colloidal assemblies with ultrasound contrast enhancement and other properties, which could be beneficial for multiple biomedical applications, especially imaging-guided treatments. In this article, we review recent developments in new colloids with applications that use ultrasound contrast enhancement. This work also highlights the emergence of colloidal materials fabricated from or modified with biologically derived and bio-inspired materials, particularly in the form of biopolymers and biomembranes. Challenges, limitations, potential developments and future directions of these next-generation colloidal systems are also presented and discussed.

Biomaterials and stem cells as drug/gene-delivery vehicles for Parkinson's treatment: an update

By introducing biomaterials and stem cells into Parkinson's disease (PD), therapeutic approaches have led to promising results due to facilitating brain targeting and blood-brain barrier permeation of the drugs and genes. Here, after reviewing the most recent drug- and gene-delivery vehicles including liposomes, exosomes, natural/synthetic polymeric particles/fibers, metallic/ceramic nanoparticles and microbubbles, used for Parkinson's disease treatment, the effect of stem cells as a reservoir of neurotrophic factors and exosomes is provided.

Nanomedicine against Alzheimer's and Parkinson's Disease

Alzheimer's and Parkinson's are the two most rampant neurodegenerative disorders worldwide. Existing treatments have a limited effect on the pathophysiology but are unable to fully arrest the progression of the disease. This is due to the inability of these therapeutic molecules to efficiently cross the blood-brain barrier. We discuss how nanotechnology has enabled researchers to develop novel and efficient nano-therapeutics against these diseases. The development of nanotized drug delivery systems has permitted an efficient, site-targeted, and controlled release of drugs in the brain, thereby presenting a revolutionary therapeutic approach. Nanoparticles are also being thoroughly studied and exploited for their role in the efficient and precise diagnosis of neurodegenerative conditions. We summarize the role of different nano-carriers and RNAi-conjugated nanoparticle-based therapeutics for their efficacy in pre-clinical studies. We also discuss the challenges underlying the use of nanomedicine with a focus on their route of administration, concentration, metabolism, and any toxic effects for successful therapeutics in these diseases.

Importance of Nanoparticles for the Delivery of Antiparkinsonian Drugs

Parkinson's disease (PD) affects around ten million people worldwide and is considered the second most prevalent neurodegenerative disease after Alzheimer's disease. In addition, there is a higher risk incidence in the elderly population. The main PD hallmarks include the loss of dopaminergic neurons and the development of Lewy bodies. Unfortunately, motor symptoms only start to appear when around 50-70% of dopaminergic neurons have already been lost. This particularly poses a huge challenge for early diagnosis and therapeutic effectiveness. Actually, pharmaceutical therapy is able to relief motor symptoms, but as the disease progresses motor complications and severe side-effects start to appear. In this review, we explore the research conducted so far in order to repurpose drugs for PD with the use of nanodelivery systems, alternative administration routes, and nanotheranostics. Overall, studies have demonstrated great potential for these nanosystems to target the brain, improve drug pharmacokinetic profile, and decrease side-effects.

Applications of Ultrasound to Stimulate Therapeutic Revascularization

Many pathological conditions are characterized or caused by the presence of an insufficient or aberrant local vasculature. Thus, therapeutic approaches aimed at modulating the caliber and/or density of the vasculature by controlling angiogenesis and arteriogenesis have been under development for many years. As our understanding of the underlying cellular and molecular mechanisms of these vascular growth processes continues to grow, so too do the available targets for therapeutic intervention. Nonetheless, the tools needed to implement such therapies have often had inherent weaknesses (i.e., invasiveness, expense, poor targeting, and control) that preclude successful outcomes. Approximately 20 years ago, the potential for using ultrasound as a new tool for therapeutically manipulating angiogenesis and arteriogenesis began to emerge. Indeed, the ability of ultrasound, especially when used in combination with contrast agent microbubbles, to mechanically manipulate the microvasculature has opened several doors for exploration. In turn, multiple studies on the influence of ultrasound-mediated bioeffects on vascular growth and the use of ultrasound for the targeted stimulation of blood vessel growth via drug and gene delivery have been performed and published over the years. In this review article, we first discuss the basic principles of therapeutic ultrasound for stimulating angiogenesis and arteriogenesis. We then follow this with a comprehensive cataloging of studies that have used ultrasound for stimulating revascularization to date. Finally, we offer a brief perspective on the future of such approaches, in the context of both further research development and possible clinical translation.

