Therapeutic potential of ultrasound microbubbles in gastrointestinal oncology: recent advances and future prospects

Effect of Microbubble Size, Composition and Multiple Sonication Points on Sterile Inflammatory Response in Focused Ultrasound-Mediated Blood-Brain Barrier Opening

Blood-brain barrier opening (BBBO) using focused ultrasound (FUS) and microbubbles (MBs) has emerged as a promising technique for delivering therapeutics to the brain. However, the influence of various FUS and MB parameters on BBBO and subsequent sterile inflammatory response (SIR) remains unclear. In this study, we investigated the effects of MB size and composition, as well as the number of FUS sonication points, on BBBO and SIR in an immunocompetent mouse model. Using MRI-guided MB+FUS, we targeted the striatum and assessed extravasation of an MRI contrast agent to assess BBBO and RNAseq to assess SIR. Our results revealed distinct effects of these parameters on BBBO and SIR. Specifically, at a matched microbubble volume dose (MVD), MB size did not affect the extent of BBBO, but smaller (1 μm diameter) MBs exhibited a lower classification of SIR than larger (3 or 5 μm diameter) MBs. Lipid-shelled microbubbles exhibited greater BBBO and a more pronounced SIR compared to albumin-shelled microbubbles, likely owing to the latter's poor in vivo stability. As expected, increasing the number of sonication points resulted in greater BBBO and SIR. Furthermore, correlation analysis revealed strong associations between passive cavitation detection measurements of harmonic and inertial MB echoes, BBBO and the expression of SIR gene sets. Our findings highlight the critical role of MB and FUS parameters in modulating BBBO and subsequent SIR in the brain. These insights inform the development of targeted drug delivery strategies and the mitigation of adverse inflammatory reactions in neurological disorders.

Metal Complexes for Cancer Sonodynamic Therapy

Sonodynamic therapy (SDT) for cancer treatment is gaining attention owing to its non-invasive property and ultrasound's (US) deep tissue penetration ability. In SDT, US activates the sonosensitizer at the target deep-seated tumors to generate reactive oxygen species (ROS), which ultimately damage tumors. However, drawbacks such as insufficient ROS production, aggregation of sonosensitizer, off-target side effects, etc., of the current organic/nanomaterial-based sonosensitizers limit the effectiveness of cancer SDT. Very recently, metal complexes with tunable physiochemical properties (such as sonostability, HOMO to LUMO energy gap, ROS generation ability, aqueous solubility, emission, etc.) have been devised as effective sonosensitizers, which could overcome the limitations of organic/nanomaterial-based sonosensitizers. This concept introduces all the reported metal-based sonosensitizers and delineates the prospects of metal complexes in cancer sonodynamic therapy. This new concept of metal-based sonosensitizer can deliver next-generation cancer drugs.

Advances and prospects of ultrasound targeted drug delivery systems using biomaterial-modified micro/nanobubbles for tumor therapy

The incidence of malignant tumors is rising rapidly and tends to be in the younger, which has been one of the most important factors endangering the safety of human life. Ultrasound micro/nanobubbles, as a noninvasive and highly specific antitumor strategy, can reach and destroy tumor tissue through their effects of cavitation and acoustic perforation under the guidance of ultrasound. Meanwhile, micro/nanobubbles are now used as a novel drug carrier, releasing drugs at a target region, especially on the prospects of biomaterial-modified micro/nanobubbles as a dual modality for drug delivery and therapeutic monitoring. and successful evaluation of the sonoporation mechanism(s), ultrasound parameters, drug type and dose will need to be addressed before translating this technology for clinical use. Therefore, this paper collects the literature on the experimental and clinical studies of ultrasound biomaterial-modified micro/nanobubbles therapy in vitro and in vivo in recent years.

