Real-Time, Transcranial Monitoring of Safe Blood-Brain Barrier Opening in Non-Human Primates

The delivery of drugs to specific neural targets faces two fundamental problems: (1) most drugs do not cross the blood-brain barrier, and (2) those that do, spread to the entire brain. To date, there exists only one non-invasive methodology with the potential to solve these problems: selective blood-brain barrier (BBB) opening using micro-bubble enhanced focused ultrasound. We have recently developed a single-element 500-kHz spherical transducer ultrasound setup for targeted BBB opening in the non-human primate that does not require simultaneous MRI monitoring. So far, however, the targeting accuracy that can be achieved with this system has not been quantified systematically. In this paper, the accuracy of this system was tested by targeting caudate nucleus and putamen of the basal ganglia in two macaque monkeys. The average lateral targeting error of the system was ∼2.5 mm while the axial targeting error, i.e., along the ultrasound path, was ∼1.5 mm. We have also developed a real-time treatment monitoring technique based on cavitation spectral analysis. This technique also allowed for delineation of a safe and reliable acoustic parameter window for BBB opening. In summary, the targeting accuracy of the system was deemed to be suitable to reliably open the BBB in specific sub-structures of the basal ganglia even in the absence of MRI-based verification of opening volume and position. This establishes the method and the system as a potentially highly useful tool for brain drug delivery

Diagnostic Ultrasound Induced Inertial Cavitation To Non-Invasively Restore Coronary And Microvascular Flow In Acute Myocardial Infarction

Ultrasound induced cavitation has been explored as a method of dissolving intravascular and microvascular thrombi in acute myocardial infarction. The purpose of this study was to determine the type of cavitation required for success, and whether longer pulse duration therapeutic impulses (sustaining the duration of cavitation) could restore both microvascular and epicardial flow with this technique. Accordingly, in 36 hyperlipidemic atherosclerotic pigs, thrombotic occlusions were induced in the mid-left anterior descending artery. Pigs were then randomized to either a) 1/2 dose tissue plasminogen activator (0.5 mg/kg) alone; or same dose plasminogen activator and an intravenous microbubble infusion with either b) guided high mechanical index short pulse (2.0 MI; 5 usec) therapeutic ultrasound impulses; or c) guided 1.0 mechanical index long pulse (20 usec) impulses. Passive cavitation detectors indicated the high mechanical index impulses (both long and short pulse duration) induced inertial cavitation within the microvasculature. Epicardial recanalization rates following randomized treatments were highest in pigs treated with the long pulse duration therapeutic impulses (83% versus 59% for short pulse, and 49% for tissue plasminogen activator alone; p \u3c 0.05). Even without epicardial recanalization, however, early microvascular recovery occurred with both short and long pulse therapeutic impulses (p \u3c 0.005 compared to tissue plasminogen activator alone), and wall thickening improved within the risk area only in pigs treated with ultrasound and microbubbles. We conclude that although short pulse duration guided therapeutic impulses from a diagnostic transducer transiently improve microvascular flow, long pulse duration therapeutic impulses produce sustained epicardial and microvascular re-flow in acute myocardial infarction

Ultrasound to Enhance a Liquid–Liquid Reaction

Liquid–liquid mass transfer with ultrasound was investigated experimentally during the hydrolysis of n-amyl acetate. Power ultrasound is supposed to improve the yield and kinetics of such multiphase chemical reactions thanks to the mechanical effects of cavitation. Indeed, implosion of micro-bubbles at the vicinity of the liquid– liquid interface generates disruption of this surface, and enhances mixing in the liquid around the inclusion, thus improving mass transfer between the two phases. This effect has been demonstrated here on the hydrolysis of n-amyl acetate by sodium hydroxide, a rather slow reaction but influenced by mass transfer; the reaction is carried out in a glass jacketed reactor, 500 mL of volume, equipped with a Rushton turbine and a 20 kHz sonotrode dipping in the solution. The ester is initially pure in the organic dispersed phase, and sodium hydroxide has an initial concentration of 300 mol/m3; one of the products, pentanol partitions between the two phases and the sodium salt stays in the aqueous phase. The initial apparent reaction rate is measured from the record of the conductivity giving the concentration of alkali versus time. The reaction rate was always found to increase when ultrasound is superimposed to mechanical stirring (at 600 rpm), with a positive influence of input power (20 and 50 W). When varying initial concentration (300 and 600 mol/m3), temperature (36 and 45°C) and ultrasound emitter (sonotrode or cuphorn), the benefit of ultrasound over mechanical agitation was systematic. The only case of a weak influence of ultrasound was the sonication of a dense medium, containing 23% of organic phase and impeding the propagation of ultrasound

