Understanding ultrasound induced sonoporation: definitions and underlying mechanisms

Acoustic tweezers for targeted drug delivery

Acoustic tweezers are a highly promising technology for targeted drug delivery thanks to their unique capabilities: (i) they can effectively operate in both in vitro and in vivo environments, (ii) they can manipulate a wide range of particle sizes and materials, and (iii) they can exert forces several orders of magnitude larger than competing techniques while remaining safe for biological tissues. In particular, tweezers capable of selectively capturing and manipulating objects in 3D with a single beam, known as 'single beam tweezers', open new perspectives for delivering drug carriers to precise locations. In this review, we first introduce the fundamental physical principles underlying the manipulation of particles using acoustic tweezers and highlight the latest advancements in the field. We then discuss essential considerations for the design of drug delivery carriers suitable for use with acoustic tweezers. Finally, we summarise recent promising studies that explore the use of acoustic tweezers for in vitro, ex vivo, and in vivo drug delivery.

Sonopermeation combined with stroma normalization enables complete cure using nano-immunotherapy in murine breast tumors

Nano-immunotherapy shows great promise in improving patient outcomes, as seen in advanced triple-negative breast cancer, but it does not cure the disease, with median survival under two years. Therefore, understanding resistance mechanisms and developing strategies to enhance its effectiveness in breast cancer is crucial. A key resistance mechanism is the pronounced desmoplasia in the tumor microenvironment, which leads to dysfunction of tumor blood vessels and thus, to hypoperfusion, limited drug delivery and hypoxia. Ultrasound sonopermeation and agents that normalize the tumor stroma have been employed separately to restore vascular abnormalities in tumors with some success. Here, we performed in vivo studies in two murine, orthotopic breast tumor models to explore if combination of ultrasound sonopermeation with a stroma normalization drug can synergistically improve tumor perfusion and enhance the efficacy of nano-immunotherapy. We found that the proposed combinatorial treatment can drastically reduce primary tumor growth and in many cases tumors were no longer measurable. Overall survival studies showed that all mice that received the combination treatment survived and rechallenge experiments revealed that the survivors obtained immunological memory. Employing ultrasound elastography and contrast enhanced ultrasound along with proteomics analysis, flow cytometry and immunofluorescene staining, we found the combinatorial treatment reduced tumor stiffness to normal levels, restoring tumor perfusion and oxygenation. Furthermore, it increased infiltration and activity of immune cells and altered the levels of immunosupportive chemokines. Finally, using machine learning analysis, we identified that tumor stiffness, CD8+ T cells and M2-type macrophages were strong predictors of treatment response.

Revolutionising Cancer Immunotherapy: Advancements and Prospects in Non-Viral CAR-NK Cell Engineering

The recent advancements in cancer immunotherapy have spotlighted the potential of natural killer (NK) cells, particularly chimeric antigen receptor (CAR)-transduced NK cells. These cells, pivotal in innate immunity, offer a rapid and potent response against cancer cells and pathogens without the need for prior sensitization or recognition of peptide antigens. Although NK cell genetic modification is evolving, the viral transduction method continues to be inefficient and fraught with risks, often resulting in cytotoxic outcomes and the possibility of insertional mutagenesis. Consequently, there has been a surge in the development of non-viral transfection technologies to overcome these challenges in NK cell engineering. Non-viral approaches for CAR-NK cell generation are becoming increasingly essential. Cutting-edge techniques such as trogocytosis, electroporation, lipid nanoparticle (LNP) delivery, clustered regularly interspaced short palindromic repeats-associated protein 9 (CRISPR-Cas9) gene editing and transposons not only enhance the efficiency and safety of CAR-NK cell engineering but also open new avenues for novel therapeutic possibilities. Additionally, the infusion of technologies already successful in CAR T-cell therapy into the CAR-NK paradigm holds immense potential for further advancements. In this review, we present an overview of the potential of NK cells in cancer immunotherapies, as well as non-viral transfection technologies for engineering NK cells.

Finely controlled bioceramic granules and sonoporation for osteogenic bone defect repair and reconstruction

Osteoporotic fractures caused by imbalance in bone homeostasis like chemotherapy, loss of ovarian function，glucocorticoid use and aging require special surgical procedure to treat and restore anatomical function. However, due to escalating bone weakness and impairment, it remains a clinical challenge to treat these types of fracture defects through conventional means. Herein, we fabricated a novel calcium silicate‑strontium (CS-Sr35) bioceramic granules with high biological properties and combined it with ultrasound aided sonoporation (sono) in augmenting osteoporotic critical-sized bone defect. The use of sonoporation mediated by microbubble was to influence efficient response for tissue permeability and delivery of bioactive ions from the bioceramic scaffold. The graded robust granule with adjustable microstructure exhibited physiochemical and biointegration properties favorable for ion release in vitro and osteogenic related activities in vivo. Herein, we compared the treatment of bone defect repair using (i) no scaffold (ii) CS-Sr35 only and (iii) CS-Sr35 + sono. The gradual bone repair process was elucidated by X-ray, histology and micro-CT analyses. Overall, our results showed that the CS-Sr35 + sono exhibited a tailored biodissolution behavior with complete defect repair and reconstruction. Meanwhile, the group with only CS-Sr35 granules had less osteoblastic healing while the blank group showed inadequate critical-sized defect repair throughout the study. Our study suggests that, the synergistic technique of combining bioceramic granule with sonoporation significantly optimizes osteogenic activity and biomineralization ability of the bioceramic granule for new bone growth in osteoporotic pathology and also this tailored technique provides versatile approach for improving the biological effect for next generation reconstruction and repair of diseased bone defect.

Phosphorodiamidate Morpholino Oligomers-Loaded Nanobubbles for Ultrasound-Mediated Delivery to the Myocardium in Muscular Dystrophy

Microbubbles (MBs) and nanobubbles (NBs) can oscillate and collapse in response to ultrasound exposure, resulting in contrast and delivery effects. Therefore, the retention of the entrapped gas is an important condition in bubble formulations, especially for MBs and NBs with lipid shells, and the stability of the lipid membrane is considered to be affected. We previously developed NBs, which are polyethylene glycol-modified liposomes entrapping an ultrasound contrast gas that can serve as nucleic acid carriers and ultrasound contrast agents. In particular, NBs containing cationic lipids were useful as systemic delivery tools that can load genes and nucleic acids on their surfaces. However, the gas retention of NBs containing cationic lipids were low, leaving room for improvement as ultrasound contrast agents. In this study, we attempted to prepare NBs containing anionic lipids to improve their stability in vivo, and found that they lasted longer in contrast time than previous NBs. In order to utilize anionic NBs, we evaluated their usefulness as systemic delivery tools for cationic-peptide-conjugated phosphorodiamidate morpholino oligomers (PMO). PMO has attracted attention as a therapeutic agent for Duchenne muscular dystrophy (DMD); however, its charge neutrality makes its delivery into muscle fibers challenging, especially more difficult to apply PMO to myocardial damage. We examined the systemic delivery of PMO to the heart using a combination of anionic NBs and ultrasound. Furthermore, we evaluated the usability of octaarginine (R8), a cationic cell-penetrating peptide (CPP), in loading PMO onto the surface of NBs and verified the potential of PMO-loaded NBs as a therapy for cardiac dysfunction in muscular dystrophy.

Focused Ultrasound: Noninvasive Image-Guided Therapy

ABSTRACT

Invasive open surgery used to be compulsory to access tumor mass to perform excision or resection. Development of minimally invasive laparoscopic procedures followed, as well as catheter-based approaches, such as stenting, endovascular surgery, chemoembolization, brachytherapy, which minimize side effects and reduce the risks to patients. Completely noninvasive procedures bring further benefits in terms of reducing risk, procedure time, recovery time, potential of infection, or other side effects. Focusing ultrasound waves from the outside of the body specifically at the disease site has proven to be a safe noninvasive approach to localized ablative hyperthermia, mechanical ablation, and targeted drug delivery. Focused ultrasound as a medical intervention was proposed decades ago, but it only became feasible to plan, guide, monitor, and control the treatment procedures with advanced radiological imaging capabilities. The purpose of this review is to describe the imaging capabilities and approaches to perform these tasks, with the emphasis on magnetic resonance imaging and ultrasound. Some procedures already are in clinical practice, with more at the clinical trial stage. Imaging is fully integrated in the workflow and includes the following: (1) planning, with definition of the target regions and adjacent organs at risk; (2) real-time treatment monitoring via thermometry imaging, cavitation feedback, and motion control, to assure targeting and safety to adjacent normal tissues; and (3) evaluation of treatment efficacy, via assessment of ablation and physiological parameters, such as blood supply. This review also focuses on sonosensitive microparticles and nanoparticles, such as microbubbles injected in the bloodstream. They enable ultrasound energy deposition down to the microvascular level, induce vascular inflammation and shutdown, accelerate clot dissolution, and perform targeted drug delivery interventions, including focal gene delivery. Especially exciting is the ability to perform noninvasive drug delivery via opening of the blood-brain barrier at the desired areas within the brain. Overall, focused ultrasound under image guidance is rapidly developing, to become a choice noninvasive interventional radiology tool to treat disease and cure patients.

