Single cell level analysis of ATP release kinetics and cell fate following ultrasound targeted microbubble cavitation using microscopy techniques.

It is known that ultrasound-targeted microbubble cavitation (UTMC) can induce vasodilation. This image-guided spatially targeted approach is called provascular therapy when used as a radiotherapy sensitizer in radiation oncology. Extracellular adenosine-5'-triphosphate (eATP), which plays an important role in vascular tone regulation, is released by cells following UTMC, possibly through sonoporation (formation of temporary and non-deadly pores in the cell membrane) and/or cell death.

Enhanced Antitumor Efficacy and Reduced Cardiotoxicity of Ultrasound-Mediated Doxorubicin Delivery by Microbubble-Liposome Complexes.

Objective: Doxorubicin (Dox) is standard of care for treatment of sarcomas, but cumulative dosing is often limited by cardiotoxicity. We hypothesized that ultrasound targeted microbubble (MB) cavitation (UTMC) of a liposomal doxorubicin (LDox) conjugated polymer microbubble complex (DoxLPX) would enhance tumor inhibition and limit Dox cardiotoxicity.

Methods: DoxLPX was intravenously injected in MCA205 sarcoma-bearing mice and concurrent ultrasound was delivered to the tumor site (DoxLPX + UTMC).

ATP released by ultrasound targeted microbubble cavitation induces vascular inflammation and improves immune checkpoint blockade efficacy.

Extracellular ATP (eATP) is a potent immune stimulant that functions as a damage-associated molecular pattern. The regulation of eATP is primarily mediated by cell surface ecto-nucleotidases (CD39 and CD73) which hydrolyze ATP into adenosine, a potent immune suppressor. CD39 and CD73 are upregulated in most cancers.

Ultrasound and Microbubble Mediated Delivery of Virus-Sensitizing Drugs Improves In Vitro Oncolytic Virotherapy Against Breast Cancer Cells.

Objective: Oncolytic virotherapy is an emerging form of cancer treatment that uses replication-competent viruses to kill cancer cells. However, as for other cancer therapies, oncolytic viruses are not effective against all cancers and there is a need to further improve treatment efficacy while maintaining low toxicity. Viral sensitizers are drugs that potentiate viral replication in tumor cells.

Ultrasound enhanced siRNA delivery using cationic liposome-microbubble complexes for the treatment of squamous cell carcinoma.

Microbubble () contrast agents combined with ultrasound targeted microbubble cavitation () are a promising platform for site-specific therapeutic oligonucleotide delivery. We investigated UTMC-mediated delivery of siRNA directed against epidermal growth factor receptor (), to squamous cell carcinoma () via a novel MB-liposome complex (). were constructed by conjugation of cationic liposomes to the surface of CF gas-filled lipid MBs using biotin/avidin chemistry, then loaded with siRNA via electrostatic interaction.

Fundamentals and Applications of Focused Ultrasound-Assisted Cancer Immune Checkpoint Inhibition for Solid Tumors.

Despite spectacular clinical successes across several cancer types, immune checkpoint inhibition is effective only in subgroups of patients and suffers from significant systemic toxicities, highlighting the need to understand and locally overcome the mechanisms of therapeutic resistance. Similarly to other therapeutics, immunotherapies face delivery challenges (for example, antibodies need to reach their targets) and immunological barriers that are unique to solid tumors and their microenvironment. Interestingly, focused ultrasound (FUS), with or without microbubbles, which has been shown to enhance gene and drug delivery, notably in oncology, has been recently found to trigger immunological responses.

Dynamic Behavior of Polymer Microbubbles During Long Ultrasound Tone-Burst Excitation and Its Application for Sonoreperfusion Therapy.

Objective: Ultrasound (US)-targeted microbubble (MB) cavitation (UTMC)-mediated therapies have been found to restore perfusion and enhance drug/gene delivery. Because of the potentially longer circulation time and relative ease of storage and reconstitution of polymer-shelled MBs compared with lipid MBs, we investigated the dynamic behavior of polymer microbubbles and their therapeutic potential for sonoreperfusion (SRP) therapy.

Methods: The fate of polymer MBs during a single long tone-burst exposure (1 MHz, 5 ms) at various acoustic pressures and MB concentrations was recorded via high-speed microscopy and passive cavitation detection (PCD).

Effect of Ultrasound Pulse Length on Sonoreperfusion Therapy.

In recent years, long- and short-pulse ultrasound (US)-targeted microbubble cavitation (UTMC) has been found to increase perfusion in healthy and ischemic skeletal muscle, in pre-clinical animal models of microvascular obstruction and in the myocardium of patients presenting with acute myocardial infarction. There is evidence that the observed microvascular vasodilation is driven by the nitric oxide pathway and purinergic signaling, but the time course of the response and the dependency on US pulse length are not well elucidated. Because our prior data supported that sonoreperfusion efficacy is enhanced by long-pulse US versus short-pulse US, in this study, we sought to compare long-pulse (5000 cycles) and short-pulse (500 × 10 cycles) US at a pressure of 1.

