Ultrasound-mediated nanomaterials for the treatment of inflammatory diseases.

US is a mechanical wave with a periodic vibration frequency exceeding 20,000 Hz. Its strong penetration, high spatial resolution, and non-invasive properties make it widely applicable in biomedical fields for diagnostic imaging and therapeutic purposes. [33] , [34] , [35] Generally, the biomedical application of US can be divided into diagnosis and treatment based on its intensity and frequency ( Fig. 2 ). Fig. 2 Application and classification of US in clinics. Created with BioRender.com . Application and classification of US in clinics. Created with BioRender.com . Diagnostic US has a long history of use in medical imaging and encompasses various imaging modalities, such as Doppler US, elastography, and three-dimensional US. [21] It is characterized by a high frequency (3.0–20 MHz) and low intensity (0.0001–0.5 W/cm 2 ). [36] High-frequency US provides superior spatial resolution in imaging. For the utmost safety considerations, the intensity of diagnostic US must be quite low to prevent tissue heating. [37] Diagnostic US has many applications, including imaging of the cardiovascular, reproductive, and digestive system, etc. [38] Therapeutic applications of US have emerged in recent decades. Compared with diagnostic US, it has lower frequencies (20 kHz–3 MHz) and higher intensities (≥0.5 W/cm 2 ). [39] Therapeutic US can be further divided into low intensity (0.5–3 W/cm 2 ) and high intensity (>3 W/cm 2 ), with intensity modified based on the specific treatment requirements. US has been utilized across diverse clinical therapeutic applications, including transdermal drug delivery, fracture healing, and tumor ablation. [21] Frequency . Theoretically, the frequency and penetration depth of US are closely related. [40] Taking 1 MHz US as an example, its penetration depth typically exceeds 30 cm. In contrast, the penetration capability of 10 MHz US is significantly lower and usually limited to a few centimeters. This is attributed to the longer wavelength of lower-frequency US waves, which allows for easier penetration into deeper tissues, whereas higher-frequency US waves with shorter wavelengths exhibit weaker penetration capabilities. Relatively low-frequency US (20 kHz–3 MHz) enables deep penetration and meets various requirements for deep tissue treatment. [41] However, the shortcoming of this modality is its relatively low spatial resolution due to its low frequency, which results in limited image resolution for treatment monitoring. [41] , [42] Irradiation mode . According to the irradiation mode of the sound beam, US can be divided into focused and non-focused US. This precise targeting enables more accurate treatment, often facilitated by specialized acoustic lens or transducer. [43] Focused ultrasound (FUS), a therapeutic technique, concentrates US within the human body and produces thermal, mechanical, or other biological effects, allowing for precise disease treatment without invasiveness. [44] Compared with FUS, which concentrates US energy in a restricted space, non-focused US can affect a large tissue area and has been reported to have fewer possible toxic side effects associated with local heating. [45] , [46] Intensity . Therapeutic US can be divided into high- and low-intensity US. High-intensity US, with high energy, causes inertial cavitation with the collapse of microbubbles, which generates localized high temperatures. For example, high-intensity focused US performs ablation by heating tumor tissue through high temperatures (≥55 °C). [47] The high temperature results from the combined effects of thermal energy and cavitation, which can cause irreversible damage or coagulative necrosis of tumor cells. In contrast, low-intensity US, which typically utilizes mechanical rather than thermal effects to produce a therapeutic effect, has garnered considerable attention from researchers. [48] Low-intensity focused ultrasound (LIFU) utilizes low-energy-level US wave to focus on the target tissue, mainly through mechanical energy. It does not cause a significant increase in tissue temperature, thereby avoiding some potential damage. [49] Emission mode . There are two emission modes: pulsed (e.g., 10 %, 20 %, or 50 % duty cycle) and continuous (100 % duty cycle). The duty cycle is denoted by a percentage, which refers to the percentage of time that US is generated over one cycle. Low-intensity pulsed US has low energy intensity and can output pulsed waves. It can induce therapeutic effects such as accelerating tissue repair or regeneration and inhibiting inflammatory responses. [48] Low-intensity continuous US is a variant of low-intensity pulsed US and has been well-studied for a wide range of clinical applications, including neuromodulation and tissue regeneration. [50] In summary, the therapeutic effect of US is influenced by the various parameters described above. Therefore, different US parameters should be selected for specific clinical applications. In the treatment of inflammatory diseases, US can exert its effects by lowering the levels of pro-inflammatory factors and increasing those of anti-inflammatory factors. US has been