Breaking through with ultrasound: TP53-driven efficacy of calcium sonoporation in pediatric rhabdomyosarcoma cells

Ultrasound-mediated sonoporation is a promising technique that temporarily permeabilizes cell membranes to enhance delivery of therapeutic agents directly to tumor sites while minimizing systemic side effects. Calcium, a critical regulator of cell death and proliferation, can be introduced into cells by ultrasound, offering a novel therapeutic approach. This study investigates calcium sonoporation (CaSP), which combines ultrasound with calcium ions and microbubbles, to target pediatric rhabdomyosarcoma A204 and RD cells. Our findings showed that CaSP disrupted cellular homeostasis by facilitating the controlled influx of calcium, leading to oxidative stress, mitochondrial dysfunction, cell cycle arrest and activation of apoptotic pathways. The study revealed that the TP53 mutational status significantly influences the cellular response to CaSP. TP53-wild-type A204 cells were particularly susceptible to CaSP, exhibiting marked increases in apoptosis and oxidative damage. In contrast, TP53-mutated RD cells exhibited a reduced oxidative stress and apoptotic response, highlighting the critical role of TP53 in mediating the effects of CaSP. This differential response underscored the potential of TP53 gene as a biomarker for predicting the efficacy of CaSP, offering a pathway toward more personalized cancer therapies. Furthermore, the study demonstrated that CaSP can selectively target cancer cells while sparing healthy tissue. The research laid the groundwork for future studies to optimise sonoporation parameters and explore its integration with existing cancer treatments. The insights gained from this study pave the way for developing more personalized cancer treatment strategies, particularly for tumors influenced by specific genetic contexts, such as TP53 mutations.

Retrospective study on the resonance of thermoacoustic emissions and their possible biological implications in cats treated with electron FLASH beams

Objective.Radiotherapy delivered at an ultra-high dose rate (UHDR) is a promising cancer treatment. In the last years, it has been shown to selectively reduce toxicity in healthy tissue by triggering the so-called FLASH effect achieved through specific temporal dose fractionation. However, the increase of the instantaneous dose rate results in the production of stronger thermoacoustic emissions for microsecond or shorter pulsed ionizing beams, which could potentially impact the treatment outcomes. Focusing on scenarios expected to create the highest acoustic intensities, the objectives of this work were to assess whether acoustic resonance can theoretically occurin vivoand how it could be mitigated in cases where it would influence the biological response.Approach.Thermoacoustic emissions were retrospectively simulated from post-treatment x-ray computed tomography scans of cats irradiated with a single high dose of electron FLASH to treat squamous carcinoma of the nasal planum. The peak dose, pressure intensity and location of the acoustic resonance were assessed for different beam positioning and reproduced for three animals.Main results.Irradiation of nasal planum in cats using a frontal electron beam results in pressure hot spots due to acoustic resonance that are observed in the vicinity of the rostral maxillary bone. The pressure distribution is mostly influenced by the anatomy (i.e. geometry and heterogeneous composition of the irradiated object), whereas its intensity largely depends on the irradiation setup. While further experimental investigation is needed to understand and mitigate potential associated risks, our results underline that acoustic phenomena so far neglected in conventional radiotherapy may need to be accounted for when using UHDR delivery.Significance.We show that specific irradiation scenarios can induce geometry-dependent thermoacoustic resonancesin vivowhich may be of sufficient magnitude to induce biological effects and impact the outcomes of FLASH radiotherapy.

Thumb-sized 3D-Printed cymbal microneedle array (CyMA) for enhanced transdermal drug delivery

Transdermal drug delivery presents a compelling alternative to both needle injection and oral ingestion of medication, as it enhances patient adherence and convenience through its non-invasive and painless administration method. The use of microneedles penetrates the barrier of the stratum corneum, facilitating the sustained delivery of drugs across the skin. However, their efficacy has been limited by the slow diffusion of molecules and often requires external triggers. Herein, a lightweight and minimized 3D-printed microneedle array is introduced, employing a cymbal-type ultrasound transducer, as the external engine for deeper and faster transdermal drug delivery. A theoretical finite element model was developed and the optimization design was conducted for structural parameters. The optimized assembled prototype was fabricated using high-precision 3D printing and weighs only 20 g. In vivo experiments using a diabetic mouse model demonstrate that local insulin delivery with CyMA achieves systemic effects comparable to intraperitoneal administration. Such compact and effective microneedle delivery technology offers considerable promise therapeutic applications on the skin and intraoral use.

Sonopermeation With Size-sorted Microbubbles Synergistically Increases Survival and Enhances Tumor Apoptosis With L-DOX by Increasing Vascular Permeability and Perfusion in Neuroblastoma Xenografts

OBJECTIVE

Despite aggressive therapy, approximately 50% of patients with neuroblastoma (NB) fail to respond, and survivors endure lifelong toxicities. Sonopermeation increases drug uptake via cell bilayer disruption through focused ultrasound and microbubbles (MBs)-gas-filled, sound sensitive lipid spheres. MB response to a given ultrasound pulse (cavitation) varies according to MB size. We asked whether size-sorted MBs (SSMB) 4 to 5 µm in diameter will more consistently and predictably enhance doxorubicin uptake, compared with polydisperse MBs (PMB, 0.5-10 µm in diameter), thereby increasing drug delivery to NB xenografts.

METHODS

Human NB cells were implanted into the left kidney of nude mice and grown for 5 to 6 wk. Mice received sonopermeation alongside either PMB or SSMB at low (0.6 MPa) or high (2 MPa) negative pressures. Some mice also received different chemotherapy agents (doxorubicin, etoposide or cyclophosphamide). Circulating tumor cells were assessed by flow cytometry 1 h after treatment. Survival was assessed for up to 21 d, a subset of mice was euthanized 24 h after treatment for histological assessment of apoptosis, vascular lumen size and tight junctions.

RESULTS

Tumors treated with SSMB and high pressure showed synergy with liposomal doxorubicin (L-DOX) owing to increased vascular lumen and disruption of tight junctions, resulting in drug uptake, apoptosis, lack of tumor growth and increased survival. We found no difference in the numbers of circulating tumor cells.

CONCLUSION

Sonopermeation with SSMB at 2 MPa synergizes with L-DOX delivery, increasing apoptosis, perfusion and vascular permeability, suggesting that SSMB sonopermeation at high pressure is promising for NB-targeted treatment, especially in combination with L-DOX.

High-frequency MHz-order vibration enables cell membrane remodeling and lipid microdomain manipulation

We elucidate the mechanism underpinning a recently discovered phenomenon in which cells respond to MHz-order mechanostimuli. Deformations induced along the plasma membrane under these external mechanical cues are observed to decrease the membrane tension, which, in turn, drives transient and reversible remodeling of its lipid structure. In particular, the increase and consequent coalescence of ordered lipid microdomains leads to closer proximity to mechanosensitive ion channels-Piezo1, in particular-that, due to crowding, results in their activation to mobilize influx of calcium (Ca2+) ions into the cell. It is the modulation of this second messenger that is responsible for the downstream signaling and cell fates that ensue. In addition, we show that such spatiotemporal control over the membrane microdomains in cells-without necessitating biochemical factors-facilitates aggregation and association of intrinsically disordered tau proteins in neuroblastoma cells, and their transformation to pathological conditions implicated in neurodegenerative diseases, thereby paving the way for the development of therapeutic intervention strategies.

Pulsed Ultrasound-Mediated Drug Delivery Enhancement Through Human Sclera

Purpose

The purpose of this study was to characterize whether pulsed ultrasound (PUS) affects transscleral drug delivery.

Methods

Fluorescein sodium (NaF, 376 Da) and fluorescein isothiocyanate-conjugated dextran 40 (FD-40, 40 kDa) were used as model drugs. Human sclera grafts were placed in modified Franz diffusion cells and were treated by PUS (1 megahertz [MHz], 0.71 W/cm2, duty cycle 30%, application time 5 minutes) once or repeatedly under various conditions to assess permeation enhancement and reservoir effect. The safety of PUS application was assessed on human sclera grafts ex vivo and rabbit eyes in vivo by histology and temperature measurements.

