Ultrasound-induced Cavitation Research Articles

Effects and mechanisms of ultrasound- and alkali-assisted enzymolysis on production of water-soluble yeast β-glucan

This study investigated the effects and related mechanisms of ultrasound- and alkali-assisted enzymolysis on production of water-soluble yeast β-glucan (WSYG). Results indicated that ultrasound and alkali pretreatments reduced the particle size of yeast β-glucan (YG) from 8.80 μm to 1.77 and 7.19 μm, respectively. Ultrasound-induced cavitation disrupted YG aggregates to a coarse appearance and exposed internal structure. Alkali penetrated into YG particles and broke the YG aggregates into a flake-like morphology by cleaving the linkages within YG chains. Both pretreatments facilitated enzymolysis by enlarging the YG surface area and increased the WSYG yield to 32.3% and 36.2%, respectively. Meanwhile, the purity of WSYG reached 98.8% after zymoprotein removal by DEAE-Sepharose fast flow column. This work not only provides a green method for producing high-purity and high-yield WSYG, but also reveals the mechanisms of ultrasound and alkali pretreatments for improving enzymolysis efficiency by loosening the YG structure and increasing the surface area.

Weighting the Passive Acoustic Mapping Technique With the Phase Coherence Factor for Passive Ultrasound Imaging of Ultrasound-Induced Cavitation.

Ultrasound (US) cavitation is currently being explored for low-invasive therapy techniques applied to a wide panel of pathologies. Because of the random behavior of cavitation, a real-time spatial monitoring system may be required. For this purpose, the US passive imaging techniques have been recently investigated. In particular, the passive acoustic mapping (PAM) beamforming method enables the reconstruction of cavitation activity maps by beamforming acoustic signals passively recorded by an array transducer. In this paper, an optimized version of PAM, PAM weighted with a phase coherence factor (PAM-PCF), is considered. A general validation process is developed including simulations on a point source and experiments on a wire. Furthermore, using a focused regulated US-induced cavitation generator, reproducible cavitation experiments are conducted in water and in agar gel. The spatial behavior of a bubble cavitation cloud is determined using the PAM-PCF beamforming method to localize the focal cavitation point in two perpendicular imaging planes.

Self-sensing cavitation detection in ultrasound-induced acoustic cavitation

The generation of cavitation by ultrasound is used in a large number of processes in different scientific and industrial applications. Chemical reactions are made possible or accelerated by locally occurring high temperatures and pressures generated by the collapse of cavitation bubbles. Mixing or separating substances, emulsification, ultrasonic cleaning, degassing, and microbiological treatment of fluids are some more applications for ultrasonic generated cavitation. In most of these applications, an optical examination of the events within the cavitating medium is not possible. Non-transparent media or closed containers prevent an optical process monitoring. In addition, the use of sensors is often impossible for cost reasons, limited construction space or disturbance of the process. In order to still enable process monitoring, the authors follow a novel approach: the analysis of the electrical signals of the ultrasound transducer used for cavitation generation. The current signal of the ultrasound transducer is inspected for frequency components, known as acoustic cavitation indicators. For this, the time signal is recorded and transferred to the frequency domain for further processing and evaluation. In previous studies, acoustical sensors like hydrophones or microphones were used as reference for the self-sensing technique.In order to link cavitation events inside the fluid container to cavitation indicators in the current signal, a photo study of the cavitation events inside a transparent water container is conducted. In contrast to previous self-sensing attempts, the ultrasound transducer’s transfer characteristic is also considered. The evaluation of the acquired data shows that a frequency component which is 3/2 times the driving frequency (∼30 kHz) can be used to determine the onset of transient cavitation. Once the transient cavitation threshold has been exceeded, broad band noise levels show a good correlation with cavitation intensity.