reported to significantly reduce the production and expression of pro-inflammatory cytokines such as interleukin-1 (IL-1), IL-6, and tumor necrosis factor-α (TNF-α), as well as chemokines like C-X-C motif chemokine ligand 1 (CXCL1), CXCL10, and C-C motif chemokine ligand 2. [51] , [52] , [53] , [54] , [55] , [56] , [57] Additionally, it is able to elevate levels of anti-inflammatory factors such as transforming growth factor-β (TGF-β) and IL-10. [58] The ability of US to diminish inflammation in the body can be achieved through various signaling pathways, including mitogen-activated protein kinase (MAPK), nuclear factor-κB (NF-κB), phosphatidylinositol-3-kinase/serine/threonine kinase (PI3K/Akt), and Toll-Like Receptors (TLRs). US can reduce the expression of MAP kinase kinase3/6 and mitogen-activated extracellular signal-regulated kinase1/2 phosphorylation induced by lipopolysaccharide (LPS) and inhibit the phosphorylation of p38 and extracellular regulated protein kinases. [57] US affects the MAPK pathway by inhibiting the phosphorylation of p38 MAPK and ERK, thereby preventing the LPS-induced increase in TNF-α and IL-6. [59] US significantly limits the expression of inflammatory cytokines in synovial fluid by activating FAK signaling and inhibiting MAPK-mediated inflammatory responses. [53] Regarding the NF-κB pathway, US suppresses both upstream and downstream factors associated with the TLR4/NF-κB pathway, including the TLR4/Myeloid differentiation primary response protein 88 (MyD88) complex, TNF-α, IL-1β, IL-6, and IL-8. [51] , [60] , [61] By diminishing the phosphorylation degradation of IκBα, US reduces NF-κB phosphorylation and its translocation into the nucleus. [55] , [62] Additionally, US activates the intracellular ubiquitin-editing protein A20, thereby inhibiting NF-κB pathway. [63] In aortic endothelial cells, US inhibits oxidative stress-induced endothelial-mesenchymal transition through the PI3K/Akt pathway. [64] It upregulates the expression of Sox9, aggrecan, type II collagen, and matrix metalloproteinase (MMP)-1 tissue inhibitors while suppressing MMP-3 secretion. [65] Furthermore, it influences the mechanochemical transduction of the integrin-FAK-PI3K/Akt axis and alters macromolecular components. [66] In the TLRs signaling pathway, US decreases the protein expression of TLR4 and MyD88 induced by LPS, [57] , [61] , [67] as well as the phosphorylated expression of TBK1 and IRF3, independent of the MyD88 signaling pathway. [57] This indicates that US influences the TLRs signaling pathway through both MyD88-dependent and TRIF-dependent mechanisms. Moreover, US can exert anti-inflammatory effects by inhibiting the TGF-β/Smad signaling pathway and the F-Box Leucine-rich 2/TNF receptor associated factor 6 signaling pathway. [68] , [69] , [70] In summary, US can regulate cytokine levels through various signaling pathways, which accounts for its extensive applications in treating numerous inflammatory diseases. Compared with other stimulus-responsive excitation sources, US has unique advantages, such as deep penetration, precise targeting, non-invasiveness, unaffected by external factors, relatively low price, and more widespread use ( Fig. 3 ). Fig. 3 The unique advantages of US over other stimulus-responsive excitation sources. Created with BioRender.com . The unique advantages of US over other stimulus-responsive excitation sources. Created with BioRender.com . Light is a key stimulus involved in the application of photodynamic therapy (PDT) and photothermal therapy (PTT) in the treatment of inflammatory diseases, which can address diseases through mechanisms such as the thermal effect and the induction of ROS. [71] , [72] However, there are several limitations in the application of light, such as insufficient penetration depth, potential damage to normal tissues, and thermal tolerance in target lesions that may affect treatment efficacy. [73] , [74] , [75] , [76] In contrast, sonodynamic therapy (SDT) utilizing offers deeper penetration and stronger targeting without harming adjacent normal tissues. [77] , [78] In addition to the thermal effects produced by light, changes in temperature can also serve as a stimulus to assist in the treatment of diseases. The temperature changes at the site of inflammation can activate the functions of NMs, making therapies highly targeted and effective. [79] , [80] However, temperature changes in the external environment tend to affect the therapeutic effect of temperature-stimulated NMs, whereas US-mediated NMs are less affected by external factors. Additionally, the magnetic field acts on NMs to produce a thermal effect, thereby facilitating diseases treatment. This treatment method boasts advantages, including non-invasiveness, deep penetration, and high specificity. Yet, it is less widespread than that of US due to the need for precise, expensive equipment and complex procedures to generate the alternating magnetic field. [81] , [82] , [83]