Nano-lipospheres as acoustically active ultrasound contrast agents: evolving tumor imaging and therapy technique

Applying nanobubbles (NBs) for contrast-enhanced ultrasound imaging has received increased attention. NBs are biocompatible, multifunctional, theranostic agents. Their properties of high echogenicity and stability create an agent suitable for ultrasonography diagnosis. Their favorable properties of size, in vivo stability, and ease of modification are being exploited to implement a theranostic platform for cancer treatment. The considerable development offers the potential to overcome drug resistance and adverse side effects that are associated with traditional chemotherapy. This review outlines the principles of ultrasonography and angiogenesis. Microbubbles and micelles are also discussed to underline the superior capabilities of NBs for the application. NBs could passively accumulate to tumor tissue by enhanced permeability and retention effect. In addition, it can also achieve the active transportation by surface modification. Active targeting modalities and stimuli-responsive drug delivery modifications generate a therapeutic vehicle. The cytotoxicity of NBs formulations, multimodal imaging capability, active targeting mechanisms, and drug delivery methods are highlighted to confirm the NB as a vehicle for targeted treatment and enhanced ultrasound imaging.

From Micro- to Nano-Multifunctional Theranostic Platform: Effective Ultrasound Imaging Is Not Just a Matter of Scale

Ultrasound Contrast Agents (UCAs) consisting of gas-filled-coated Microbubbles (MBs) with diameters between 1 and 10 µm have been used for a number of decades in diagnostic imaging. In recent years, submicron contrast agents have proven to be a viable alternative to MBs for ultrasound (US)-based applications for their capability to extravasate and accumulate in the tumor tissue via the enhanced permeability and retention effect. After a short overview of the more recent approaches to ultrasound-mediated imaging and therapeutics at the nanoscale, phase-change contrast agents (PCCAs), which can be phase-transitioned into highly echogenic MBs by means of US, are here presented. The phenomenon of acoustic droplet vaporization (ADV) to produce bubbles is widely investigated for both imaging and therapeutic applications to develop promising theranostic platforms.

Preparation and characterization of a novel silicon-modified nanobubble

Nanobubbles (NBs) opened a new field of ultrasound imaging. There is still no practical method to control the diameter of bubbles. In this study, we developed a new method to control the size by incorporating of silicon hybrid lipids into the bubble membrane. The range of particle size of resulting NBs is between 523.02 ± 46.45 to 857.18 ± 82.90, smaller than the conventional microbubbles. The size of resulting NBs increased with the decrease in amount of silicon hybrid lipids, indicating the diameter of NBs can be regulated through modulating the ratio of silicon hybrid lipids in the bubble shell. Typical harmonic signals could be detected. The in vitro and in vivo ultrasound imaging experiments demonstrated these silicon-modified NBs had significantly improved ultrasound contrast enhancement abilities. Cytotoxicity assays revealed that these NBs had no obvious cytotoxicity to the 293 cell line at the tested bubble concentration. Our results showed that the novel NBs could use as nanoscale ultrasound contrast agents, providing the foundation for NBs in future applications including contrast-enhanced imaging and drug/gene delivery.

Stably engineered nanobubbles and ultrasound - An effective platform for enhanced macromolecular delivery to representative cells of the retina

Herein we showcase the potential of ultrasound-responsive nanobubbles in enhancing macromolecular permeation through layers of the retina, ultimately leading to significant and direct intracellular delivery; this being effectively demonstrated across three relevant and distinct retinal cell lines. Stably engineered nanobubbles of a highly homogenous and echogenic nature were fully characterised using dynamic light scattering, B-scan ultrasound and transmission electron microscopy (TEM). The nanobubbles appeared as spherical liposome-like structures under TEM, accompanied by an opaque luminal core and darkened corona around their periphery, with both features indicative of efficient gas entrapment and adsorption, respectively. A nanobubble +/- ultrasound sweeping study was conducted next, which determined the maximum tolerated dose for each cell line. Detection of underlying cellular stress was verified using the biomarker heat shock protein 70, measured before and after treatment with optimised ultrasound. Next, with safety to nanobubbles and optimised ultrasound demonstrated, each human or mouse-derived cell population was incubated with biotinylated rabbit-IgG in the presence and absence of ultrasound +/- nanobubbles. Intracellular delivery of antibody in each cell type was then quantified using Cy3-streptavidin. Nanobubbles and optimised ultrasound were found to be negligibly toxic across all cell lines tested. Macromolecular internalisation was achieved to significant, yet varying degrees in all three cell lines. The results of this study pave the way towards better understanding mechanisms underlying cellular responsiveness to ultrasound-triggered drug delivery in future ex vivo and in vivo models of the posterior eye.

