Comparison of the synergistic effect of lipid nanobubbles and SonoVue microbubbles for high intensity focused ultrasound thermal ablation of tumors

Interaction Between Microbubbles and Microwave Ablation: A Phantom and Rabbit Model

OBJECTIVES

This study aimed to explore the interactions between microbubbles and microwave ablation (MWA).

METHODS

The study employed custom-made phantoms (in vitro) and white New Zealand rabbits (in vivo). MWA was performed with or without microbubbles in the phantoms (2 × 105 particles mL-1) and rabbit livers (intravenous injection of 0.05 mL/kg SonoVue). During the MWA, K-type thermocouple probes were used to monitor the MWA-induced temperature increase. Contrast-enhanced ultrasound imaging (CEUS) was used to monitor and analyze the microbubbles signal intensity. After MWA, the ablation-zone volumes were evaluated and compared between the groups with and without microbubbles.

RESULTS

In both the phantom models and rabbits, microbubbles showed no significant influence on MWA, including the ablation range and MWA-induced temperature increase. In phantoms and rabbit livers filled with microbubbles, MWA caused the formation of a gradually expanding microbubble-defect region over the ablation time. An increase in the temperature caused microbubble destruction.

CONCLUSIONS

Microbubbles had no significant influence on MWA. However, MWA induced the destruction of microbubbles in a temperature-dependent manner. Thus, the poor thermotolerance of microbubbles is a non-negligible barrier when using CEUS to monitor the ablation range during MWA in real-time.

Immunomodulation and targeted drug delivery with high intensity focused ultrasound (HIFU): Principles and mechanisms

High intensity focused ultrasound (HIFU) is a non-invasive and non-ionizing sonic energy-based therapeutic technology for inducing thermal and non-thermal effects in tissues. Depending on the parameters, HIFU can ablate tissues by heating them to >55 °C to induce denaturation and coagulative necrosis, improve radio- and chemo-sensitizations and local drug delivery from nanoparticles at moderate hyperthermia (~41-43 °C), and mechanically fragment cells using acoustic cavitation (also known as histotripsy). HIFU has already emerged as an attractive modality for treating human prostate cancer, veterinary cancers, and neuromodulation. Herein, we comprehensively review the role of HIFU in enhancing drug delivery and immunotherapy in soft and calcified tissues. Specifically, the ability of HIFU to improve adjuvant treatments from various classes of drugs is described. These crucial insights highlight the opportunities and challenges of HIFU technology and its potential to support new clinical trials and translation to patients.

Low frequency nanobubble-enhanced ultrasound mechanotherapy for noninvasive cancer surgery

Scaling down the size of microbubble contrast agents to the nanometer level holds the promise for noninvasive cancer therapy. However, the small size of nanobubbles limits the obtained bioeffects as a result of ultrasound cavitation, when operating near the nanobubble resonance frequency. Here we show that coupled with low energy insonation at a frequency of 80 kHz, well below the resonance frequency of these agents, nanobubbles serve as noninvasive therapeutic warheads that trigger potent mechanical effects in tumors following a systemic injection. We demonstrate these capabilities in tissue mimicking phantoms, where a comparison of the acoustic response of micro- and nano-bubbles after insonation at a frequency of 250 or 80 kHz revealed that higher pressures were needed to implode the nanobubbles compared to microbubbles. Complete nanobubble destruction was achieved at a mechanical index of 2.6 for the 250 kHz insonation vs. 1.2 for the 80 kHz frequency. Thus, the 80 kHz insonation complies with safety regulations that recommend operation below a mechanical index of 1.9. In vitro in breast cancer tumor cells, the cell viability was reduced to 17.3 ± 1.7% of live cells. In vivo, in a breast cancer tumor mouse model, nanobubble tumor distribution and accumulation were evaluated by high frequency ultrasound imaging. Finally, nanobubble-mediated low frequency insonation of breast cancer tumors resulted in effective mechanical tumor ablation and tumor tissue fractionation. This approach provides a unique theranostic platform for safe, noninvasive and low energy tumor mechanotherapy.

Low-intensity pulsed ultrasound/nanomechanical force generators enhance osteogenesis of BMSCs through microfilaments and TRPM7

BACKGROUND

Low-intensity pulsed ultrasound (LIPUS) has been reported to accelerate fracture healing, but the mechanism is unclear and its efficacy needs to be further optimized. Ultrasound in combination with functionalized microbubbles has been shown to induce local shear forces and controllable mechanical stress in cells, amplifying the mechanical effects of LIPUS. Nanoscale lipid bubbles (nanobubbles) have high stability and good biosafety. However, the effect of LIPUS combined with functionalized nanobubbles on osteogenesis has rarely been studied.