PO-116 Indium-111 afterloading of preformed EGF-containing liposomes for molecularly targeted radionuclide delivery via ultrasound-induced cavitation

Introduction Radiolabelled nuclear localising peptides are a promising cancer therapy. However, These peptides have unfavourable circulation kinetics and are highly susceptible to degradation and elimination by local enzymes. Liposome nanoparticles consist of a phospholipid bilayer structure which can encapsulate a therapeutic payload. Such encapsulation can improve pharmacokinetic profiles. One promising method for targeted therapeutic delivery is through the use of ultrasound, a longitudinal pressure wave of frequency >20 kHz. Ultrasound can be efficiently delivered through the body and cause Liposomes to crack and release their payload. The aim of this proposal is to develop a clinically relevant method of loading the therapeutic Indium labelled Epidermal Growth Factor (111In-DTPA-hEGF) into liposomes which can be released at the target site via externally applied ultrasound. Material and methods hEGF-DTPA was created and passively loaded into liposomes. Liposomes were then loaded with indium via incubation with indium chloride for 1 hour followed by loading efficiency analysis by TLC. Liposome structure was analysed via TEM and size distribution was analysed via DLS. For therapeutic efficacy liposomes were incubated with an EGFR positive cell (468) and an EGFR negative cell line (MCF7). After application of ultrasound cells were seeded in 6 well plates and colony analysis was performed after 14 days along with all controls. Uptake studies were also performed along with γ-H2AX staining. The biodistribution of the liposomes was examined in nude mice. Results and discussions BY TEM and DLS liposome size was approximately 200 nm. Protein loaded liposomes had a 93% loading efficiency for Indium encapsulation whereas empty liposomes only loaded 34% of the Indium. The Liposomes were found to be stable over 5 days. Uptake results indicated that cell uptake of 111In-DTPA-hEGF from liposomes was dependent on ultrasound application. An EGFR expressing cell line exposed to 111In-hEGF-DTPA loaded liposomes and ultrasound showed a>90% decrease in colony survival. A biodistribution in vivo has been obtained. Conclusion A protein loaded liposome has been successfully created and loaded Indium within one hour imitating techniques currently used in radiopharmacies. The liposome was shown to crack upon application of ultrasound and release 111In-hEGF-DTPA which resulted in a statistically significant impact on EGFR positive cells. This technology can be utilised for ultrasound targeted delivery of radiotherapeutics to tumours.

Layered acoustofluidic resonators for the simultaneous optical and acoustic characterisation of cavitation dynamics, microstreaming, and biological effects.

The study of the effects of ultrasound-induced acoustic cavitation on biological structures is an active field in biomedical research. Of particular interest for therapeutic applications is the ability of oscillating microbubbles to promote both cellular and tissue membrane permeabilisation and to improve the distribution of therapeutic agents in tissue through extravasation and convective transport. The mechanisms that underpin the interaction between cavitating agents and tissues are, however, still poorly understood. One challenge is the practical difficulty involved in performing optical microscopy and acoustic emissions monitoring simultaneously in a biologically compatible environment. Here we present and characterise a microfluidic layered acoustic resonator (μLAR) developed for simultaneous ultrasound exposure, acoustic emissions monitoring, and microscopy of biological samples. The μLAR facilitates in vitro ultrasound experiments in which measurements of microbubble dynamics, microstreaming velocity fields, acoustic emissions, and cell-microbubble interactions can be performed simultaneously. The device and analyses presented provide a means of performing mechanistic in vitro studies that may benefit the design of predictable and effective cavitation-based ultrasound treatments.

Ultrasound-mediated cavitation-enhanced extravasation of mesoporous silica nanoparticles for controlled-release drug delivery

Mesoporous silica nanoparticles have been reported as suitable drug carriers, but their successful delivery to target tissues following systemic administration remains a challenge. In the present work, ultrasound-induced inertial cavitation was evaluated as a mechanism to promote their extravasation in a flow-through tissue-mimicking agarose phantom. Two different ultrasound frequencies, 0.5 or 1.6 MHz, with pressures in the range 0.5–4 MPa were used to drive cavitation activity which was detected in real time. The optimal ultrasound conditions identified were employed to deliver dye-loaded nanoparticles as a model for drug-loaded nanocarriers, with the level of extravasation evaluated by fluorescence microscopy. The same nanoparticles were then co-injected with submicrometric polymeric cavitation nuclei as a means to promote cavitation activity and decrease the required in-situ acoustic pressure required to attain extravasation. The overall cavitation energy and penetration of the combination was compared to mesoporous silica nanoparticles alone. The results of the present work suggest that combining mesoporous silica nanocarriers and submcrometric cavitation nuclei may help enhance the extravasation of the nanocarrier, thus enabling subsequent sustained drug release to happen from those particles already embedded in the tumour tissue.