Recent advances in ultrasound-based diagnosis and therapy with micro- and nanometer-sized formulations

Ultrasound (US) is one of the most frequently used imaging methods in the clinic. The broad spectrum of its applications can be increased by the use of gas-filled microbubbles (MB) as ultrasound contrast agents (UCA). In recent years, also nanoscale UCA like nanobubbles (NB), echogenic liposomes (ELIP) and nanodroplets have been developed, which in contrast to MB, are able to extravasate from the vessels into the tissue. New disease-specific UCA have been designed for the assessment of tissue biomarkers and advanced US to a molecular imaging modality. For this purpose, specific binding moieties were coupled to the UCA surface. The vascular endothelial growth factor receptor-2 (VEGFR-2) and P-/E-selectin are prominent examples of molecular US targets to visualize tumor blood vessels and inflammatory diseases, respectively. Besides their application in contrast-enhanced imaging, MB can also be employed for drug delivery to tumors and across the blood-brain barrier (BBB). This review summarizes the development of micro- and nanoscaled UCA and highlights recent advances in diagnostic and therapeutic applications, which are ready for translation into the clinic.

Generation and Stability of Bulk Nanobubbles

Recently, extremely small bubbles, referred to as nanobubbles, have drawn increased attention due to their novel properties and great potential for various applications. In this study, a novel method for the generation of bulk nanobubbles (BNBs) was introduced, and stability of fabricated BNBs was investigated. BNBs were created from CO₂ gas with a mixing method; the chemical identity and phase state of these bubbles can be determined via infrared spectroscopy. The presence of BNBs was observed with a nanoparticle tracking analysis (NTA). The ATR-FTIR spectra of BNBs indicate that the BNBs were filled with CO₂ gas. Furthermore, the BNB concentration and its ζ-potential were about 2.94 × 10⁸ particles/mL and -20 mV, respectively (24 h after BNB generation with a mixing time of 120 min). This indicates the continued existence and stability of BNBs in water for an extended period of time.

Nanomedicine to Overcome Current Parkinson's Treatment Liabilities: A Systematic Review

Nanoparticles might be produced and manipulated to present a large spectrum of properties. The physicochemical features of the engineered nanomaterials confer to them different features, including the ability to cross the blood-brain barrier. The main objective of this review is to present the state-of-art research in nano manipulation concerning Parkinson's disease (PD). In the past few years, the association of drugs with nanoparticles solidly improved treatment outcomes. We systematically reviewed 28 studies, describing their potential contributions regarding the role of nanomedicine to increase the efficacy of known pharmacological strategies for PD treatment. Data from animal models resulted in the (i) improvement of pharmacological properties, (ii) more stable drug concentrations, (iii) longer half-live and (iv) attenuation of pharmacological adverse effects. As this approach is recent, with many of the described works being published less than 5 years ago, the expectancy is that this knowledge gives support to an improvement in the current clinical methods to the management of PD and other neurodegenerative diseases.

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.

Drug Delivery Systems for Imaging and Therapy of Parkinson's Disease

BACKGROUND

Although a variety of therapeutic approaches are available for the treatment of Parkinson's disease, challenges limit effective therapy. Among these challenges are delivery of drugs through the blood brain barier to the target brain tissue and the side effects observed during long term administration of antiparkinsonian drugs. The use of drug delivery systems such as liposomes, niosomes, micelles, nanoparticles, nanocapsules, gold nanoparticles, microspheres, microcapsules, nanobubbles, microbubbles and dendrimers is being investigated for diagnosis and therapy.

METHODS

This review focuses on formulation, development and advantages of nanosized drug delivery systems which can penetrate the central nervous system for the therapy and/or diagnosis of PD, and highlights future nanotechnological approaches.

RESULTS

It is esential to deliver a sufficient amount of either therapeutic or radiocontrast agents to the brain in order to provide the best possible efficacy or imaging without undesired degradation of the agent. Current treatments focus on motor symptoms, but these treatments generally do not deal with modifying the course of Parkinson's disease. Beyond pharmacological therapy, the identification of abnormal proteins such as α -synuclein, parkin or leucine-rich repeat serine/threonine protein kinase 2 could represent promising alternative targets for molecular imaging and therapy of Parkinson's disease.

CONCLUSION

Nanotechnology and nanosized drug delivery systems are being investigated intensely and could have potential effect for Parkinson's disease. The improvement of drug delivery systems could dramatically enhance the effectiveness of Parkinson's Disease therapy and reduce its side effects.

