Safety and efficacy of a new transpulmonary echo contrast agent in echocardiographic studies in patients

A Comprehensive Review of Nanoparticles: From Classification to Application and Toxicity

Nanoparticles are structures that possess unique properties with high surface area-to-volume ratio. Their small size, up to 100 nm, and potential for surface modifications have enabled their use in a wide range of applications. Various factors influence the properties and applications of NPs, including the synthesis method and physical attributes such as size and shape. Additionally, the materials used in the synthesis of NPs are primary determinants of their application. Based on the chosen material, NPs are generally classified into three categories: organic, inorganic, and carbon-based. These categories include a variety of materials, such as proteins, polymers, metal ions, lipids and derivatives, magnetic minerals, and so on. Each material possesses unique attributes that influence the activity and application of the NPs. Consequently, certain NPs are typically used in particular areas because they possess higher efficiency along with tenable toxicity. Therefore, the classification and the base material in the NP synthesis hold significant importance in both NP research and application. In this paper, we discuss these classifications, exemplify most of the major materials, and categorize them according to their preferred area of application. This review provides an overall review of the materials, including their application, and toxicity.

Enhanced Glioblastoma Selectivity of Harmine via the Albumin Carrier

Glioblastoma, the most common tumor in the brain, has witnessed very little clinical progress over the last decades. Exploring and discovering new therapeutic strategies for glioblastoma has become a critical problem. Harmine (HM), belonging to the beta-carboline alkaloid, is a natural product and isolated from the seeds of Peganum harmala L., which own notable antitumor activity in vitro. However, the poor water solubility and less selectivity of HM severely limit its clinical use. For enhancing its selective ability to tumor cells, we fabricated a kind of protein nanoparticles (BSA-HM NPs), composed of the modified bovine serum albumin (BSA) and HM. It was substantiated through in vitro and in vivo experiment that BSA-HM NPs could predominantly accumulate in tumor tissues and exhibited remarkably enhanced antitumor efficacy. This study provides a promising strategy to improve the bioavailability and avoid side effects of HM as antitumor agents by choosing BSA as carriers.

Bioactive compounds: Application of albumin nanocarriers as delivery systems

Enriched products with bioactive compounds (BCs) show the capacity to produce a wide range of possible health effects. Most BCs are essentially hydrophobic and sensitive to environmental factors; so, encapsulation becomes a strategy to solve these problems. Many globular proteins have the intrinsic ability to bind, protect, encapsulate, and introduce BCs into nutraceutical or pharmaceutical matrices. Among them, albumins as human serum albumin (HSA), bovine serum albumin (BSA), ovalbumin (OVA) and α-lactalbumin (ALA) are widely abundant, available, and applied in many industrial sectors, becoming promissory materials to encapsulate BCs. Therefore, this review focuses on researches about the main groups of natural origin BCs (namely phenolic compounds, lipids, vitamins, and carotenoids), the different types of nanostructures based on albumins to encapsulate them and the main fields of application for BCs-loaded albumin systems. In this context, phenolic compounds (catechins, quercetin, and chrysin) are the most extensively BCs studied and encapsulated in albumin-based nanocarriers. Other extensively studied subgroups are stilbenes and curcuminoids. Regarding lipids and vitamins; terpenes, carotenoids (β-carotene), and xanthophylls (astaxanthin) are the most considered. The main application areas of BCs are related to their antitumor, anti-inflammatory, and antioxidant properties. Finally, BSA is the most used albumin to produced BCs-loaded nanocarriers.

Curcumin-Loaded Human Serum Albumin Nanoparticles Prevent Parkinson’s Disease-like Symptoms in C. elegans

Parkinson’s disease is one of the most common degenerative disorders and is characterized by observable motor dysfunction and the loss of dopaminergic neurons. In this study, we fabricated curcumin nanoparticles using human serum albumin as a nanocarrier. Encapsulating curcumin is beneficial to improving its aqueous solubility and bioavailability. The curcumin-loaded HSA nanoparticles were acquired in the particle size and at the zeta potential of 200 nm and −10 mV, respectively. The curcumin-loaded human serum albumin nanoparticles ameliorated Parkinson’s disease features in the C. elegans model, including body movement, basal slowing response, and the degeneration of dopaminergic neurons. These results suggest that curcumin nanoparticles have potential as a medicinal nanomaterial for preventing the progression of Parkinson’s disease.

Human Clinical Relevance of the Porcine Model of Pseudoallergic Infusion Reactions

Pigs provide a highly sensitive animal model for pseudoallergic infusion reactions, which are mild-to-severe hypersensitivity reactions (HSRs) that arise following intravenous administration of certain nanoparticulate drugs (nanomedicines) and other macromolecular structures. This model has been used in research for three decades and was also proposed by regulatory bodies for preclinical assessment of the risk of HSRs in the clinical stages of nano-drug development. However, there are views challenging the human relevance of the model and its utility in preclinical safety evaluation of nanomedicines. The argument challenging the model refers to the “global response” of pulmonary intravascular macrophages (PIM cells) in the lung of pigs, preventing the distinction of reactogenic from non-reactogenic particles, therefore overestimating the risk of HSRs relative to its occurrence in the normal human population. The goal of this review is to present the large body of experimental and clinical evidence negating the “global response” claim, while also showing the concordance of symptoms caused by different reactogenic nanoparticles in pigs and hypersensitive man. Contrary to the model’s demotion, we propose that the above features, together with the high reproducibility of quantifiable physiological endpoints, validate the porcine “complement activation-related pseudoallergy” (CARPA) model for safety evaluations. However, it needs to be kept in mind that the model is a disease model in the context of hypersensitivity to certain nanomedicines. Rather than toxicity screening, its main purpose is specific identification of HSR hazard, also enabling studies on the mechanism and mitigation of potentially serious HSRs.

Self-assembled PEGylated albumin nanoparticles (SPAN) as a platform for cancer chemotherapy and imaging

Paclitaxel (PTX) is used as a major antitumor agent for the treatment of recurrent and metastatic breast cancer. For the clinical application of PTX, it needs to be dissolved in an oil/detergent-based solvent due to its poor solubility in an aqueous medium. However, the formulation often causes undesirable complications including hypersensitivity reactions and limited tumor distribution, resulting in a lower dose-dependent antitumor effect. Herein, we introduce a facile and oil-free method to prepare albumin-based PTX nanoparticles for efficient systemic cancer therapy using a conjugate of human serum albumin (HSA) and poly(ethyleneglycol) (PEG). PTX were efficiently incorporated in the self-assembled HSA-PEG nanoparticles (HSA-PEG/PTX) using a simple film casting and re-hydration procedure without additional processes such as application of high pressure/shear or chemical crosslinking. The spherical HSA-PEG nanoparticle with a hydrodynamic diameter of ca. 280 nm mediates efficient cellular delivery, leading to comparable or even higher cytotoxicity in various breast cancer cells than that of the commercially available Abraxane^®. When systemically administered in a mouse xenograft model for human breast cancer, the HSA-PEG-based nanoparticle formulation exhibited an extended systemic circulation for more than 96 h and enhanced intratumoral accumulation, resulting in a remarkable anticancer effect and prolonged survival of the animals.