Ultrasound-Induced Microbubble Cavitation for the Treatment of Catheterization-Induced Vasospasm

Highlights •In a porcine model, we investigated the therapeutic effectiveness of microbubble enhanced sonothrombolysis for treatment of catheter-induced vasospasm and vascular injury, a common complication after femoral arterial catheterization, particularly in children. •Our results show that microbubble cavitation mediated by brief application of diagnostic high mechanical index impulses is an effective noninvasive method for relieving catheter-induced vasospasm. •This approach could have potential as an effective treatment for reversal of pulse loss after peripheral arterial injury and vasospasm.

Dendrites fragmentation induced by oscillating cavitation bubbles in ultrasound field

The fragmentation of the dendrites of succinonitrile (SCN)-2-wt.% acetone organic transparent alloy caused by ultrasound-induced cavitation bubbles was studied by using ultra-high-speed digital camera with a rate of 40,000fps. Real-time imaging reveals that the vibrating cavitation bubbles can fragment not only secondary arms but also the primary ones under high ultrasound power. The secondary arms always broke at their roots as a result of stress concentration induced by oscillated cavitation bubble and then ripped off from their primary arms. Generally the fragment process takes tens of milliseconds from bending to breaking, while the break always occurs immediately in less than 25μs.

An ultra-effective method of generating extramultipotent cells from human fibroblasts by ultrasound.

Multipotent cells have similar basic features of all stem cells but limitation in ability of self-renewal and differentiation compared with pluripotent cells. Here, we have developed an ultra effective, gene- and chemical-free method of generating extra multipotent (xpotent) cells which have differentiation potential more than limited cell types, by the mechanism of ultrasound-directed permeation of environmental transition-guided cellular reprogramming (Entr). Ultrasound stimulus generated a massive number of Entr-mediated xpotent (x/Entr) spheroids from human dermal fibroblasts (HDFs) 6 days after treatment. The emergence of x/Entr was first initiated by the introduction of human embryonic stem cell (ESC) environments into the HDFs to start fast cellular reprogramming including activation of stress-related kinase signaling pathways, subsequent chromatin remodeling, and expression of pluripotent-related genes via transient membrane damage caused by ultrasound-induced cavitation. And then, pluripotent markers were transported into their adjacent HDFs via direct cell-to-cell connections in order to generate xpotent clusters. The features of x/Entr cells were intermediate between pluripotency and multipotency in terms of pluripotency with three germ layer markers, multi-lineage differentiation potential, and no teratoma formation. This physical stimulus-mediated reprogramming strategy was cost-effective, simple, quick, produced significant yields, and was safe, and can therefore provide a new paradigm for clinical application.

Sonodynamic therapy combined with novel anti-cancer agents, sanguinarine and ginger root extract: Synergistic increase in toxicity in the presence of PANC-1 cells in vitro

The presence of ultrasound-induced cavitation in sonodynamic therapy (SDT) treatments has previously enhanced the activity and delivery of certain sonosensitisers in biological systems. The purpose of this work was to investigate the potential for two novel anti-cancer agents from natural derivatives, sanguinarine and ginger root extract (GRE), as sonosensitisers in an SDT treatment with in vitro PANC-1 cells. Both anti-cancer compounds had a dose-dependent cytotoxicity in the presence of PANC-1 cells. A range of six discreet ultrasound power-frequency configurations were tested and it was found that the cell death caused directly by ultrasound was likely due to the sonomechanical effects of cavitation. Combined treatment used dosages of 100μM sanguinarine or 1mM of GRE with 15s sonication at 500kHz and 10W. The sanguinarine-SDT and GRE-SDT treatments showed a 6% and 17% synergistic increase in observed cell death, respectively. Therefore both sanguinarine and GRE were found to be effective sonosensitisers and warrant further development for SDT, with a view to maximising the magnitude of synergistic increase in toxicity.

Effects of ultrasound irradiation on enzymatic hydrolysis of protein and application for the determination of tetracyclines in complex matrices.

