Enhancement of ultrasound-induced apoptosis and cell lysis by echo-contrast agents

Ultrasound-stimulated microbubbles enhances radiosensitivity in cervical cancer

BACKGROUND

Ultrasound-stimulated microbubble (USMB) therapy has proven efficacy of targeting tumor vasculature and enhancing the effect of radiation in tumor xenografts. In this investigation, we studied whether this treatment enhances the sensitivity of cervical cancer to radiation.

METHODS

Human cervical cancer (ME-180 and SiHa) cells were treated with USMB or exposed to radiation (0, 2, 4, 6 and 8 Gy) or radiation (8 Gy) in combination with USMB. Clone formation assay and CCK-8 assay were used to analyze the proliferation capacity of cells. Apoptosis and DNA double-strand breaks were detected using flow cytometry and immunofluorescence staining of gamma-H2AX (γ-H2AX), respectively. Matrigel tubule formation was performed to evaluate the angiogenesis of human umbilical vein endothelial cells. In xenograft model of SiHa cells, tumor tissue expression of CD31 was detected by immunohistochemistry.

RESULTS

USMB and radiation synergistically restrained the growth of ME-180 and SiHa cells. USMB promoted radiation-induced apoptosis by enhancing the levels of proapoptotic proteins. Furthermore, USMB enhanced radiation-induced γ-H2AX foci to induce DNA double-strand breaks in cervical cancer cells. USMB in combination with radiation reduced the angiogenic capacity of endothelial cells in vitro. Moreover, USMB strengthened the inhibitory effect of radiation on tumor growth and angiogenesis in xenograft models.

CONCLUSION

In conclusion, USMB exposure effectively enhanced the destructive effect of radiation on cervical cancer, suggesting that USMB might be a promising sensitizer of radiotherapy to treat cervical cancer.

The promising interplay between sonodynamic therapy and nanomedicine

Sonodynamic therapy (SDT) is a non-invasive approach for cancer treatment in which chemical compounds, named sonosensitizers, are activated by non-thermal ultrasound (US), able to deeply penetrate into the tissues. Despite increasing interest, the underlying mechanisms by which US triggers the sonosensitizer therapeutic activity are not yet clearly elucidate, slowing down SDT clinical application. In this review we will discuss the main mechanisms involved in SDT with particular attention to the sonosensitizers involved for each described mechanism, in order to highlight how much important are the physicochemical properties of the sonosensitizers and their cellular localization to predict their bioeffects. Moreover, we will also focus our attention on the pivotal role of nanomedicine providing the sonodynamic anticancer approach with the ability to shape US-responsive agents to enhance specific sonodynamic effects as the sonoluminescence-mediated anticancer effects. Indeed, SDT is one of the biomedical fields that has significantly improved in recent years due to the increased knowledge of nanosized materials. The shift of the nanosystem from a delivery system for a therapeutic agent to a therapeutic agent in itself represents a real breakthrough in the development of SDT. In doing so, we have also highlighted potential areas in this field, where substantial improvements may provide a valid SDT implementation as a cancer therapy.

Ultrasound-Induced DNA Damage and Cellular Response: Historical Review, Mechanisms Analysis, and Therapeutic Implications

The biological effects of ultrasound may be classified into thermal and nonthermal mechanisms. The nonthermal effects may be further classified into cavitational and noncavitational mechanisms. DNA damage induced by ultrasound is considered to be related to nonthermal cavitations. For this aspect, many in vitro studies on DNA have been conducted for evaluating the safety of diagnostic ultrasound, particularly in fetal imaging. Technological advancement in detecting DNA damage both in vitro and in vivo have elucidated the mechanism of DNA damage formation and their cellular response. Damage to DNA, and the residual damages after DNA repair are implicated in the biological effects. Here, we discuss the historical evidence of ultrasound on DNA damage and the mechanism of DNA damage formation both in vitro and in vivo, compared with those induced by ionizing radiation. We also offer a commentary on the safety of ultrasound over X-ray-based imaging. Also, understanding the various mechanisms involved in the bioeffects of ultrasound will lead us to alternative strategies for use of ultrasound for therapy.

Low-intensity ultrasound inhibits melanoma cell proliferation in vitro and tumor growth in vivo

PURPOSE

To determine the effect of low-intensity ultrasound on cancer cell proliferation in vitro and tumor growth in vivo.

METHODS

In vitro, several cancer cell lines were exposed to low-intensity ultrasound at 0.11 W/cm² for 2 min. Of the cell lines screened, melanoma C32 is one of the cell lines that showed sensitivity to growth inhibition by ultrasound and was therefore used in succeeding experiments. In vivo, under the same ultrasound conditions used in vitro, C32 tumors in mice were exposed to ultrasound daily for 2 weeks, and the tumor volumes were monitored weekly using sonography.

RESULTS

In vitro, C32 cell growth was inhibited, attaining 43.2% inhibition on the 3rd day. In vivo, tumor growth was significantly inhibited, with the treated tumors exhibiting 2.7-fold slowed tumor growth vs. untreated tumors at week 2. Such inhibition was not associated with increased cell death. Several genes related to the cell cycle and proliferation were among those significantly regulated.

CONCLUSION

These findings highlight the potential of low-intensity ultrasound to inhibit tumor growth in a noninvasive, safe, and easy-to-administer way. In addition, this may suggest that the mechanical stress induced by ultrasound on C32 cells may have affected the intrinsic biomolecular mechanism related to the cell growth of this particular cell line. Further research is needed to identify which of the regulated genes played key roles in growth inhibition.

Investigation of the Therapeutic Effect of Doxorubicin Combined With Focused Shockwave on Glioblastoma

BACKGROUND

Glioblastoma multiforme (GBM) is currently the most devastating brain tumor globally and produces a high mortality rate. GBM is also challenging to eradicate using surgery due to its invasive characteristics. Moreover, the blood-brain barrier (BBB) increases the difficulty of transporting most therapeutic drugs to tumor sites. The use of transcranial focused ultrasound (FUS) has recently been investigated for opening the BBB to facilitate drug delivery. A special form of FUS, the shockwave (SW), has also been shown to open BBB efficiently. SW has several advantages including no heating effect, less reactive oxygen species production, good transcranial ability, and no need to supply microbubbles.

METHODS

We employed a commercial SW device, which is a common tool used for musculoskeletal disorders, to improve doxorubicin delivery across the BBB and evaluated its therapeutic efficacy on GBM rat models. SW emits relatively short but stronger mechanical pulses comparing with FUS.

RESULTS

The results demonstrated that doxorubicin combined with SW treatment substantially inhibited tumor growth and prolonged overall survival.

CONCLUSIONS

The present study shows the non-invasive transcranial SW may have potential for the treatment of GBM in future clinical setting.

Ultrasound-Stimulated Microbubbles Inhibit Aggressive Phenotypes and Promotes Radiosensitivity of esophageal squamous cell carcinoma

Ultrasound (US) is reported to improve the delivery efficiency of drugs loading onto large nanoparticles due to the sonoporation effect. Microbubbles (MBs) can be used as contrast agents of US expanding and contracting under low-amplitude US pressure waves. Ultrasound-stimulated microbubbles (USMBs) therapy is a promising option for the treatment of various cancers as a radiosensitizer. However, its role in esophageal squamous cell carcinoma (ESCC) remains unknown. In our study, human ESCC cell lines (KYSE-410, KYSE-1140) were treated with radiation solely, US alone, or radiation in combination with US or USMBs. The migration and invasion abilities of ESCC cells were examined by wound healing and Transwell assays. ESCC cell apoptosis was assessed using flow cytometry analysis and TUNEL assays. The levels of proteins associated with cell apoptosis and angiogenesis were measured by western blot analysis. A tube formation assay was performed to detect the ESCC cell angiogenesis. We found that USMBs at high levels most effectively most efficiently enhanced the effect of radiation, and significant changes in the viability (48%-51%), proliferation (1%), migration (63%-71%), invasion (52%) and cell apoptosis (31%-50%) of ESCC cells were observed compared with the control group in vitro. The ESCC angiogenesis was inhibited by US or radiation treatment and further inhibited by a combination of radiation and US or USMBs. USMBs at high levels most effectively enhanced the inhibitory effect of radiotherapy on ESCC cell apoptosis. Overall, USMBs enhanced the radiosensitivity of esophageal squamous cell carcinoma cells.Graphical abstractUSMBs treatment enhanced the anti-tumor effect of radiation on ESCC cell proliferation, migration, invasion, angiogenesis and apoptosis in vitro.1USMBs enhance the radiation-induced inhibition on ESCC cell growth2USMBs promote the radiation effect on ESCC cell apoptosis3USMBs enhance radiation-caused suppression on ESCC cell migration and invasion4USMBs enhance the suppression of radiation on ESCC angiogenesis[Figure: see text].