Design of an Anticancer Copper(II) Prodrug Based on the Lys199 Residue of the Active Targeting Human Serum Albumin Nanoparticle Carrier

We not only modified the types and numbers of coordinated ligands in a metal agent to enhance its anticancer activity, but we also designed a metal prodrug based on the N-donor residues of the human serum albumin (HSA) IIA subdomain to improve its delivery efficiency and selectivity in vivo. However, there may be a conflict in simultaneously achieving the two goals because Lys199 and His242 in the IIA subdomain of HSA can replace its two coordinated ligands, which will decrease its anticancer activity relative to the original metal agent. Thus, to improve the delivery efficiency of the metal agent and simultaneously avoid decreasing its anticancer activity in vivo, we decided to develop an anticancer metal prodrug by regulating its pharmacophore ligand so that it would not be displaced by the Lys199 residue of the folic acid (FA)-functionalized HSA nanoparticle (NP) carrier. To this end, we first synthesized two (E)-N'-(5-chloro-2-hydroxybenzylidene)benzohydrazide Schiff base (HL) Cu(II) compounds by designing a second ligand with a different coordinating atom with Cu²⁺/Cu(L)(QL)(Br) [C1, QL = quinolone] and Cu(L)(DMF)(Br) [C2, DMF = N,N-dimethylformamide]. As revealed by the structures of the two HSA complexes, the Cu compounds bind to the hydrophobic cavity in the HSA IIA subdomain. The QL ligand of C1 is replaced by Lys199, which coordinates with Cu²⁺, whereas the DMF ligand of C2 is kept intact and His242 is replaced with Br^- of C2 and coordinates with Cu²⁺. The cytotoxicity of the Cu compounds was enhanced by the FA-HSA NPs in the Bel-7402 cells approximately 2-4-fold; however, they raise the cytotoxicity levels in the normal cells in vitro, and the FA-HSA NPs did not. Importantly, the in vivo data showed that FA-HSA-C2 NPs increased selectivity and the capacity to inhibit tumor growth and were less toxic than HSA-C2 NPs and C2. Moreover, C2/HSA-C2 NPs/FA-HSA-C2 NPs induced Bel-7402 cell death by potentially multiple mechanisms.

Maghemite-human serum albumin hybrid nanoparticles: towards a theranostic system with high MRI r2* relaxivity

Human Serum Albumin (HSA) is the most abundant plasma protein in human blood, and therefore, it is the material of choice for the development of particulate formulations due to its biodegradable and biocompatible nature. Over the last decade, HSA nanoparticles (NPs) have been prepared mostly using desolvation techniques and evaluated as promising drug carriers. In addition, controlling the particle size has become a primary concern while formulating such nanoparticulate systems. Since many of these HSA-based carrier systems have often demonstrated batch-to-batch fabrication variability, significant efforts have been made to develop and characterize HSA-based NPs featuring a robust and controllable particle size, by using a desolvation/cross-linking-type Divinyl Sulfone (DVS)-mediated nanofabrication method. For this purpose and for global multi-parameter fabrication process optimization, a statistically significant Design of Experiment (DoE, MINITAB® 17 DoE software) methodology has been successfully implemented. It aimed to disclose an optimal set of HSA NP fabrication conditions in order to afford highly reproducible and stable 23.05 ± 5.3 nm-sized DoE-globally optimized core HSA NPs. Due to the use of bifunctional DVS as a cross-linker for the preparation of such DoE-optimized HSA NPs, their surface contains a variety of free functional groups which are available for further second step functional modifications. Moreover, related hybrid organic/inorganic nanosystems consisting of DoE-optimized HSA NPs that encapsulated hydrophilic (NH₄)₂Ce(IV)(NO₃)₆ (Ceric Ammonium Nitrate - CAN) modified γ-Fe₂O₃ NPs (CAN-maghemite or CAN-γ-Fe₂O₃ NPs), which enable medical imaging using magnetic resonance imaging (MRI), have also been fabricated and characterized. The resulting hybrid magnetic NPs are a quite powerful T₂* contrast agent (r₂* of 482 mM^-1 s^-1), which may be used as a powerful dual phase platform for both therapeutic (drug delivery) and diagnostic imaging (MRI) applications.

Combined image guided monitoring the pharmacokinetics of rapamycin loaded human serum albumin nanoparticles with a split luciferase reporter

Imaging guided techniques have been increasingly employed to investigate the pharmacokinetics (PK) and biodistribution of nanoparticle based drug delivery systems. In most cases, however, the PK profiles of drugs could vary significantly from those of drug delivery carriers upon administration in the blood circulation, which complicates the interpretation of image findings. Herein we applied a genetically encoded luciferase reporter in conjunction with near infrared (NIR) fluorophores to investigate the respective PK profiles of a drug and its carrier in a biodegradable drug delivery system. In this system, a prototype hydrophobic agent, rapamycin (Rapa), was encapsulated into human serum albumin (HSA) to form HSA Rapa nanoparticles, which were then labeled with Cy5 fluorophore to facilitate the fluorescence imaging of HSA carrier. Meanwhile, we employed transgenetic HN12 cells that were modified with a split luciferase reporter, whose bioluminescence function is regulated by Rapa, to reflect the PK profile of the encapsulated agent. It was interesting to discover that there existed an obvious inconsistency of PK behaviors between HSA carrier and rapamycin in vitro and in vivo through near infrared fluorescence imaging (NIFRI) and bioluminescence imaging (BLI) after treatment with Cy5 labeled HSA Rapa. Nevertheless, HSA Rapa nanoparticles manifested favorable in vivo PK and tumor suppression efficacy in a follow-up therapeutic study. The developed strategy of combining a molecular reporter and a fluorophore in this study could be extended to other drug delivery systems to provide profound insights for non-invasive real-time evaluation of PK profiles of drug-loaded nanoparticles in pre-clinical studies.

