Cardiovascular diseases (CVDs) remains the predominant cause of mortality and premature death in China, accounting for 48% and 45.86% of total deaths in rural and urban populations respectively (1, 2). Atherosclerosis, the most prevalent form of CVDs, manifests as lipid accumulation and chronic inflammation in large arteries, leading to critical complications including ischemic heart disease and cerebrovascular accidents (3). Over the past three decades, China has faced escalating challenges in CVDs management due to the dual pressures of rising atherosclerotic cases and demographic aging, which necessitates innovative approaches for prevention and therapeutic intervention (4).

Ultrasound has a long history as a diagnostic imaging technique. Additionally, it has the capacity to modulate the spatial and temporal release of medication. Due to its biocompatibility and low attenuation in tissue, ultrasound demonstrates the potential for remote activation, which has driven the development of smart medicine delivery systems. In recent years, this field has expanded to therapeutic applications, such as ultrasound-targeted microbubble destruction (UTMD) (5, 6). The non-invasive and target-specific nature of UTMD renders it a promising drug and gene delivery strategy (7). Recent studies suggest a promising future for UTMD-based therapies in the management of CVDs (8–10), indicating a potential for advancement in the field of precision medicine (Figure 1).

A systematic literature search was conducted in PubMed using the key term “ultrasound-targeted microbubble disruption” to evaluate the therapeutic advancements of UTMD in CVDs over the past decade. Particular emphasis was placed on innovative approaches for microbubble functionalization. Furthermore, a critical examination of current technological limitations and translational challenges is undertaken to inform future research directions.

Ultrasound serves as a critical diagnostic modality providing non-invasive real-time imaging capabilities in clinical practice. Microbubbles, when employed as contrast agents, significantly enhance the assessment of tissue perfusion, hemodynamic parameters, and pathological features such as lesions or vascular abnormalities — capabilities that establish them as indispensable tools for the diagnosis and clinical evaluation of cardiovascular diseases (11).

In 1998, Dr. Price and colleagues advanced the notion of UTMD in a publication in the “Circulation” journal (12). Over recent decades, UTMD has evolved into a prominent therapeutic strategy. Ultrasound-mediated techniques have garnered significant attention for their tripartite capability in precisely controlling drug activation, real-time monitoring, and spatiotemporally regulated release. Functioning as acoustic energy transducers, microbubbles serve as critical vectors for ultrasound-triggered delivery of both chemical agents and engineered nanoparticles. Several methods are employed to prepare microbubbles, such as atomization and reconstitution, cross-linking polymerization, and emulsion solvent evaporation (13). Gas-filled microbubbles (MBs) with diameters of 1–8 μm are conventionally employed as intravascular ultrasound contrast agents. The gaseous core provides the necessary echogenicity, while the surrounding shell prevents rapid dissolution of the core, thereby ensuring MB stability. These shells may consist of albumin, surfactants, phospholipids, proteins, mesoporous silica, or biocompatible and biodegradable polymers (14, 15). The utilization of insoluble, high-density inert gases—such as perfluorocarbons and sulfur hexafluoride—as core materials significantly enhances microbubble stability. Due to their low blood solubility, these gases prolong microbubble circulation within the vascular system. For instance, air-filled contrast agents (e.g., Albunex and Levovist) exhibit circulation times of approximately 5 min. In contrast, microbubbles containing fluorinated gases (e.g., SonoVue and Optison) demonstrate circulation times exceeding 10 min (16).

A significant disparity in their capabilities of drug delivery was observed due to substantial discrepancies in microbubble shell composition, gaseous composition, and size distribution. In addition, through surface functionalization or core-loading strategies, these microcarriers can encapsulate diverse therapeutic payloads including small-molecule drugs, nucleic acids, and immunotherapeutic antigens. Following intravenous administration, the acoustically driven inertial cavitation of microbubbles at target sites generates localized shear stresses and microstreaming effects, enabling site-specific payload release with enhanced bioavailability (Figure 2) (15).

The mechanical effects induced by ultrasonic fields, including acoustic radiation force, microstreaming, shear stress, and related phenomena, stem from the momentum transfer associated with sound waves. The occurrence of more substantial mechanical effects is plausible when the MBs interact with ultrasonic beams (17). In the context of low acoustic pressures, these MBs undergo symmetrically periodic expansion and compression, oscillating synchronously with the incident ultrasonic wave. The process in question is referred to as “stable cavitation.” During this process, the MBs undergo an expansion phase in which they extend to the point of coming into proximity with the blood vessel wall. This expansion causes the adjacent endothelium to separate from its neighbors. During the subsequent compression phase, the MBs undergo a process of shrinkage, causing invaginations in the endothelial cells that line the vessel. This process disrupt the tight junctions between the endothelial cells, resulting in a disruption of the tissue's structural integrity (18, 19). In the presence of elevated acoustic pressures, MBs undergo a violent collapse during the compression phase. This process is referred to as inertial cavitation. The propensity of microbubbles to undergo sustained stable cavitation or inertial cavitation depends on multiple factors, chief among which is the mechanical index (MI)—defined as the peak negative acoustic pressure divided by the square root of the ultrasound frequency. The collapse of MBs has been demonstrated to generate shock waves of increased strength, as well as microstreaming, micro-jetting, and tangential stresses. These phenomena have been observed to result in the perforation of cellular membranes. Impulse forces exerted on the endothelial cell membrane can directly result in the formation of transient, nonselective, and repairable pores, a phenomenon referred to as the sonoporation effect (15, 20).