Results

Single PUS application yielded a significant increase in FD-40 permeation (P <  0.05). Repeated PUS applications led to a further enhancement in FD-40 permeation and also significantly promoted NaF permeation (more than 8.51-fold, P <  0.05). The human scleral permeability was temporarily modified by PUS, as evidenced by the increased scleral permeability during PUS application and the unchanged permeability coefficients at steady state. The reservoir effect of human sclera was also enhanced by PUS application. Cavitation was detected under PUS. A minor increase in graft temperature rise (<1°C) and no ocular damage was caused by PUS.

Conclusions

PUS is an efficient and safe method to enhance model drugs to transport across human sclera by increasing the scleral permeability transiently and improving the reservoir effect. The enhancement was correlated with the molecule size and further promoted by the repeated PUS application.

Translational Relevance

Our study provides proof of concept for using PUS to enhance drug delivery to the posterior eye segment.

Ultrasound and Microbubble-Induced Reduction of Functional Vasculature Depends on the Microbubble, Tumor Type and Time After Treatment

OBJECTIVE

Ultrasound in combination with microbubbles can enhance accumulation and improve the distribution of various therapeutic agents in tumor tissue, leading to improved efficacy. Understanding the impact of treatment on the tumor microenvironment, concurrently with how microenvironment attributes affect treatment outcome, will be important for selecting appropriate patient cohorts in future clinical trials. The main aim of this work was to investigate the influence of ultrasound and microbubbles on the functional vasculature of cancer tissue.

METHODS

Four different tumor models in mice (bone, pancreatic, breast and colon cancer) were characterized with respect to vascular parameters using contrast-enhanced ultrasound imaging. The effect of treatment with microbubbles and ultrasound was then investigated using immunohistochemistry and confocal microscopy, quantifying the total amount of vasculature and fraction of functional vessels. Two different microbubbles were used, the clinical contrast agent SonoVue and the large bubbles generated by Acoustic Cluster Therapy (ACT), tailored for therapeutic purposes.

RESULTS

The colon cancer model displayed slower flow but a higher vascular volume than the other models. The pancreatic model showed the fastest flow but also the lowest vascular volume. Ultrasound and SonoVue transiently reduced the amount of functional vasculature in breast and colon tumors immediately after treatment. No reduction was observed for ACT, likely due to shorter ultrasound pulses and lower pressures applied.

CONCLUSION

Variation between tumor models due to tissue characteristics emphasizes the importance of evaluating treatment suitability in the specific tissue of interest, as altered perfusion could have a large impact on drug delivery and therapeutic outcome.

Smart Ultrasound-responsive Polymers for Drug Delivery: An Overview on Advanced Stimuli-sensitive Materials and Techniques

In recent years, a notable advancement has occurred in the domain of drug delivery systems via the integration of intelligent polymers that respond to ultrasound. The implementation of this groundbreaking methodology has significantly revolutionised the controlled and precise delivery of therapeutic interventions. An in-depth investigation is conducted into the most recent developments in ultrasonic stimulus-responsive materials and techniques for the purpose of accomplishing precise medication administration. The investigation begins with an exhaustive synopsis of the foundational principles underlying drug delivery systems that react to ultrasonic stimuli, focusing specifically on the complex interplay between polymers and ultrasound waves. Significant attention is devoted to the development of polymers that demonstrate tailored responsiveness to ultrasound, thereby exemplifying their versatility in generating controlled drug release patterns. Numerous classifications of intelligent polymers are examined in the discussion, including those that react to variations in temperature, pH, and enzymes. When coupled with ultrasonic stimuli, these polymers offer a sophisticated framework for the precise manipulation of drug release in terms of both temporal and spatial dimensions. The present study aims to examine the synergistic effects of responsive polymers and ultrasound in overcoming biological barriers such as the blood-brain barrier and the gastrointestinal tract. By doing so, it seeks to shed light on the potential applications of these materials in intricate clinical scenarios. The issues and future prospects of intelligent ultrasound-responsive polymers in the context of drug delivery are critically analysed in this article. The objective of this study is to offer valuable perspectives on the challenges that must be overcome to enable the effective implementation of these technologies. The primary objective of this comprehensive review is to furnish researchers, clinicians, and pharmaceutical scientists with a wealth of information that will serve as a guide for forthcoming developments in the development and enhancement of intelligent drug delivery systems that employ ultrasound-responsive polymers to attain superior therapeutic outcomes.

Recent Advances and Future Directions in Sonodynamic Therapy for Cancer Treatment

Deep-tissue solid cancer treatment has a poor prognosis, resulting in a very low 5-year patient survival rate. The primary challenges facing solid tumor therapies are accessibility, incomplete surgical removal of tumor tissue, the resistance of the hypoxic and heterogeneous tumor microenvironment to chemotherapy and radiation, and suffering caused by off-target toxicities. Here, sonodynamic therapy (SDT) is an evolving therapeutic approach that uses low-intensity ultrasound to target deep-tissue solid tumors. The ability of ultrasound to deliver energy safely and precisely into small deep-tissue (>10 cm) volumes makes SDT more effective than conventional photodynamic therapy. While SDT is currently in phase 1/2 clinical trials for glioblastoma multiforme, its use for other solid cancer treatments, such as breast, pancreatic, liver, and prostate cancer, is still in the preclinical stage, with further investigation required to improve its therapeutic efficacy. This review, therefore, focuses on recent advances in SDT cancer treatments. We describe the interaction between ultrasound and sonosensitizer molecules and the associated energy transfer mechanism to malignant cells, which plays a central role in SDT-mediated cell death. Different sensitizers used in clinical and preclinical trials of various cancer treatments are listed, and the critical ultrasound parameters for SDT are reviewed. We also discuss approaches to improve the efficacies of these sonosensitizers, the role of the 3-dimensional spheroid in vitro investigations, ultrasound-controlled CAR-T cell and SDT-based multimodal therapy, and machine learning for sonosensitizer optimization, which could facilitate clinical translation of SDT.

Innovative Approaches to Brain Cancer: The Use of Magnetic Resonance-guided Focused Ultrasound in Glioma Therapy

Gliomas are a wide group of common brain tumors, with the most aggressive type being glioblastoma multiforme (GBM), with a 5-year survival rate of less than 5% and a median survival time of approximately 12-14 months. The standard treatment of GBM includes surgical excision, radiotherapy, and chemotherapy with temozolomide (TMZ). However, tumor recurrence and progression are common. Therefore, more effective treatment for GBM should be found. One of the main obstacles to the treatment of GBM and other gliomas is the blood-brain barrier (BBB), which impedes the penetration of antitumor chemotherapeutic agents into glioblastoma cells. Nowadays, one of the most promising novel methods for glioma treatment is Magnetic Resonance-guided Focused Ultrasound (MRgFUS). Low-intensity FUS causes the BBB to open transiently, which allows better drug delivery to the brain tissue. Under magnetic resonance guidance, ultrasound waves can be precisely directed to the tumor area to prevent side effects in healthy tissues. Through the open BBB, we can deliver targeted chemotherapeutics, anti-tumor agents, immunotherapy, and gene therapy directly to gliomas. Other strategies for MRgFUS include radiosensitization, sonodynamic therapy, histotripsy, and thermal ablation. FUS can also be used to monitor the treatment and progression of gliomas using blood-based liquid biopsy. All these methods are still under preclinical or clinical trials and are described in this review to summarize current knowledge and ongoing trials.

RNA-Seq Reveals the Mechanism of Pyroptosis Induced by Oxygen-Enriched IR780 Nanobubbles-Mediated Sono-Photodynamic Therapy

Background

Sono-photodynamic therapy (SPDT), the combination of sonodynamic therapy (SDT) and photodynamic therapy (PDT), is a promising tumor treatment method. However, the hypoxic tumor microenvironment greatly compromises the efficacy of SPDT. Pyroptosis, a new type of programmed cell death, is mainly induced by some chemotherapeutic drugs in the current research, and rarely by SPDT. RNA sequencing (RNA-seq) is a high-throughput sequencing technique that comprehensively profiles the transcriptome, revealing the full spectrum of RNA molecules in a cell. Here, we constructed IR780@O2 nanobubbles (NBs) with photoacoustic dual response and hypoxia improvement properties to fight triple negative breast cancer (TNBC), and demonstrated that SPDT could kill TNBC cells through pyroptosis pathway. RNA-seq further revealed potential mechanisms and related differentially expressed genes.

Methods

Thin-film hydration and mechanical vibration method were utilized to synthesize IR780@O2 NBs. Subsequently, we characterized IR780@O2 NBs and examined the cytotoxicity as well as ROS production ability. A series of experiments were conducted to verify that SPDT killed TNBC cells through pyroptosis.