Preparation of albumin based nanoparticles for delivery of fisetin and evaluation of its cytotoxic activity

Fisetin is a well known flavonoid that shows several properties such as antioxidant, antiviral and anticancer activities. Its use in the pharmaceutical field is limited due to its poor aqueous solubility which results in poor bioavailability and poor permeability. The aim of our present study is to prepare fisetin loaded human serum albumin nanoparticles to improve its bioavailability. The nanoparticles were prepared by a desolvation method and characterized by spectroscopic and microscopic techniques. The particles were smooth and spherical in nature with an average size of 220 ± 8 nm. The encapsulation efficiency was found to be 84%. The in vitro release profile showed a biphasic pattern and the release rate increases with increase in ionic strength of solution. We have also confirmed the antioxidant activity of the prepared nanoparticles by a DPPH (2,2-diphenyl-1-picrylhydrazyl) assay. Further its anticancer activity was evaluated using MCF-7 breast cancer cell lines. Our findings suggest that fisetin loaded HSA nanoparticles could be used to transfer fisetin to target areas under specific conditions and thus may find use as a delivery vehicle for the flavonoid.

Enhanced cellular uptake of albumin-based lyophilisomes when functionalized with cell-penetrating peptide TAT in HeLa cells

Lyophilisomes are a novel class of biodegradable proteinaceous nano/micrometer capsules with potential use as drug delivery carrier. Cell-penetrating peptides (CPPs) including the TAT peptide have been successfully implemented for intracellular delivery of a broad variety of cargos including various nanoparticulate pharmaceutical carriers. In the present study, lyophilisomes were modified using CPPs in order to achieve enhanced cellular uptake. Lyophilisomes were prepared by a freezing, annealing, and lyophilization method and a cystein-elongated TAT peptide was conjugated to the lyophilisomes using a heterobifunctional linker. Fluorescent-activated cell sorting (FACS) was utilized to acquire a lyophilisome population with a particle diameter smaller than 1000 nm. Cultured HeLa, OVCAR-3, Caco-2 and SKOV-3 cells were exposed to unmodified lyophilisomes and TAT-conjugated lyophilisomes and examined with FACS. HeLa cells were investigated in more detail using a trypan blue quenching assay, confocal microscopy, and transmission electron microscopy. TAT-conjugation strongly increased binding and cellular uptake of lyophilisomes in a time-dependent manner in vitro, as assessed by FACS. These results were confirmed by confocal microscopy. Transmission electron microscopy indicated rapid cellular uptake of TAT-conjugated lyophilisomes via phagocytosis and/or macropinocytosis. In conclusion, TAT-peptides conjugated to albumin-based lyophilisomes are able to enhance cellular uptake of lyophilisomes in HeLa cells.

Nanoparticles in relation to peptide and protein aggregation

Over the past two decades, there has been considerable research interest in the use of nanoparticles in the study of protein and peptide aggregation, and of amyloid-related diseases. The influence of nanoparticles on amyloid formation yields great interest due to its small size and high surface area-to-volume ratio. Targeting nucleation kinetics by nanoparticles is one of the most searched for ways to control or induce this phenomenon. The observed effect of nanoparticles on the nucleation phase is determined by particle composition, as well as the amount and nature of the particle's surface. Various thermodynamic parameters influence the interaction of proteins and nanoparticles in the solution, and regulate the protein assembly into fibrils, as well as the disaggregation of preformed fibrils. Metals, organic particles, inorganic particles, amino acids, peptides, proteins, and so on are more suitable candidates for nanoparticle formulation. In the present review, we attempt to explore the effects of nanoparticles on protein and peptide fibrillation processes from both perspectives (ie, as inducers and inhibitors on nucleation kinetics and in the disaggregation of preformed fibrils). Their formulation and characterization by different techniques have been also addressed, along with their toxicological effects, both in vivo and in vitro.

Prevention of arteriovenous shunt occlusion using microbubble and ultrasound mediated thromboprophylaxis

Background

Palliative shunts in congenital heart disease patients are vulnerable to thrombotic occlusion. High mechanical index (MI) impulses from a modified diagnostic ultrasound (US) transducer during a systemic microbubble (MB) infusion have been used to dissolve intravascular thrombi without anticoagulation, and we sought to determine whether this technique could be used prophylactically to reduce thrombus burden and prevent occlusion of surgically placed extracardiac shunts.

Methods and Results

Heparin‐bonded ePTFE tubular vascular shunts of 4 mm×2.5 cm (Propaten; W.L Gore) were surgically placed in 18 pigs: a right‐sided side‐to‐side arteriovenous (AV, carotid‐jugular) shunt, and a left‐sided arterio‐arterial (AA, carotid‐carotid) interposition shunt in each animal. After shunt implantation, animals were randomly assigned to one of 3 groups. Transcutaneous, weekly 30‐minute treatments (total of 4 treatments) of either guided high MI US+MB (Group 1; n=6) using a 3% MRX‐801 MB infusion, or US alone (Group 2; n=6) were given separately to each shunt. The third group of 6 pigs received no treatments. The shunts were explanted after 4 weeks and analyzed by histopathology to quantify luminal thrombus area (mm²) for the length of each shunt. No pigs received antiplatelet agents or anticoagulants during the treatment period. The median overall thrombus burden in the 3 groups for AV shunts was 5.10 mm² compared with 4.05 mm² in AA (P=0.199). Group 1 pigs had significantly less thrombus burden in the AV shunts (median 2.5 mm²) compared with Group 2 (median 5.6 mm²) and Group 3 (median 7.5 mm²) pigs (P=0.006). No difference in thrombus burden was seen between groups for AA shunts.

Conclusion

Transcutaneous US with intravenous MB is capable of preventing thrombus accumulation in arteriovenous shunts without the need for antiplatelet agents, and may be a method of preventing progressive occlusion of palliative shunts.