A novel UTMD system facilitating nucleic acid delivery into MDA-MB-231 cells

Gene therapy is emerging as a promising method for the treatment of various diseases. The safe and efficient delivery of therapeutic nucleic acids is a gene therapy prerequisite. Ultrasound, particularly in combination with microbubbles composed of biocompatible materials such as lipid, PLGA and chitosan, is a novel non-viral tool for gene transportation. Under ultrasound irradiation, microbubbles explode and generate pores in the cell membrane. Hence, genes can enter cells more easily. In order to transfect nucleic acids into MDA-MB-231 cells in a low-cost and non-viral manner for further breast cancer gene therapy studies, we explored ultrasound targeted microbubble destruction (UTMD) technology and evaluated the efficiency and safety of the delivery of plasmid encoding enhanced green fluorescent protein (pEGFP) and a microRNA-34a (miR-34a) mimic by UTMD. Sonovitro ultrasonic apparatus was employed to generate ultrasonic field, which was developed by our group. Ultrasonic parameters, including acoustic intensity (AI), exposure time (ET) and duty cycle (DC), were optimized at 0.6 W/cm² AI, 20 s ET and 20% DC, the cell viability was not obviously impaired. Under these conditions, the UTMD-mediated transfection efficiency of pEGFP was greater than 40%. In addition to plasmid DNA, an miR-34a mimic was also successfully introduced into the cytoplasm by UTMD and found to inhibit proliferation, induce apoptosis of MDA-MB-231 cells and regulate downstream molecules. The present study indicates that further in vivo UTMD-mediated gene therapy studies are warranted.

Acoustofection: High-Frequency Vibrational Membrane Permeabilization for Intracellular siRNA Delivery into Nonadherent Cells

The internalization of therapeutic molecules into cells-a critical step in enabling a suite of autologous ex vivo gene and cell therapies-is highly regulated by the lipid barrier imposed by the cell membrane. Strategies to increase the efficiency of delivering these exogenous payloads into the cell, while maintaining the integrity of both the therapeutic molecules to be delivered as well as the host cells they are delivered to, are therefore required. This is especially the case for suspension cells that are particularly difficult to transfect. In this work, we show that it is possible to enhance the uptake of short interfering RNA (siRNA) into nonadherent Jurkat and HuT 78 cells with a rapid poration-free method involving high-frequency (MHz order) acoustic excitation. The 2-fold enhancement in gene knockdown is almost comparable with that obtained with conventional nucleofection, which is among the most widely used intracellular delivery methods, but with considerably higher cell viabilities (>91% compared to approximately 76%) owing to the absence of pore formation. The rapid and effective delivery afforded by the platform, together with its low cost and scalability, therefore renders it a potent tool in the cell engineering pipeline.

Therapeutic ultrasound experiments in vitro: Review of factors influencing outcomes and reproducibility

Current in vitro sonication experiments show immense variability in experimental set-ups and methods used. As a result, there is uncertainty in the ultrasound field parameters experienced by sonicated samples, poor reproducibility of these experiments and thus reduced scientific value of the results obtained. The scope of this narrative review is to briefly describe mechanisms of action of ultrasound, list the most frequently used experimental set-ups and focus on a description of factors influencing the outcomes and reproducibility of these experiments. The factors assessed include: proper reporting of ultrasound exposure parameters, experimental geometry, coupling medium quality, influence of culture vessels, formation of standing waves, motion/rotation of the sonicated sample and the characteristics of the sample itself. In the discussion we describe pros and cons of particular exposure geometries and factors, and make a few recommendations as to how to increase the reproducibility and validity of the experiments performed.

TRPV4 promotes acoustic wave-mediated BBB opening via Ca2+/PKC-δ pathway

Introduction

Numerous studies have shown the ability of low-energy acoustic waves such as focused ultrasound or shockwave to transiently open blood-brain barrier (BBB) and facilitate drug delivery to the brain. Preclinical and clinical evidences have well demonstrated the efficacy and safety in treating various brain disorders. However, the molecular mechanisms of acoustic waves on the BBB are still not fully understood.

Objectives

The present study aimed at exploring the possible molecular mechanisms of acoustic wave stimulation on brains.

Methods: Briefly describe the experimental design

The left hemisphere of the rat‘s brain was treated with pulsed ultrasound from a commercial focused shockwave or a planar ultrasound device, and the right hemisphere served as a control. One hour after the mechanical wave stimulation or overnight, the rats were sacrificed and the brains were harvested for protein or histological analysis. Agonists and antagonists related to the signal transduction pathways of tight junction proteins were used to investigate the possible intracellular mechanisms.

Results

Intracellular signal transduction analysis shows calcium influx through transient receptor potential vanilloid 4 (TRPV4) channels, and the activation of PKC-δ pathway to mediate dissociation of ZO-1 and occludin after acoustic wave stimulation. The activation of TRPV4 or PKC-δ signaling further increased the expression level of TRPV4, suggesting a feedback loop to regulate BBB permeability. Moreover, the tight junction proteins dissociation can be reversed by administration of PKC-δ inhibitor and TRPV4 antagonist.

Conclusion

The present study shows the crucial role of TRPV4 in acoustic wave-mediated BBB permeability, specifically its effect on compromising tight junction proteins, ZO-1 and occludin. Our findings provide a new molecular perspective to explain acoustic wave-mediated BBB opening. Moreover, activation of TRPV4 by agonists may reduce the threshold intensity level of acoustic waves for BBB opening, which may prevent undesirable mechanical damages while maintaining efficient BBB opening.

GHz Ultrasonic Chip-Scale Device Induces Ion Channel Stimulation in Human Neural Cells

Emergent trends in the device development for neural prosthetics have focused on establishing stimulus localization, improving longevity through immune compatibility, reducing energy re-quirements, and embedding active control in the devices. Ultrasound stimulation can single-handedly address several of these challenges. Ultrasonic stimulus of neurons has been studied extensively from 100 kHz to 10 MHz, with high penetration but less localization. In this paper, a chip-scale device consisting of piezoelectric Aluminum Nitride ultrasonic transducers was engineered to deliver gigahertz (GHz) ultrasonic stimulus to the human neural cells. These devices provide a path towards complementary metal oxide semiconductor (CMOS) integration towards fully controllable neural devices. At GHz frequencies, ultrasonic wavelengths in water are a few microns and have an absorption depth of 10-20 µm. This confinement of energy can be used to control stimulation volume within a single neuron. This paper is the first proof-of-concept study to demonstrate that GHz ultrasound can stimulate neurons in vitro. By utilizing optical calcium imaging, which records calcium ion flux indicating occurrence of an action potential, this paper demonstrates that an application of a nontoxic dosage of GHz ultrasonic waves [Formula: see text] caused an average normalized fluorescence intensity recordings >1.40 for the calcium transients. Electrical effects due to chip-scale ultrasound delivery was discounted as the sole mechanism in stimulation, with effects tested at α = 0.01 statistical significance amongst all intensities and con-trol groups. Ionic transients recorded optically were confirmed to be mediated by ion channels and experimental data suggests an insignificant thermal contributions to stimulation, with a predicted increase of 0.03 ^oC for [Formula: see text] This paper paves the experimental framework to further explore chip-scale axon and neuron specific neural stimulation, with future applications in neural prosthetics, chip scale neural engineering, and extensions to different tissue and cell types.