Ultrasound and nanomaterial: an efficient pair to fight cancer

Ultrasounds are often used in cancer treatment protocols, e.g. to collect tumor tissues in the right location using ultrasound-guided biopsy, to image the region of the tumor using more affordable and easier to use apparatus than MRI and CT, or to ablate tumor tissues using HIFU. The efficacy of these methods can be further improved by combining them with various nano-systems, thus enabling: (i) a better resolution of ultrasound imaging, allowing for example the visualization of angiogenic blood vessels, (ii) the specific tumor targeting of anti-tumor chemotherapeutic drugs or gases attached to or encapsulated in nano-systems and released in a controlled manner in the tumor under ultrasound application, (iii) tumor treatment at tumor site using more moderate heating temperatures than with HIFU. Furthermore, some nano-systems display adjustable sizes, i.e. nanobubbles can grow into micro-bubbles. Such dual size is advantageous since it enables gathering within the same unit the targeting properties of nano bubbles via EPR effect and the enhanced ultrasound contrasting properties of micro bubbles. Interestingly, the way in which nano-systems act against a tumor could in principle also be adjusted by accurately selecting the nano-system among a large choice and by tuning the values of the ultrasound parameters, which can lead, due to their mechanical nature, to specific effects such as cavitation that are usually not observed with purely electromagnetic waves and can potentially help destroying the tumor. This review highlights the clinical potential of these combined treatments that can improve the benefit/risk ratio of current cancer treatments.

Ultrasonic technologies in imaging and drug delivery

Ultrasonic technologies show great promise for diagnostic imaging and drug delivery in theranostic applications. The development of functional and molecular ultrasound imaging is based on the technical breakthrough of high frame-rate ultrasound. The evolution of shear wave elastography, high-frequency ultrasound imaging, ultrasound contrast imaging, and super-resolution blood flow imaging are described in this review. Recently, the therapeutic potential of the interaction of ultrasound with microbubble cavitation or droplet vaporization has become recognized. Microbubbles and phase-change droplets not only provide effective contrast media, but also show great therapeutic potential. Interaction with ultrasound induces unique and distinguishable biophysical features in microbubbles and droplets that promote drug loading and delivery. In particular, this approach demonstrates potential for central nervous system applications. Here, we systemically review the technological developments of theranostic ultrasound including novel ultrasound imaging techniques, the synergetic use of ultrasound with microbubbles and droplets, and microbubble/droplet drug-loading strategies for anticancer applications and disease modulation. These advancements have transformed ultrasound from a purely diagnostic utility into a promising theranostic tool.

The promising shadow of microbubble over medical sciences: from fighting wide scope of prevalence disease to cancer eradication

Microbubbles are typically 0.5-10 μm in size. Their size tends to make it easier for medication delivery mechanisms to navigate the body by allowing them to be swallowed more easily. The gas included in the microbubble is surrounded by a membrane that may consist of biocompatible biopolymers, polymers, surfactants, proteins, lipids, or a combination thereof. One of the most effective implementation techniques for tiny bubbles is to apply them as a drug carrier that has the potential to activate ultrasound (US); this allows the drug to be released by US. Microbubbles are often designed to preserve and secure medicines or substances before they have reached a certain area of concern and, finally, US is used to disintegrate microbubbles, triggering site-specific leakage/release of biologically active drugs. They have excellent therapeutic potential in a wide range of common diseases. In this article, we discussed microbubbles and their advantageous medicinal uses in the treatment of certain prevalent disorders, including Parkinson's disease, Alzheimer's disease, cardiovascular disease, diabetic condition, renal defects, and finally, their use in the treatment of various forms of cancer as well as their incorporation with nanoparticles. Using microbubble technology as a novel carrier, the ability to prevent and eradicate prevalent diseases has strengthened the promise of effective care to improve patient well-being and life expectancy.

An ultrasound responsive microbubble-liposome conjugate for targeted irinotecan-oxaliplatin treatment of pancreatic cancer

Survival rates in pancreatic cancer have remained largely unchanged over the past four decades with less than 5% of patients surviving five years following initial diagnosis. FOLFIRINOX chemotherapy, a combination of folinic acid, 5-fluoruracil, irinotecan and oxaliplatin, has shown the greatest survival benefit for patients with advanced disease but is only indicated for those with good physical performance status due to its extreme off-target toxicity. Ultrasound targeted microbubble destruction (UTMD) has emerged as an effective strategy for the targeted delivery of drug payloads to solid tumours and involves using low intensity ultrasound to disrupt (burst) MBs in the tumour vasculature, releasing encapsulated or attached drugs in a targeted manner. In this manuscript, we describe the preparation of a microbubble-liposome complex (IRMB-OxLipo) carrying two of the three cytotoxic drugs present in the FOLFIRINOX combination, namely irinotecan and oxaliplatin. Efficacy of the IRMB-OxLipo complex following UTMD was determined in Panc-01 3D spheroid and BxPC-3 human xenograft murine models of pancreatic cancer. The results revealed that tumours treated with the IRMB-OxLipo complex and ultrasound were 136% smaller than tumours treated with the same concentration of irinotecan/oxaliplatin but delivered in a conventional manner, i.e. as a non-complexed mixture. This suggests that UTMD facilitates a more effective delivery of irinotecan/oxaliplatin improving the overall effectiveness of this drug combination and to the best of our knowledge, is the first reported example of a microbubble-liposome complex used to deliver these two chemotherapies.