Lyophilisomes as a new generation of drug delivery capsules

Nanoparticulate drug delivery systems are currently explored to overcome critical challenges associated with classical administration forms. In this study, we present a drug delivery system based on a novel class of proteinaceous biodegradable nano/micro capsules, lyophilisomes. Lyophilisomes can be prepared from biomolecules without the need for amphiphilicity. Albumin-based lyophilisomes were prepared by freezing, annealing and lyophilizing, resulting in capsules ranging from 100 to 3000 nm. Lyophilisomes were loaded with the anti-tumor drugs doxorubicin and curcumin using different concentrations and time/temperature regimes. Incubation in 0.1 mg/ml doxorubicin or 1.0 mg/ml curcumin resulted in an entrapment efficiency of 95±1% and 4±1%, respectively. This corresponds to a drug loading of 0.24 mg doxorubicin per milligram albumin and 0.10 mg curcumin per milligram albumin. Drug release profiles from doxorubicin and curcumin-loaded lyophilisomes were studied in culture medium and showed slow release for doxorubicin (2.7% after 72 h), and rapid release for curcumin (55% after 72 h). When applied to cells, non-loaded lyophilisomes did not influence cell viability, even at high concentrations (1 mg/ml). Lyophilisomes were internalized by cells. When loaded with doxorubicin and curcumin, lyophilisomes strongly reduced cell proliferation and viability of SKOV-3 and HeLa cells, respectively, to a level similar or better compared to an equal amount of free drugs. In conclusion, albumin lyophilisomes show potential as (nano)carriers of drugs for tumor cell elimination.

Nanoparticles based on albumin: preparation, characterization and the use for 5-flurouracil delivery

The aim of the study was to formulate and evaluate nanoparticles based on albumin to deliver 5-fluorouracil. The nanoparticles were prepared by coacervation method. The nanoparticles were characterized for particle size, surface charge, size distribution and drug loading capacity. The drug loading capacity varied from 4.22% to 19.8% (w/w). The mean particle size was 141.9 nm and surface charge was -30.3 mV. The drug loaded particles exerted a bi-phasic release pattern with an initial burst effect followed by a sustained release in pH 7.4 phosphate buffer. The drug release was first order diffusion controlled and the mechanism was Fickian. The drug loaded nanoparticles showed superior cytotoxicity when compared to the free drug.

Molecular switch for the assembly of lipophilic drug incorporated plasma protein nanoparticles and in vivo image

A strategy to manipulate the disulfide bond breaking triggered unfolding, and subsequently assembly of human serum albumin (HSA) in a lipophilic drug-dependent manner is present. In this study, the hydrophobic region, a molecular switch of the HSA, was regulated to form HSA-paclitaxel (HSA-PTX) nanoparticles by a facile route. High-resolution transmission electron microscopy and fluorescence quenching indicate that HSA coassembled with PTX, which acts as a bridge to form core-shell nanoparticles about 50-240 nm in size, and that PTX might bind to the subdomain IIA sites of HSA. Change of ultraviolet absorption and circular dichroism spectra reveal the formation of HSA-PTX nanoparticles, which is a safety, injectable pharmaceutic nanocarrier system for tumor target. This method to prepare nanocarrier systems for hydrophobic guest molecules reveals a general principle of self-assembly for other plasma proteins and other pharmacologically active substances with poor water solubility. It also provides a basis for developing nanocarrier systems for a wide range of applications in nanomedicine, from drug delivery to bioimaging systems.

Albumin-based nanoparticles as potential controlled release drug delivery systems

Albumin, a versatile protein carrier for drug delivery, has been shown to be nontoxic, non-immunogenic, biocompatible and biodegradable. Therefore, it is ideal material to fabricate nanoparticles for drug delivery. Albumin nanoparticles have gained considerable attention owing to their high binding capacity of various drugs and being well tolerated without any serious side-effects. The current review embodies an in-depth discussion of albumin nanoparticles with respect to types, formulation aspects, major outcomes of in vitro and in vivo investigations as well as site-specific drug targeting using various ligands modifying the surface of albumin nanoparticles with special insights to the field of oncology. Specialized nanotechnological techniques like desolvation, emulsification, thermal gelation and recently nano-spray drying, nab-technology and self-assembly that have been investigated for fabrication of albumin nanoparticles, are also discussed. Nanocomplexes of albumin with other components in the area of drug delivery are also included in this review.

Fabrication of a nanocarrier system through self-assembly of plasma protein and its tumor targeting

Human serum albumin (HSA) nanoparticles hold great promise as a nanocarrier system for targeted drug delivery. The objective of this study was to explore the possibility of preparing size controllable albumin nanoparticles using the disulfide bond breaking reagent β-mercaptoethanol (β-ME). The results showed that the protein concentration and temperature had positive effects on the sizes of the albumin nanoparticles, while pH had a negative effect on the rate of nanoparticle formation. The addition of β-ME induced changes in HSA secondary structure and exposed the hydrophobic core of HSA, leading to the formation of nanoparticles. Human serum albumin nanoparticles could be internalized by MCF-7 cells and mainly accumulated in cytoplasm. After injection in tumor bearing mice, the HSA nanoparticles accumulated in tumor tissues, demonstrating the targeting ability of the nanoparticles. Therefore, human serum albumin can be fabricated into nanoparticles by breaking the disulfide bonds and these nanoparticles exhibit high tumor targeting ability. Human serum albumin nanoparticles could be ideal for the targeted delivery of pharmacologically active substances.

Preparation and characterization of water-soluble albumin-bound curcumin nanoparticles with improved antitumor activity

Curcumin (CCM), a yellow natural polyphenol extracted from turmeric (Curcuma longa), has potent anti-cancer properties as has been demonstrated in various human cancer cells. However, the widespread clinical application of this efficient agent in cancer and other diseases has been limited by its poor aqueous solubility and bioavailability. In this study, we prepared novel CCM-loaded human serum albumin (HSA) nanoparticles (CCM-HSA-NPs) for intravenous administration using albumin bound technology. Field emission scanning electron microscopy (FE-SEM) and dynamic light scattering (DLS) investigation confirmed a narrow size distribution in the 130-150nm range. Furthermore, CCM-HSA-NPs showed much greater water solubility (300-fold) than free CCM, and on storage, the biological activity of CCM-HSA-NPs was preserved with negligible activity loss. In vivo distributions and vascular endothelial cells transport studies demonstrated the superiority of CCM-HSA-NPs over CCM. Amounts of CCM in tumors after treatment with CCM-HSA-NPs were about 14 times higher at 1h after injection than that achieved by CCM. Furthermore, vascular endothelial cell binding of CCM increased 5.5-fold, and transport of CCM across a vascular endothelial cell monolayer by Transwell testing was 7.7-fold greater for CCM-HSA-NPs than CCM. Finally, in vivo antitumor tests revealed that CCM-HSA-NPs (10 or 20mg/kg) had a greater therapeutic effect (50% or 66% tumor growth inhibition vs. PBS-treated controls) than CCM (18% inhibition vs. controls) in tumor xenograft HCT116 models without inducing toxicity. We attribute this potent antitumor activity of CCM-HSA-NPs to enhanced water solubility, increased accumulation in tumors, and an ability to traverse vascular endothelial cell.