The Optimized Fabrication of Nanobubbles as Ultrasound Contrast Agents for Tumor Imaging

Nanobubbles, which have the potential for ultrasonic targeted imaging and treatment in tumors, have been a research focus in recent years. With the current methods, however, the prepared uniformly sized nanobubbles either undergo post-formulation manipulation, such as centrifugation, after the mixture of microbubbles and nanobubbles, or require the addition of amphiphilic surfactants. These processes influence the nanobubble stability, possibly create material waste, and complicate the preparation process. In the present work, we directly prepared uniformly sized nanobubbles by modulating the thickness of a phospholipid film without the purification processes or the addition of amphiphilic surfactants. The fabricated nanobubbles from the optimal phospholipid film thickness exhibited optimal physical characteristics, such as uniform bubble size, good stability, and low toxicity. We also evaluated the enhanced imaging ability of the nanobubbles both in vitro and in vivo. The in vivo enhancement intensity in the tumor was stronger than that of SonoVue after injection (UCA; 2 min: 162.47 ± 8.94 dB vs. 132.11 ± 5.16 dB, P < 0.01; 5 min: 128.38.47 ± 5.06 dB vs. 68.24 ± 2.07 dB, P < 0.01). Thus, the optimal phospholipid film thickness can lead to nanobubbles that are effective for tumor imaging.

Effects of the microbubble shell physicochemical properties on ultrasound-mediated drug delivery to the brain

Lipid-shelled microbubbles have been used in ultrasound-mediated drug delivery. The physicochemical properties of the microbubble shell could affect the delivery efficiency since they determine the microbubble mechanical properties, circulation persistence, and dissolution behavior during cavitation. Therefore, the aim of this study was to investigate the shell effects on drug delivery efficiency in the brain via blood-brain barrier (BBB) opening in vivo using monodisperse microbubbles with different phospholipid shell components. The physicochemical properties of the monolayer were varied by using phospholipids with different hydrophobic chain lengths (C16, C18, and C24). The dependence on the molecular size and acoustic energy (both pressure and pulse length) were investigated. Our results showed that a relatively small increase in the microbubble shell rigidity resulted in a significant increase in the delivery of 40-kDa dextran, especially at higher pressures. Smaller (3kDa) dextran did not show significant difference in the delivery amount, suggesting that the observed shell effect was molecular size-dependent. In studying the impact of acoustic energy on the shell effects, it was found that they occurred most significantly at pressures causing microbubble destruction (450kPa and 600kPa); by increasing the pulse length to deliver the 40-kDa dextran, the difference between C16 and C18 disappeared while C24 still achieved the highest delivery efficiency. These indicated that the acoustic energy could be used to modulate the shell effects. The acoustic cavitation emission revealed the physical mechanisms associated with different shells. Overall, lipid-shelled microbubbles with long hydrophobic chain length could achieve high delivery efficiency for larger molecules especially with high acoustic energy. Our study, for the first time, offered evidence directly linking the microbubble monolayer shell with their efficacy for drug delivery in vivo.

Pharmacokinetics of quercetin-loaded nanodroplets with ultrasound activation and their use for bioimaging

Bubble formulations have both diagnostic and therapeutic applications. However, research on nanobubbles/nanodroplets remains in the initial stages. In this study, a nanodroplet formulation was prepared and loaded with a novel class of chemotherapeutic drug, ie, quercetin, to observe its pharmacokinetic properties and ultrasonic bioimaging of specific sites, namely the abdominal vein and bladder. Four parallel groups were designed to investigate the effects of ultrasound and nanodroplets on the pharmacokinetics of quercetin. These groups were quercetin alone, quercetin triggered with ultrasound, quercetin-encapsulated in nanodroplets, and quercetin encapsulated in nanodroplets triggered with ultrasound. Spherical vesicles with a mean diameter of 280 nm were formed, and quercetin was completely encapsulated within. In vivo ultrasonic imaging confirmed that the nanodroplets could be treated by ultrasound. The results indicate that the initial 5-minute serum concentration, area under the concentration–time curve, elimination half-life, and clearance of quercetin were significantly enhanced by nanodroplets with or without ultrasound.