Ultrasound Microbubble-Mediated microRNA-505 Regulates Cervical Cancer Cell Growth via AKT2

The application of ultrasound and microbubbles (USMB-) mediated microRNA (miR) is a promising approach of gene delivery for cancer treatment. We aimed to discuss the effects of USMB-miR-505 on cervical cancer (CC) development. miR-505 mediated by USMB was prepared. The effect of miR-505 on its transfection efficiency and the effect of miR-505 on HeLa cell proliferation, cell cycle, apoptosis, migration, and invasion were studied. The target gene of miR-505 was predicted, and its expression in CC was detected. The effect of the target gene on HeLa cells was further verified. USMB-miR-505 showed a higher transfection efficiency than miR-505 alone. The inhibitory effect of miR-505 mediated by USMB on HeLa cells was better than miR-505. miR-505 targeted AKT2, which was upregulated in CC. Overexpression of AKT2 reversed the inhibitory effect of USMB-miR-505 on HeLa cell malignant behaviors. Overall, we highlighted that USMB-miR-505 inhibited HeLa cell malignant behaviors by targeting AKT2.

Ultrasound-Responsive Carriers for Therapeutic Applications

Ultrasound (US)-responsive carriers have emerged as promising theranostic candidates because of their ability to enhance US-contrast, promote image-guided drug delivery, cause on-demand pulsatile release of drugs in response to ultrasound stimuli, as well as to enhance the permeability of physiological barriers such as the stratum corneum, the vascular endothelium, and the blood-brain barrier (BBB). US-responsive carriers include microbubbles MBs, liposomes, droplets, hydrogels, and nanobubble-nanoparticle complexes and have been explored for cavitation-mediated US-responsive drug delivery. Recently, a transient increase in the permeability of the BBB by microbubble (MB)-assisted low-frequency US has shown promise in enhancing the delivery of therapeutic agents in the case of neurological disorders. Further, the periodic mechanical stimulus generated by US-responsive MBs have also been explored in tissue engineering and has directly influenced the differentiation of mesenchymal stem cells into cartilage. This Review discusses the various types of US-responsive carriers and explores their emerging roles in therapeutics ranging from drug delivery to tissue engineering.

Acoustic Energy Controlled Nanoparticle Aggregation for Nanotherapy

Patients with unresectable or nonablatable tumors are difficult to cure, but nanotherapy combining targeted nanoparticles has many severe side effects due to the toxicities of anticancer drugs. We found that acoustic energy can produce a local region with high concentration from a low concentration suspended liquid of nano-SiO₂ particles at 2.5 MHz. Our calculated results show that the main reason for aggregation is the synthesized effect of the potential well of acoustic energy and streaming to trap them. In addition, the aggregated region can be manipulated to a targeted position in the vessel phantom by moving the ultrasound transducer external to the body. This noninvasive manipulation of suspended nanoparticles can rapidly increase the local drug concentration, but reduce the total dosage of anticancer drugs, which has the potential to be used for patients with advanced tumors by improving the physiological effects and reducing the side effects.

Ultrasound-Responsive Materials for Drug/Gene Delivery

Ultrasound is one of the most commonly used methods in the diagnosis and therapy of diseases due to its safety, deep penetration into tissue, and non-invasive nature. In the drug/gene delivery systems, ultrasound shows many advantages in terms of site-specific delivery and spatial release control of drugs/genes and attracts increasing attention. Microbubbles are the most well-known ultrasound-responsive delivery materials. Recently, nanobubbles, droplets, micelles, and nanoliposomes have been developed as novel carriers in this field. Herein, we review advances of novel ultrasound-responsive materials (nanobubbles, droplets, micelles and nanoliposomes) and discuss the challenges of ultrasound-responsive materials in delivery systems to boost the development of ultrasound-responsive materials as delivery carriers.