Safety of a new transpulmonary echocontrast agent (Albunex) in repeated echocardiographic studies in patients

BACKGROUND AND HYPOTHESIS

Multiple contrast-enhanced echocardiographic studies are to be expected in patients with cardiac ischemic disease, but the sonication process used to produce the echocontrast agent Albunex may result in new epitopes that could cause an immunogenic response.

METHODS

Repeated exposures to intravenous Albunex over a period of time long enough to allow development of an eventual immune reaction were performed in 12 patients while monitoring for lymphocyte transformation, microsphere specific IgE and IgG antibodies, and systemic, pulmonary artery, capillary wedge, and right atrial pressures, as well as cardiac output, left ventricular fractional shortening, and blood gases.

RESULTS

No significant 3H-thymidine incorporation and thus no specific blastic transformation of the patients' lymphocytes were observed either for high or low Albunex concentrations, corresponding to the expected hepatic and plasma concentrations of microspheres. No formation of microsphere-specific IgE and IgG antibodies was observed after the first or second Albunex exposure. Furthermore, no clinically significant hemodynamic or respiratory adverse reactions were observed in any patient.

CONCLUSION

These results suggest that repeated exposures to intravenous Albunex induce no adverse effect on the cellular and humoral immune systems and on left and right heart hemodynamics in patients.

NC100100, a new echo contrast agent for the assessment of myocardial perfusion--safety and comparison with technetium-99m sestamibi single-photon emission computed tomography in a randomized multicenter study

BACKGROUND AND HYPOTHESIS

Myocardial contrast echocardiography using second-generation agents has been proposed to study myocardial perfusion. A placebo-controlled, multicenter trial was conducted to evaluate the safety, optimal dose, and imaging mode for NC100100, a novel intravenous second-generation echo contrast agent, and to compare this technique with technetium-99m sestamibi (MIBI) single-photon emission computed tomography (SPECT).

METHODS

In a placebo-controlled, multicenter trial, 203 patients with myocardial infarction > 5 days and < 1 year previously underwent rest SPECT and MCE. Fundamental and harmonic imaging modes combined with continuous and electrocardiogram-- (ECG) triggered intermittent imaging were used. Six dose groups (0.030, 0.100, and 0.300 microliter particles/kg body weight for fundamental imaging; and 0.006, 0.030, and 0.150 microliter particles/kg body weight for harmonic imaging) were tested. A saline group was also included. Safety was followed for 72 h after contrast injection. Myocardial perfusion by MCE was compared with myocardial rest perfusion imaging using MIBI as a tracer.

RESULTS

NC100100 was well tolerated. No serious adverse events or deaths occurred. No clinically relevant changes in vital signs, laboratory parameters, and ECG recordings were noted. There was no significant difference between adverse events in the NC100100 (25.7%) and in the placebo group (17.9%, p = 0.3). Intermittent harmonic imaging using the intermediate dose was superior to all other modalities, allowing the assessment of perfusion in 76% of all segments. Eighty segments (96%) with normal perfusion by SPECT imaging also showed myocardial perfusion with MCE. However, a substantial percentage of segments (61-80%) with perfusion defects by SPECT imaging also showed opacification by MCE. This resulted in an overall agreement of 66-81% and a high specificity (80-96%), but in low sensitivity (20-39%) of MCE for the detection of perfusion defects.

CONCLUSION

NC100100 is safe in patients with myocardial infarction. Intermittent harmonic imaging with a dose of 0.03 microliter particles/kg body weight can be proposed as the best imaging protocol. Myocardial contrast echocardiography with NC 100100 provides perfusion information in approximately 76% of segments and results in myocardial opacification in the vast majority of segments with normal perfusion as assessed by SPECT. Although the discrepancies between MCE and SPECT with regard to the definition of perfusion defects requires further investigation, MCE with NC 100100 is a promising technique for the noninvasive assessment of myocardial perfusion.

The acute effect of an echo-contrast agent on right ventricular dimensions and contractility in pigs

BACKGROUND

: The aim of the present study was to examine the effect of the second-generation ultrasound contrast agent (2nd GUCA) SonoVue on right ventricular (RV) dimensions and contractility and to investigate whether a dose-related interaction exists between the contrast agent and RV function.

METHODS

: Twenty-eight pigs were randomly assigned to 3 groups for intravenous administration: a low-dose group (0.5 cc of SonoVue), a high-dose group (1 cc of SonoVue), and a control group (2 cc of normal saline). RV end-diastolic (EDD) and end-systolic dimension (ESD) and pulmonary pressure (PP) were measured, and the fractional shortening (FS%) was calculated before the administration of SonoVue or normal saline and after the return of the RV-EDD or PP to the baseline value. The time to reach maximal RV-EDD or PP value and the time until the return of RV-EDD or PP to the baseline value were also measured.

RESULTS

: Contrast agent infusion was followed by an acute transient increase of RV-EDD, RV-ESD, FS, and PP in both the low-dose and high-dose groups, but the increase was greater in the high-dose group. FS and PP did not change significantly in the control group. A dose-dependent delay in the time from baseline to maximum RV-EDD and PP was detected in the high-dose group (P < 0.001 for both) as well as a delay in the return from maximum to the baseline values (P < 0.001 for both).

CONCLUSIONS

: Administration of the 2nd GUCA SonoVue is associated with an acute, transient, dose-dependent RV dilatation and an increase in pulmonary pressure with a consequent impact on RV contractility.

Preparation, characterisation and maintenance of drug efficacy of doxorubicin-loaded human serum albumin (HSA) nanoparticles

Human serum albumin (HSA) nanoparticles represent promising drug carrier systems. Binding of cytostatics to HSA nanoparticles may diminish their toxicity, optimise their body distribution and/or may overcome multidrug resistance. In the present study, doxorubicin-loaded HSA nanoparticle preparations were prepared. Doxorubicin was loaded to the HSA nanoparticles either by adsorption to the nanoparticles' surfaces or by incorporation into the particle matrix. Both loading strategies resulted in HSA nanoparticles of a size range between 150nm and 500nm with a loading efficiency of 70-95%. The influence on cell viability of the resulting nanoparticles was investigated in two different neuroblastoma cell lines. The anti-cancer effects of the drug-loaded nanoparticles were increased in comparison to doxorubicin solution. Based on these result a standard protocol for the preparation of doxorubicin-loaded HSA nanoparticles for further antitumoural studies was established.