Stimulation of bioprocesses by ultrasound

Ultrasound (US) has become a ubiquitous technological process in a large variety of scientific disciplines. However, little information exists on the use of ultrasound to enhance biological processes and/or processing and consequently this paper provides an overview of work reported to date on this topic. This review provides a brief introduction to ultrasound and the history of ultrasound as applied to bioprocesses. This is followed by a discussion of the influence of US on discrete enzyme systems, enzymes used in bioremediation, microbial fermentations and enzymatic hydrolysis of biopolymers. Augmentation of anaerobic digestion by US is then considered along with enhancement of enzymes in food science and technology. The use of ultrasonically stimulated enzymes in synthesis is then considered and other relevant miscellaneous topics are described. It is concluded that the precise mechanism of action of US in bio-processing remains to be elucidated though a variety of plausible suggestions are made

Ultrasound assisted siRNA delivery using PEG-siPlex loaded microbubbles

Short interfering RNA (siRNA) attracts much attention for the treatment of various diseases. However, its delivery, especially via systemic routes, remains a challenge. Indeed, naked siRNAs are rapidly degraded, while complexed siRNAs massively aggregate in the blood or are captured by macrophages. Although this can be circumvented by PEGylation, we found that PEGylation had a strong negative effect on the gene silencing efficiency of siRNA-liposome complexes (siPlexes). Recently, ultrasound combined with microbubbles has been used to deliver naked siRNA but the gene silencing efficiency is rather low and very high amounts of siRNA are required. To overcome the negative effects of PEGylation and to enhance the efficiency of ultrasound assisted siRNA delivery, we coupled PEGylated siPlexes (PEG-siPlexes) to microbubbles. Ultrasound radiation of these microbubbles resulted in massive release of unaltered PEG-siPlexes. Interestingly, PEG-siPlexes loaded on microbubbles were able to enter cells after exposure to ultrasound, in contrast to free PEG-siPlexes, which were not able to enter cells rapidly. Furthermore, these PEG-siPlex loaded microbubbles induced, in the presence of ultrasound, much higher gene silencing than free PEG-siPlexes. Additionally, the PEG-siPlex loaded microbubbles only silenced the expression of genes in the presence of ultrasound, which allows space and time controlled gene silencing

Multimodality imaging in vivo for preclinical assessment of tumor-targeted doxorubicin nanoparticles.

This study presents a new multimodal imaging approach that includes high-frequency ultrasound, fluorescence intensity, confocal, and spectral imaging to improve the preclinical evaluation of new therapeutics in vivo. Here we use this approach to assess in vivo the therapeutic efficacy of the novel chemotherapy construct, HerDox during and after treatment. HerDox is comprised of doxorubicin non-covalently assembled in a viral-like particle targeted to HER2+ tumor cells, causing tumor cell death at over 10-fold lower dose compared to the untargeted drug, while sparing the heart. Whereas our initial proof-of-principle studies on HerDox used tumor growth/shrinkage rates as a measure of therapeutic efficacy, here we show that multimodal imaging deployed during and after treatment can supplement traditional modes of tumor monitoring to further characterize the particle in tissues of treated mice. Specifically, we show here that tumor cell apoptosis elicited by HerDox can be monitored in vivo during treatment using high frequency ultrasound imaging, while in situ confocal imaging of excised tumors shows that HerDox indeed penetrated tumor tissue and can be detected at the subcellular level, including in the nucleus, via Dox fluorescence. In addition, ratiometric spectral imaging of the same tumor tissue enables quantitative discrimination of HerDox fluorescence from autofluorescence in situ. In contrast to standard approaches of preclinical assessment, this new method provides multiple/complementary information that may shorten the time required for initial evaluation of in vivo efficacy, thus potentially reducing the time and cost for translating new drug molecules into the clinic