Micro/nano-bubble-assisted ultrasound to enhance the EPR effect and potential theranostic applications

Drug delivery for tumor theranostics involves the extensive use of the enhanced permeability and retention (EPR) effect. Previously, various types of nanomedicines have been demonstrated to accumulate in solid tumors via the EPR effect. However, EPR is a highly variable phenomenon because of tumor heterogeneity, resulting in low drug delivery efficacy in clinical trials. Because ultrasonication using micro/nanobubbles as contrast agents can disrupt blood vessels and enhance the specific delivery of drugs, it is an effective approach to improve the EPR effect for the passive targeting of tumors. In this review, the basic thermal effect, acoustic streaming, and cavitation mechanisms of ultrasound, which are characteristics that can be utilized to enhance the EPR effect, are briefly introduced. Second, micro/nanobubble-enhanced ultrasound imaging is discussed to understand the validity and variability of the EPR effect. Third, because the tumor microenvironment is complicated owing to elevated interstitial fluid pressure and the deregulated extracellular matrix components, which may be unfavorable for the EPR effect, few new trends in smart bubble drug delivery systems, which may improve the accuracy of EPR-mediated passive drug targeting, are summarized. Finally, the challenging and major concerns that should be considered in the next generation of micro/nanobubble-contrast-enhanced ultrasound theranostics for EPR-mediated passive drug targeting are also discussed.

Nano-Enhanced Drug Delivery and Therapeutic Ultrasound for Cancer Treatment and Beyond

While ultrasound is most widely known for its use in diagnostic imaging, the energy carried by ultrasound waves can be utilized to influence cell function and drug delivery. Consequently, our ability to use ultrasound energy at a given intensity unlocks the opportunity to use the ultrasound for therapeutic applications. Indeed, in the last decade ultrasound-based therapies have emerged with promising treatment modalities for several medical conditions. More recently, ultrasound in combination with nanomedicines, i.e., nanoparticles, has been shown to have substantial potential to enhance the efficacy of many treatments including cancer, Alzheimer disease or osteoarthritis. The concept of ultrasound combined with drug delivery is still in its infancy and more research is needed to unfold the mechanisms and interactions of ultrasound with different nanoparticles types and with various cell types. Here we present the state-of-art in ultrasound and ultrasound-assisted drug delivery with a particular focus on cancer treatments. Notably, this review discusses the application of high intensity focus ultrasound for non-invasive tumor ablation and immunomodulatory effects of ultrasound, as well as the efficacy of nanoparticle-enhanced ultrasound therapies for different medical conditions. Furthermore, this review presents safety considerations related to ultrasound technology and gives recommendations in the context of system design and operation.

Liposomes in Active, Passive and Acoustically-Triggered Drug Delivery

Cancer has become one of the most deadly noncommunicable diseases globally. Several modalities used to treat cancer patients exist today yet many have failed to prove high efficacy with low side effects. The most common example of such modalities is the use of chemotherapeutic drugs to treat cancerous cells and deter their uncontrolled proliferation. In addition to the destruction of cancerous tissues, chemotherapy destroys healthy tissues as it lacks the specificity to annihilate cancerous cells only and preferentially, which result in adverse side effects including nausea, hair fall and myocardial infarction. To prevent the side effects of non-selective chemotherapy, cancer therapy research has been focused on the implementation of nanocarrier systems that act as vehicles to encapsulate drugs and selectively transport their agent to the tumor site. In this paper, we shed light on liposomes along with three anticancer drug delivery approaches: passive, active and ultrasound-triggered drug delivery.

Ultrasound-mediated delivery of siESE complexed with microbubbles attenuates HER2+/- cell line proliferation and tumor growth in rodent models of breast cancer