Assessment of the biodistribution of an [(18) F]FDG-loaded perfluorocarbon double emulsion using dynamic micro-PET in rats

Perfluorocarbon (PFC) double emulsions loaded with a water-soluble, therapeutic agent can be triggered by ultrasound in a process known as acoustic droplet vaporization. Elucidating the stability and biodistribution of these sonosensitive vehicles and encapsulated agents is critical in developing targeted drug delivery strategies using ultrasound. [(18) F]fluorodeoxyglucose (FDG) was encapsulated in a PFC double emulsion and the in vitro diffusion of FDG was assessed using a Franz diffusion cell. Using dynamic micro-positron emission tomography and direct tissue sampling, the biodistribution of FDG administered as a solution (i.e. non-emulsified) or as an emulsion was studied in Fisher 344 rats (n = 6) bearing subcutaneous 9L gliosarcoma. Standardized uptake values (SUVs) and area under the curve of the SUV (AUCSUV ) of FDG were calculated for various tissues. The FDG flux from the emulsion decreased by up to a factor of 6.9 compared with the FDG solution. FDG uptake, calculated from the AUCSUV , decreased by 36% and 44% for brain and tumor, respectively, when comparing FDG solution vs FDG emulsion (p < 0.01). Decreases in AUCSUV in highly metabolic tissues such as brain and tumor demonstrated retention of FDG within the double emulsion. No statistically significant differences in lung AUCSUV were observed, suggesting minimal accumulation of the emulsion in the pulmonary capillary bed. The liver AUCSUV increased by 356% for the FDG emulsion, thus indicating significant hepatic retention of the emulsion.

Cationic surfactants in the form of nanoparticles and micelles elicit different human neutrophil responses: a toxicological study

Cationic surfactants are an ingredient commonly incorporated into nanoparticles for clinical practicability; however, the toxicity of cationic surfactants in nanoparticles is not fully elucidated. We aimed to evaluate the inflammatory responses of cationic nanobubbles and micelles in human neutrophils. Soyaethyl morpholinium ethosulfate (SME) and hexadecyltrimethyl-ammonium bromide (CTAB) are the two cationic surfactants employed in this study. The zeta potential of CTAB nanobubbles was 80 mV, which was the highest among all formulations. Nanobubbles, without cationic surfactants, showed no cytotoxic effects on neutrophils in terms of inflammatory responses. Cationic nanobubbles caused a concentration-dependent cytotoxicity of degranulation (elastase release) and membrane damage (release of lactate dehydrogenase, LDH). Among all nanoparticles and micelles, CTAB-containing nanosystems showed the greatest inflammatory responses. A CTAB nanobubble diluent (1/150) increased the LDH release 80-fold. Propidium iodide staining and scanning electron microscopy (SEM) verified cell death and morphological change of neutrophils treated by CTAB nanobubbles. SME, in a micelle form, strengthened the inflammatory response more than SME-loaded nanobubbles. Membrane interaction and subsequent Ca(2+) influx were the mechanisms that triggered inflammation. The information obtained from this work is beneficial in designing nanoparticulate formulations for balancing clinical activity and toxicity.

Acoustic droplet-hydrogel composites for spatial and temporal control of growth factor delivery and scaffold stiffness

Wound healing is regulated by temporally and spatially restricted patterns of growth factor signaling, but there are few delivery vehicles capable of the "on-demand" release necessary for recapitulating these patterns. Recently we described a perfluorocarbon double emulsion that selectively releases a protein payload upon exposure to ultrasound through a process known as acoustic droplet vaporization (ADV). In this study, we describe a delivery system composed of fibrin hydrogels doped with growth factor-loaded double emulsion for applications in tissue regeneration. Release of immunoreactive basic fibroblast growth factor (bFGF) from the composites increased up to 5-fold following ADV and delayed release was achieved by delaying exposure to ultrasound. Releasates of ultrasound-treated materials significantly increased the proliferation of endothelial cells compared to sham controls, indicating that the released bFGF was bioactive. ADV also triggered changes in the ultrastructure and mechanical properties of the fibrin as bubble formation and consolidation of the fibrin in ultrasound-treated composites were accompanied by up to a 22-fold increase in shear stiffness. ADV did not reduce the viability of cells suspended in composite scaffolds. These results demonstrate that an acoustic droplet-hydrogel composite could have broad utility in promoting wound healing through on-demand control of growth factor release and/or scaffold architecture.