Targeted Anti-Cancer Provascular Therapy Using Ultrasound, Microbubbles, and Nitrite to Increase Radiotherapy Efficacy.

Hypoxia is an important mechanism of resistance to radiation therapy in many human malignancies including prostate cancer. It has been recently shown that ultrasound targeted microbubble cavitation (UTMC) can increase blood perfusion in skeletal muscle by triggering nitric oxide signaling. Interestingly, this effect was amplified with a sodium nitrite coinjection.

Quantitative ultrasound imaging of soft biological tissues: a primer for radiologists and medical physicists.

Quantitative ultrasound (QUS) aims at quantifying interactions between ultrasound and biological tissues. QUS techniques extract fundamental physical properties of tissues based on interactions between ultrasound waves and tissue microstructure. These techniques provide quantitative information on sub-resolution properties that are not visible on grayscale (B-mode) imaging.

Lytic Release of Cellular ATP: Physiological Relevance and Therapeutic Applications.

The lytic release of ATP due to cell and tissue injury constitutes an important source of extracellular nucleotides and may have physiological and pathophysiological roles by triggering purinergic signalling pathways. In the lungs, extracellular ATP can have protective effects by stimulating surfactant and mucus secretion. However, excessive extracellular ATP levels, such as observed in ventilator-induced lung injury, act as a danger-associated signal that activates NLRP3 inflammasome contributing to lung damage.

The effect of ultrasound pulse length on microbubble cavitation induced antibody accumulation and distribution in a mouse model of breast cancer.

In solid tumors, the limited diffusion of therapeutic molecules in the perivascular space is a known limitation impacting treatment efficacy. Ultrasound Targeted Microbubble Cavitation (UTMC) has been shown to increase vascular permeability and improve the delivery of therapeutic compounds including small molecules, antibodies (mAb), nanoparticles and even cells, notably across the blood-brain-barrier (BBB). In this study, we hypothesized that UTMC could improve the accumulation and biodistribution of mAb targeting the adenosinergic pathway (i.

Sonoreperfusion therapy for microvascular obstruction: A step toward clinical translation.

Sonoreperfusion therapy is being developed as an intervention for the treatment of microvascular obstruction. We investigated the reperfusion efficacy of two clinical ultrasound systems (a modified Philips EPIQ and a Philips Sonos 7500) in a rat hindlimb microvascular obstruction model. Four ultrasound conditions were tested using 20 min treatments: Sonos single frame, Sonos multi-frame, EPIQ low pressure and EPIQ high pressure.

The Role of Nitric Oxide during Sonoreperfusion of Microvascular Obstruction.

Microembolization during PCI for acute myocardial infarction can cause microvascular obstruction . MVO severely limits the success of reperfusion therapies, is associated with additional myonecrosis, and is linked to worse prognosis, including death. We have shown, both in and models, that ultrasound and microbubble therapy (termed "sonoreperfusion" or "") is a theranostic approach that relieves MVO and restores perfusion, but the underlying mechanisms remain to be established.

Influence of erythrocyte aggregation on radial migration of platelet-sized spherical particles in shear flow.

Blood platelets when activated are involved in the mechanisms of hemostasis and thrombosis, and their migration toward injured vascular endothelium necessitates interaction with red blood cells (RBCs). Rheology co-factors such as a high hematocrit and a high shear rate are known to promote platelet mass transport toward the vessel wall. Hemodynamic conditions promoting RBC aggregation may also favor platelet migration, particularly in the venous system at low shear rates.

Inertial Cavitation Ultrasound with Microbubbles Improves Reperfusion Efficacy When Combined with Tissue Plasminogen Activator in an In Vitro Model of Microvascular Obstruction.

We have previously reported that long-tone-burst, high-mechanical-index ultrasound (US) and microbubble (MB) therapy can restore perfusion in both in vitro and in vivo models of microvascular obstruction (MVO). Addition of MBs to US has been found to potentiate the efficacy of thrombolytics on large venous thrombi; however, the optimal US parameters for achieving microvascular reperfusion of MVO caused by microthrombi, when combined with tissue plasminogen activator (tPA), are unknown. We sought to elucidate the specific effects of US, with and without tPA, for effective reperfusion of MVO in an in vitro model using both venous and arterial microthrombi.

Sonoreperfusion Therapy Kinetics in Whole Blood Using Ultrasound, Microbubbles and Tissue Plasminogen Activator.