The widespread use of tetracyclines (TCs) in food animals has led to concerns regarding unsafe residue levels in feed, food and manure. The determination of TCs in such matrices suffers from interference by the interactions between proteins and TCs. Three deproteination methods were compared in this study. In contrast with acid deproteination, which caused a large loss of TCs due to the strong adsorption of TCs on protein precipitates, a normal enzymatic hydrolysis was confirmed to have a merit of effectively releasing TCs from protein matrices, but required treatment time as long as 16h. The adoption of ultrasound irradiation was proposed to shorten the enzymatic hydrolysis time. After investigating the effects of ultrasound power and irradiation time, the conditions of the ultrasound-enhanced enzymatic hydrolysis were optimized as ultrasound power of 100W and irradiation time of 6min. The ultrasound-enhanced enzymatic hydrolysis treatment of 6min yielded recovery of TCs (from protein-containing matrices) as high as that obtained by the normal enzymatic hydrolysis treatment of 16h. The acceleration effect of ultrasound irradiation was attributed to ultrasound-induced cavitation, which increased exposure of both the functional groups of trypsin and the C-terminal amino acid in the protein that was a cleavage site for trypsin attack. When the ultrasound-enhanced enzymatic hydrolysis method was used to determine TCs in complex matrices, it was found that this new method achieved recoveries of 89.5, 117.7, 110.4 and 100.0% for oxytetracycline, tetracycline, chlortetracycline and doxycycline, being much higher than those (29.6-39.4%) obtained using the common acid deproteination process. Copyright © 2017 John Wiley & Sons, Ltd.

Ultrasound-mediated transdermal drug delivery of fluorescent nanoparticles and hyaluronic acid into porcine skin in vitro**Project partially supported by the National Natural Science Foundation of China (Grant Nos. 81127901, 81227004, 81473692, 81673995, 11374155, 11574156, 11274170, 11274176, 11474001, 11474161, 11474166, and 11674173), the Natural Science Foundation of Jiangsu Province, China (Grant No. BK2011812), the Fundamental Research Funds for the Central Universities, and

Transdermal drug delivery (TDD) can effectively bypass the first-pass effect. In this paper, ultrasound-facilitated TDD on fresh porcine skin was studied under various acoustic parameters, including frequency, amplitude, and exposure time. The delivery of yellow–green fluorescent nanoparticles and high molecular weight hyaluronic acid (HA) in the skin samples was observed by laser confocal microscopy and ultraviolet spectrometry, respectively. The results showed that, with the application of ultrasound exposures, the permeability of the skin to these markers (e.g., their penetration depth and concentration) could be raised above its passive diffusion permeability. Moreover, ultrasound-facilitated TDD was also tested with/without the presence of ultrasound contrast agents (UCAs). When the ultrasound was applied without UCAs, low ultrasound frequency will give a better drug delivery effect than high frequency, but the penetration depth was less likely to exceed 200 μm. However, with the help of the ultrasound-induced microbubble cavitation effect, both the penetration depth and concentration in the skin were significantly enhanced even more. The best ultrasound-facilitated TDD could be achieved with a drug penetration depth of over 600 μm, and the penetration concentrations of fluorescent nanoparticles and HA increased up to about 4–5 folds. In order to get better understanding of ultrasound-facilitated TDD, scanning electron microscopy was used to examine the surface morphology of skin samples, which showed that the skin structure changed greatly under the treatment of ultrasound and UCA. The present work suggests that, for TDD applications (e.g., nanoparticle drug carriers, transdermal patches and cosmetics), protocols and methods presented in this paper are potentially useful.

Ultrasound-induced inertial cavitation from gas-stabilizing nanoparticles.

The understanding of cavitation from nanoparticles has been hindered by the inability to control nanobubble size. We present a method to manufacture nanoparticles with a tunable single hemispherical depression (nanocups) of mean diameter 90, 260, or 650 nm entrapping a nanobubble. A modified Rayleigh-Plesset crevice model predicts the inertial cavitation threshold as a function of cavity size and frequency, and is verified experimentally. The ability to tune cavitation nanonuclei and predict their behavior will be useful for applications ranging from cancer therapy to ultrasonic cleaning.