RESULTS

In this study, we report cyclic arginine-glycine-aspartic acid-modified nanobubbles (cRGD-NBs), with a particle size of ~ 500 nm, able to actively target bone marrow mesenchymal stem cells (BMSCs) via integrin receptors. cRGD-NBs can act as nanomechanical force generators on the cell membrane, and further enhance the BMSCs osteogenesis and bone formation promoted by LIPUS. The polymerization of actin microfilaments and the mechanosensitive transient receptor potential melastatin 7 (TRPM7) ion channel play important roles in BMSCs osteogenesis promoted by LIPUS/cRGD-NBs. Moreover, the mutual regulation of TRPM7 and actin microfilaments promote the effect of LIPUS/cRGD-NBs. The extracellular Ca^2 + influx, controlled partly by TRPM7, could participated in the effect of LIPUS/cRGD-NBs on BMSCs.

CONCLUSIONS

The nanomechanical force generators cRGD-NBs could promote osteogenesis of BMSCs and bone formation induced by LIPUS, through regulation TRPM7, actin cytoskeleton, and intracellular calcium oscillations. This study provides new directions for optimizing the efficacy of LIPUS for fracture healing, and a theoretical basis for the further application and development of LIPUS in clinical practice.

Biomedical nanobubbles and opportunities for microfluidics

The use of bulk nanobubbles in biomedicine is increasing in recent years, which is attributable to the array of therapeutic and diagnostic tools promised by developing bulk nanobubble technologies. From cancer drug delivery and ultrasound contrast enhancement to malaria detection and the diagnosis of acute donor tissue rejection, the potential applications of bulk nanobubbles are broad and diverse. Developing these technologies to the point of clinical use may significantly impact the quality of patient care. This review compiles and summarizes a representative collection of the current applications, fabrication techniques, and characterization methods of bulk nanobubbles in biomedicine. Current state-of-the-art generation methods are not designed to create nanobubbles of high concentration and low polydispersity, both characteristics of which are important for several bulk nanobubble applications. To date, microfluidics has not been widely considered as a tool for generating nanobubbles, even though the small-scale precision and real-time control offered by microfluidics may overcome the challenges mentioned above. We suggest possible uses of microfluidics for improving the quality of bulk nanobubble populations and propose ways of leveraging existing microfluidic technologies, such as organ-on-a-chip platforms, to expand the experimental toolbox of researchers working to develop biomedical nanobubbles.

The use of bulk nanobubbles in biomedicine is increasing in recent years. This translates into new opportunities for microfluidics, which may enable the generation of higher quality nanobubbles that lead to advances in diagnostics and therapeutics.

Phase-changeable nanoparticle-mediated energy conversion promotes highly efficient high-intensity focused ultrasound ablation

This review describes how phase-changeable nanoparticles enable highly efficient high-intensity focused ultrasound ablation (HIFU). HIFU is effective in the clinical treatment of solid malignant tumors. However, it has intrinsic disadvantages for treating some deep lesions, such as damage to surrounding normal tissues. When phase-changeable nanoparticles are used in HIFU treatment, they could serve as good synergistic agents because they are transported in the blood and permeated and accumulated effectively in tissues. HIFU's thermal effects can trigger nanoparticles to undergo a special phase transition, thus enhancing HIFU ablation efficiency. Nanoparticles can also carry anticancer agents and release them in the targeted area to achieve chemo-synergistic therapy response. Although the formation of nanoparticles is complicated and HIFU applications are still in an early stage, the potential for their use in synergy with HIFU treatment shows promising results.

Contrast-Enhanced Ultrasonography in the Diagnosis and Treatment Modulation of Breast Cancer

The aim of this paper is to highlight the role of contrast-enhanced ultrasound in breast cancer in terms of diagnosis, staging and follow-up of the post-treatment response. Contrast-enhanced ultrasound (CEUS) is successfully used to diagnose multiple pathologies and has also clinical relevance in breast cancer. CEUS has high accuracy in differentiating benign from malignant lesions by analyzing the enhancement characteristics and calculating the time-intensity curve’s quantitative parameters. It also has a significant role in axillary staging, especially when the lymph nodes are not suspicious on clinical examination and have a normal appearance on gray-scale ultrasound. The most significant clinical impact consists of predicting the response to neoadjuvant chemotherapy, which offers the possibility of adjusting the therapy by dynamically evaluating the patient. CEUS is a high-performance, feasible, non-irradiating, accessible, easy-to-implement imaging method and has proven to be a valuable addition to breast ultrasound.