Clinical utility of contrast-enhanced echocardiography

Over the past three decades, echocardiography has become a major diagnostic tool in the arsenal of clinical cardiology for real-time imaging of cardiac dynamics. More and more, cardiologists' decisions are based on images created from ultrasound wave reflections. From the time ultrasound imaging technology provided the first insight into a human heart, our diagnostic capabilities have increased exponentially as a result of our growing knowledge and developing technologies. One of the most intriguing developments that brought about a decade-long combination of expectations and disappointments was the introduction of echocardiographic contrast agents. Despite repeated waves of controversy regarding the readiness of this technology for clinical use, it has overcome multiple hurdles and currently provides useful clinical information that helps cardiologists to diagnose heart disease accurately. Since the initial reports on the use of ultrasound contrast media such as agitated saline or renografin, the major advances in the field of contrast echocardiography have included (1) the development of stable perfluorocarbon-filled microbubbles, frequently referred to as second-generation contrast agents; and (2) the development of contrast-targeted nonlinear imaging modes, such as harmonic imaging, pulse inversion, and power modulation, which allow consistent real-time visualization of these agents. These contrast agents in conjunction with the new imaging technology constitute powerful tools that improve our ability to evaluate left ventricular function and myocardial perfusion, and allow differential diagnosis of thrombi and intravascular masses. In this manuscript, we briefly review some of the literature that has provided the scientific basis for the use of echocardiographic contrast agents in the context of these important variables.

Clinical Application and Technical Considerations for the Use of Contrast Agents in the Echocardiography Laboratory

Contrast imaging represents a new and exciting application to the field of ultrasonography. As with the introduction of new imaging modes (i.e., color flow imaging) or examination (i.e., stress echocardiog-raphy), a learning phase will be necessary. For optimal contrast use, it is important to understand what microbubbles are designed to enhance, how to optimize the imaging system, and how to interpret the resulting images. Types of administration and use of the agents are also important to understand. This article will offer technical tips and helpful hints to shorten the sonographer's learning curve to successfully implement optimal contrast imaging for cardiac applications.

Noninvasive assessment of left ventricular isovolumic contraction and relaxation with continuous wave Doppler aortic regurgitant velocity signals: an in vivo validation study

The purpose of this study was to provide fundamental in vivo validation of a method with the use of aortic regurgitant (AR) jet signals recorded with continuous wave (CW) Doppler for assessing left ventricular (LV) isovolumic contraction and relaxation. Preliminary studies have suggested that analysis of CW Doppler AR velocity signals permits the estimation of LV positive and negative dP/dt. We studied 19 hemodynamically different states in 6 sheep with surgically induced chronic aortic regurgitation. CW AR velocity spectra and high-fidelity LV and aortic pressures were recorded simultaneously. Rates of LV pressure rise and fall (RPR and RPF) were calculated by determining the time interval between points at 1 m/s and 2.5 m/s in the deceleration and acceleration slopes of the CW Doppler AR velocity envelope (corresponding to a pressure change of 21 mm Hg). RPR and RPF calculated by CW Doppler analysis for each state were compared with the peak positive dP/dt and negative dP/dt, obtained from the corresponding high-fidelity LV pressure curve, respectively. The LV peak positive and negative dP/dt derived by catheter ranged from 817 to 2625 mm Hg/s and from 917 to 2583 mm Hg/s, respectively. Multiple regression analysis showed that Doppler RPR correlated well with catheter peak positive dP/dt (r = 0.93; mean differences, -413 +/- 250 mm Hg/s). There was also good correlation and agreement between Doppler RPF and the catheter peak negative dP/dt (r = 0.89; mean difference, -279 +/- 239 mm Hg/s). Both Doppler-determined RPR and RPF underestimated their respective LV peak dP/dt. CW Doppler AR spectra can provide a reliable noninvasive estimate of LV dP/dt and could be helpful in the serial assessment of ventricular function in patients with aortic regurgitation.

Digital analysis of myocardial contrast echocardiography: a clinical study using an air-filled agent in normal subjects

The purpose of the present study was to determine whether direct digital image analysis would allow improved detection of myocardial contrast. Eighteen normal subjects were recruited and separated into two groups. In group 1, the time-brightness curves of the left ventricular cavity and three myocardial perfusion beds were formed from digitized video tape, with output power and imaging time as secondary variables. In group 2, curves constructed from direct polar digital data were compared, with fundamental and second harmonic image formation as variables. In group 1 subjects, using fundamental imaging, the area under the curve in the left ventricular cavity increased slightly with intermittent imaging. No consistent myocardial opacification was identified. In group 2 subjects, using intermittent imaging, the area under the myocardial curve and peak intensity increased with high output, second harmonic imaging in the left anterior descending and right coronary artery regions. Intermittent, second harmonic imaging and digital processing can demonstrate myocardial contrast even with an air-filled agent.

The role of echocardiographic harmonic imaging and contrast enhancement for improvement of endocardial border delineation

Despite advances in imaging technology, many myocardial segments remain poorly visualized with echocardiography; however, both contrast enhancement and harmonic imaging have shown promise for improving endocardial definition. Fifty subjects with technically limited echocardiograms were studied with fundamental and harmonic imaging as well as during echocardiographic contrast injection. Overall endocardial visualization scores improved with both techniques compared with fundamental imaging. Harmonic imaging improved endocardial visualization in 43% of all segments and in 57% of segments nonvisualized with fundamental imaging. The benefit of harmonic imaging was seen in all segments. Contrast echocardiography had similar overall improvements in visualization (42% of all segments, 67% of segments nonvisualized with fundamental imaging) but was not helpful in all regions. Harmonic imaging outperformed contrast in 9 of 22 segments, whereas contrast was superior in 4 of 22. In a subgroup of patients with very poor images, contrast enhancement was superior, with a greater increase in overall score and a higher salvage rate than harmonic (68% vs 40%).

Safety of the transpulmonary ultrasound contrast agent NC100100: a clinical and haemodynamic evaluation in patients with suspected or proved coronary artery disease

OBJECTIVE

To evaluate the clinical and haemodynamic safety of NC100100, a new transpulmonary ultrasound contrast agent intended for vascular use.

DESIGN

Pulmonary artery pressures and gas exchange, left ventricular and systemic blood pressure and ECG were measured at baseline, after saline injection, and after each of two increasing doses of NC100100 injected intravenously.

PATIENTS

30 patients who were evaluated for suspected coronary artery disease.

RESULTS

No change was detected in any of the haemodynamic variables, or in haematological or clinical chemical parameters. Blood gases were unchanged, as were heart rhythm and arterial oxygen saturation. No serious adverse reactions were reported.