The highly tunable, noninvasive and spatially targeted nature of microbubble-enhanced, ultrasound-guided (MB+US) drug delivery makes it desirable for a wide variety of therapies. In breast cancer, both HER2+ and HER2- type neoplasms pose significant challenges to conventional therapeutics in greater than 40% of breast cancer patients, even with the widespread application of biologics such as trastuzumab. To address this therapeutic challenge, we examined the novel combination of tumor-injected microbubble-bound siRNA complexes and monodisperse size-isolated microbubbles (4-µm diameter) to attenuate tumor growth in vivo, as well as MB+US-facilitated shRNA and siRNA knockdown of ESE-1, an effector linked to dysregulated HER2 expression in HER2+/- cell line propagation. We first screened six variants of siESE and shESE for efficient knockdown of ESE in breast cancer cell lines. We demonstrated efficient reduction of BT-474 (PR+, ER+, HER2+; luminal B) and MDA-MB-468 (PR-, ER-, HER2-; triple-negative) clonogenicity and non-adherent growth after knockdown of ESE-1. A significant reduction in proliferative potential was seen for both cell lines using MB+US to deliver shESE and siESE. We then demonstrated significant attenuation of BT-474 xenograft tumor growth in Nod/SCID female mice using direct injection of microbubble-adsorbed siESE to the tumor and subsequent sonication. Our results suggest a positive effect on drug delivery from MB+US, and highlights the feasibility of using RNAi and MB+US for breast cancer pathologies. RNAi coupled with MB+US may also be an effective theranostic approach to treat other acoustically accessible tumors, such as melanoma, thyroid, parotid and skin cancer.

Employment of enhanced permeability and retention effect (EPR): Nanoparticle-based precision tools for targeting of therapeutic and diagnostic agent in cancer

In tumorous tissues, the absence of vasculature supportive tissues intimates the formation of leaky vessels and pores (100 nm to 2 μm in diameter) and the poor lymphatic system offers great opportunity to treat cancer and the phenomenon is known as Enhanced permeability and retention (EPR) effect. The trends in treating cancer by making use of EPR effect is increasing day by day and generate multitudes of possibility to design novel anticancer therapeutics. This review aimed to present various factors affecting the EPR effect along with important things to know about EPR effect such as tumor perfusion, lymphatic function, interstitial penetration, vascular permeability, nanoparticle retention etc. This manuscript expounds the current advances and cross-talks the developments made in the of EPR effect-based therapeutics in cancer therapy along with a transactional view of its current clinical and industrial aspects.

A combination of ultrasound-targeted microbubble destruction with transplantation of bone marrow mesenchymal stem cells promotes recovery of acute liver injury

Background

Bone marrow mesenchymal stem cells (BMSCs) can provide an additional source of therapeutic stem cells for regeneration of liver cells during acute liver injury (ALI). However, the insufficient hepatic homing by the transplanted BMSCs limits their applications. Ultrasound-targeted microbubble destruction (UTMD) has been reported to promote the homing of transplanted stem cells into the ischemic myocardium. In this study, we investigated whether UTMD promotes the hepatic homing of BMSCs in ALI rats and evaluated the therapeutic effect.

Methods

BMSCs were isolated from the femurs and tibias of Sprague-Dawley (SD) rats. The isolated BMSCs were stably transfected with a lentivirus expressing enhanced green fluorescent protein (EGFP) that can be visualized and quantified in vivo after transplantation. Both tumor necrosis factor α (TNF-α) and stromal cell-derived factor 1 (SDF-1) were used to verify the appropriate ultrasound parameters. The ALI rats were divided into four groups: control, BMSCs, UTMD, and UTMD + BMSCs. The protein and mRNA expression levels of SDF-1, intercellular cell adhesion molecule (ICAM-1), vascular cell adhesion molecule 1 (VCAM-1), hepatocyte growth factor (HGF), and monocyte chemotactic protein 1 (MCP-1) in the exposed livers were analyzed at 48 h after treatment. ALI recovery was determined by serum biochemical parameters and histology.

Results

The isolated rat BMSCs demonstrated a good proliferation potential that was both osteogenic and adipogenic in differentiation and expressed cluster of differentiation (CD) 29 and CD90, but not CD45 or CD11b/c. After BMSC and/or UTMD treatment, the number of GFP-labeled BMSCs in the UTMD + BMSCs group was significantly higher than that of the BMSCs group (9.8 ± 2.3 vs. 5.2 ± 1.1/per high-power field). Furthermore, the expression of GFP mRNA was performed for evaluation of the homing rate of BMSCs in injury sites as well. In addition, the expression levels of SDF-1, ICAM-1, VCAM-1, HGF, and MCP-1 were higher (p < 0.01) in UTMD+BMSCs group. The serum levels of biomarkers were significantly lower in the UTMD + BMSCs group, and the apoptotic rate of hepatocytes in the UTMD + BMSCs group was markedly lower than that of the BMSCs group (all p < 0.05). The hepatic pathology was significantly alleviated in the UTMD + BMSCs group.