Enzymatically crosslinked silk and silk-gelatin hydrogels with tunable gelation kinetics, mechanical properties and bioactivity for cell culture and encapsulation

Silk fibroin (SF) was enzymatically crosslinked with tyramine-substituted silk fibroin (SF-TA) or gelatin (G-TA) to fabricate hybrid hydrogels with tunable gelation kinetics, mechanical properties and bioactivity. Horseradish peroxidase (HRP)/hydrogen peroxide (H2O2) mediated crosslinking of SF in physiological buffers results in slow gelation and limited mechanical properties. Moreover, SF lacks cell attachment sequences, leading to poor cell-material interactions. These shortcomings can limit the uses of enzymatically crosslinked silk hydrogels in injectable tissue fillings, 3D bioprinting or cell microencapsulation, where rapid gelation and high bioactivity are desired. Here SF/SF-TA and SF/G-TA composite hydrogels were characterized for hydrogel properties and the influence of conjugated cyclic arginine-glycine-aspartic acid (RGD) peptide or G-TA content on bioactivity was explored. Both SF-TA and G-TA significantly increased gelation kinetics, improved mechanical properties and delayed enzymatic degradation in a concentration-dependent manner. β-Sheet formation and hydrogel stiffening were accelerated by SF-TA content but delayed by G-TA. Both cyclic RGD and G-TA significantly improved morphology and metabolic activity of human mesenchymal stem cells (hMSCs) cultured on or encapsulated in composite hydrogels. The hydrogel formulations introduced in this study provide improved control of gel formation and properties, along with biocompatible systems that can be utilized in tissue engineering and cell delivery applications.

High Frequency Sonoprocessing: A New Field of Cavitation-Free Acoustic Materials Synthesis, Processing, and Manipulation

Ultrasound constitutes a powerful means for materials processing. Similarly, a new field has emerged demonstrating the possibility for harnessing sound energy sources at considerably higher frequencies (10 MHz to 1 GHz) compared to conventional ultrasound (⩽3 MHz) for synthesizing and manipulating a variety of bulk, nanoscale, and biological materials. At these frequencies and the typical acoustic intensities employed, cavitation-which underpins most sonochemical or, more broadly, ultrasound-mediated processes-is largely absent, suggesting that altogether fundamentally different mechanisms are at play. Examples include the crystallization of novel morphologies or highly oriented structures; exfoliation of 2D quantum dots and nanosheets; polymer nanoparticle synthesis and encapsulation; and the possibility for manipulating the bandgap of 2D semiconducting materials or the lipid structure that makes up the cell membrane, the latter resulting in the ability to enhance intracellular molecular uptake. These fascinating examples reveal how the highly nonlinear electromechanical coupling associated with such high-frequency surface vibration gives rise to a variety of static and dynamic charge generation and transfer effects, in addition to molecular ordering, polarization, and assembly-remarkably, given the vast dimensional separation between the acoustic wavelength and characteristic molecular length scales, or between the MHz-order excitation frequencies and typical THz-order molecular vibration frequencies.

A novel study on curcumin metal complexes: solubility improvement, bioactivity, and trial burn wound treatment in rats

This paper describes a new technique to enhance the solubility of metal curcumin complexes.

SPIO labeling of endothelial cells using ultrasound and targeted microbubbles at diagnostic pressures

In vivo cell tracking of therapeutic, tumor, and endothelial cells is an emerging field and a promising technique for imaging cardiovascular disease and cancer development. Site-specific labeling of endothelial cells with the MRI contrast agent superparamagnetic iron oxide (SPIO) in the absence of toxic agents is challenging. Therefore, the aim of this in vitro study was to find optimal parameters for efficient and safe SPIO-labeling of endothelial cells using ultrasound-activated CD31-targeted microbubbles for future MRI tracking. Ultrasound at a frequency of 1 MHz (10,000 cycles, repetition rate of 20 Hz) was used for varying applied peak negative pressures (10–160 kPa, i.e. low mechanical index (MI) of 0.01–0.16), treatment durations (0–30 s), time of SPIO addition (-5 min– 15 min with respect to the start of the ultrasound), and incubation time after SPIO addition (5 min– 3 h). Iron specific Prussian Blue staining in combination with calcein-AM based cell viability assays were applied to define the most efficient and safe conditions for SPIO-labeling. Optimal SPIO labeling was observed when the ultrasound parameters were 40 kPa peak negative pressure (MI 0.04), applied for 30 s just before SPIO addition (0 min). Compared to the control, this resulted in an approximate 12 times increase of SPIO uptake in endothelial cells in vitro with 85% cell viability. Therefore, ultrasound-activated targeted ultrasound contrast agents show great potential for effective and safe labeling of endothelial cells with SPIO.

Low-intensity pulsed ultrasound in combination with SonoVue induces cytotoxicity of human renal glomerular endothelial cells via repression of the ERK1/2 signaling pathway

OBJECTIVES

Low-intensity pulsed ultrasound (LIPUS) and SonoVue have been used widely for diagnosis and therapeutic treatment. The effects of LIPUS and SonoVue on the microvascular system and underlying molecular mechanisms have not been established.

METHODS

Cultured human renal glomerular endothelial cells (HRGECs) were treated with 5-min ultrasonic irradiation, 20% SonoVue or the combination of both treatments. Cell proliferation, viablity, and apoptosis were measured by MTT assay, Trypan blue exclusion assay and flow cytometry, respectively. Activation of extracellular regulated protein kinases (ERK) were examined by Western blot.

RESULTS

We found that LIPUS and SonoVue alone do not induce cytotoxicity of HRGECs; however, the combination of the two treatments reduces cell proliferation and increases cell death. In addition, the combination of LIPUS and SonoVue suppressed the activation of ERK 1/2 in HRGRCs. With pretreatment of the inhibitor of ERK1/2 signaling, PD98059, LIPUS, and SonoVue does not induce additional cell death and inhibition of proliferation.

CONCLUSIONS

LIPUS combined with SonoVue induces cytotoxicity of HRGECs via repression of the ERK1/2 signaling pathway.

Acoustically-mediated intracellular delivery

Recent breakthroughs in gene editing have necessitated practical ex vivo methods to rapidly and efficiently re-engineer patient-harvested cells. Many physical membrane-disruption or pore-forming techniques for intracellular delivery, however, result in poor cell viability, while most carrier-mediated techniques suffer from suboptimal endosomal escape and hence cytoplasmic or nuclear targeting. In this work, we show that short exposure of cells to high frequency (>10 MHz) acoustic excitation facilitates temporal reorganisation of the lipid structure in the cell membrane that enhances translocation of gold nanoparticles and therapeutic molecules into the cell within just ten minutes. Due to its transient nature, rapid cell self-healing is observed, leading to high cellular viabilities (>97%). Moreover, the internalised cargo appears to be uniformly distributed throughout the cytosol, circumventing the need for strategies to facilitate endosomal escape. In the case of siRNA delivery, the method is seen to enhance gene silencing by over twofold, demonstrating its potential for enhancing therapeutic delivery into cells.