CONCLUSIONS

NC100100 appeared to be haemodynamically inert and safe in patients with coronary artery disease.

Adherence of albunex to an apical left ventricular thrombus

A previously unrecognized left ventricular thrombus developed a distinct echogenic rim after intravenous injection of albumin microbubbles despite no visible opacification of the left-sided chambers. Absence of visible left ventricular opacification suggests a low density of microbubbles crossing the pulmonary vasculature and a high affinity of the microbubbles for the thrombus or its endothelial surface. These findings support previous observations that albumin microbubbles demonstrate transient adherence to abnormal endothelium.

Clinical applications of transpulmonary contrast echocardiography

BACKGROUND

The recent development of new fluorocarbon-based echocardiographic contrast agents that are capable of opacification of the left-sided cardiac chambers after intravenous injection is a major new advance in diagnostic cardiac imaging.

METHODS AND RESULTS

This is a review article focusing on these novel contrast agents, new echocardiographic imaging techniques to optimize their efficacy, and their clinical applications. Specific clinical applications of these agents are (1) enhancement of endocardial border definition to improve assessment of regional and global left ventricular function, (2) myocardial perfusion imaging by intravenous contrast echocardiography, (3) augmentation of spectral and color flow Doppler images, and (4) tissue-specific targeting of microbubbles for delivery of therapeutic agents.

CONCLUSIONS

New intravenous contrast agents offer the possibility to assess myocardial perfusion echocardiographically. It is also possible to use these agents for delivery of therapeutic agents, including gene therapy.

New concept in echocardiography: harmonic imaging of tissue without use of contrast agent

BACKGROUND

Endocardial border detection is important for echocardiographic assessment of left-ventricular function. Second harmonic imaging of contrast agents enhances this border detection. We discovered that harmonic imaging improves tissue visualisation even before contrast injection. We therefore sought objectively to demonstrate the degree of enhancement of endocardial and myocardial visualisation.

METHODS

An ATL HDI-3000 scanner with software for contrast harmonic imaging was used to record short-axis images of the left ventricle in 27 patients with possible myocardial disease and 22 controls, in the fundamental mode and with harmonic imaging. A computer program measured the relative grey-scale values within six segments of the endocardium and myocardium. An Acuson Sequoia scanner equipped with software for tissue harmonic imaging was used to investigate the reproducibility of ejection-fraction calculations in 22 patients with ischaemic heart disease.

FINDINGS

Harmonic imaging produced brighter endocardium within each segment. Relative to the mean grey value of the total imaging sector, the values for harmonic and fundamental imaging were 171.5 vs 85.6% (p<0.0001) in end diastole and 194.1 vs 106.7% (p<0.0001) in end systole. Results for the myocardial segments were also significantly better for harmonic imaging. Structure enhancement of similar magnitude was seen among patients and healthy controls. Use of harmonic imaging reduced the proportion of unacceptable images by 14-46% in different views and improved the reproducibility of biplane ejection-fraction measurements.

INTERPRETATION

In comparison with fundamental imaging, the relative endocardial and myocardial brightness is enhanced by harmonic imaging.

Improved left ventricular endocardial border delineation and opacification with OPTISON (FS069), a new echocardiographic contrast agent. Results of a phase III Multicenter Trial

OBJECTIVES

The echocardiographic contrast-enhancing effects and safety profile of ALBUNEX (a suspension of air-filled albumin microspheres) were compared with the new contrast agent OPTISON (formerly FS069: a suspension of albumin microspheres containing the gas perfluoropropane) in 203 patients with inadequate noncontrast echocardiograms.

BACKGROUND

The efficacy of ALBUNEX has been limited by its short duration of action. By using perfluoropropane instead of air within the microsphere, its duration of action is increased.

METHODS

Each patient received ALBUNEX (0.8 and 0.22 mL/kg) and OPTISON (0.2, 0.5, 3.0, and 5.0 mL) on separate days a minimum of 48 hours apart. Echocardiograms were evaluated for increase in left ventricular (LV) endocardial border length, degree of LV opacification, number of LV endocardial border segments visualized, conversion from a nondiagnostic to a diagnostic echocardiogram, and duration of contrast enhancement. A thorough safety evaluation was conducted.

RESULTS

Compared with ALBUNEX, OPTISON more significantly improved every measure of contrast enhancement. OPTISON increased well-visualized LV endocardial border length by 6.0+/-5.1, 6.9+/-5.4, 7.5+/-4.7, and 7.6+/-4.8 cm, respectively, for each of the four doses, compared with only 2.2+/-4.5 and 3.4+/-4.6 cm, respectively, for the two ALBUNEX doses (p < 0.001). 100% LV opacification was achieved in 61%, 73%, 87%, and 87% of the patients with the four doses of OPTISON, but in only 16% and 36% of the patients with the two ALBUNEX doses (p < 0.001). Conversion of nondiagnostic to diagnostic echocardiograms with contrast occurred in 74% of patients with the optimal dose of OPTISON (3.0 mL) compared with only 26% with the optimal dose of ALBUNEX (0.22 mL/kg) (p < 0.001). The duration of contrast effect was also significantly greater with OPTISON than with ALBUNEX. In a subset of patients with potentially poor transpulmonary transit of contrast (patients with chronic lung disease or dilated cardiomyopathy), OPTISON more significantly improved the same measures of contrast enhancement compared with ALBUNEX and did so to the same extent as in the overall population. Side effects were similar and transient with the two agents.

CONCLUSION

OPTISON appears to be a safe, well-tolerated echocardiographic contrast agent that is superior to ALBUNEX.

Characterization of left ventricular opacification using sonicated serum albumin in patients with dilated cardiomyopathy and myocardial infarction

To elucidate whether the mode of left ventricular opacification using sonicated serum albumin (SSA) is dependent upon the severity of left ventricular dysfunction, SSA was administered intravenously to 26 patients with dilated cardiomyopathy, 24 patients with anteroseptal myocardial infarction, and 9 normal control subjects. The left ventricular inflow pattern in echocardiograms on the apical 4-chamber view was classified into 2 types: straight or whirling. The ratio of left ventricular opacified area to left ventricular end-diastolic area, called the percent left ventricular effective fraction (%LVEF), was also calculated. The inflow pattern was straight in all normal control subjects and 9 myocardial infarction patients, whereas 15 myocardial infarction and all dilated cardiomyopathy patients showed the whirling pattern. Percent LVEF was significantly smaller in patients with dilated cardiomyopathy (45 +/- 22%, p < 0.0001) and myocardial infarction (65 +/- 14%, p < 0.001) than in normal control subjects (84 +/- 7%). The area that was not opacified was observed only in the infarcted area in cases of myocardial infarction, and over wide regions in cases of dilated cardiomyopathy. In addition, there were significant correlations between %LVEF and ejection fraction or peak filling rate. These findings indicate that contrast echocardiography using SSA can reflect sensitively the severity of left ventricular dysfunctions and detect the regions involved in patients with dilated cardiomyopathy and myocardial infarction.