Experimental evidence confirms that microbubble-mediated vascular permeability enhancement—driven by ultrasound-induced shear stress (e.g., 1 MHz, MI = 0.8)—is typically transient and occurs without vascular rupture when using pulsed ultrasound (0.1–10 ms pulses) with low duty cycles, restoring endothelial barrier function within minutes to hours while triggering Ca²⁺ signaling. However, excessive acoustic energy [e.g., high mechanical index (MI >1.3), prolonged burst length, or extended exposure] can induce violent microbubble collapse, causing localized endothelial damage through large-amplitude oscillations, endothelial cell death due to delayed pore resealing, and—under extreme conditions (MI 1.3–2.0)—vascular rupture and hemorrhage (21). Critical damage thresholds depend on both acoustic parameters (pulse scheme, microbubble properties/concentration) and biological factors (calcium-dependent repair mechanisms, membrane composition), as well as tissue-specific vessel characteristics (22).

Microbubble suspensions exhibit excellent biocompatibility as delivery platforms, demonstrating minimal systemic toxicity and negligible immunogenicity (23). This favorable safety profile stems from the fate of their components: Perfluorocarbon (PFC) gases (e.g., perfluoropropane, sulfur hexafluoride) are chemically inert, non-metabolized, and primarily eliminated via exhalation through the lungs within minutes to hours after administration. Meanwhile, the encapsulating shell materials (lipids, proteins, polymers) undergo biodegradation and renal clearance. Supporting this safety, Qin et al.'s cardiomyopathy study using repeated ultrasound-mediated delivery (three sessions at 1-day intervals) of Sirt3 plasmid via cationic microbubbles suppressed hypertrophic phenotypes—including cardiac enlargement, fibrosis, and apoptosis—at both 7 days and 2 months post-treatment. Critically, multi-organ assessment (kidneys, liver, lungs) confirmed no treatment-related damage, demonstrating high safety with minimal off-target effects (24).

Clinically administered via peripheral intravenous injection, these contrast agents enable non-invasive ultrasound-targeted microbubble destruction (UTMD) procedures—a key translational advantage for therapeutic applications (25). Microbubbles crucially protect encapsulated bioactive molecules from enzymatic degradation and immune clearance during circulation. Subsequent ultrasound-triggered inertial cavitation then enables site-specific payload release. This mechanism enhances therapeutic precision while minimizing off-target effects. Furthermore, microbubbles with functionalized surfaces achieve molecular-level targeting, significantly improving spatiotemporal control in diagnostics and therapeutics. Preclinical evidence confirms that molecularly targeted microbubbles substantially enhance gene delivery efficiency compared to non-targeted agents. For instance, in cardiovascular models, Xie et al. demonstrated the feasibility of endothelial-targeted (P-selectin/ICAM-1) gene-carrying microbubbles, achieving a 5-fold higher transfection efficiency than non-targeted controls at MI 0.6 in murine hindlimb ischemia (26). Similarly, Zhou et al. used ICAM-1-targeted microbubbles to deliver Ang1 in rabbit myocardial infarction models, yielding approximately 3-fold greater delivery efficiency vs. non-targeted bubbles using a Philips iE33 system (1.7 MHz, MI 1.3) (27).

Under ultrasound irradiation, commercially available microbubbles exemplified by SonoVue® (Bracco Imaging) demonstrate significant cardioprotective properties even when not loaded with therapeutics. Mechanistic studies attribute these effects to the upregulation of key signaling molecules including vascular endothelial growth factor-α (VEGF-α), insulin-like growth factor-1 (IGF-1), and caveolin-3 (Cav-3), coupled with the liberation of bioactive mediators such as nitric oxide (NO) and adenosine triphosphate (ATP) (104, 106). Notably, UTMD technology has emerged as a promising strategy for enhancing stem cell homing efficacy. Experimental evidence confirms that UTMD not only promotes targeted migration of mesenchymal stem cells (MSCs) to lesion sites but also preserves their fundamental biological characteristics, including proliferation capacity, apoptotic regulation, and cell cycle dynamics (38, 101). Furthermore, microbubble-assisted exosomal delivery systems have demonstrated therapeutic potential in cardiovascular applications. While therapeutic exosome administration shows cardioprotective benefits against toxic injury, limitations persist in cardiac-specific targeting efficiency. UTMD-mediated cavitation effects offer a technological breakthrough by significantly improving myocardial accumulation of exosomal therapeutics, thereby addressing current delivery challenges (62, 63).