The Study of Enhanced High-Intensity Focused Ultrasound Therapy by Sonodynamic N2O Microbubbles

High-intensity focused ultrasound (HIFU) is a representative non-invasive method of cancer therapy, but its low therapeutic efficacy and risk of damage to surrounding normal tissue hinder its further clinical development and application. Sonodynamic therapy (SDT) kills tumor cells through reactive oxygen molecules produced by sonosensitizers during ultrasound treatment. SDT can enhance HIFU efficacy like microbubbles. In this work, we developed nanoscale N₂O microbubbles (N₂O-mbs) by an improved mechanical oscillation method. These microbubbles showed good biocompatibility and tumor cell binding. The sonosensitivity of the N₂O-mbs was detected both extracellularly and intracellularly through the detection of reactive oxygen species generation. The toxic effects of these sonodynamic microbubbles on tumor cells and the synergistic effect on HIFU treatment were evaluated. Significant apoptosis was caused by reactive oxygen species produced by N₂O-mbs under ultrasound irradiation. N₂O-mbs combined with HIFU increased tumor cell necrosis and apoptosis in vitro and the coagulative necrotic volume and echo intensity in the bovine liver target area ex vivo. These sonodynamic microbubbles have been also demonstrated to efficiently inhibit tumor growth in vivo. N₂O-mbs have a significant impact on the treatment and ablation effect of HIFU due to the advantages of microbubble and extraordinary sonosensitivity. This finding suggests that N₂O-mbs may be a novel auxiliary agent for ultrasound that can be used to promote HIFU tumor thermal ablation.

Enhancement of HIFU ablation by sonosensitizer-loading liquid fluorocarbon nanoparticles with pre-targeting in a mouse model

High intensity focused ultrasound (HIFU) is a noninvasive thermal ablation technique for the treatment of benign and malignant solid masses. To improve the efficacy of HIFU ablation, we developed poly (lactide-co-glycolide) (PLGA) nanoparticles encapsulating perfluoropentane (PFP) and hematoporphyrin monomethyl ether (HMME) as synergistic agents (HMME+PFP/PLGA). Two-step biotin-avidin pre-targeting technique was applied for the HIFU ablation. We further modified the nanoparticles with streptavidin (HMME+PFP/PLGA-SA). HMME+PFP/PLGA-SA were highly dispersed with spherical morphology (477.8 ± 81.8 nm in diameter). The encapsulation efficiency of HMME and PFP were 46.6 ± 3.3% and 40.1 ± 2.6%, respectively. The binding efficiency of nanoparticles to streptavidin was 95.5 ± 2.5%. The targeting ability of the HMME+PFP/PLGA-SA nanoparticles was tested by parallel plate flow chamber in vitro. In the pre-targeting group (HMME+PFP/PLGA-SA), a large number of nanoparticles bound to the peripheral and surface of the cell. In the HIFU ablation experiment in vivo, compared with the other groups, the largest gray-scale changes and coagulation necrosis areas were observed in the pre-targeting (HMME+PFP/PLGA-SA) group, with the lowest energy efficiency factor value. Moreover, the microvessel density and proliferation index declined, while the apoptotic index increased, in the tumor tissue surrounding the coagulation necrosis area in the pre-targeting group. Meanwhile, the survival time of the tumor-bearing nude mice in the pre-targeting group was significantly longer than that in the HIFU treatment group. These results suggest that HMME+PFP/PLGA-SA have high potential to act as synergistic agents in HIFU ablation.

Clinical Usefulness of the Microbubble Contrast Agent SonoVue in Enhancing the Effects of High-Intensity Focused Ultrasound for the Treatment of Adenomyosis

OBJECTIVE

To evaluate the clinical usefulness of the microbubble contrast agent SonoVue in enhancing high-intensity focused ultrasound (HIFU) for the treatment of adenomyosis.

METHODS

A total of 102 patients with adenomyosis, assessed from August 2015 to April 2017, were randomly divided into 1-minute (A) and 10-minute (B) groups, respectively. In groups A and B, HIFU started 1 minute and 10 minutes, respectively, after SonoVue injection. All patients underwent a magnetic resonance imaging scan before and after HIFU treatment.

RESULTS

The occurrence rates of massive gray scale change, nonperfused volume, and fractional ablation were similar in both groups (P > .05). Meanwhile, sonication time to massive gray scale change was reduced in group A compared with group B (P < .05). In addition, mean power, total energy, and energy efficiency factor were lower in group A than group B (all P < .05). The incidence rates of most perioperative and all postoperative adverse events were similar in both groups (P > .05). The incidence rates of pain in the treated region, leg pain, and sciatic or buttock pain during HIFU were substantially lower in group A than group B (P < .05).

CONCLUSIONS

Overall, starting HIFU sonication at 1 minute after SonoVue injection enhances HIFU ablation by cavitation and heating and is safe. Early massive gray scale change, lower total energy, and reduced mean power are potential safety factors.