Sonodynamic therapy (SDT): a novel strategy for cancer nanotheranostics

Sonodynamic therapy (SDT) is a promising non-invasive therapeutic modality. Compared to photo-inspired therapy, SDT provides many opportunities and benefits, including deeper tissue penetration, high precision, less side effects, and good patient compliance. Thanks to the facile engineerable nature of nanotechnology, nanoparticles-based sonosensitizers exhibit predominant advantages, such as increased SDT efficacy, binding avidity, and targeting specificity. This review aims to summarize the possible mechanisms of SDT, which can be expected to provide the theoretical basis for SDT development in the future. We also extensively discuss nanoparticle-assisted sonosensitizers to enhance the outcome of SDT. Additionally, we focus on the potential strategy of combinational SDT with other therapeutic modalities and discuss the limitations and challenges of SDT toward clinical applications.

Ultrasound-Mediated Microbubble Destruction Suppresses Melanoma Tumor Growth

Melanoma is one of the most aggressive types of cancer, and its incidence has increased rapidly in the past few decades. In this study, we investigated a novel treatment approach, the use of low-intensity ultrasound (2.3 W/cm² at 1 MHz)-mediated Optison microbubble (MB) destruction (UMMD) to treat melanoma in a flank tumor model. The effect of UMMD was first evaluated in the melanoma cell line B16 F10 (B16) in vitro and then in mice inoculated with B16 cells. MB⁺B16 cells were exposed to US in vitro, resulting in significant cell death proportional to duty cycle (R² = 0.74): approximately 30%, 50%, 80% and 80% cell death at 10%, 30%, 50% and 100% DC respectively. Direct implantation of tumors with MBs, followed by sonication, resulted in retarded tumor growth and improved survival (p = 0.0106). Immunohistochemical analyses confirmed the significant changes in expression of the cell proliferation marker Ki67 (p = 0.037) and a microtubule-associated protein 2 (p = 0.048) after US + MB treatment. These results suggest that UMMD could be used as a possible treatment approach in isolated melanoma and has the potential to translate to clinical trials.

Ultrasound-triggered PLGA microparticle destruction and degradation for controlled delivery of local cytotoxicity and drug release

In this study, we investigated the low intensity ultrasound (US)-controlled delivery of local cytotoxicity and drug release via induced destruction and degradation of microparticles (MPs) made of poly(lactic-co-glycolic acid) (PLGA). This study was conducted in vitro with potential application towards tumor treatment in conjunction with direct injection. MPs, either loaded with or without doxorubicin (DOX), were prepared using a double-emulsion solvent-evaporation technique. First, the MPs were exposed to US with duty cycle (DC)-modulation. The destruction and degradation of MPs were evaluated using light and scanning electron microscopy. Second, the effects of US-mediated destruction/degradation of MPs on the local cytotoxicity as well as DOX release were evaluated. US-triggered MP destruction/degradation significantly enhanced nearby cell death and DOX release. These affects occurred in proportion to the DC. Our findings indicate that controlled cytotoxicity and DOX release by US could be useful in developing the minimally invasive therapeutic applications for tumor treatment.

Low-Intensity Ultrasound Enhances Histone Acetylation and Inhibition of Interleukin 6 Messenger RNA Expression by the Histone Deacetylase Inhibitor Sodium Butyrate in Fibroblasts

OBJECTIVES

Sodium butyrate, an inhibitor of histone deacetylase, has several therapeutic actions, including anti-inflammation. These actions depend on the concentration of sodium butyrate. In addition, lower concentrations have shown no effect on inflammation. Sonoporation by ultrasound can modify the permeability of the cell plasma membrane. Thus, the effects of sodium butyrate may be enhanced by the ultrasonic acoustics. Therefore, the facilitative effects of low-intensity ultrasound on histone acetylation and interleukin 6 (IL-6) regulation by sodium butyrate were investigated in this study.

METHODS

Human dermal fibroblasts were treated with 1-mM sodium butyrate for 3 hours with 20 minutes of 0.1-W/cm² pulsed or continuous ultrasound irradiation at the beginning of the sodium butyrate treatments.

RESULTS

The combination of treatments with sodium butyrate and ultrasound significantly increased histone acetylation in fibroblasts (P < .05), whereas sodium butyrate could not increase histone acetylation. In addition, this combined treatment significantly suppressed the IL-6 messenger RNA expression level with lipopolysaccharide stimulation for 1 hour (P < .05). Meanwhile, the treatment with sodium butyrate alone could not suppress IL-6 messenger RNA expression in fibroblasts. These effects were achieved with both 20% pulsed and continuous ultrasound but not observed with ultrasound treatment alone.

CONCLUSIONS

These results suggest that low-intensity ultrasound treatment promotes the physiologic actions of sodium butyrate as a histone deacetylase inhibitor.

Induction of Apoptosis in U937 Cells by Using a Combination of Bortezomib and Low-Intensity Ultrasound

Background

We scrutinized the feasibility of apoptosis induction in blood cancer cells by means of low-intensity ultrasound and the proteasome inhibitor bortezomib (Velcade).

Material/Methods

Human leukemic monocyte lymphoma U937 cells were subjected to ultrasound in the presence of bortezomib and the echo contrast agent Sonazoid. Two types of acoustic intensity (0.18 W/cm² and 0.05 W/cm²) were used for the experiments. Treated U937 cells were analyzed for viability and levels of early and late apoptosis. In addition, scanning electron microscopy analysis of treated cells was performed.

Results

The percentage of cells that underwent early apoptosis in the group treated with ultrasound and Sonazoid was 8.0±1.31% (intensity 0.18 W/cm²) and 7.0±1.69% (0.05 W/cm²). However, coupling of bortezomib and Sonazoid resulted in an increase in the percentage of cells in the early apoptosis phase, up to 32.50±3.59% (intensity 0.18 W/cm²) and 33.0±4.90% (0.05 W/cm²). The percentage of U937 cells in the late apoptosis stage was not significantly different from that in the group treated with bortezomib only.

Conclusions

Our findings indicate the feasibility of apoptosis induction in blood cancer cells by using a combination of bortezomib, ultrasound contrast agents, and low-intensity ultrasound.

Suppression of human 8-oxoguanine DNA glycosylase (OGG1) augments ultrasound-induced apoptosis in cervical cancer cells

PURPOSE

Human 8-oxoguanine DNA glycosylase (OGG1) is a major base excision repair enzyme, and it was reported to suppress the activation of intrinsic apoptotic signaling pathway in response to oxidative stress. In this study, our aim was to investigate the effects of OGG1 downregulation on ultrasound-induced apoptosis in cervical cancer cells.

METHODS

OGG1 expression was silenced by shRNA in the cervical cancer SW756 and CaSki cells. Cell viability was evaluated by MTT assay after OGG1 knockdown following ultrasound treatment. Ultrasound-induced apoptosis was measured by Annexin V-FITC/propidium iodide. Intracellular reactive oxygen species (ROS) production and Ca(2+) concentration were detected using a fluorescent probe, 2',7'-dichlorofluorescin diacetate (DCFH-DA) and a green fluorescent dye fluo-4AM, respectively. Western blotting was used to analyze the expression of Bcl-2, Bax, cleaved caspase-3, and nuclear factor-κB p65 (NF-κB p65).

RESULTS

The results indicated that OGG1 knockdown did not suppress cell proliferation, but significantly augmented ultrasound-induced inhibitory effects on the cell viability, and increased ultrasound-induced early apoptosis and late apoptosis and necrosis in the SW756 and CaSki cells when exposure to ultrasound (1MHz) at 1.5W/cm(2) for 30 and 60s. OGG1 knockdown significantly increased intracellular ROS production and Ca(2+) concentration after incubation of 6, 24, and 48h post-ultrasound treatment. The downregulation of Bcl-2 protein and the upregulation of Bax, cleaved caspase-3, and NF-κB p65 protein levels were observed in the shRNA-OGG1 cells and mock-shRNA cells, but no significant change of these protein levels was found between of them.