Recent breakthroughs in MB nanotechnology have transformed gas-core contrast agents into multifunctional therapeutic systems through advanced engineering strategies. In cardiovascular applications, ligand-functionalized MBs enable molecular-level targeting via specific ligand-receptor interactions. The utilization of dual-modality theranostic contrast agents, compatible with ultrasound and MRI imaging, can be achieved by loading drugs and magnetic materials into the MBs. Furthermore, the polymeric MBs' thicker shell can accommodate a greater quantity of ultrasmall superparamagnetic iron oxide (USPIO) nanoparticles, a property that facilitates the mediation and monitoring of drug delivery (107). It is noteworthy that nanoscale bubbles have the capacity to extend their effects beyond the vascular confinement, thereby facilitating the transport of therapeutic agents across cellular barriers. The utilization of biosynthetic gas vesicles holds considerable promise for facilitating large-scale, non-invasive imaging techniques, thereby enabling the visualization of genetically modified bacteria within living subjects. This development stands to significantly contribute to the advancement of diagnostic and therapeutic cellular agents (108).

Gene delivery systems represent a frontier application with transformative potential in ultrasound-mediated therapy. The process of gene delivery is of paramount importance, as it pertains to the transplantation of foreign DNA to the cells of a host organism. This process is employed within the realm of biomedical research and gene therapy (109). There exist two fundamental gene delivery systems: viral and non-viral. Sonoporation, due to its non-invasiveness, high spatio-temporal resolution and tissue penetration through ultrasound-induced microbubble cavitation, has clear advantages over other modalities. Mechanically, ultrasonic excitation at the appropriate frequency and energy can cause microbubbles to vibrate, expand and collapse, leading to various stable or inertial cavitation effects including microstreams and microjets (110, 111). These physical forces result in the formation of transient and repairable pores in the cellular membrane, thereby facilitating the entry of foreign substances. Pre-clinical investigations have demonstrated that microbubble cavitation-based gene delivery holds considerable promise as a therapeutic modality (112). It has been employed extensively for the delivery of transgenes in the treatment of numerous diseases. Viral vectors are a means of facilitating the transfer of genetic material from one organism to another. This process, known as transduction, involves the use of viruses as vehicles to introduce foreign DNA into the cells of a recipient organism. Despite their capacity to elicit effective gene expression due to their viral configuration, which hinders degradation, numerous studies have demonstrated that the utilization of these carriers is encumbered by several limitations. These limitations encompass immunogenicity (113), off-target delivery (114), and arduous vector production (115). The substantial internal space of ultrasound-responsive microbubbles renders them optimal for use as viral vectors. Consequently, gene transfer strategies that employ acoustically triggered microbubble collapse might effectively circumvent antiviral immune responses while improving targeting. Non-viral gene carriers have gained significant interest due to their comparatively reduced toxicity and immunogenicity in contrast to viral vectors. Nevertheless, the limitations inherent to non-viral carriers include the low levels of protein expression and the inefficient gene transfer efficiency (116). To address this issue, Xie et al. (117) proposed a gene delivery strategy that utilizes ultrasound to directly deliver plasmid DNA into nuclei via gas vesicles (GVs)-based intracellular cavitation. The pDNA-binding GVs are internalized by cells, leading to the formation of intracellular cavitation when exposed to acoustic irradiation, thereby delivering their pDNA payloads into the nuclei.

These innovative targeting approaches - encompassing biochemical specificity, physical guidance, and nanoscale biodistribution - are redefining precision medicine in cardiovascular interventions, particularly for pathologies requiring temporally controlled, site-specific treatment administration. Building upon this paradigm shift in therapeutic delivery, over the past decade, therapeutic research in cardiovascular diseases has predominantly centered on acute myocardial infarction and heart failure, while peripheral arterial disease and cerebrovascular disorders have remained relatively underexplored in preclinical investigations (Table 1). This research gap persists despite growing clinical needs, notably in cerebrovascular therapeutics where conventional drug delivery systems face substantial anatomical barriers. Emerging as a technological breakthrough in this context, the integration of focused ultrasound (FUS) with microbubbles (MBs) has demonstrated significant potential for treating cerebrovascular diseases (118, 119). This noninvasive method enables targeted drug delivery to the brain. At relatively low frequencies, concentrated ultrasound waves can traverse the skull to generate an acoustic field within the brain tissue. When MBs circulate in an ultrasonic field, they undergo oscillation at the same frequency as the ultrasound, a process termed cavitation. In this context, MBs function as cavitation nuclei, moderating the effects of ultrasound while simultaneously inducing transient and reproducible openings of the blood-brain barrier (BBB) (120). The mechanism underpinning FUS-mediated BBB disruption involves the dynamic biomechanical interaction between oscillating MBs and the cerebrovascular structures within the ultrasonic field. This interaction exhibits pronounced parametric sensitivity, being critically dependent on three interrelated factors: 1. acoustic exposure parameters, 2. The physicochemical properties of MBs, and 3. regional vascular density (121). Ultrasound-mediated BBB disruption, supported by well-established mechanisms, preclinical research, and clinical trials, has confirmed its scalability and favorable safety profile. Repeated administrations have not resulted in any clinically detectable tissue damage or neurological complications.