Interfacial reaction behavior and mechanical properties of ultrasonically brazed Cu/Zn–Al/Cu joints

Abstract Ultrasound-assisted fluxless brazing of Cu/Zn–Al/Cu joint was performed in this study. Evolutions of the microstructure and mechanical properties of Cu alloy joints ultrasonically brazed with Zn–3Al and Zn–14Al filler metals were investigated. Results showed that excellent metallurgic bonding between the Zn–3Al filler metal and the Cu substrate could be obtained by brazing at 450 °C for 4 s, accompanied with the creation of thick CuZn 5 and Cu 5 Zn 8 intermetallic compounds (IMCs) layers on the Zn–3Al/Cu interface. Compared with the Zn–3Al/Cu system, much longer ultrasonic vibration time was needed for the completely wetting of the Zn–14Al filler metal on the Cu substrate, but the thick Cu 5 Zn 8 IMC layer was replaced with a thin Cu based diffusion layer on the Zn–14Al/Cu interface. The wetting of Zn–3Al filler metal on the Cu substrate was attributed to the combined effects of ultrasound-induced cavitation and Cu/Zn metallurgic reaction, while the wetting of Zn–14Al filler metal on the Cu substrate was mainly attributed to the ultrasound-induced cavitation effects. The shear strength of the Cu/Zn–3Al/Cu and Cu/Zn–14Al/Cu joint was 37.9 MPa and 92.1 MPa, respectively; the shearing failure took place within the Cu interfacial layer in all case.

Microalgal cell disruption via ultrasonic nozzle spraying.

The objective of this study was to understand the effect of operating parameters, including ultrasound amplitude, spraying pressure, nozzle orifice diameter, and initial cell concentration on microalgal cell disruption and lipid extraction in an ultrasonic nozzle spraying system (UNSS). Two algal species including Scenedesmus dimorphus and Nannochloropsis oculata were evaluated. Experimental results demonstrated that the UNSS was effective in the disruption of microalgal cells indicated by significant changes in cell concentration and Nile red-stained lipid fluorescence density between all treatments and the control. It was found that increasing ultrasound amplitude generally enhanced cell disruption and lipid recovery although excessive input energy was not necessary for best results. The effect of spraying pressure and nozzle orifice diameter on cell disruption and lipid recovery was believed to be dependent on the competition between ultrasound-induced cavitation and spraying-generated shear forces. Optimal cell disruption was not always achieved at the highest spraying pressure or biggest nozzle orifice diameter; instead, they appeared at moderate levels depending on the algal strain and specific settings. Increasing initial algal cell concentration significantly reduced cell disruption efficiency. In all UNSS treatments, the effectiveness of cell disruption and lipid recovery was found to be dependent on the algal species treated.

Relations between acoustic cavitation and skin resistance during intermediate- and high-frequency sonophoresis.

Enhanced skin permeability is known to be achieved during sonophoresis due to ultrasound-induced cavitation. However, the mechanistic role of cavitation during sonophoresis has been extensively investigated only for low-frequency (LFS, <100 kHz) applications. Here, mechanisms of permeability-enhancing stable and inertial cavitation were investigated by passively monitoring subharmonic and broadband emissions arising from cavitation isolated within or external to porcine skin in vitro during intermediate- (IFS, 100-700 kHz) and high-frequency sonophoresis (HFS, >1 MHz). The electrical resistance of skin, a surrogate measure of the permeability of skin to a variety of compounds, was measured to quantify the reduction and subsequent recovery of the skin barrier during and after exposure to pulsed (1 second pulse, 20% duty cycle) 0.41 and 2.0 MHz ultrasound over a range of acoustic powers (0-21.7 W) for 30 min. During IFS, significant skin resistance reductions and acoustic emissions from cavitation were measured exclusively when cavitation was isolated outside of the skin. Time-dependent skin resistance reductions measured during IFS correlated significantly with subharmonic and broadband emission levels. During HFS, significant skin resistance reductions were accompanied by significant acoustic emissions from cavitation measured during trials that isolated cavitation activity either outside of skin or within skin. Time-dependent skin resistance reductions measured during HFS correlated significantly greater with subharmonic than with broadband emission levels. The reduction of the skin barrier due to sonophoresis was reversible in all trials; however, effects incurred during IFS recovered more slowly and persisted over a longer period of time than HFS. These results quantitatively demonstrate the significance of cavitation during sonophoresis and suggest that the mechanisms and post-treatment longevity of permeability enhancement due to IFS and HFS treatments are different.

Kinetic analysis of mechanochemical chain scission of linear poly(phthalaldehyde).