CONCLUSIONS

These results indicate that downregulation of OGG1 expression can augment ultrasound-induced apoptosis in cervical cancer cells, which suggests that OGG1 suppression might provide a new insight for ultrasound-induced therapeutic effects on cervical cancer treatment.

Gene delivery systems by the combination of lipid bubbles and ultrasound

Gene therapy is promising for the treatment of many diseases including cancers and genetic diseases. From the viewpoint of safety, ultrasound (US)-mediated gene delivery with nano/ microbubbles was recently developed as a novel non-viral vector system. US-mediated gene delivery using nano/microbubbles are able to produce transient changes in the permeability of the cell membrane after US-induced cavitation while reducing cellular damage and enables the tissue-specific or the site-specific intracellular delivery of gene both in vitro and in vivo. We have recently developed novel lipid nanobubbles (Lipid Bubbles). These nanobubbles can also be used to enhance the efficacy of the US-mediated genes (plasmid DNA, siRNA, and miRNA etc.) delivery. In this review, we describe US-mediated delivery systems combined with nano/microbubbles and discuss their feasibility as non-viral vector systems.

Study of cellular response induced by low intensity ultrasound frequency sweep pattern on myelomonocytic lymphoma U937 cells

PURPOSE

This study will analyze the mechanical effects (immediate lysis) and biological effects (cell survival, apoptosis, cell cycle) on U937 cells subjected to different sonication conditions with increasing and decreasing frequencies and burst rate (number of burst of a repeating signal in a specific time unit), in order to determine the best conditions of sonication to produce high mortality, apoptosis and inhibition of hyperproliferation.

METHOD

Cells are been stressed by pulse wave ultrasounds with increasing and decreasing frequencies between 400 and 620 kHz, at burst rates of 0.5, 10, 50 Hz and 50 % duty cycle (percentage of one period in which a signal is active), ultrasound intensities (spatial average-temporal peak) 0.045 and 0.09 W/cm(2). The sonication durations were 90 and 180 s.

RESULTS

The decreasing mode was found to be better than the increasing mode for 10 and 50 Hz burst rates, while at 0.5 Hz the increasing mode gave better results for the time of 180 s. For 10 Hz burst rate, decreasing frequency, 180 s, 0.09 W/cm(2), 20 % survival rate was found; after 6-h incubation, cells showed 13 % of early apoptosis and 11 % of late apoptosis. For these conditions of sonication, the hyperproliferation of cells was inhibited.

CONCLUSION

Survival rate decreases for increasing intensity and duration with each burst rate. The best performance is decreasing mode in a range between 620 and 400 kHz, duty cycle 50 %, burst rate 10 Hz. In these conditions after 180 s duration, the average survival rate is 20 %, the survived cells manifest apoptosis after 6-h incubation and hyperproliferation is prevented. The results seem to lead toward a non-invasive and effective purging of leukemic cells.

Tumor growth suppression by the combination of nanobubbles and ultrasound

We previously developed novel liposomal nanobubbles (Bubble liposomes [BL]) that oscillate and collapse in an ultrasound field, generating heat and shock waves. We aimed to investigate the feasibility of cancer therapy using the combination of BL and ultrasound. In addition, we investigated the anti-tumor mechanism of this cancer therapy. Colon-26 cells were inoculated into the flank of BALB/c mice to induce tumors. After 8 days, BL or saline was intratumorally injected, followed by transdermal ultrasound exposure of tumor tissue (1 MHz, 0-4 W/cm2 , 2 min). The anti-tumor effects were evaluated by histology (necrosis) and tumor growth. In vivo cell depletion assays were performed to identify the immune cells responsible for anti-tumor effects. Tumor temperatures were significantly higher when treated with BL + ultrasound than ultrasound alone. Intratumoral BL caused extensive tissue necrosis at 3-4 W/cm2 of ultrasound exposure. In addition, BL + ultrasound significantly suppressed tumor growth at 2-4 W/cm2 . In vivo depletion of CD8+ T cells (not NK or CD4+ T cells) completely blocked the effect of BL + ultrasound on tumor growth. These data suggest that CD8+ T cells play a critical role in tumor growth suppression. Finally, we concluded that BL + ultrasound, which can prime the anti-tumor cellular immune system, may be an effective hyperthermia strategy for cancer treatment.

Harmonic responses and cavitation activity of encapsulated microbubbles coupled with magnetic nanoparticles

Encapsulated microbubbles coupled with magnetic nanoparticles, one kind of hybrid agents that can integrate both ultrasound and magnetic resonance imaging/therapy functions, have attracted increasing interests in both research and clinic communities. However, there is a lack of comprehensive understanding of their dynamic behaviors generated in diagnostic and therapeutic applications. In the present work, a hybrid agent was synthesized by integrating superparamagnetic iron oxide nanoparticles (SPIOs) into albumin-shelled microbubbles (named as SPIO-albumin microbubbles). Then, both the stable and inertial cavitation thresholds of this hybrid agent were measured at varied SPIO concentrations and ultrasound parameters (e.g., frequency, pressure amplitude, and pulse length). The results show that, at a fixed acoustic driving frequency, both the stable and inertial cavitation thresholds of SPIO-albumin microbubble should decrease with the increasing SPIO concentration and acoustic driving pulse length. The inertial cavitation threshold of SPIO-albumin microbubbles also decreases with the raised driving frequency, while the minimum sub- and ultra-harmonic thresholds appear at twice and two thirds resonance frequency, respectively. It is also noticed that both the stable and inertial cavitation thresholds of SonoVue microbubbles are similar to those measured for hybrid microbubbles with a SPIO concentration of 114.7 μg/ml. The current work could provide better understanding on the impact of the integrated SPIOs on the dynamic responses (especially the cavitation activities) of hybrid microbubbles, and suggest the shell composition of hybrid agents should be appropriately designed to improve their clinical diagnostic and therapeutic performances of hybrid microbubble agents.

Multiparameter evaluation of in vivo gene delivery using ultrasound-guided, microbubble-enhanced sonoporation

More than 1800 gene therapy clinical trials worldwide have targeted a wide range of conditions including cancer, cardiovascular diseases, and monogenic diseases. Biological (i.e. viral), chemical, and physical approaches have been developed to deliver nucleic acids into cells. Although viral vectors offer the greatest efficiency, they also raise major safety concerns including carcinogenesis and immunogenicity. The goal of microbubble-mediated sonoporation is to enhance the uptake of drugs and nucleic acids. Insonation of microbubbles is thought to facilitate two mechanisms for enhanced uptake: first, deflection of the cell membrane inducing endocytotic uptake, and second, microbubble jetting inducing the formation of pores in the cell membrane. We hypothesized that ultrasound could be used to guide local microbubble-enhanced sonoporation of plasmid DNA. With the aim of optimizing delivery efficiency, we used nonlinear ultrasound and bioluminescence imaging to optimize the acoustic pressure, microbubble concentration, treatment duration, DNA dosage, and number of treatments required for in vivo Luciferase gene expression in a mouse thigh muscle model. We found that mice injected with 50μg luciferase plasmid DNA and 5×10(5) microbubbles followed by ultrasound treatment at 1.4MHz, 200kPa, 100-cycle pulse length, and 540 Hz pulse repetition frequency (PRF) for 2min exhibited superior transgene expression compared to all other treatment groups. The bioluminescent signal measured for these mice on Day 4 post-treatment was 100-fold higher (p<0.0001, n=5 or 6) than the signals for controls treated with DNA injection alone, DNA and microbubble injection, or DNA injection and ultrasound treatment. Our results indicate that these conditions result in efficient gene delivery and prolonged gene expression (up to 21days) with no evidence of tissue damage or off-target delivery. We believe that these promising results bear great promise for the development of microbubble-enhanced sonoporation-induced gene therapies.