Results

IR780@O2 NBs were successfully prepared and had certain stability. Compared with SDT alone, SPDT increased therapeutic effect by 1.67 times by generating more ROS, and the introduction of NBs and O2 NBs (2.23 times and 2.93 times compared with SDT alone) could further promote this process. Other experiments proved that TNBC cells died by pyroptosis pathway. Moreover, the in-depth mechanism revealed that colony stimulating factor (CSF) and C-X-C motif chemokine ligand (CXCL) could be potential targets for the occurrence of pyroptosis in TNBC cells.

Conclusion

The IR780@O2 NBs prepared in this study increased the degree of TNBC cell pyroptosis through SPDT effect and alleviation of hypoxia, and cellular senescence might be a biological process closely related to pyroptosis in TNBC.

The molecular impact of sonoporation: A transcriptomic analysis of gene regulation profile

Sonoporation has long been known to disrupt intracellular signaling, yet the involved molecules and pathways have not been identified with clarity. In this study, we employed whole transcriptome shotgun sequencing (RNA-seq) to profile sonoporation-induced gene responses after membrane resealing has taken place. Sonoporation was achieved by microbubble-mediated ultrasound (MB-US) exposure in the form of 1 MHz ultrasound pulsing (0.50 MPa peak negative pressure, 10 % duty cycle, 30 s exposure period) in the presence of microbubbles (1:1 cell-to-bubble ratio). Using propidium iodide (PI) and calcein respectively as cell viability and cytoplasmic uptake labels, post-exposure flow cytometry was performed to identify three viable cell populations: 1) unsonoporated cells, 2) sonoporated cells with low uptake, and 3) sonoporated cells with high uptake. Fluorescence-activated cell sorting was then conducted to separate the different groups followed by RNA-seq analysis of the gene expressions in each group of cells. We found that sonoporated cells with low or high calcein uptake showed high similarity in the gene responses, including the activation of multiple heat shock protein (HSP) genes and immediate early response genes mediating apoptosis and transcriptional regulation. In contrast, unsonoporated cells exhibited a more extensive gene expression alteration that included the activation of more HSP genes and the upregulation of diverse apoptotic mediators. Four oxidative stress-related and three immune-related genes were also differentially expressed in unsonoporated cells. Our results provided new information for understanding the intracellular mobilization in response to sonoporation at the molecular level, including the identification of new molecules in the sonoporation-induced apoptosis regulatory network. Our data also shed light on the innovative therapeutic strategy which could potentially leverage the responses of viable unsonoporated cells as a synergistic effector in the microenvironment to favor tumor treatment.

Manipulating long-term fates of sonoporated cells by regulating intracellular calcium for improving sonoporation-based delivery

Sonoporation-based delivery has great promise for noninvasive drug and gene therapy. After short-term membrane resealing, the long-term function recovery of sonoporated cells affects the efficiency and biosafety of sonoporation-based delivery. It is necessary to identify the key early biological signals that influence cell fate and to develop strategies for manipulating the long-term fates of sonoporated cells. Here, we used a customized experimental platform with a single cavitating microbubble induced by a single ultrasound pulse (frequency: 1.5 MHz, pulse length:13.33 μs, peak negative pressure: ∼0.40 MPa) to elicit single-site reversible sonoporation on a single HeLa cell model. We used a living-cell microscopic imaging system to trace the long-term fates of sonoporated HeLa cells in real-time for 48 h. Fluorescence from intracellular propidium iodide and Fluo-4 was used to evaluate the degree of sonoporation and intracellular calcium fluctuation (ICF), respectively. Changes in cell morphology were used to assess the long-term cell fates (i.e., proliferation, arrest, or death). We found that heterogeneously sonoporated cells had different long-term fates. With increasing degree of sonoporation, the probability of normal (proliferation) and abnormal fates (arrest and death) in sonoporated cells decreased and increased, respectively. We identified ICF as an important early event for triggering different long-term fates. Reversibly sonoporated cells exhibited stronger proliferation and restoration at lower extents of ICF. We then regulated ICF dynamics in sonoporated cells using 2-APB or BAPTA treatment to reduce calcium release from intracellular organelles and enhance intracellular calcium clearance, respectively. This significantly enhanced the proliferation and restoration of sonoporated cells and reduced the occurrence of cell-cycle arrest and death. Finally, we found that the long-term fates of sonoporated cells at multiple sites and neighboring cells were also dependent on the extent of ICF, and that 2-APB significantly enhanced their viability and reduced death. Thus, using a single HeLa cell model, we demonstrated that regulating intracellular calcium can effectively enhance the proliferation and restoration capabilities of sonoporated cells, therefore rescuing the long-term viability of sonoporated cells. These findings add to our understanding of the biophysical process of sonoporation and help design new strategies for improving the efficiency and biosafety of sonoporation-based delivery.

Drug Release via Ultrasound-Activated Nanocarriers for Cancer Treatment: A Review

Conventional cancer chemotherapy often struggles with safely and effectively delivering anticancer therapeutics to target tissues, frequently leading to dose-limiting toxicity and suboptimal therapeutic outcomes. This has created a need for novel therapies that offer greater efficacy, enhanced safety, and improved toxicological profiles. Nanocarriers are nanosized particles specifically designed to enhance the selectivity and effectiveness of chemotherapy drugs while reducing their toxicity. A subset of drug delivery systems utilizes stimuli-responsive nanocarriers, which enable on-demand drug release, prevent premature release, and offer spatial and temporal control over drug delivery. These stimuli can be internal (such as pH and enzymes) or external (such as ultrasound, magnetic fields, and light). This review focuses on the mechanics of ultrasound-induced drug delivery and the various nanocarriers used in conjunction with ultrasound. It will also provide a comprehensive overview of key aspects related to ultrasound-induced drug delivery, including ultrasound parameters and the biological effects of ultrasound waves.

Low-boiling-point perfluorocarbon nanodroplets for adaptable ultrasound-induced blood-brain barrier opening

Low-boiling point perfluorocarbon nanodroplets (NDs) are valued as effective sonosensitive agents, encapsulating a liquid perfluorocarbon that would instantaneously vaporize at body temperature without the NDs shell. Those NDs have been explored for both therapeutic and diagnostic purposes. Here, phospholipid-shelled nanodroplets containing octafluoropropane (C3F8) or decafluorobutane (C4F10) formed by condensation of microbubbles were thoroughly characterized before blood-brain (BBB) permeabilization. Transmission electron microscopy (TEM) and cryo-TEM were employed to confirm droplet formation while providing high-resolution insights into the droplet surface and lipid arrangement assessed from electron density observation after condensation. The vaporization threshold of NDs was determined with a high-speed camera, and the frequency signal emitted by the freshly vaporized bubbles was analyzed using cavitation detection. C3F8 NDs exhibited vaporization at 0.3 MPa (f0 = 1.5 MHz, 50 cycles), and emitted signals at 2 f0 and 1.5 f0 from 0.45 MPa onwards (f0 = 1.5 MHz, 50 cycles), while broadband noise was measured starting from 0.55 MPa. NDs with the higher boiling point C4F10 vaporized at 1.15 MPa and emitted signals at 2 f0 from 0.65 MPa and 1.5 f0 from 0.9 MPa, while broadband noise was detected starting from 0.95 MPa. Both ND formulations were used to permeabilize the BBB in healthy mice using tailored ultrasound sequences, allowing for the identification of optimal applications for each NDs type. C3F8 NDs proved suitable and safe for permeabilizing a large area, potentially the entire brain, at low acoustic pressure. Meanwhile, C4F10 droplets facilitated very localized (400 μm isotropic) permeabilization at higher pressure. This study prompts a closer examination of the structural rearrangements occurring during the condensation of microbubbles into NDs and highlights the potential to tailor solutions for different brain pathologies by choosing the composition of the NDs and adjusting the ultrasound sequence.

Clinical Applications of Micro/Nanobubble Technology in Neurological Diseases

Nanomedicine, leveraging the unique properties of nanoparticles, has revolutionized the diagnosis and treatment of neurological diseases. Among various nanotechnological advancements, ultrasound-mediated drug delivery using micro- and nanobubbles offers promising solutions to overcome the blood-brain barrier (BBB), enhancing the precision and efficacy of therapeutic interventions. This review explores the principles, current clinical applications, challenges, and future directions of ultrasound-mediated drug delivery systems in treating stroke, brain tumors, neurodegenerative diseases, and neuroinflammatory disorders. Additionally, ongoing clinical trials and potential advancements in this field are discussed, providing a comprehensive overview of the impact of nanomedicine on neurological diseases.