Conclusions

UTMD treatment efficiently induced a favorable microenvironment for cell engraftment, resulting in improvement of hepatic homing of BMSCs, which was probably mediated through upregulation of the expression of adhesion molecules and cytokines. UTMD treatment appeared to be an effective and noninvasive approach to achieve better efficacy of BMSC-based therapy for repairing a severely injured liver.

Electronic supplementary material

The online version of this article (10.1186/s13287-018-1098-4) contains supplementary material, which is available to authorized users.

Modalities for image- and molecular-guided cancer surgery

BACKGROUND

Surgery is the cornerstone of treatment for many solid tumours. A wide variety of imaging modalities are available before surgery for staging, although surgeons still rely primarily on visual and haptic cues in the operating environment. Image and molecular guidance might improve the adequacy of resection through enhanced tumour definition and detection of aberrant deposits. Intraoperative modalities available for image- and molecular-guided cancer surgery are reviewed here.

METHODS

Intraoperative cancer detection techniques were identified through a systematic literature search, with selection of peer-reviewed publications from January 2012 to January 2017. Modalities were reviewed, described and compared according to 25 predefined characteristics. To summarize the data in a comparable way, a three-point rating scale was applied to quantitative characteristics.

RESULTS

The search identified ten image- and molecular-guided surgery techniques, which can be divided into four groups: conventional, optical, nuclear and endogenous reflectance modalities. Conventional techniques are the most well known imaging modalities, but unfortunately have the drawback of a defined resolution and long acquisition time. Optical imaging is a real-time modality; however, the penetration depth is limited. Nuclear modalities have excellent penetration depth, but their intraoperative use is limited by the use of radioactivity. Endogenous reflectance modalities provide high resolution, although with a narrow field of view.

CONCLUSION

Each modality has its strengths and weaknesses; no single technique will be suitable for all surgical procedures. Strict selection of modalities per cancer type and surgical requirements is required as well as combining techniques to find the optimal balance.

Sonosensitive MRI Nanosystems as Cancer Theranostics: A Recent Update

In the tireless search for innovative and more efficient cancer therapies, sonosensitive Magnetic Resonance Imaging (MRI) agents play an important role. Basically, these systems consist of nano/microvesicles composed by a biocompatible membrane, responsive to ultrasound-induced thermal or mechanical effects, and an aqueous core, filled up with a MRI detectable probe and a therapeutic agent. They offer the possibility to trigger and monitor in real time drug release in a spatio-temporal domain, with the expectation to predict the therapeutic outcome. In this review, the key items to design sonosensitive MRI agents will be examined and an overview on the different approaches available so far will be given. Due to the extremely wide range of adopted ultrasound settings and formulations conceived, it is hard to compare the numerous preclinical studies reported. However, in general, a significantly better therapeutic outcome was noticed when exploiting ultrasound triggered drug release in comparison to traditional therapies, thus paving the way to the possible clinical translation of optimized sonosensitive MRI agents.

Controlled drug release from ultrasound-visualized elastic eccentric microcapsules using different resonant modes

The release rate of drug from elastic eccentric microcapsules can be regulated, based on their mode shapes and resonant natural frequencies.

Combinational light emitting diode-high frequency focused ultrasound treatment for HeLa cell

PURPOSE

Light sources such as laser and light emitting diode or ultrasound devices have been widely used for cancer therapy and regenerative medicines, since they are more cost-effective and less harmful than radiation therapy, chemotherapy or magnetic treatment. Compared to laser and low intensity ultrasound techniques, light emitting diode and high frequency focused ultrasound shows enhanced therapeutic effects, especially for small tumors.

MATERIALS AND METHODS

We propose combinational light emitting diode-high frequency focused ultrasound treatment for human cervical cancer HeLa cells. Individual red, green, and blue light emitting diode light only, high frequency focused ultrasound only, or light emitting diode light combined with high frequency focused ultrasound treatments were applied in order to characterize the responses of HeLa cells.

RESULTS

Cell density exposed by blue light emitting diode light combined with high frequency focused ultrasound (2.19 ± 0.58%) was much lower than that of cells exposed by red and green light emitting diode lights (81.71 ± 9.92% and 61.81 ± 4.09%), blue light emitting diode light (11.19 ± 2.51%) or high frequency focused ultrasound only (9.72 ± 1.04%).