With the remarkable advances of nanotechnology, many well-designed nanosystems have emerged that can be triggered under exogenous US stimulation. [26] Over the past few decades, nanomedicine has made rapid advancements in utilizing the properties of NMs for molecular-level diagnosis and treatment of diseases. [84] As the foundation of nanotechnology, NMs possess unique physical and chemical properties due to their size and shape falling within the nanoscale range, typically with at least one dimension of 100 nm. [85] Compared with macroscopic materials, NMs have the following advantages in controlling inflammation. [86] , [87] The EPR effect was mostly reported in anti-cancer NMs, but studies indicate that NMs can also accumulate in target areas through the EPR effect for the treatment of inflammatory diseases. The elevated expression of histamine, bradykinin, leukotrienes, and serotonin in inflamed tissues leads to increased intraendothelial gaps. [88] , [89] , [90] These fenestrations facilitate the specific extravasation of NMs into the inflamed tissue. [91] Additionally, during inflammation caused by infection, the pathogens responsible may secrete factors that increase vascular permeability, thereby promoting the EPR effect. [92] , [93] The EPR effect has been reported in the treatment of various inflammatory diseases, including atherosclerosis, pulmonary fibrosis, inflammatory bowel disease, and rheumatoid arthritis, etc. NMs, with their smaller size, accumulate in various inflamed tissues such as the heart, intestines, and joints through the EPR effect and exhibit high permeability to enter cells. Active targeting involves the conjugation of inflammatory molecules and cell-specific entities onto the surface of NMs, allowing for flexible design of these NMs with high specificity for targeted delivery. Inflammatory targets encompass the inflamed vascular system, pathogens, immune cells, and inflammatory mediators or products. [22] Nanoscale platforms can load various anti-inflammatory drugs or molecules, delivering anti-inflammatory agents to inflammation sites while enhancing drug absorption and providing sustained release, effectively addressing solubility and stability issues. On the other hand, NMs can serve as drug carriers and therapeutic agents for inflammatory diseases without the need for additional anti-inflammatory drugs. Furthermore, NMs can modulate inflammation at different stages, demonstrating good biocompatibility. [22] During treatment, NMs can be triggered by internal stimuli like pH, enzymes, reactive oxygen species (ROS), and reductive oxidation, as well as by external stimuli such as US, temperature, magnetic fields, light, voltage, and mechanical friction. Among external stimuli, US can provide better control over the release of NMs, thus allowing external intervention and improving manipulability. NMs have other advantages over conventional materials. Take sonosensitizers, for example, which are the most extensively employed US-responsive agents and can generate ROS. [94] First-generation sonosensitizers, such as porphyrin derivatives, are organic small molecules derived from photosensitizers used in photodynamic therapy (PDT). [95] Despite their success in sonodynamic therapy (SDT), their widespread clinical application remains limited owing to several issues, including low bioavailability, poor pharmacokinetics (susceptibility to clearance by the immune system), poor tissue EPR effect, non-specific distribution, high dose dependence, low stability, and even toxicity. With the development of nanotechnology, the innovative combination of nanotechnology and sonosensitizers has brought about nanosized sonosensitizers, which can significantly overcome the shortcomings of conventional sonosensitizers, thereby enhancing their therapeutic efficacy. [96] Classical treatments for certain inflammatory diseases often involve the use of NSAIDs and glucocorticoids, which can cause numerous side effects. For instance, excessive use may trigger complications, such as exogenous Cushing's syndrome, and regardless of the mode of administration, long-term glucocorticoid therapy can result in complications such as obesity, insulin resistant, hypertension. [97] , [98] , [99] In contrast to hormones that affect the entire body even when administered locally, US-mediated NMs offer improved targeting, and the controllability of US allows these materials to exert therapeutic effects at the lesion sites with less impact on other tissues and organs ( Fig. 4 A ). Fig. 4 A) The advantages of US-mediated nanomedicine over NSAIDs. B) The interaction between US and NMs facilitates the treatment of both infectious and aseptic inflammatory diseases through three distinct mechanisms, respectively, thereby alleviating the symptoms associated with specific inflammatory conditions. Created with BioRender.com . A) The advantages of US-mediated nanomedicine over NSAIDs. B) The interaction between US and NMs facilitates the treatment of both infectious and aseptic inflammatory diseases through three distinct mechanisms, respectively, thereby alleviating the symptoms associated with specific inflammatory conditions. Created with BioRender.com . Additionally, the combination of US and NMs can accelerate the accumulation of drugs in target tissues, leading to more rapid therapeutic effects. The clinical significance of the EPR effect of NMs in disease treatment