Calcium ion delivery by microbubble-assisted sonoporation stimulates cell death in human gastrointestinal cancer cells

Ultrasound-mediated cell membrane permeabilization - sonoporation, enhances drug delivery directly to tumor sites while reducing systemic side effects. The potential of ultrasound to augment intracellular calcium uptake - a critical regulator of cell death and proliferation - offers innovative alternative to conventional chemotherapy. However, calcium therapeutic applications remain underexplored in sonoporation studies. This research provides a comprehensive analysis of calcium sonoporation (CaSP), which combines ultrasound treatment with calcium ions and SonoVue microbubbles, on gastrointestinal cancer cells LoVo and HPAF-II. Initially, optimal sonoporation parameters were determined: an acoustic wave of 1 MHz frequency with a 50 % duty cycle at intensity of 2 W/cm2. Subsequently, various cellular bioeffects, such as viability, oxidative stress, metabolism, mitochondrial function, proliferation, and cell death, were assessed following CaSP treatment. CaSP significantly impaired cancer cell function by inducing oxidative and metabolic stress, evidenced by increased mitochondrial depolarization, decreased ATP levels, and elevated glucose uptake in a Ca2+ dose-dependent manner, leading to activation of the intrinsic apoptotic pathway. Cellular response to CaSP depended on the TP53 gene's mutational status: colon cancer cells were more susceptible to CaSP-induced apoptosis and G1 phase cell cycle arrest, whereas pancreatic cancer cells showed a higher necrotic response and G2 cell cycle arrest. These promising results encourage future research to optimize sonoporation parameters for clinical use, investigate synergistic effects with existing treatments, and assess long-term safety and efficacy in vivo. Our study highlights CaSP's clinical potential for improved safety and efficacy in cancer therapy, offering significant implications for the pharmaceutical and biomedical fields.

Remote-Controlled Gene Delivery in Coaxial 3D-Bioprinted Constructs using Ultrasound-Responsive Bioinks

Introduction

Coaxial 3D bioprinting has advanced the formation of tissue constructs that recapitulate key architectures and biophysical parameters for in-vitro disease modeling and tissue-engineered therapies. Controlling gene expression within these structures is critical for modulating cell signaling and probing cell behavior. However, current transfection strategies are limited in spatiotemporal control because dense 3D scaffolds hinder diffusion of traditional vectors. To address this, we developed a coaxial extrusion 3D bioprinting technique using ultrasound-responsive gene delivery bioinks. These bioink materials incorporate echogenic microbubble gene delivery particles that upon ultrasound exposure can sonoporate cells within the construct, facilitating controllable transfection.

Methods

Phospholipid-coated gas-core microbubbles were electrostatically coupled to reporter transgene plasmid payloads and incorporated into cell-laden alginate bioinks at varying particle concentrations. These bioinks were loaded into the coaxial nozzle core for extrusion bioprinting with CaCl2 crosslinker in the outer sheath. Resulting bioprints were exposed to 2.25 MHz focused ultrasound and evaluated for microbubble activation and subsequent DNA delivery and transgene expression.

Results

Coaxial printing parameters were established that preserved the stability of ultrasound-responsive gene delivery particles for at least 48 h in bioprinted alginate filaments while maintaining high cell viability. Successful sonoporation of embedded cells resulted in DNA delivery and robust ultrasound-controlled transgene expression. The number of transfected cells was modulated by varying the number of focused ultrasound pulses applied. The size region over which DNA was delivered was modulated by varying the concentration of microbubbles in the printed filaments.

Conclusions

Our results present a successful coaxial 3D bioprinting technique designed to facilitate ultrasound-controlled gene delivery. This platform enables remote, spatiotemporally-defined genetic manipulation in coaxially bioprinted tissue constructs with important applications for disease modeling and regenerative medicine.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12195-024-00818-x.

Future challenges of contrast media in radiology

Contrast media (CM) were first used soon after the discovery of X-rays in 1895. Ever since, continuous technological development and pharmaceutical research has led to tremendous progress in radiology, more available techniques and contrast media, and expanded knowledge around their indications. A greater prevalence of chronic diseases, population ageing, and the rise in diagnosis and survival times among cancer patients have resulted in a growing demand for diagnostic imaging and an increased consumption of CM. This article presents the main lines of research in CM development which seek to minimise toxicity and maximise efficacy, opening up new diagnostic and therapeutic possibilities through new molecules or nanomedicine. The sector, which is continuously evolving, faces challenges such as shortages and the need for more equitable and sustainable practices.

Nanobubble-mediated co-delivery of siTRIM37 and IR780 for gene and sonodynamic combination therapy against triple negative breast cancer

Gene therapy often fails due to enzyme degradation and low transfection efficiency, and single gene therapy usually cannot completely kill tumor cells. Several studies have reported that tripartite motif-containing protein 37 (TRIM37) plays a significant role in promoting the occurrence and development of triple negative breast cancer (TNBC). Herein, we constructed siTRIM37 and IR780 co-loaded nanobubbles (NBs) to achieve the combination of gene therapy and sonodynamic therapy (SDT) against TNBC. On the one hand, ultrasound irradiation causes siRNA@IR780 NBs rupture to produce ultrasound targeted NB destruction effect, which promotes the entry of IR780 and siTRIM37 into cells, increasing the local concentration of IR780 and gene transfection efficiency. On the other hand, under the stimulation of ultrasound, IR780 generates reactive oxygen species to kill TNBC cells. Mechanism studies reveal that TRIM37 is an anti-apoptotic gene in TNBC, and inhibiting TRIM37 expression can induce cell death through the apoptotic pathway. And the combination of siTRIM37 and SDT can aggravate the degree of apoptosis to increase cell death. Therefore, siRNA@IR780 NBs-mediated combination therapy may provide a new treatment approach for TNBC in the future.

Characterisation of Gas Vesicles as Cavitation Nuclei for Ultrasound Therapy using Passive Acoustic Mapping

Genetically encodable gas filled particles known as gas vesicles (GVs) have shown promise as a biomolecular contrast agent for ultrasound imaging and have the potential to be used as cavitation nuclei for ultrasound therapy. In this study, we used passive acoustic mapping techniques to characterize GV-seeded cavitation, utilizing 0.5 and 1.6 MHz ultrasound over peak rarefactional pressures ranging from 100 to 2200 kPa. We found that GVs produce cavitation for the duration of the first applied pulse, up to at least 5000 cycles, but that bubble activity diminishes rapidly over subsequent pulses. At 0.5 MHz the frequency content of cavitation emissions was predominantly broadband in nature, whilst at 1.6 MHz narrowband content at harmonics of the main excitation frequency dominated. Simulations and high-speed camera imaging suggest that the received cavitation emissions come not from individual GVs but instead from the coalescence of GV-released gas into larger bubbles during the applied ultrasound pulse. These results will aid the future development of GVs as cavitation nuclei in ultrasound therapy.

Ultrasound-stimulated microbubbles to enhance radiotherapy: A scoping review

INTRODUCTION

Primarily used as ultrasound contrast agents, microbubbles have recently emerged as a versatile therapeutic vector that can be 'burst' to deliver payloads in the presence of suitably optimised ultrasound fields. Ultrasound-stimulated microbubbles (USMB) have recently demonstrated improvements in treatment outcomes across a variety of clinical applications. This scoping review investigates whether this potential translates into the context of radiation therapy by evaluating the application of this technology across all three phases of radiation action.

METHODS

Primary research articles, excluding poster presentations and conference proceedings, were identified through systematic searches of the PubMed NCBI/Medline, Embase/OVID, Web of Science and CINAHL/EBSCOhost databases, with additional articles identified via manual Google Scholar searching. Articles were dual screened for inclusion using the Covidence systematic review platform and classified against all three phases of radiation action.

RESULTS

Overall, 57 eligible publications from a total of 1389 identified articles were included in the review, with studies dating back to 2012. Study heterogeneity prevented formal statistical analysis; however, most articles reported improved outcomes using USMB in the presence of radiation compared to that of radiation alone. These improvements appear to result from the use of USMB as either a biovascular disruptor causing tumour cell damage via indirect mechanisms, or as a localised treatment vector that directly increases tumour cell uptake of other therapeutic and physical agents designed to enhance radiation action.

CONCLUSIONS

USMB demonstrate exciting potential to enhance the effects of radiation treatments due to their versatility and capacity to target all three phases of radiation action.

Recent development in CRISPR-Cas systems for cardiac disease

The CRISPR-Cas system has emerged as a revolutionary tool in genetic research, enabling highly precise gene editing and significantly advancing the field of cardiovascular science. This chapter provides a comprehensive overview of the latest developments in utilizing CRISPR-Cas technologies to investigate and treat heart diseases. It delves into the application of CRISPR-Cas9 for creating accurate models of complex cardiac conditions, such as hypertrophic cardiomyopathy (HCM), dilated cardiomyopathy (DCM), and various arrhythmias, which are essential for understanding disease mechanisms and testing potential therapies. The therapeutic potential of gene editing is also explored, with a focus on genes like PCSK9 and ANGPTL3 that play critical roles in lipid metabolism and cardiovascular health, offering promising avenues for new treatments. Furthermore, the expanding applications of CRISPR in heart tissue regeneration are examined, which could revolutionize the repair of damaged heart tissue. Cutting-edge techniques such as base editing and prime editing are discussed, highlighting their potential to further refine genetic interventions. The discussion concludes by addressing the challenges associated with delivering CRISPR components efficiently and safely, while also exploring recent innovations that may overcome these hurdles, providing insights into the future directions of CRISPR technology in cardiovascular medicine.