Toxicological effects of cationic nanobubbles on the liver and kidneys: biomarkers for predicting the risk

Nanobubbles with acoustical activity are used as both diagnostic and therapeutic carriers for detecting and treating diseases. We aimed to prepare nanobubbles and assess toxic responses to them in the liver and kidneys. The cytotoxicity of nanobubbles was determined by examining the viability of liver (HepG2) and kidney (293T) cell lines after a 24-h treatment at various concentrations (0.01-2%). Toxic effects of different formulations were compared by determining functional markers such as γ-glutamyl transferase (γ-GT) and blood urea nitrogen (BUN) after intravenous administration of nanobubbles. Cationic nanobubbles caused concentration-dependent cytotoxicity against cultured cells with a more significant effect in the liver than in the kidneys. A significant reduction of viability was revealed at a concentration as low as 0.1%. Cational systems with soyaethyl morpholinium ethosulfate (SME) exhibited the greatest γ-GT level at 6-fold higher than the control. Immunohistochemistry detected liver fibrosis and inflammation with nanobubbles treatment, especially SME-containing ones at higher doses. According to plasma proteomic profiles, gelsolin and fetuin-B were significantly downregulated 3-fold in the high-dose SME-treated group. Transthyretin decreased by 6-fold in this group. The fibrinogen gamma chain expression was highly elevated. The results suggest that these protein biomarkers are sensitive for assessing the risk of nanobubble exposure. This study is the first to systematically evaluate the possible toxicity of nanobubbles in the liver and kidneys.

Theranostic liposomes loaded with quantum dots and apomorphine for brain targeting and bioimaging

Quantum dots (QDs) and apomorphine were incorporated into liposomes to eliminate uptake by the liver and enhance brain targeting. We describe the preparation, physicochemical characterization, in vivo bioimaging, and brain endothelial cell uptake of the theranostic liposomes. QDs and the drug were mainly located in the bilayer membrane and inner core of the liposomes, respectively. Spherical vesicles with a mean diameter of ~140 nm were formed. QDs were completely encapsulated by the vesicles. Nearly 80% encapsulation percentage was achieved for apomorphine. A greater fluorescence intensity was observed in mouse brains treated with liposomes compared to free QDs. This result was further confirmed by ex vivo imaging of the organs. QD uptake by the heart and liver was reduced by liposomal incorporation. Apomorphine accumulation in the brain increased by 2.4-fold after this incorporation. According to a hyperspectral imaging analysis, multifunctional liposomes but not the aqueous solution carried QDs into the brain. Liposomes were observed to have been efficiently endocytosed into bEND3 cells. The mechanisms involved in the cellular uptake were clathrin- and caveola-mediated endocytosis, which were energy-dependent. To the best of our knowledge, our group is the first to develop liposomes with a QD-drug hybrid for the aim of imaging and treating brain disorders.

Combined strategies of apomorphine diester prodrugs and nanostructured lipid carriers for efficient brain targeting

Our aim is to develop nanostructured lipid carriers (NLCs) for loading the apomorphine diester prodrugs, diacetyl apomorphine (DAA) and diisobutyryl apomorphine (DIA), into the brain. NLCs were prepared using sesame oil/cetyl palmitate as the lipid matrices. Experiments were performed with the objective of evaluating the physicochemical characteristics, drug release, safety and brain-targeting efficacy of the NLCs. The size of regular NLCs (N-NLCs) was 214 nm. The addition of Forestall (FE) and polyethylene glycol (PEG) to the NLCs (P-NLCs) increased the particle diameter to 250 nm. The zeta potentials of N-NLCs and P-NLCs were respectively shown to be - 21 and 48 mV. Diester prodrugs were more lipophilic and more chemically stable than the parent apomorphine. The hydrolysis study indicated that the prodrugs underwent bioconversion in plasma and brain extract, with DAA exhibiting faster degradation than DIA. Sustained release was achieved through the synergistic effect of integrating strategies of prodrugs and NLCs, with the longer carbon chain showing the slower release (DIA < DAA). None of the NLCs tested here exhibited a toxicity problem according to the examination of neutrophil lactate dehydrogenase (LDH) release and hemolysis. Results of a bioimaging study in mice showed that P-NLCs largely accumulated in the brain. The distribution duration of the fluorescent dye in the brain region was also prolonged by the nanocarriers.

A tissue-mimicking ultrasound test object using droplet vaporization to create point targets

Ultrasound test objects containing reference point targets could be useful for evaluating ultrasound systems and phase aberration correction methods. Polyacrylamide gels containing albumin-stabilized droplets (3.6 μm mean diameter) of dodecafluoropentane (DDFP) are being developed for this purpose. Perturbation by ultrasound causes spontaneous vaporization of the superheated droplets to form gas bubbles, a process termed acoustic droplet vaporization (ADV). The resulting bubbles (20 to 160 μmm diameter) are small compared with acoustic wavelengths in diagnostic ultrasound and are theoretically suitable for use as point targets (phase errors < 20° for typical f-numbers). Bubbles distributed throughout the material are convenient for determining the point spread function in an imaging plane or volume. Cooling the gel causes condensation of the DDFP droplets, which may be useful for storage. Studying ADV in such viscoelastic media could provide insight into potential bioeffects from rapid bubble formation.