Apoptosis Induced by Microbubble-Assisted Acoustic Cavitation in K562 Cells: The Predominant Role of the Cyclosporin A-Dependent Mitochondrial Permeability Transition Pore

Acoustic cavitation of microbubbles has been described as inducing tumor cell apoptosis that is partly associated with mitochondrial dysfunction; however, the exact mechanisms have not been fully characterized. Here, low-intensity pulsed ultrasound (1 MHz, 0.3-MPa peak negative pressure, 10% duty cycle and 1-kHz pulse repetition frequency) was applied to K562 chronic myelogenous leukemia cells for 1 min with 10% (v/v) SonoVue microbubbles. After ultrasound exposure, the apoptotic index was determined by flow cytometry with annexin V-fluorescein isothiocyanate/propidium iodide. In addition, mitochondrial membrane potential (ΔΨm) was determined with the JC-1 assay. Translocation of apoptosis-associated protein cytochrome c was evaluated by Western blotting. We found that microbubble-assisted acoustic cavitation can increase the cellular apoptotic index, mitochondrial depolarization and cytochrome c release in K562 cells, compared with ultrasound treatment alone. Furthermore, mitochondrial dysfunction and apoptosis were significantly inhibited by cyclosporin A, a classic inhibitor of the mitochondrial permeability transition pore; however, the inhibitor of Bax protein, Bax-inhibiting peptide, could not suppress these effects. Our results suggest that mitochondrial permeability transition pore opening is involved in mitochondrial dysfunction after exposure to microbubble-assisted acoustic cavitation. Moreover, the release of cytochrome c from the mitochondria is dependent on cyclosporin A-sensitive mitochondrial permeability transition pore opening, but not formation of the Bax-voltage dependent anion channel complex or Bax oligomeric pores. These data provide more insight into the mechanisms underlying mitochondrial dysfunction induced by acoustic cavitation and can be used as a basis for therapy.

CO2 bubbling-based 'Nanobomb' System for Targetedly Suppressing Panc-1 Pancreatic Tumor via Low Intensity Ultrasound-activated Inertial Cavitation

Noninvasive and targeted physical treatment is still desirable especially for those cancerous patients. Herein, we develop a new physical treatment protocol by employing CO₂ bubbling-based 'nanobomb' system consisting of low-intensity ultrasound (1.0 W/cm²) and a well-constructed pH/temperature dual-responsive CO₂ release system. Depending on the temperature elevation caused by exogenous low-intensity therapeutic ultrasound irradiation and the low pH caused by the endogenous acidic-environment around/within tumor, dual-responsive CO₂ release system can quickly release CO₂ bubbles, and afterwards, the generated CO₂ bubbles waves will timely explode before dissolution due to triggering by therapeutic ultrasound waves. Related bio-effects (e.g., cavitation, mechanical, shock waves, etc) caused by CO₂ bubbles' explosion effectively induce instant necrosis of panc-1 cells and blood vessel destruction within panc-1 tumor, and consequently inhibit the growth of panc-1 solid tumor, simultaneously minimizing the side effects to normal organs. This new physiotherapy employing CO₂ bubbling-based 'nanobomb' system promises significant potentials in targetedly suppressing tumors, especially for those highly deadly cancers.

Nonviral gene delivery systems by the combination of bubble liposomes and ultrasound

The combination of therapeutic ultrasound (US) and nano/microbubbles is an important system for establishing a novel and noninvasive gene delivery system. Genes are delivered more efficiently using this system compared with a conventional nonviral vector system such as the lipofection method, resulting in higher gene expression. This higher efficiency is due to the gene being delivered into the cytosol and bypassing the endocytosis pathway. Many in vivo studies have demonstrated US-mediated gene delivery with nano/microbubbles, and several gene therapy feasibility studies for various diseases have been reported. In addition, nano/microbubbles can deliver genes site specifically by the control of US exposure site. In the present review, we summarize the gene delivery systems by the combination of nano/microbubbles and US, describe their properties, and assess applications and challenges of US theranostics.

Low-frequency low energy ultrasound combined with microbubbles induces distinct apoptosis of A7r5 cells

The present study aimed to investigate whether low frequency low energy ultrasound combined with microbubbles induces apoptotic cell death of A7r5 rat aortic vascular smooth muscle cells, and to identify the possible mechanisms underlying this effect. Ultrasonic waves (45 kHz with 0.3 Wcm2 of intensity for 0, 10, 20 and 30 sec) were used together with different dosages of SonoVue™ microbubbles (0, 14, 28, 42 and 56 µl), respectively. The cell viability and apoptotic rate were determined by trypan blue staining immediately following treatment and flow cytometry 24 h thereafter. The treatment conditions resulting in the lowest amount of necrosis, highest apoptotic rate and lowest microbubble dosage was selected for the US+MB group, which was treated with ultrasound combined with microbubbles. The cell proliferation 24 h following treatment was determined and western blot analysis was applied to examine the expression of apoptosis‑associated proteins, B-cell lymphoma 2 (Bcl‑2) and Bcl-2-associated X (Bax). The harmonic acoustic pressure amplitude was measured to obtain the cavitation intensity. The combination of 20 sec ultrasound irradiation and 14 µl SonoVue™ was selected as the treatment conditions for the US+MB group. The results demonstrated that both ultrasound alone (the US group) and in combination with microbubbles significantly inhibited the proliferation of A7r5 cells compared with that of the control (P<0.01), and the suppression in the US+MB group was significantly greater (P<0.01). The apoptotic rate in A7r5 cells induced by this combination treatment (16.62±0.93%) was significantly higher than that in the control (3.93±0.39%; P<0.01) and US (6.88±1.87%; P<0.01) groups. Treatment with ultrasound combined with microbubbles increased the expression of Bax and decreased the ratio of Bcl‑2/Bax compared with those in the control and US groups. The cavitation induced by ultrasound combined with microbubble treatment was more intense than that by ultrasound alone. The results demonstrated that the cell death and apoptosis of A7r5 cells were associated with ultrasound duration and microbubble dosage. Low frequency ultrasound combined with microbubbles induced apoptosis in A7r5 cells through the upregulation of Bax and the downregulation of the Bcl‑2/Bax ratio, where the cavitation effect may have an important role.

Combined low-frequency ultrasound and microbubble contrast agent for the treatment of benign prostatic hyperplasia

BACKGROUND AND PURPOSE

Benign prostatic hyperplasia is one of the most common conditions in middle-aged and elderly men. The aim of the study was to investigate the treatment effects of low-frequency ultrasound combined with a microbubbles agent on benign prostatic hyperplasia.

METHODS

Eighteen 7-year-old male beagles with prostatic hyperplasia were randomly divided into six groups (n=3): Control group, 21 kHz ultrasound group, 21 kHz ultrasound and microbubble contrast agent group, 1 MHz ultrasound group, 1 MHz ultrasound and microbubble contrast agent group, and microbubble contrast agent group. The histopathologic damage to prostate cells was assessed via transmission electron microscopy and optical microscopy. The protein expressions of prostate-specific antigen (PSA), inducible nitric oxide synthase (iNOS), and super oxidase dimutase (SOD) were detected by enzyme-linked immunosorbent assay. Levels of aspartate aminotransferase (AST), alanine aminotransferase (ALT), blood urea nitrogen (BUN), and creatinine (Cr) were detected by the Biochemistry Automatic Analyzer.

RESULTS

Significant tissue injury, mitochondria injury, and cell apoptosis were observed in 21 kHz ultrasound and the microbubble contrast agent group. Compared with the control and microbubbles contrast agent groups, the decrease in levels of PSA or increase in levels of iNOs and SOD in the other four groups were statistically significant (P<0.05). The lowest level of PSA and the highest levels of iNOs and SOD were observed in the 21 kHz ultrasound and microbubbles contrast agent group. No significant changes in levels of AST, ALT, BUN, and Cr were observed between the six groups.