remains controversial, so it is still uncertain whether NMs alone can accumulate rapidly in the lesion. [100] , [101] However, the incorporation of US facilitates the smoother entry of NMs into the tissue, which means the drugs can accumulate more quickly and extensively, thereby achieving better therapeutic outcomes. [22] . For specific inflammatory diseases, the interaction between US and NMs can achieve anti-inflammatory effects and alleviate disease symptoms in different ways. In inflammatory diseases caused by infections (mainly bacterial infections), therapeutic US and US-responsive NMs exert therapeutic effects such as neutralizing bacterial toxins through sufficient ROS production, eradicating bacterial biofilms, and killing bacteria. While in aseptic inflammatory diseases, these approaches include the production of ROS to induce apoptosis, anti-inflammatory phenotype transition of inflammatory cells (such as macrophages), inhibition of the expression of inflammatory cells and factors ( Fig. 4 B ). A variety of action modes are involved in US-mediated NMs for the treatment of inflammatory diseases ( Fig. 5 A ), which can be categorized as follows: Fig. 5 A) Inflammatory diseases which can treated by US-mediated NMs. B) US facilitates the delivery of NMs. C) US controls the release of drugs from NMs. D) US and NMs combine to play a role in SDT. Created with BioRender.com . A) Inflammatory diseases which can treated by US-mediated NMs. B) US facilitates the delivery of NMs. C) US controls the release of drugs from NMs. D) US and NMs combine to play a role in SDT. Created with BioRender.com . US with energy will produce cavitation effect in the course of its action. [102] , [103] The cavitation effect refers to the formation of bubbles by the compression of gases in the medium, which produces a powerful mechanical effect when the bubbles expand and collapse rapidly under the action of sound waves. The microjet generated by the cavitation effect can propel drugs into tissues and reversibly permeabilize tissue, thereby facilitating drug uptake. [104] The cavitation effect of US is utilized in treating neurological disorders, where US can alter the instantaneous permeability of the blood brain barrier, thus promoting the entry of nanomedicines into the brain to treat diseases such as post-traumatic stress disorder. [105] , [106] , [107] US treatment can also lead to the disruption of bacterial biofilms, thereby increasing the penetration of nanomedicines to achieve better therapeutic outcomes, which plays an important role in treating several infection-associated inflammatory diseases. [108] , [109] , [110] Notably, US-promoted delivery is affected by many properties of the NMs themselves, including their size, shape, elasticity, charge, and surface characteristics. [111] , [112] , [113] , [114] Therefore, by adjusting the material properties and US parameters, it is possible to better control the targeted delivery of NMs to the site of inflammation for therapeutic purposes ( Fig. 5 B ). US not only facilitates the delivery of NMs in vivo but also, through its mechanical and thermal effects, causes the NMs to conformationally change once they reach the target, leading to the release of the drugs or genes loaded in them. [115] Zhou et al. constructed platelet biomimetic rapamycin-loaded poly (lactic-co-glycolic acid) (PLGA) NPs for the treatment of atherosclerosis. They found that the combined use of SonoVue™ and US enhanced the efficiency of rapamycin release from NPs, resulting in improved plaque stability and inhibition of atherosclerotic plaque formation. [116] In a study to treat age-related macular degeneration, researchers similarly utilized US to assist in the delivery and release of pirfenidone encapsulated in PLGA NPs or a polyurethane-based nanocapsule system to modulate inflammation and fibrosis. [117] Using US to actively regulate the release of nanomedicines enhances the targeting of the drugs and achieves precision therapy, yielding improved outcomes in managing inflammatory diseases ( Fig. 5 C ). The main interaction mechanisms between US and NMs in SDT include ROS generation, mechanical effects, and thermal effects. [118] First, NMs can be activated to generate ROS after absorbing the energy from US. The ROS generation occurs through sonochemical effects, including sonoluminescence and pyrolysis processes. [119] Sonoluminescence is a phenomenon in which bubbles caused by the cavitation effect under US irradiation collapse quickly and release energy to trigger brief light emission. The specific mechanism is still unclear. Pyrolysis is another theory that explains the production of ROS; however, its specific mechanism has not been fully understood. [120] Second, the mechanical effects primarily include cavitation and sonoporation effects. The cavitation effect is an important mechanism in US therapy and can be categorized into stable and inertial cavitation. Stable cavitation is induced by low-intensity US, causing bubbles to undergo periodic oscillation and exert shear forces on the surrounding environment. Inertial cavitation occurs when bubbles become unstable and collapse under local high temperatures and pressures, leading to the production of ROS, such as hydroxyl radicals. Additionally, the rupture of a cavitation bubble produces sonomechanical effects, such as shock waves and shear stress, and high temperatures in local cells or tissue. [118] , [121] The sonoporation effect refers to the formation of pores in the cell membrane under US, which facilitates the transportation of molecules and NMs into cells. Sonoporation can enhance the absorption and accumulation of drug molecules, genes, or NPs. [27] Lastly, the thermal effect means the elevation in tissue temperature because of the absorption of thermal energy converted from US ( Fig. 5 D ). [122]