Cavitation-threshold Determination and Rheological-parameters Estimation of Albumin-stabilized Nanobubbles

Nanobubbles (NBs) are of high interest for ultrasound (US) imaging as contrast agents and therapy as cavitation nuclei. Because of their instability (Laplace pressure bubble catastrophe) and low sensitivity to US, reducing the size of commonly used microbubbles to submicron-size is not trivial. We introduce stabilized NBs in the 100-250-nm size range, manufactured by agitating human serum albumin and perfluoro-propane. These NBs were exposed to 3.34- and 5.39-MHz US, and their sensitivity to US was proven by detecting inertial cavitation. The cavitation-threshold information was used to run a numerical parametric study based on a modified Rayleigh-Plesset equation (with a Newtonian rheology model). The determined values of surface tension ranged from 0 N/m to 0.06 N/m. The corresponding values of dilatational viscosity ranged from 5.10-10 Ns/m to 1.10-9 Ns/m. These parameters were reported to be 0.6 N/m and 1.10-8 Ns/m for the reference microbubble contrast agent. This result suggests the possibility of using albumin as a stabilizer for the nanobubbles that could be maintained in circulation and presenting satisfying US sensitivity, even in the 3-5-MHz range.

On-Demand Drug Release from Dual-Targeting Small Nanoparticles Triggered by High-Intensity Focused Ultrasound Enhanced Glioblastoma-Targeting Therapy

Glioblastoma is one of the most challenging and intractable tumors with the difficult treatment and poor prognosis. Unsatisfactory traditional systemic chemotherapies for glioblastoma are mainly attributed to the insufficient and nonspecific drug delivery into the brain tumors as well as the incomplete drug release at the tumor sites. Inspired by the facts that angiopep-2 peptide is an acknowledged dual-targeting moiety for brain tumor-targeting delivery and high-intensity focused ultrasound (HIFU) is an ideal trigger for drug release with an ultrahigh energy and millimeter-sized focus ability, in the present study, a novel HIFU-responsive angiopep-2-modified small poly(lactic-co-glycolic acid) (PLGA) hybrid nanoparticle (NP) drug delivery system holding doxorubicin/perfluorooctyl bromide (ANP-D/P) was designed to increase the intratumoral drug accumulation, further trigger on-demand drug release at the glioblastoma sites, and enhance glioblastoma therapy. It was shown that the ANP-D/P was stable and had a small size of 41 nm. The angiopep-2 modification endowed the ANP-D/P with improved blood-brain barrier transportation and specific accumulation in glioblastoma tissues by 17 folds and 13.4 folds compared with unmodified NPs, respectively. Under HIFU irradiation, the ANP-D/P could release 47% of the drug within 2 min and induce the apoptosis of most tumor cells. HIFU-triggered instantaneous drug release at the glioblastoma sites eventually enabled the ANP-D/P to achieve the strongest antiglioblastoma efficacy with the longest median survival time (56 days) of glioblastoma-bearing mice and the minimum vestiges of tumor cells in the pathological slices among all groups. In conclusion, the HIFU-responsive ANP-D/P in this study provided a new way for glioblastoma therapy with a great potential for clinical applications.

Ultrasound-Triggered Destruction of Folate-Functionalized Mesoporous Silica Nanoparticle-Loaded Microbubble for Targeted Tumor Therapy

A multifunctional drug delivery vehicle, which combines the active targeted mesoporous silica nanoparticle (MSN) and microbubble (MB) drug delivery system, is proposed and fabricated. The resulting delivery vehicle integrates the merits of high drug loading capacity, multitargeting, and ultrasound-guided releasing. Folate (FA), which serves as an active ligand, is modified to the surface of MSN (MSN-FA) to enhance cell membrane translocation. MSN-FA is loaded with tanshinone IIA (TAN), then encapsulated in a microbubble (denoted as MSN-FA-TAN-MB) for more precise tumor targeting. The conjunction between FA and MSN is confirmed by fourier transform infrared spectroscopy (FTIR). The characteristics and morphology of MSN-FA-TAN-MB are investigated by confocal microscopy and transmission electron microscopy. In vitro cytotoxicity and cellular uptake studies of MSN-FA-TAN-MB are conducted on A549 and HeLa tumor cells. FA-facilitated MSN-FA-TAN uptake is shown by HeLa cells that overexpress FA receptors via a FA-receptor-mediated endocytosis mechanism. The ultrasound response property of MSN-FA-TAN-MB is also verified. MSN-FA-TAN-MB shows significant antitumor efficacy in vivo with the assistance of FA, MB, and an external ultrasound irradiation. Thus, this multifunctional vehicle may provide a novel strategy for tumor targeting and imaging in tumor therapy.