Functionalized lipid nanoparticles-cellophane hybrid films for molecular delivery: preparation, physicochemical characterization, and stability

Lipid nanoparticles functionalized with the sunscreen 2,4-dihydroxybenzophenone (FLNPs) have been prepared by the ultrasound method and embedded in highly hydrophilic cellophane supports (regenerated cellulose, RC), creating biocompatible hybrid films (RC-FLNPs samples). The morphology of the FLNPs was studied with transmission microscopy, whereas the surface and interior chemical composition was analyzed by micro-Raman spectroscopy. RC-FLNPs hybrid films were prepared from the immersion of two cellophane supports with different thicknesses and water uptake properties (RC-3 and RC-6) in an aqueous dispersion of FLNPs. The structure of this hybrid material was visualized with bright-field microscopy, which clearly showed the inclusion of the FLNPs in the cellophane matrix. The stability of the RC-FLNPs films with respect to both aqueous environments and time was demonstrated by NaCl diffusion measurements. The reduction in the diffusion coefficient through the nanoparticle-modified films compared with the original supports confirms the presence of nanoparticles for concentration gradients of up to 0.4 M (osmotic pressure around 10 bar), indicating the stability of the hybrid hydrophilic material, even in aqueous environments and under matter flow conditions for a period of 21 days.

Delivery of water-soluble drugs using acoustically triggered perfluorocarbon double emulsions

PURPOSE

Ultrasound can be used to release a therapeutic payload encapsulated within a perfluorocarbon (PFC) emulsion via acoustic droplet vaporization (ADV), a process whereby the PFC phase is vaporized and the agent is released. ADV-generated microbubbles have been previously used to selectively occlude blood vessels in vivo. The coupling of ADV-generated drug delivery and occlusion has therapeutically synergistic potentials.

METHODS

Micron-sized, water-in-PFC-in-water (W(1)/PFC/W(2)) emulsions were prepared in a two-step process using perfluoropentane (PFP) or perfluorohexane (PFH) as the PFC phase. Fluorescein or thrombin was contained in the W(1) phase.

RESULTS

Double emulsions containing fluorescein in the W(1) phase displayed a 5.7±1.4-fold and 8.2±1.3-fold increase in fluorescein mass flux, as measured using a Franz diffusion cell, after ADV for the PFP and PFH emulsions, respectively. Thrombin was stably retained in four out of five double emulsions. For three out of five formulations tested, the clotting time of whole blood decreased, in a statistically significant manner (p < 0.01), when incubated with thrombin-loaded emulsions exposed to ultrasound compared to emulsions not exposed to ultrasound.

CONCLUSIONS

ADV can be used to spatially and temporally control the delivery of water-soluble compounds formulated in PFC double emulsions. Thrombin release could extend the duration of ADV-generated, microbubble occlusions.

Physicochemical characterization and in vivo bioluminescence imaging of nanostructured lipid carriers for targeting the brain: apomorphine as a model drug

Nanostructured lipid carriers (NLCs) were prepared to investigate whether the duration of brain targeting and accumulation of drugs in the brain can be improved by intravenous delivery. NLCs were developed using cetyl palmitate as the lipid matrix, squalene as the cationic surfactant, and Pluronic F68, polysorbate 80 and polyethylene glycol as the interfacial additives. Solid lipid nanoparticles (SLNs) and lipid emulsions (LEs) were also prepared for comparison. An anti-Parkinson's drug, apomorphine, was used as the model drug. Nuclear magnetic resonance and differential scanning calorimetry showed possible interactions between the solid and liquid lipids in the inner core. The lipid nanoparticles with different compositions were characterized by mean size, zeta potential, apomorphine encapsulation and in vitro drug release. NLCs were 370-430 nm in size, which was between the sizes of the SLNs and LEs. A cationic surfactant was used to produce a positive surface charge of 42-50 mV. The base form of apomorphine was successfully entrapped by NLCs with an entrapment percentage of > 60%. The loading of apomorphine in nanoparticles resulted in a slower release behavior compared to the aqueous solution, with LEs showing the lowest release. In vivo real-time bioluminescence imaging of the rat brain revealed that NLCs could be targeted, through certain vessels, to selected brain regions. This effect was further confirmed by imaging the entire brain and brain slices. The results indicated that NLCs with moderate additives are a promising controlled-release and drug-targeting system.