Biomodulatory Effects of Molecular Delivery in Human T Cells Using 3D-Printed Acoustofluidic Devices

OBJECTIVE

Cell-based therapies have shown significant promise for treating many diseases, including cancer. Current cell therapy manufacturing processes primarily utilize viral transduction to insert genomic material into cells, which has limitations, including variable transduction efficiency and extended processing times. Non-viral transfection techniques are also limited by high variability or reduced molecular delivery efficiency. Novel 3D-printed acoustofluidic devices are in development to address these challenges by delivering biomolecules into cells within seconds via sonoporation.

METHODS

In this study, we assessed biological parameters that influence the ultrasound-mediated delivery of fluorescent molecules (i.e., calcein and 150 kDa FITC-Dextran) to human T cells using flow cytometry and confocal imaging.

RESULTS

Low cell plating densities (100,000 cells/mL) enhanced molecular delivery compared to higher cell plating densities (p < 0.001), even though cells were resuspended at equal concentrations for acoustofluidic processing. Additionally, cells in the S phase of the cell cycle had enhanced intracellular delivery compared to cells in the G2/M phase (p < 0.001) and G0/G1 phase (p < 0.01), while also maintaining higher viability compared to G0/G1 phase (p < 0.001). Furthermore, the calcium chelator (EGTA) decreased overall molecular delivery levels. Confocal imaging indicated that the actin cytoskeleton had important implications on plasma membrane recovery dynamics after sonoporation. In addition, confocal imaging indicates that acoustofluidic treatment can permeabilize the nuclear membrane, which could enable rapid intranuclear delivery of nucleic acids.

CONCLUSIONS

The results of this study demonstrate that a 3D-printed acoustofluidic device can enhance molecular delivery to human T cells, which may enable improved techniques for non-viral processing of cell therapies.

High-Speed Optical Characterization of Protein-and-Nanoparticle-Stabilized Microbubbles for Ultrasound-Triggered Drug Release

OBJECTIVE

Ultrasound-triggered bubble-mediated local drug delivery has shown potential to increase therapeutic efficacy and reduce systemic side effects, by loading drugs into the microbubble shell and triggering delivery of the payload on demand using ultrasound. Understanding the behavior of the microbubbles in response to ultrasound is crucial for efficient and controlled release.

METHODS

In this work, the response of microbubbles with a coating consisting of poly(2-ethyl-butyl cyanoacrylate) (PEBCA) nanoparticles and denatured casein was characterized. High-speed recordings were taken of single microbubbles, in both bright field and fluorescence.

RESULTS

The nanoparticle-loaded microbubbles show resonance behavior, but with a large variation in response, revealing a substantial interbubble variation in mechanical shell properties. The probability of shell rupture and the probability of nanoparticle release were found to strongly depend on microbubble size, and the most effective size was inversely proportional to the driving frequency. The probabilities of both rupture and release increased with increasing driving pressure amplitude. Rupture of the microbubble shell occurred after fewer cycles of ultrasound as the driving pressure amplitude or driving frequency was increased.

CONCLUSION

The results highlight the importance of careful selection of the driving frequency, driving pressure amplitude and duration of ultrasound to achieve the most efficient ultrasound-triggered shell rupture and nanoparticle release of protein-and-nanoparticle-stabilized microbubbles.

MOF-Derived Nanoparticles with Enhanced Acoustical Performance for Efficient Mechano-Sonodynamic Therapy

Ultrasound (US) generates toxic reactive oxygen species (ROS) by acting on sonosensitizers for cancer treatment, and the mechanical damage induced by cavitation effects under US is equally significant. Therefore, designing a novel sonosensitizer that simultaneously possesses efficient ROS generation and enhanced mechanical effects is promising. In this study, carbon-doped zinc oxide nanoparticles (C-ZnO) are constructed for mechano-sonodynamic cancer therapy. The presence of carbon (C) doping optimizes the electronic structure, thereby enhancing the ROS generation triggered by US, efficiently inducing tumor cell death. On the other hand, the high specific surface area and porous structure brought about by C doping enable C-ZnO to enhance the mechanical stress induced by cavitation bubbles under US irradiation, causing severe mechanical damage to tumor cells. Under the dual effects of sonodynamic therapy (SDT) and mechanical therapy mediated by C-ZnO, excellent anti-tumor efficacy is demonstrated both in vitro and in vivo, along with a high level of biological safety. This is the first instance of utilizing an inorganic nanomaterial to achieve simultaneous enhancement of ROS production and US-induced mechanical effects for cancer therapy. This holds significant importance for the future development of novel sonosensitizers and advancing the applications of US in cancer treatment.

A systematic review of preclinical and clinical transcranial ultrasound neuromodulation and opportunities for functional connectomics

BACKGROUND

Low-intensity transcranial ultrasound has surged forward as a non-invasive and disruptive tool for neuromodulation with applications in basic neuroscience research and the treatment of neurological and psychiatric conditions.

OBJECTIVE

To provide a comprehensive overview and update of preclinical and clinical transcranial low intensity ultrasound for neuromodulation and emphasize the emerging role of functional brain mapping to guide, better understand, and predict responses.

METHODS

A systematic review was conducted by searching the Web of Science and Scopus databases for studies on transcranial ultrasound neuromodulation, both in humans and animals.

RESULTS

187 relevant studies were identified and reviewed, including 116 preclinical and 71 clinical reports with subjects belonging to diverse cohorts. Milestones of ultrasound neuromodulation are described within an overview of the broader landscape. General neural readouts and outcome measures are discussed, potential confounds are noted, and the emerging use of functional magnetic resonance imaging is highlighted.

CONCLUSION

Ultrasound neuromodulation has emerged as a powerful tool to study and treat a range of conditions and its combination with various neural readouts has significantly advanced this platform. In particular, the use of functional magnetic resonance imaging has yielded exciting inferences into ultrasound neuromodulation and has the potential to advance our understanding of brain function, neuromodulatory mechanisms, and ultimately clinical outcomes. It is anticipated that these preclinical and clinical trials are the first of many; that transcranial low intensity focused ultrasound, particularly in combination with functional magnetic resonance imaging, has the potential to enhance treatment for a spectrum of neurological conditions.

Ultrasound-stimulated Microbubbles for Treatment of Pancreatic Cancer Cells with Radiation and Nanoparticles: In vitro Study

Purpose

This study aims to investigate the radiation enhancement effects of ultrasound-stimulated microbubbles (USMB) with X-rays and nanoparticles on pancreatic cancer cells in vitro.

Methods

Sonazoid™ microbubbles were used for USMB treatment with a commercially available ultrasound unit. The characterization of the microbubbles before and after ultrasound exposure with different mechanical parameters was evaluated microscopically. Two pancreatic cancer cell lines, MIAPaCa-2 and PANC-1, were treated with different concentrations of microbubbles in combination with 150 kVp X-rays and hydrogen peroxide-modified titanium dioxide nanoparticles. Cell viability was evaluated using a water-soluble tetrazolium dye and a colony formation assay. In addition, intracellular reactive oxygen species (ROS) induced by the combined treatment were assessed.

Results

The number of burst microbubbles increased with ultrasound's higher mechanical index and the exposure time. A significant radiation enhancement effect with a significant increase in ROS levels was observed in MIAPaCa-2 cells treated with USMB and 6 Gy X-rays, whereas it was not significant in PANC-1 cells treated with the same. When a higher concentration of USMB was applied with X-rays, no radiation enhancement effects were observed in either cell line. Moreover, there was no radiation enhancement effect by USMB between cells treated with and without nanoparticles.

Conclusions

The results indicate that USMB treatment can additively enhance the therapeutic efficacy of radiation therapy on pancreatic cancer cells, while the synergistic enhancement effects are likely to be cell type and microbubble concentration dependent. In addition, USMB did not improve the efficacy of nanoparticle-induced radiosensitization in the current setting.