Photo-acoustic tomography in a rotating setting

Photo-acoustic tomography is a coupled-physics (hybrid) medical imaging modality that aims to reconstruct optical parameters in biological tissues from ultrasound measurements. As propagating light gets partially absorbed, the resulting thermal expansion generates minute ultrasonic signals (the photo-acoustic effect) that are measured at the boundary of a domain of interest. Standard inversion procedures first reconstruct the source of radiation by an inverse ultrasound (boundary) problem and second describe the optical parameters from internal information obtained in the first step. This paper considers the rotating experimental setting. Light emission and ultrasound measurements are fixed on a rotating gantry, resulting in a rotation-dependent source of ultrasound. The two-step procedure we just mentioned does not apply. Instead, we propose an inversion that directly aims to reconstruct the optical parameters quantitatively. The mapping from the unknown (absorption and diffusion) coefficients to the ultrasound measurement via the unknown ultrasound source is modeled as a composition of a pseudo-differential operator and a Fourier integral operator. We show that for appropriate choices of optical illuminations, the above composition is an elliptic Fourier integral operator. Under the assumption that the coefficients are unknown on a sufficiently small domain, we derive from this a (global) injectivity result (measurements uniquely characterize our coefficients) combined with an optimal stability estimate. The latter is the same as that obtained in the standard (non-rotating experimental) setting

Chemotherapy-Response Monitoring of Breast Cancer Patients Using Quantitative Ultrasound-Based Intra-Tumour Heterogeneities

© 2017 The Author(s). Anti-cancer therapies including chemotherapy aim to induce tumour cell death. Cell death introduces alterations in cell morphology and tissue micro-structures that cause measurable changes in tissue echogenicity. This study investigated the effectiveness of quantitative ultrasound (QUS) parametric imaging to characterize intra-tumour heterogeneity and monitor the pathological response of breast cancer to chemotherapy in a large cohort of patients (n = 100). Results demonstrated that QUS imaging can non-invasively monitor pathological response and outcome of breast cancer patients to chemotherapy early following treatment initiation. Specifically, QUS biomarkers quantifying spatial heterogeneities in size, concentration and spacing of acoustic scatterers could predict treatment responses of patients with cross-validated accuracies of 82 ± 0.7%, 86 ± 0.7% and 85 ± 0.9% and areas under the receiver operating characteristic (ROC) curve of 0.75 ± 0.1, 0.80 ± 0.1 and 0.89 ± 0.1 at 1, 4 and 8 weeks after the start of treatment, respectively. The patients classified as responders and non-responders using QUS biomarkers demonstrated significantly different survivals, in good agreement with clinical and pathological endpoints. The results form a basis for using early predictive information on survival-linked patient response to facilitate adapting standard anti-cancer treatments on an individual patient basis

Solitonic State in Microscopic Dynamic Failures

Onset of permanent deformation in crystalline materials under a sharp indenter tip is accompanied by nucleation and propagation of defects. By measuring the spatio-temporal strain field nearthe indenter tip during indentation tests, we demonstrate that the dynamic strain history at the moment of a displacement burst carries characteristics of formation and interaction of local excitations, or solitons. We show that dynamic propagation of multiple solitons is followed by a short time interval where the propagating fronts can accelerate suddenly. As a result of such abrupt local accelerations, duration of the fast-slip phase of a failure event is shortened. Our results show that formation and annihilation of solitons mediate the microscopic fast weakening phase, during which extreme acceleration and collision of solitons lead to non-Newtonian behavior and Lorentz contraction, i.e., shortening of solitons characteristic length. The results open new horizons for understanding dynamic material response during failure and, more generally, complexity of earthquake sources

Tissue plasminogen activator-based clot busting: Controlled delivery approaches.

Cardiovascular diseases are the leading cause of death worldwide. Thrombosis, the formation of blood clot (thrombus) in the circulatory system obstructing the blood flow, is one of the main causes behind various ischemic arterial syndromes such as ischemic stroke and myocardial infarction, as well as vein syndromes such as deep vein thrombosis, and consequently, pulmonary emboli. Several thrombolytic agents have been developed for treating thrombosis, the most common being tissue plasminogen activator (tPA), administrated systemically or locally via IV infusion directly proximal to the thrombus, with the aim of restoring and improving the blood flow. TPA triggers the dissolution of thrombi by inducing the conversion of plasminogen to protease plasmin followed by fibrin digestion that eventually leads to clot lysis. Although tPA provides powerful thrombolytic activity, it has many shortcomings, including poor pharmacokinetic profiles, impairment of the reestablishment of normal coronary flow, and impairment of hemostasis, leading to life-threatening bleeding consequences. The bleeding consequence is ascribed to the ability of tPA to circulate throughout the body and therefore can lysis all blood clots in the circulation system, even the good ones that prevent the bleeding and promote injury repair. This review provides an overview of the different delivery approaches for tPA including: liposomes, ultrasound-triggered thrombolysis, anti-fibrin antibody-targeted tPA, camouflaged-tPA, tpA-loaded microcarriers, and nano-modulated delivery approaches