Nanoparticles as contrast agents for in-vivo bioimaging: current status and future perspectives

Nanoparticle-based contrast agents are quickly becoming valuable and potentially transformative tools for enhancing medical diagnostics for a wide range of in-vivo imaging modalities. Compared with conventional molecular-scale contrast agents, nanoparticles (NPs) promise improved abilities for in-vivo detection and potentially enhanced targeting efficiencies through longer engineered circulation times, designed clearance pathways, and multimeric binding capacities. However, NP contrast agents are not without issues. Difficulties in minimizing batch-to-batch variations and problems with identifying and characterizing key physicochemical properties that define the in-vivo fate and transport of NPs are significant barriers to the introduction of new NP materials as clinical contrast agents. This manuscript reviews the development and application of nanoparticles and their future potential to advance current and emerging clinical bioimaging techniques. A focus is placed on the application of solid, phase-separated materials, for example metals and metal oxides, and their specific application as contrast agents for in-vivo near-infrared fluorescence (NIRF) imaging, magnetic resonance imaging (MRI), positron emission tomography (PET), computed tomography (CT), ultrasound (US), and photoacoustic imaging (PAI). Clinical and preclinical applications of NPs are identified for a broad spectrum of imaging applications, with commentaries on the future promise of these materials. Emerging technologies, for example multifunctional and theranostic NPs, and their potential for clinical advances are also discussed.

Delivery of chlorambucil using an acoustically-triggered perfluoropentane emulsion

Ultrasound-mediated delivery systems have mainly focused on microbubble contrast agents as carriers of drugs or genetic material. This study uses micron-sized, perfluoropentane (PFP) emulsions as carriers of chlorambucil (CHL), a lipophilic chemotherapeutic. The release of CHL is achieved via acoustic droplet vaporization (ADV), whereby the superheated emulsion is converted into gas bubbles using ultrasound. Emulsions were made using an albumin shell and soybean oil as the CHL carrier. The ratio of the PFP to soybean oil phases in the droplets and the fraction of droplets that vaporize per ultrasound exposure were shown to correlate with droplet diameter. A 60-min incubation with the CHL-loaded emulsion caused a 46.7% cellular growth inhibition, whereas incubation with the CHL-loaded emulsion that was exposed to ultrasound at 6.3 MHz caused an 84.3% growth inhibition. This difference was statistically significant (p < 0.01), signifying that ADV can be used as a method to substantially enhance drug delivery.

Formulation and characterization of echogenic lipid-Pluronic nanobubbles

The advent of microbubble contrast agents has enhanced the capabilities of ultrasound as a medical imaging modality and stimulated innovative strategies for ultrasound-mediated drug and gene delivery. While the utilization of microbubbles as carrier vehicles has shown encouraging results in cancer therapy, their applicability has been limited by a large size which typically confines them to the vasculature. To enhance their multifunctional contrast and delivery capacity, it is critical to reduce bubble size to the nanometer range without reducing echogenicity. In this work, we present a novel strategy for formulation of nanosized, echogenic lipid bubbles by incorporating the surfactant Pluronic, a triblock copolymer of ethylene oxide copropylene oxide coethylene oxide into the formulation. Five Pluronics (L31, L61, L81, L64 and P85) with a range of molecular weights (M(w): 1100 to 4600 Da) were incorporated into the lipid shell either before or after lipid film hydration and before addition of perfluorocarbon gas. Results demonstrate that Pluronic-lipid interactions lead to a significantly reduced bubble size. Among the tested formulations, bubbles made with Pluronic L61 were the smallest with a mean hydrodynamic diameter of 207.9 +/- 74.7 nm compared to the 880.9 +/- 127.6 nm control bubbles. Pluronic L81 also significantly reduced bubble size to 406.8 +/- 21.0 nm. We conclude that Pluronic is effective in lipid bubble size control, and Pluronic M(w), hydrophilic-lipophilic balance (HLB), and Pluronic/lipid ratio are critical determinants of the bubble size. Most importantly, our results have shown that although the bubbles are nanosized, their stability and in vitro and in vivo echogenicity are not compromised. The resulting nanobubbles may be better suited for contrast enhanced tumor imaging and subsequent therapeutic delivery.