CONCLUSIONS

We believe that the proposed combinational blue light emitting diode-high frequency focused ultrasound treatment could have therapeutic benefits to alleviate cancer cell proliferation.

Efficient Enhancement of Blood-Brain Barrier Permeability Using Acoustic Cluster Therapy (ACT)

The blood-brain barrier (BBB) is a major obstacle in drug delivery for diseases of the brain, and today there is no standardized route to surpass it. One technique to locally and transiently disrupt the BBB, is focused ultrasound in combination with gas-filled microbubbles. However, the microbubbles used are typically developed for ultrasound imaging, not BBB disruption. Here we describe efficient opening of the BBB using the promising novel Acoustic Cluster Therapy (ACT), that recently has been used in combination with Abraxane® to successfully treat subcutaneous tumors of human prostate adenocarcinoma in mice. ACT is based on the conjugation of microbubbles to liquid oil microdroplets through electrostatic interactions. Upon activation in an ultrasound field, the microdroplet phase transfers to form a larger bubble that transiently lodges in the microvasculature. Further insonation induces volume oscillations of the activated bubble, which in turn induce biomechanical effects that increase the permeability of the BBB. ACT was able to safely and temporarily permeabilize the BBB, using an acoustic power 5-10 times lower than applied for conventional microbubbles, and successfully deliver small and large molecules into the brain.

Intracellular delivery and ultrasonic activation of folate receptor-targeted phase-change contrast agents in breast cancer cells in vitro

Breast cancer is a diverse and complex disease that remains one of the leading causes of death among women. Novel, outside-of-the-box imaging and treatment methods are needed to supplement currently available technologies. In this study, we present evidence for the intracellular delivery and ultrasound-stimulated activation of folate receptor (FR)-targeted phase-change contrast agents (PCCAs) in MDA-MB-231 and MCF-7 breast cancer cells in vitro. PCCAs are lipid-coated, perfluorocarbon-filled particles formulated as nanoscale liquid droplets capable of vaporization into gaseous microbubbles for imaging or therapy. Cells were incubated with 1:1 decafluorobutane (DFB)/octafluoropropane (OFP) PCCAs for 1h, imaged via confocal microscopy, exposed to ultrasound (9MHz, MI=1.0 or 1.5), and imaged again after insonation. FR-targeted PCCAs were observed intracellularly in both cell lines, but uptake was significantly greater (p<0.001) in MDA-MB-231 cells (93.0% internalization at MI=1.0, 79.5% at MI=1.5) than MCF-7 cells (42.4% internalization at MI=1.0, 35.7% at MI=1.5). Folate incorporation increased the frequency of intracellular PCCA detection 45-fold for MDA-MB-231 cells and 7-fold for MCF-7 cells, relative to untargeted PCCAs. Intracellularly activated PCCAs ranged from 500nm to 6μm (IQR=800nm-1.5μm) with a mean diameter of 1.15±0.59 (SD) microns. The work presented herein demonstrates the feasibility of PCCA intracellular delivery and activation using breast cancer cells, illuminating a new platform toward intracellular imaging or therapeutic delivery with ultrasound.

Acoustic Cluster Therapy (ACT) enhances the therapeutic efficacy of paclitaxel and Abraxane® for treatment of human prostate adenocarcinoma in mice

Acoustic cluster therapy (ACT) is a novel approach for ultrasound mediated, targeted drug delivery. In the current study, we have investigated ACT in combination with paclitaxel and Abraxane® for treatment of a subcutaneous human prostate adenocarcinoma (PC3) in mice. In combination with paclitaxel (12mg/kg given i.p.), ACT induced a strong increase in therapeutic efficacy; 120days after study start, 42% of the animals were in stable, complete remission vs. 0% for the paclitaxel only group and the median survival was increased by 86%. In combination with Abraxane® (12mg paclitaxel/kg given i.v.), ACT induced a strong increase in the therapeutic efficacy; 60days after study start 100% of the animals were in stable, remission vs. 0% for the Abraxane® only group, 120days after study start 67% of the animals were in stable, complete remission vs. 0% for the Abraxane® only group. For the ACT+Abraxane group 100% of the animals were alive after 120days vs. 0% for the Abraxane® only group. Proof of concept for Acoustic Cluster Therapy has been demonstrated; ACT markedly increases the therapeutic efficacy of both paclitaxel and Abraxane® for treatment of human prostate adenocarcinoma in mice.