Nanomedicine Tumor Targeting

Nanomedicines are extensively explored for cancer therapy. By delivering drug molecules more efficiently to pathological sites and by attenuating their accumulation in healthy organs and tissues, nanomedicine formulations aim to improve the balance between drug efficacy and toxicity. More than 20 cancer nanomedicines are approved for clinical use, and hundreds of formulations are in (pre)clinical development. Over the years, several key pitfalls have been identified as bottlenecks in nanomedicine tumor targeting and translation. These go beyond materials- and production-related issues, and particularly also encompass biological barriers and pathophysiological heterogeneity. In this manuscript, the author describes the most important principles, progress, and products in nanomedicine tumor targeting, delineates key current problems and challenges, and discusses the most promising future prospects to create clinical impact.

Stimuli-Responsive Delivery Systems for Intervertebral Disc Degeneration

As a major cause of low back pain, intervertebral disc degeneration is an increasingly prevalent chronic disease worldwide that leads to huge annual financial losses. The intervertebral disc consists of the inner nucleus pulposus, outer annulus fibrosus, and sandwiched cartilage endplates. All these factors collectively participate in maintaining the structure and physiological functions of the disc. During the unavoidable degeneration stage, the degenerated discs are surrounded by a harsh microenvironment characterized by acidic, oxidative, inflammatory, and chaotic cytokine expression. Loss of stem cell markers, imbalance of the extracellular matrix, increase in inflammation, sensory hyperinnervation, and vascularization have been considered as the reasons for the progression of intervertebral disc degeneration. The current treatment approaches include conservative therapy and surgery, both of which have drawbacks. Novel stimuli-responsive delivery systems are more promising future therapeutic options than traditional treatments. By combining bioactive agents with specially designed hydrogels, scaffolds, microspheres, and nanoparticles, novel stimuli-responsive delivery systems can realize the targeted and sustained release of drugs, which can both reduce systematic adverse effects and maximize therapeutic efficacy. Trigger factors are categorized into internal (pH, reactive oxygen species, enzymes, etc.) and external stimuli (photo, ultrasound, magnetic, etc.) based on their intrinsic properties. This review systematically summarizes novel stimuli-responsive delivery systems for intervertebral disc degeneration, shedding new light on intervertebral disc therapy.

Programmable ultrasound imaging guided theranostic nanodroplet destruction for precision therapy of breast cancer

Ultrasound-stimulated contrast agents have gained significant attention in the field of tumor treatment as drug delivery systems. However, their limited drug-loading efficiency and the issue of bulky, imprecise release have resulted in inadequate drug concentrations at targeted tissues. Herein, we developed a highly efficient approach for doxorubicin (DOX) precise release at tumor site and real-time feedback via an integrated strategy of "programmable ultrasonic imaging guided accurate nanodroplet destruction for drug release" (PND). We synthesized DOX-loaded nanodroplets (DOX-NDs) with improved loading efficiency (15 %) and smaller size (mean particle size: 358 nm). These DOX-NDs exhibited lower ultrasound activation thresholds (2.46 MPa). By utilizing a single diagnostic transducer for both ultrasound stimulation and imaging guidance, we successfully vaporized the DOX-NDs and released the drug at the tumor site in 4 T1 tumor-bearing mice. Remarkably, the PND group achieved similar tumor remission effects with less than half the dose of DOX required in conventional treatment. Furthermore, the ultrasound-mediated vaporization of DOX-NDs induced tumor cell apoptosis with minimal damage to surrounding normal tissues. In summary, our PND strategy offers a precise and programmable approach for drug delivery and therapy, combining ultrasound imaging guidance. This approach shows great potential in enhancing tumor treatment efficacy while minimizing harm to healthy tissues.

Ultrasound-Sensitive Intelligent Nanosystems: A Promising Strategy for the Treatment of Neurological Diseases

Neurological diseases are a major global health challenge, affecting hundreds of millions of people worldwide. Ultrasound therapy plays an irreplaceable role in the treatment of neurological diseases due to its noninvasive, highly focused, and strong tissue penetration capabilities. However, the complexity of brain and nervous system and the safety risks associated with prolonged exposure to ultrasound therapy severely limit the applicability of ultrasound therapy. Ultrasound-sensitive intelligent nanosystems (USINs) are a novel therapeutic strategy for neurological diseases that bring greater spatiotemporal controllability and improve safety to overcome these challenges. This review provides a detailed overview of therapeutic strategies and clinical advances of ultrasound in neurological diseases, focusing on the potential of USINs-based ultrasound in the treatment of neurological diseases. Based on the physical and chemical effects induced by ultrasound, rational design of USINs is a prerequisite for improving the efficacy of ultrasound therapy. Recent developments of ultrasound-sensitive nanocarriers and nanoagents are systemically reviewed. Finally, the challenges and developing prospects of USINs are discussed in depth, with a view to providing useful insights and guidance for efficient ultrasound treatment of neurological diseases.

Focused Ultrasound-Enhanced Liquid Biopsy: A Promising Diagnostic Tool for Brain Tumor Patients

The performance of minimally invasive molecular diagnostic tools in brain tumors, such as liquid biopsy, has so far been limited by the blood-brain barrier (BBB). The BBB hinders the release of brain tumor biomarkers into the bloodstream. The use of focused ultrasound in conjunction with microbubbles has been shown to temporarily open the BBB (FUS-BBBO). This may enhance blood-based tumor biomarker levels. This systematic review provides an overview of the data regarding FUS-BBBO-enhanced liquid biopsy for primary brain tumors. A systematic search was conducted in PubMed and Embase databases with key terms "brain tumors", "liquid biopsy", "FUS" and their synonyms, in accordance with PRISMA statement guidelines. Five preclinical and two clinical studies were included. Preclinical studies utilized mouse, rat and porcine glioma models. Biomarker levels were found to be higher in sonicated groups compared to control groups. Both stable and inertial microbubble cavitation increased biomarker levels, whereas only inertial cavitation induced microhemorrhages. In clinical studies involving 14 patients with high-grade brain tumors, biomarker levels were increased after FUS-BBBO with stable cavitation. In conclusion, FUS-BBBO-enhanced liquid biopsy using stable cavitation shows diagnostic potential for primary brain tumors. Further research is imperative before integrating FUS-BBBO for liquid biopsy enhancement into clinical practice.

Bridging Smart Nanosystems with Clinically Relevant Models and Advanced Imaging for Precision Drug Delivery

Intracellular delivery of nano-drug-carriers (NDC) to specific cells, diseased regions, or solid tumors has entered the era of precision medicine that requires systematic knowledge of nano-biological interactions from multidisciplinary perspectives. To this end, this review first provides an overview of membrane-disruption methods such as electroporation, sonoporation, photoporation, microfluidic delivery, and microinjection with the merits of high-throughput and enhanced efficiency for in vitro NDC delivery. The impact of NDC characteristics including particle size, shape, charge, hydrophobicity, and elasticity on cellular uptake are elaborated and several types of NDC systems aiming for hierarchical targeting and delivery in vivo are reviewed. Emerging in vitro or ex vivo human/animal-derived pathophysiological models are further explored and highly recommended for use in NDC studies since they might mimic in vivo delivery features and fill the translational gaps from animals to humans. The exploration of modern microscopy techniques for precise nanoparticle (NP) tracking at the cellular, organ, and organismal levels informs the tailored development of NDCs for in vivo application and clinical translation. Overall, the review integrates the latest insights into smart nanosystem engineering, physiological models, imaging-based validation tools, all directed towards enhancing the precise and efficient intracellular delivery of NDCs.

How Microbubble-Enhanced Shock Waves Promote the Delivery of Lipid-siRNA across Neuronal Plasma Membrane: A Computational Study

In this computational study, we examine the potential of microbubble-enhanced shock waves to improve the delivery of lipid-siRNA nanoparticles across neuronal plasma membranes with the ultimate aim of enhancing brain tumor treatment. We critically evaluate several variables related to experiments, including the bubble size, the shock speed and action time, and the amount of siRNA encapsulated in the liposome. Our findings reveal that microbubble-enhanced shock waves are essential for the high delivery of small lipid vesicles (under 30 nm diameter); its corresponding variables significantly impact drug penetration and absorption rates and influence the overall efficacy of the drug delivery system. Long-time recovery simulations further provide valuable insights into the self-healing ability of the plasma membrane following shock wave exposure and the subsequent absorption dynamics of siRNA. This work provides the dynamic process of siRNA released from lipid vesicles with shock wave and nanobubbles, thereby serving as a molecular mechanism support for developing tunable delivery systems for RNA-based therapy in brain tumors.