CONCLUSIONS

Our results suggest that lower frequency ultrasound may have a better effect on benign prostatic hyperplasia, and microbubble contrast agent application further strengthens this biological effect.

Induction of endoplasmic reticulum stress by sonoporation: linkage to mitochondria-mediated apoptosis initiation

The use of cavitational means to create transient membrane pores on living cells (i.e., sonoporation) may potentially induce a broad range of downstream bio-effects that disrupt the functioning of various organelles. Here we observed that on HL-60 leukemia cells, sonoporation may induce endoplasmic reticulum (ER) stress on a time-lapse basis and, in turn, signal the mitochondria to commit a cell toward apoptosis. Our observations were derived from in vitro ultrasound exposure experiments performed on HL-60 cells in the presence of lipid-shelled microbubbles (1:1 cell-to-bubble ratio; 1-MHz frequency; 0.45-MPa in situ peak negative pressure; 100-cycle pulse length; 1-kHz pulse repetition frequency; 60-s exposure period). Using flow cytometry, we found that sonoporated cells exhibited a progressive loss of functional ER mass over a 6-h period. Also, post-exposure Western blot assays (between 0 and 24 h) revealed various indications of post-sonoporation ER stress: (i) upregulation of ER-resident enzymes responsible for catalyzing protein folding; (ii) activation of trans-ER-membrane stress sensors; (iii) increased expression of ER-induced regulatory proteins that mediate pro-apoptotic signals to the mitochondria. These results corresponded to flow cytometry observations that depicted a progressive depolarization of a sonoporated cell's mitochondrial outer membrane potential. They were also consistent with another Western blot assay that found, in sonoporated cells, a time-lapse increase of caspase-9 (a mitochondria-activated apoptosis initiator protein). Taken together, our findings indicate that sonoporation may upset ER homeostasis, and this may ultimately result in initiation of apoptosis.

Investigation on the inertial cavitation threshold and shell properties of commercialized ultrasound contrast agent microbubbles

The inertial cavitation (IC) activity of ultrasound contrast agents (UCAs) plays an important role in the development and improvement of ultrasound diagnostic and therapeutic applications. However, various diagnostic and therapeutic applications have different requirements for IC characteristics. Here through IC dose quantifications based on passive cavitation detection, IC thresholds were measured for two commercialized UCAs, albumin-shelled KangRun(®) and lipid-shelled SonoVue(®) microbubbles, at varied UCA volume concentrations (viz., 0.125 and 0.25 vol. %) and acoustic pulse lengths (viz., 5, 10, 20, 50, and 100 cycles). Shell elastic and viscous coefficients of UCAs were estimated by fitting measured acoustic attenuation spectra with Sarkar's model. The influences of sonication condition (viz., acoustic pulse length) and UCA shell properties on IC threshold were discussed based on numerical simulations. Both experimental measurements and numerical simulations indicate that IC thresholds of UCAs decrease with increasing UCA volume concentration and acoustic pulse length. The shell interfacial tension and dilatational viscosity estimated for SonoVue (0.7 ± 0.11 N/m, 6.5 ± 1.01 × 10(-8) kg/s) are smaller than those of KangRun (1.05 ± 0.18 N/m, 1.66 ± 0.38 × 10(-7) kg/s); this might result in lower IC threshold for SonoVue. The current results will be helpful for selecting and utilizing commercialized UCAs for specific clinical applications, while minimizing undesired IC-induced bioeffects.

Effects of low-frequency ultrasound and microbubbles on angiogenesis-associated proteins in subcutaneous tumors of nude mice

It has been shown that 1 and 3 MHz low-intensity ultrasound was able to affect the fragile and leaky angiogenic blood vessels in a tumor. However, the biological effects of 21 kHz low-intensity ultrasound on tumors remain unclear. The aim of the present study was to explore the effects of 21 kHz ultrasound with microbubbles on the regulation of vascular endothelial growth factor (VEGF), cyclooxygenase-2 (COX-2) and apoptosis in subcutaneous prostate tumors in nude mice. The study included three parts, each with 20 tumor-bearing nude mice. Twenty nude mice were divided into four groups: control (sham treatment), microbubble ultrasound contrast agent (UCA), low-frequency ultrasound (US) and US+UCA groups. The UCA used was a microbubble contrast agent (SonoVue). The parameter of ultrasound: 21 kHz, an intensity of 26 mW/cm2, 40% duty cycle (on 2 sec, off 3 sec), 3 min, once every other day for 2 weeks. In the first study, all subcutaneous tumors were examined by contrast-enhanced ultrasonography (CEUS) at the initiation and completion of the experiments. Peak intensity (PI), time to peak intensity (TTP) and area under the curve (AUC) on the time intensity curve (TIC) were analyzed. In the second study, the intensity of VEGF and COX-2 protein expression in the vascular endothelium and cytoplasm was evaluated using immunohistochemistry and laser confocal microscopy. In the third study, terminal deoxynucleotidyl transferase (TdT)-mediated dUTP nick end labeling (TUNEL) assay was used for the evaluation of cell apoptosis in tumor tissues. The tumor cells and vasculature were examined by transmission electron microscopy (TEM). Only in the US+UCA group, PI and AUC decreased. The intensity of COX-2 and VEGF in the US+UCA group in immunohistochemical staining and laser confocal microscopy was lower compared to that of the other three groups. More cell apoptosis was found in the US+UCA group compared to the other 3 groups. In the control, UCA and US groups, the tumors had intact vascular endothelium and vessel lumens in TEM. However, lumen occlusion of vessels was observed in the US+UCA group. Twenty-one kHz low-intensity ultrasound with microbubbles may have anti-angiogenic effects on subcutaneous tumors in nude mice.

Enhancing HSP70-ShRNA transfection in 22RV1 prostate cancer cells by combination of sonoporation, liposomes and HTERT/CMV chimeric promoter

Gene therapy is a potentially viable approach for treating hormone-refractory prostate cancer (HRPC), it requires efficient delivery systems and a target gene. Inducing carcinoma cell apoptosis by inhibition of heat shock protein 70 (HSP70) overexpression has been emerging as an attractive strategy for cancer therapy. In our study, the high tumor-specificity of human telomerase reverse transcriptase (HTERT) expression prompted the use of an HTERT/cytomegalovirus (CMV) chimeric promoter to drive HSP70-ShRNA expression to induce HRPC 22RV1 cell apoptosis. At the same time, sonoporation induced by ultrasound-targeted microbubble destruction (UTMD) was utilized for delivery of plasmid loaded with HTERT/CMV promoter. Our results indicated the combination of sonoporation, low-dose liposomes and HTERT/CMV chimeric promoter as a delivery system has the potential to promote efficient gene transfer with lower cytotoxicity.

Targeted manipulation of apoptotic pathways by using High Intensity Focused Ultrasound in cancer treatment

Apoptosis, or programmed cell death, is a mechanism of cell death, which has been exploited for the treatment of cancers over the past few years. The understanding of apoptosis pathways (intrinsic and extrinsic) has led to discovery of treatment strategies which selectively target the cancer cells and spare the normal ones. This article reviews the current understanding of the apoptotic pathways which are utilized for targeting cancer cells using High Intensity Focused Ultrasound (HIFU).