Improvement of pulmonary venous flow Doppler signal after intravenous injection of Levovist

The analysis of the pulmonary venous flow Doppler pattern can assist in the determination of the severity of mitral regurgitation and, in conjunction with transmitral flow pattern, the assessment of left ventricular diastolic dysfunction. In approximately one third of the cases, however, transthoracic ultrasonography is not able to record an adequately analyzable pulmonary venous flow pattern. The aim of the study was to examine and compare the effect of the echo-enhancing agent Levovist on the pulsed-wave Doppler flow quality of the transthoracic (TTE) and transesophageal (TEE) recorded pulmonary venous flow. In 26 consecutive patients a qualitative (score system) and quantitative analysis of pulmonary venous flow pattern was obtained before and after peripheral venous injection of Levovist at concentrations of 200 mg/ml (low dose) and 400 mg/ml (high dose). The amount of measurable studies for the antegrade pulmonary venous flow increased after the injection of Levovist from 85% to 96% for TTE and from 96% to 100% for TEE. The retrograde flow as seen by TTE was adequately analyzable in only 46% before and in 73% after the injection of Levovist (p < 0.02). Before any contrast enhancement the retrograde pulmonary venous flow recorded by TEE could be analyzed in 77% of the patients, with the percentage increasing to 88% and 92% after the administration of a low and high dose of Levovist, respectively (p < 0.05). In particular, the quality score of the retrograde flow was significantly altered by the administration of Levovist (increase from 1.8 +/- 1.0 to 2.6 +/- 1.1 [low dose Levovist], p < 0.05 and to 2.7 +/- 1.3 [high dose Levovist], p < 0.05). The pulsed-wave Doppler interrogation by TTE without Levovist underestimated the velocities of the antegrade and retrograde pulmonary venous flow. After Levovist was administered, the recorded values were comparable to those obtained by TEE. An analogous pattern is encountered when quantifying the duration of the retrograde flow component. Thus the peripheral venous injection of Levovist leads to an improved quality of the pulmonary venous flow Doppler signal recorded by TTE. On qualitative and quantitative evaluation the values recorded by TTE after administration of Levovist are comparable to those of the TEE technique without an echo-enhancing agent.

Ultrasound contrast media and their use in obstetrics and gynecology

Contrast media have gained acceptance to enhance ultrasonography in many fields of medicine; in particular, cardiology. Several agents have been described and many more are being manufactured and tested. By increasing the number of strong sound scatterers, these agents improve images by increasing the amount of echoes. This is true both for grey-scale and color or Doppler imaging. Their use in obstetrics is very limited at the moment because of safety issues. In a laboratory setup, they have been shown to markedly enhance placental imaging. In gynecology, imaging of the uterine cavity and Fallopian tubes is greatly improved. A potential area where ultrasound contrast may find a role is gynecological oncology. Vascularity is increased in many tumors, but usually vessel diameter is small and velocity low. One can therefore expect future use of the ultrasound contrast agents in ovarian or other gynecological neoplasms.

Hemodynamic effects of microbubble echo contrast

The dose-related hemodynamic effects of an active (bubble-rich) echo contrast agent were compared with those of a bubble-free contrast agent and saline solution to determine whether the microbubbles contained in the echo contrast agent are truly passive indicators in the circulation or whether they actively alter the hemodynamic state independent of the volume and osmotic loading associated with such injections. The study population consisted of 13 fully instrumented open-chest mongrel dogs. Four hundred ninety-two bolus injections were made of three different types: active contrast agent (Levovist, Schering AG, Berlin) (n = 333), saline solution (n = 112), and bubble-free contrast agent (n = 47). Levovist was administered in five dose ranges spanning 0.013 to 0.341 gm/kg and, like the saline solution, was administered in bolus volumes of 0.053 to 1.136 ml/kg. For each injection type, the percent change in hemodynamic parameters after administration of the bolus were calculated on the basis of the dose or volume of the injectate. Audio Doppler signal intensity was used to document the presence of bubbles in the injectate. Statistical significance was defined at the p = 0.05 level; clinical significance was defined as a greater than 15% change in a hemodynamic parameter. Statistically, but not clinically, significant changes were noted in almost all hemodynamic parameters regardless of injection type, and at all dose and volume ranges. Although statistically significant, injection of an active contrast agent in the human dose range resulted in a < 5% change in hemodynamic parameters. High doses of a contrast agent (active or bubble-free) increased the left atrial pressure and had associated changes in peripheral vascular hemodynamics because of the osmotic load. Clinically significant increases (> 15%) in pulmonary artery pressure and pulmonary vascular resistance were unique to the active contrast agent at high dose ranges. Standard doses of the active contrast agent changed the hemodynamics by less than 5% in healthy dogs. Transient clinically significant increases in pulmonary artery pressure and pulmonary vascular resistance are a unique side effect to high dose bolus injections of microbubble echo contrast agent.

Myocardial imaging with a new transpulmonary lipid-fluorocarbon echo contrast agent: experimental studies in pigs

The development of echo contrast agents that can provide reliable opacification of the myocardium after intravenous injection is an important advancement for the clinical application of contrast echocardiography. In this study, the hemodynamic effects and echocardiographic characteristics of a new lipid-fluorocarbon echo contrast agent, Aerosomes MRX 115 (ImaRx Pharmaceutical Corp., Tucson, Ariz.) were studied in six anesthetized ventilated pigs. Intravenous injection of this new agent in doses ranging from 0.0005 to 0.01 ml/kg produced significant measurable and visible myocardial opacification without any effect on heart rate, systemic pressure, partial pressure of oxygen, or left ventricular systolic function. The two largest doses (0.005 and 0.01 ml/kg), however, resulted in mild reversible increases in mean pulmonary artery pressure of 12 and 16 mm Hg, respectively. In four animals, epicardial images were obtained before and during coronary artery occlusion. Intravenous contrast injection during coronary occlusion permitted delineation of the hypoperfused myocardial segment. This capability may further expand the utility of contrast echocardiography.