Release of extracellular vesicles triggered by low-intensity pulsed ultrasound: immediate and delayed reactions

Previous studies have shown that ultrasound may stimulate the release of extracellular vesicles, improving the efficiency of tumor detection. However, it is unclear whether ultrasonic stimulation affects the distribution of extracellular vesicles, and the duration of such stimulation release has not been extensively studied. In this study, we stimulated cells with low-intensity pulsed ultrasound and used liposomes containing black hole quenchers to simulate natural extracellular vesicles, confirming that ultrasound has a destructive effect on vesicles and thus affects particle size distribution. Furthermore, we used proteomics technology to examine the protein expression profile of small vesicles and discovered that the expression of proteins involved in exosome biogenesis was down-regulated. We then looked into the regulation of the actin cytoskeleton and endocytosis pathways, which are required for intracellular vesicle transport, and discovered that ultrasound might induce F-actin depolymerization. The intracellular transport of the cation-independent mannose-6-phosphate receptor (CI-MPR) in the trans-Golgi network (TGN) and the amount of Rab7a protein were proportional to the culture time after LIPUS treatment.

MnO2/Ce6 microbubble-mediated hypoxia modulation for enhancing sono-photodynamic therapy against triple negative breast cancer

Sono-photodynamic therapy (SPDT) has emerged as a promising treatment modality for triple negative breast cancer (TNBC). However, the hypoxic tumor microenvironment hinders the application of SPDT. Herein, in this study, a multifunctional platform (MnO2/Ce6@MBs) was designed to address this issue. A sono-photosensitizer (Ce6) and a hypoxia modulator (MnO2) were loaded into microbubbles and precisely released within tumor tissues under ultrasound irradiation. MnO2in situ reacted with the excess H2O2 and H+ and produced O2 within the TNBC tumor, which alleviated hypoxia and augmented SPDT by increasing ROS generation. Meanwhile, the reaction product Mn2+ was able to achieve T1-weighted MRI for enhanced tumor imaging. Additionally, Ce6 and microbubbles served as a fluorescence imaging contrast agent and a contrast-enhanced ultrasound imaging agent, respectively. In in vivo anti-tumor studies, under the FL/US/MR imaging guidance, MnO2/Ce6@MBs combined with SPDT significantly reversed tumor hypoxia and inhibited tumor growth in 4T1-tumor bearing mice. This work presents a theragnostic system for reversing tumor hypoxia and enhancing TNBC treatment.

A proof-of-principle for decontamination of transplantation kidney through UV-C exposition of the perfusate solution

Kidney transplantation is a common yet highly demanding medical procedure worldwide, enhancing the quality of life for patients with chronic kidney disease. Despite its prevalence, the procedure faces a shortage of available organs, partly due to contamination by microorganisms, leading to significant organ disposal. This study proposes utilizing photonic techniques associated with organ support machines to prevent patient contamination during kidney transplantation. We implemented a decontamination system using ultraviolet-C (UV-C) irradiation on the preservation solution circulating through pigs' kidneys between harvest and implant. UV-C irradiation, alone or combined with ultrasound (US) and Ps80 detergent during ex-vivo swine organ perfusion in a Lifeport® Kidney Transporter machine, aimed to reduce microbiological load in both fluid and organ. Results show rapid fluid decontamination compared to microorganism release from the organ, with notable retention. By including Ps80 detergent at 0.5% during UV-C irradiation 3 log10 (CFU mL-1) of Staphylococcus aureus bacteria previously retained in the organ were successfully removed, indicating the technique's feasibility and effectiveness.

From concept to early clinical trials: 30 years of microbubble-based ultrasound-mediated drug delivery research

Ultrasound mediated drug delivery, a promising therapeutic modality, has evolved remarkably over the past three decades. Initially designed to enhance contrast in ultrasound imaging, microbubbles have emerged as a main vector for drug delivery, offering targeted therapy with minimized side effects. This review addresses the historical progression of this technology, emphasizing the pivotal role microbubbles play in augmenting drug extravasation and targeted delivery. We explore the complex mechanisms behind this technology, from stable and inertial cavitation to diverse acoustic phenomena, and their applications in medical fields. While the potential of ultrasound mediated drug delivery is undeniable, there are still challenges to overcome. Balancing therapeutic efficacy and safety and establishing standardized procedures are essential areas requiring attention. A multidisciplinary approach, gathering collaborations between researchers, engineers, and clinicians, is important for exploiting the full potential of this technology. In summary, this review highlights the potential of using ultrasound mediated drug delivery in improving patient care across various medical conditions.

Expanding CAR-T cell immunotherapy horizons through microfluidics

Chimeric antigen receptor (CAR)-T cell therapies have revolutionized cancer treatment, particularly in hematological malignancies. However, their application to solid tumors is limited, and they face challenges in safety, scalability, and cost. To enhance current CAR-T cell therapies, the integration of microfluidic technologies, harnessing their inherent advantages, such as reduced sample consumption, simplicity in operation, cost-effectiveness, automation, and high scalability, has emerged as a powerful solution. This review provides a comprehensive overview of the step-by-step manufacturing process of CAR-T cells, identifies existing difficulties at each production stage, and discusses the successful implementation of microfluidics and related technologies in addressing these challenges. Furthermore, this review investigates the potential of microfluidics-based methodologies in advancing cell-based therapy across various applications, including solid tumors, next-generation CAR constructs, T-cell receptors, and the development of allogeneic "off-the-shelf" CAR products.

Delivery of Anticancer Drugs Using Microbubble-Assisted Ultrasound in a 3D Spheroid Model

Tumor spheroids are promising three-dimensional (3D) in vitro tumor models for the evaluation of drug delivery methods. The design of noninvasive and targeted drug methods is required to improve the intratumoral bioavailability of chemotherapeutic drugs and reduce their adverse off-target effects. Among such methods, microbubble-assisted ultrasound (MB-assisted US) is an innovative modality for noninvasive targeted drug delivery. The aim of the present study is to evaluate the efficacy of this US modality for the delivery of bleomycin, doxorubicin, and irinotecan in colorectal cancer (CRC) spheroids. MB-assisted US permeabilized the CRC spheroids to propidium iodide, which was used as a drug model without affecting their growth and viability. Histological analysis and electron microscopy revealed that MB-assisted US affected only the peripheral layer of the CRC spheroids. The acoustically mediated bleomycin delivery induced a significant decrease in CRC spheroid growth in comparison to spheroids treated with bleomycin alone. However, this US modality did not improve the therapeutic efficacy of doxorubicin and irinotecan on CRC spheroids. In conclusion, this study demonstrates that tumor spheroids are a relevant approach to evaluate the efficacy of MB-assisted US for the delivery of chemotherapeutics.

A unifying Rayleigh-Plesset-type equation for bubbles in viscoelastic media

Understanding the ultrasound pressure-driven dynamics of microbubbles confined in viscoelastic materials is relevant for multiple biomedical applications, ranging from contrast-enhanced ultrasound imaging to ultrasound-assisted drug delivery. The volumetric oscillations of spherical bubbles are analyzed using the Rayleigh-Plesset equation, which describes the conservation of mass and momentum in the surrounding medium. Several studies have considered an extension of the Rayleigh-Plesset equation for bubbles embedded into viscoelastic media, but these are restricted to a particular choice of constitutive model and/or to small deformations. Here, we derive a unifying equation applicable to bubbles in viscoelastic media with arbitrary complex moduli and that can account for large bubble deformations. To derive this equation, we borrow concepts from finite-strain theory. We validate our approach by comparing the result of our model to previously published results and extend it to show how microbubbles behave in arbitrary viscoelastic materials. In particular, we use our viscoelastic Rayleigh-Plesset model to compute the bubble dynamics in benchmarked viscoelastic liquids and solids.

Review on the Significant Interactions between Ultrafine Gas Bubbles and Biological Systems

Having sizes comparable with living cells and high abundance, ultrafine bubbles (UBs) are prone to inevitable interactions with different types of cells and facilitate alterations in physiological properties. The interactions of four typical cell types (e.g., bacterial, fungal, plant, and mammalian cells) with UBs have been studied over recent years. For bacterial cells, UBs have been utilized in creating the capillary force to tear down biofilms. The release of high amounts of heat, pressure, and free radicals during bubble rupture is also found to affect bacterial cell growth. Similarly, the bubble gas core identity plays an important role in the development of fungal cells. By the proposed mechanism of attachment of UBs on hydrophobin proteins in the fungal cell wall, oxygen and ozone gas-filled ultrafine bubbles can either promote or hinder the cell growth rate. On the other hand, reactive oxygen species (ROS) formation and mass transfer facilitation are two means of indirect interactions between UBs and plant cells. Likewise, the use of different gas cores in generating bubbles can produce different physical effects on these cells, for example, hydrogen gas for antioxidation against infections and oxygen for oxidation of toxic metal ions. For mammalian cells, the importance of investigating their interactions with UBs lies in the bubbles' action on cell viability as membrane poration for drug delivery can greatly affect cells' survival. UBs have been utilized and tested in forming the pores by different methods, ranging from bubble oscillation and microstream generation through acoustic cavitation to bubble implosion.