Targeted delivery of biodegradable nanoparticles with ultrasound-targeted microbubble destruction-mediated hVEGF-siRNA transfection in human PC-3 cells in vitro

A potentially viable approach for treating late-stage prostate cancer is gene therapy. Successful gene therapy requires safe and efficient delivery systems. In this study, we report the efficient delivery of small interfering RNA (siRNA) via the use of biodegradable nanoparticles (NPs) made from monomethoxypoly(ethylene glycol)-poly(lactic-co-glycolic acid)-poly-l-lysine (mPEG-PLGA-PLL) triblock copolymers. On the basis of previous findings, cyclic Arg-Gly-Asp (cRGD) peptides were conjugated to NPs to recognize the target site, integrin αvβ3, expressed in high levels in PC-3 prostate cancer cells. The suppression of angiogenesis by the downregulation of vascular endothelial growth factor (VEGF) expression has been widely used to inhibit the growth of malignant tumors. In our study, human VEGF (hVEGF)-siRNA was encapsulated in NPs to inhibit VEGF expression in PC-3 cells. Concurrently, sonoporation induced by ultrasound-targeted microbubble destruction (UTMD) was utilized for the delivery of siRNA-loaded NPs. Our results showed low cytotoxicity and high gene transfection efficiency, demonstrating that the targeted delivery of biodegradable NPs with UTMD may be potentially applied as new vector system for gene delivery.

Targeted microbubbles in the experimental and clinical setting

BACKGROUND

Microbubbles have improved ultrasonography imaging techniques over the past 2 decades. Their safety, versatility, and easiness of use have rendered them equal or even superior in some instances to other imaging modalities such as computed tomography and magnetic resonance imaging. Herein, we conducted a literature review to present their types, general behavior in tissues, and current and potential use in clinical practice.

METHODS

A literature search was conducted for all preclinical and clinical studies involving microbubbles and ultrasonography.

RESULTS

Different types of microbubbles are available. These generally improve the enhancement of tissues during ultrasonography imaging. They also can be attached to ligands for the target of several conditions such as inflammation, angiogenesis, thrombosis, apoptosis, and might have the potential of carrying toxic drugs to diseased sites, thereby limiting the systemic adverse effects.

CONCLUSIONS

The use of microbubbles is evolving rapidly and can have a significant impact on the management of various conditions. The potential for their use as targeting agents and gene and drug delivery vehicles looks promising.

Low-intensity ultrasound enhances the anticancer activity of cetuximab in human head and neck cancer cells

The potential clinical use of ultrasound in inducing cell apoptosis and enhancing the effects of anticancer drugs in the treatment of cancers has previously been investigated. In this study, the combined effects of low-intensity ultrasound (LIU) and cetuximab, an anti-epidermal growth factor receptor (EGFR) antibody, on cell killing and induction of apoptosis in HSC-3 and HSC-4 head and neck cancer cells, and its mechanisms were investigated. Experiments were divided into 4 groups: non-treated (CNTRL), cetuximab-treated (CETU), ultrasound-treated (UST) and the combination of cetuximab and US-treated (COMB). Cell viability was assessed by trypan blue staining assay and induction of apoptosis was detected by fluorescein isothiocyanate (FITC)-Annexin V and propidium iodide (PI) staining assay at 24 h after cetuximab and/or US treatment. To elucidate the effect of cetuximab and US on EGFR signaling and apoptosis in head and neck cancer cells after the treatments, the expression of EGFR, phospho-EGFR, and the activation of caspase-3 were evaluated with western blotting. More cell killing features were evident in the COMB group in HSC-3 and HSC-4 cells compared with the other groups. No differences in EGFR expression among the CETU, UST and COMB groups was observed, while the expression of phospho-EGFR in the CETU group was downregulated compared with that in the CNTRL group. Phospho-EGFR expression was much more downregulated in the COMB group compared with that in the other groups. In addition, the activation of caspase-3 in the UST group was upregulated compared with that in the CNTRL group. Caspase-3 activation was much more upregulated in the COMB group than that in the other groups. These data indicated that LIU was able to enhance the anticancer effect of cetuximab in HSC-3 and HSC-4 head and neck cancer cells.

Involvement of reactive oxygen species in sonodynamically induced apoptosis using a novel porphyrin derivative

In this study, we investigated the induction of apoptosis by ultrasound in the presence of the novel porphyrin derivative DCPH-P-Na(I). HL-60 cells were exposed to ultrasound for up to 3 min in the presence and absence of DCPH-P-Na(I), and the induction of apoptosis was examined by analyzing cell morphology, DNA fragmentation, and caspase-3 activity. Reactive oxygen species were measured by means of ESR and spin trapping technique. Cells treated with 8 μM DCPH-P-Na(I) and ultrasound clearly showed membrane blebbing and cell shrinkage, whereas significant morphologic changes were not observed in cells exposed to either ultrasound or DCPH-P-Na(I) alone. Also, DNA ladder formation and caspase-3 activation were observed in cells treated with both ultrasound and DCPH-P-Na(I) but not in cells treated with ultrasound or DCPH-P-Na(I) alone. In addition, the combination of DCPH-P-Na(I) and the same acoustical arrangement of ultrasound substantially enhanced nitroxide generation by the cells. Sonodynamically induced apoptosis, caspase-3 activation, and nitroxide generation were significantly suppressed by histidine. These results indicate that the combination of ultrasound and DCPH-P-Na(I) induced apoptosis in HL-60 cells. The significant reduction in sonodynamically induced apoptosis, nitroxide generation, and caspase-3 activation by histidine suggests active species such as singlet oxygen are important in the sonodynamic induction of apoptosis. These experimental results support the possibility of sonodynamic treatment for cancer using the induction of apoptosis.

Nonviral gene therapy targeting cardiovascular system

The goal of gene therapy is either to introduce a therapeutic gene into or replace a defective gene in an individual's cells and tissues. Gene therapy has been urged as a potential method to induce therapeutic angiogenesis in ischemic myocardium and peripheral tissues after extensive investigation in recent preclinical and clinical studies. A successful gene therapy mainly relies on the development of the gene delivery vector. Developments in viral and nonviral vector technology including cell-based gene transfer will further improve transgene delivery and expression efficiency. Nonviral approaches as alternative gene delivery vehicles to viral vectors have received significant attention. Recently, a simple and safe approach of gene delivery into target cells using naked DNA has been improved by combining several techniques. Among the physical approaches, ultrasonic microbubble gene delivery, with its high safety profile, low costs, and repeatable applicability, can increase the permeability of cell membrane to macromolecules such as plasmid DNA by its bioeffects and can provide as a feasible tool in gene delivery. On the other hand, among the promising areas for gene therapy in acquired diseases, ischemic cardiovascular diseases have been widely studied. As a result, gene therapy using advanced technology may play an important role in this regard. The aims of this review focus on understanding the cellular and in vivo barriers in gene transfer and provide an overview of currently used chemical vectors and physical tools that are applied in nonviral cardiovascular gene transfer.

Ultrasound-microbubble mediated cavitation of plant cells: effects on morphology and viability

The interaction between ultrasound pulses and microbubbles is known to generate acoustic cavitation that may puncture biological cells. This work presents new experimental findings on the bioeffects of ultrasound-microbubble mediated cavitation in plant cells with emphasis on direct observations of morphological impact and analysis of viability trends in tobacco BY-2 cells that are widely studied in higher plant physiology. The tobacco cell suspensions were exposed to 1 MHz ultrasound pulses in the presence of 1% v/v microbubbles (10% duty cycle; 1 kHz pulse repetition frequency; 70 mm between probe and cells; 1-min exposure time). Few bioeffects were observed at low peak negative pressures (<0.4 MPa) where stable cavitation presumably occurred. In contrast, at 0.9 MPa peak negative pressure (with more inertial cavitation activities according to our passive cavitation detection results), random pores were found on tobacco cell wall (observed via scanning electron microscopy) and enhanced exogenous uptake into the cytoplasm was evident (noted in our fluorescein isothiocyanate dextran uptake analysis). Also, instant lysis was observed in 23.4% of cells (found using trypan blue staining) and programmed cell death was seen in 23.3% of population after 12 h (determined by terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end labeling [TUNEL]). These bioeffects generally correspond in trend with those for mammalian cells. This raises the possibility of developing ultrasound-microbubble mediated cavitation into a targeted gene transfection paradigm for plant cells and, conversely, adopting plant cells as experimental test-beds for sonoporation-based gene therapy in mammalian cells.