Coronary intervention for myocardial infarction often results in microvascular embolization of thrombus. Sonoreperfusion therapy (SRP) using ultrasound and microbubbles restored perfusion in our in vitro flow model of microvascular obstruction. In this study, we assessed SRP efficacy using whole blood as the perfusate with and without tissue plasminogen activator (tPA).

Effect of Thrombus Composition and Viscosity on Sonoreperfusion Efficacy in a Model of Micro-Vascular Obstruction.

Distal embolization of micro-thrombi during stenting for myocardial infarction causes micro-vascular obstruction (MVO). We have previously shown that sonoreperfusion (SRP), a microbubble (MB)-mediated ultrasound (US) therapy, resolves MVO from venous micro-thrombi in vitro in saline. However, blood is more viscous than saline, and arterial thrombi that embolize during stenting are mechanically distinct from venous clot.

Low Intensity Ultrasound Mediated Liposomal Doxorubicin Delivery Using Polymer Microbubbles.

Cardiotoxicity is the major dose-limiting factor in the chemotherapeutic use of doxorubicin (Dox). A delivery vehicle that can be triggered to release its payload in the tumoral microvasculature but not in healthy tissue would help improve the therapeutic window of the drug. Delivery strategies combining liposomal encapsulated Dox (LDox), microbubbles (MBs), and ultrasound (US) have been shown to improve therapeutic efficacy of LDox, but much remains to be known about the mechanisms and the US conditions that maximize cytotoxicity using this approach.

Unifying Concepts of Statistical and Spectral Quantitative Ultrasound Techniques.

Quantitative ultrasound (QUS) techniques using radiofrequency (RF) backscattered signals have been used for tissue characterization of numerous organ systems. One approach is to use the magnitude and frequency dependence of backscatter echoes to quantify tissue structures. Another approach is to use first-order statistical properties of the echo envelope as a signature of the tissue microstructure.

Radial modulation contrast imaging using a 20-MHz single-element intravascular ultrasound catheter.

Contrast-enhanced intravascular ultrasound imaging is a promising tool for the characterization of coronary vasa vasorum proliferation, which has been identified as a marker of, and possible etiologic factor in, the development of high-risk atherosclerotic plaques. Resonance-based nonlinear detection methods have required the development of prototype catheters which are not commercially available, thus limiting clinical translation. In this study, we investigated the performances of a radial modulation imaging approach (25/3 MHz combination) using simulations, implemented it on a clinical 20-MHz rotating catheter, and tested it in a wall-less tissue-mimicking flow phantom perfused with lipid-encapsulated microbubbles (MBs).

Flexible integration of high-imaging-resolution and high-power arrays for ultrasound-induced thermal strain imaging (US-TSI).

Ultrasound-induced thermal strain imaging (USTSI) for carotid artery plaque detection requires both high imaging resolution (<100 μm) and sufficient US-induced heating to elevate the tissue temperature (~1°C to 3°C within 1 to 3 cardiac cycles) to produce a noticeable change in sound speed in the targeted tissues. Because the optimization of both imaging and heating in a monolithic array design is particularly expensive and inflexible, a new integrated approach is presented which utilizes independent ultrasound arrays to meet the requirements for this particular application. This work demonstrates a new approach in dual-array construction.

Volumetric quantification of in vitro sonothrombolysis with microbubbles using high-resolution optical coherence tomography.

Several in vitro and in vivo studies have established accelerated thrombolysis using ultrasound (US) induced microbubble (MB) cavitation. However, the mechanisms underlying MB mediated sonothrombolysis are still not completely elucidated. We performed three-dimensional (3-D) volumetric optical coherence tomography (OCT) imaging before and after the application of contrast US to thrombus.

Effect of acoustic conditions on microbubble-mediated microvascular sonothrombolysis.

Ultrasound (US) mediated microbubble (MB) destruction facilitates thrombolysis of the epicardial coronary artery in acute myocardial infarction (AMI) but its effect on microvascular thromboemboli remains largely unexplored. We sought to define the acoustic requirements for effective microvascular sonothrombolysis. To model microembolization, microthrombi were injected and entrapped in a 40 μm pore mesh, increasing upstream pressure, which was measured as an index of thrombus burden.

Ultrasound characterization of red blood cell aggregation with intervening attenuating tissue-mimicking phantoms.

The analysis of the ultrasonic frequency-dependent backscatter coefficient of aggregating red blood cells reveals information about blood structural properties. The difficulty in applying this technique in vivo is due to the frequency-dependent attenuation caused by intervening tissue layers that distorts the spectral content of signals backscattered by blood. An optimization method is proposed to simultaneously estimate tissue attenuation and blood structure properties, and was termed the structure factor size and attenuation estimator (SFSAE).