The kinetics of mechanochemical chain scission of poly(phthalaldehyde) (PPA) are investigated. Ultrasound-induced cavitation is capable of causing chain scission in the PPA backbone that ultimately leads to rapid depolymerization of each resulting polymer fragment when above the polymer's ceiling temperature (Tc ). An interesting feature of the mechanochemical breakdown of PPA is that "half-chain" daughter fragments are not observed, since the depolymerization is rapid following chain scission. These features facilitate the determination of rate constants of activation for multiple molecular weights from a single sonication experiment. Additionally, the degradation kinetics are modified with chain-end trapping agents through variation of the nature and amount of small molecule nucleophile or electrophile.

Fetal Membrane Transport Enhancement Using Ultrasound for Drug Delivery and Noninvasive Detection

The purpose of this research was to evaluate the effect of ultrasound on mass transport across fetal membrane for direct fetal drug delivery and sensing of the amniotic fluid in a noninvasive manner. Post-delivery human fetal membranes (chorioamnion) were used for in vitro experiments, in which the effect of ultrasound on transport across fetal membrane of fluorescent model molecule (250 kDa) was evaluated. Ex vivo experiments were carried out on a whole rat amniotic sac. The model molecule or alpha-fetoprotein was injected into the amniotic sac through the placenta. Transport of these molecules across pre- and post-insonation of the amniotic sac was evaluated. The ultrasound enhancement's mechanism was also assessed. The greatest enhancement in mass transport (43-fold) in vitro was achieved for 5 min of insonation (20 kHz, 4.6 W/cm(2), 5 mm distance). Ex vivo results showed a rapid increase (23-fold) in mass transport of the model molecule and also for alphafetoprotein following 30 s of insonation (20 kHz, 4.6 W/cm(2), 5 mm distance). Mass transport across fetal membranes was enhanced post-insonation both in vitro and ex vivo in a reversible and transient manner. We suggest that exterior (to the amniotic sac) ultrasound-induced cavitation is the main mechanism of action.

Evaluation of sub-micron, ultrasound-responsive particles as a drug delivery strategy

Substantial portions of tumors are largely inaccessible to drugs due to their irregular vasculature and high intratumoral pressure. The enhanced permeability and retention effect causes drug carriers within the size range of 100–800 nm to passively accumulate within tumors; however, they remain localized close to the vasculature. Failure to penetrate into and throughout the tumor ultimately limits treatment efficacy. Ultrasound-induced cavitation events have been cited as a method of stimulating greater drug penetration. At present, this targeting strategy is limited by the difference in size between the nano-scale drug carriers used and the cavitation nuclei available, i.e., the micron-scale contrast agent SonoVue. In vivo this results in spatial separation of the two agents, limiting the capacity for one to impact upon the other. Our group has successfully formulated two different monodisperse suspensions of nanoparticles that are of a size that will permit better co-localization of cavitation nuclei and therapeutics. A mixture of these nanoparticles and a model drug carrier were passed through a tissue mimicking phantom to provide an in vitro simulation of flow through a tumor. The impact of ultrasound on the penetration of drug carrier from the flow channel was compared between both of our ultrasound-responsive particles and SonoVue.

Intramembrane Cavitation as a Predictive Bio-Piezoelectric Mechanism for Ultrasonic Brain Stimulation

Low-intensity ultrasonic waves can remotely and nondestructively excite central nervous system (CNS) neurons. While diverse applications for this effect are already emerging, the biophysical transduction mechanism underlying this excitation remains unclear. Recently, we suggested that ultrasound-induced intramembrane cavitation within the bilayer membrane could underlie the biomechanics of a range of observed acoustic bioeffects. In this paper, we show that, in CNS neurons, ultrasound-induced cavitation of these nanometric bilayer sonophores can induce a complex mechanoelectrical interplay leading to excitation, primarily through the effect of currents induced by membrane capacitance changes. Our model explains the basic features of CNS acoustostimulation and predicts how the experimentally observed efficacy of mouse motor cortical ultrasonic stimulation depends on stimulation parameters. These results support the hypothesis that neuronal intramembrane piezoelectricity underlies ultrasound-induced neurostimulation, and suggest that other interactions between the nervous system and pressure waves or perturbations could be explained by this new mode of biological piezoelectric transduction.