Beyond current clinical trials of focused ultrasound-mediated blood-brain barrier opening for brain tumors, Alzheimer's disease, Parkinson's disease, and amyotrophic lateral sclerosis, emerging applications target neuropsychiatric disorders (including major depression and substance addiction) and central pain syndromes. To translate these diverse applications into clinical practice, integrated systems enabling real-time therapy control and safety validation become paramount. The combination of clinically approved MRI-guided focused ultrasound (MRgFUS) with engineered, shell-optimized microbubbles establishes a robust platform for evaluating therapeutic interventions across diverse patient groups. Real-time MRI monitoring, coupled with advanced microbubble formulations, further provides critical evidence regarding safety and feasibility, particularly for cohorts with neurological impairments that require therapies targeting the central nervous system (CNS) (122).

UTMD embodies precision medicine principles through its unique mechanism, demonstrating substantial clinical promise. Preclinical studies validate its safety profile, with microbubbles exhibiting high circulatory stability and biocompatibility in vivo. Surface modification strategies further enhance microbubble localization, enabling UTMD to achieve tissue-specific targeting. Nevertheless, technical challenges persist regarding clinical translation.

The current absence of mass-production manufacturing methodologies for ultrasound-responsive microbubbles remains a critical barrier. Furthermore, refining the physicochemical composition of these contrast agents represents a pivotal challenge for their clinical translation. Specifically, next-generation formulations must simultaneously demonstrate enhanced drug-loading efficiency, consistent acoustic responsiveness, and convenient production-preservation-transportation workflows to meet clinical demands. Beyond these engineering bottlenecks, the transition from preclinical validation to human applications introduces additional biological complexities. While the feasibility of UTMD has been extensively validated in rodent models, the inherent anatomical complexity and physiological heterogeneity of human systems necessitate a phased translational approach. This progression should prioritize rigorous validation in large-animal models before advancing to controlled human trials, ensuring interspecies compatibility in microbubble-mediated therapeutic delivery.

The clinical implementation of UTMD necessitates stringent control over interdependent acoustic parameters - including frequency, mechanical index (MI), pulse duration, and duty cycle (5) - which require systematic calibration to achieve therapeutic bioeffects (mechanical/thermal) while avoiding off-target tissue damage. This precision engineering challenge is particularly evident in focused ultrasound-mediated BBB opening, where safety profiles exhibit significant context-dependency influenced not only by acoustic variables but also by microbubble characteristics (size distribution, shell composition) and vascular anatomical constraints (123). The complex interplay between inertial cavitation thresholds, microbubble oscillation dynamics, and non-linear acoustic interactions mandates the development of multiparametric optimization frameworks. Such protocols must balance BBB permeability enhancement with preservation of neurovascular integrity, requiring real-time feedback systems capable of adjusting sonication parameters in response to dynamic physiological feedback. Emerging evidence indicates that FUS-mediated BBB opening may inadvertently provoke neuroinflammatory cascades (124). Therefore, a critical technological barrier persists: the absence of robust, non-invasive tools for real-time tracking of neuroinflammatory dynamics in vivo. Addressing this unmet need requires prioritized development of targeted molecular imaging probes capable of selectively detecting inflammation-associated biomarkers. Such innovations would not only enable safety profiling during FUS interventions but also facilitate precision modulation of treatment parameters to optimize therapeutic outcomes while mitigating adverse effects.

UTMD has demonstrated unique advantages in cardiovascular disease management, particularly through its capacity for targeted drug/gene delivery mediated by ultrasound-triggered microbubble cavitation. The convergence of these platforms could address critical challenges in cardiovascular therapies, including tissue specificity, delivery efficiency, and safety. However, clinical translation requires systematic validation of their synergistic mechanisms, long-term biocompatibility, and spatiotemporal control precision. By advancing these ultrasound-mediated technologies, we may pioneer a new era in cardiovascular care—from molecular level interventions to organ monitoring—driving a shift towards personalised medicine.