Inflammatory diseases pose significant global health threats with far-reaching sociomedical implications. US-mediated NMs exhibit therapeutic potential for various diseases, including inflammatory diseases and cancer. Presently, US-mediated NMs demonstrate advantages including targeted delivery, theranostic platforms, and the ability to facilitate combination therapies, which indicates broad prospects for managing inflammatory diseases. However, their clinical translation faces several challenges, and future enhancements are required ( Fig. 18 ). Fig. 18 The future directions of US-mediated NMs in treating inflammatory diseases. The future directions of US-mediated NMs in treating inflammatory diseases. The efficacy of US therapy is largely dependent on the type of sonosensitizer used. Ideal sonosensitizers should exhibit low toxicity, high therapeutic efficacy, and enhanced bioavailability. However, NMs used for US therapy have been found to potentially cause some side effects in humans. Previous reports indicate that NMs are associated with an increased risk of inflammation, allergies, and certain reproductive system diseases. [263] , [264] Therefore, long-term toxicity studies of NMs, particularly non-degradable inorganic NMs, are required to ensure their biological safety. Current research indicates that the interactions between NMs and blood, tissues, cells, and biomolecules such as nucleic acids and proteins in the body may lead to toxicity formation. [265] , [266] , [267] , [268] The interaction of biomolecules with NMs causes the formation of biomolecular-nanoparticle-surface-corona, which can disrupt proteins and induce immunotoxicity. [269] , [270] NMs can also interfere with cells and disrupt homeostasis by damaging cell membrane structures. [271] , [272] Moreover, intracellular NMs may harm mitochondria and cause damage to the human body through ROS. [273] , [274] The toxicity of NMs is influenced by dose, route of administration, surrounding environment, and the size, shape, and surface chemistry of the NMs themselves. [275] , [276] , [277] For example, the toxicity of zinc oxide NMs is related to the generation of reactive oxygen species and the release of Zn 2+ , [278] while the toxicity of titanium dioxide NMs is produced through cell capture. [279] Ag NMs induce embryonic developmental disorders, affecting the cardiovascular and respiratory systems, thereby causing toxicity. [280] Therefore, strategies to mitigate the side effects of different NMs must be tailored to specific circumstances, aiding in their clinical translation. At the same time, the residual products generated after US interaction with NMs should not be ignored because of their potential to damage normal cells and tissues. Comprehensive biosafety assessments are crucial before nano-sonosensitizers advance to the clinical trial phase. Notably, design and synthesis issues are also critical for the clinical translation of therapeutic nanomedicines, which face challenges such as poor reproducibility, low efficiency in large-scale synthesis, and variable physicochemical properties. The synthesis process of nanomedicines needs to be further improved and simplified, and single-component NPs should be selected when they can satisfy the therapeutic effect to minimize adverse effects and risks and facilitate clinical translation. [26] The application of NMs in the field of medicine was expected to have a revolutionary impact on healthcare. Despite this, nanomedicine still lacks clarity regarding regulatory oversight for clinical use, which greatly hinders its translation. [281] It is crucial to establish internationally standardized regulatory frameworks and guidelines specific to NMs. This necessitates the development of reliable technologies and tools to assess toxicity, thereby accurately estimating their potential hazards and limitations. [282] To harness the diverse benefits of nanotechnology across various sectors, global regulatory agencies are actively working to establish frameworks for the oversight of NMs. In the realm of pharmaceuticals, nanotechnology-based products require specialized strategies to ensure the optimization of their safety, quality, efficacy, and performance, ensuring effective oversight and public health protection. The precise targeting of drugs is important in the treatment of diseases. Currently, some treatments used in clinical practice feature “always-on”, which may lead to off-target effects, poor therapeutic outcomes, and even side effects on the human body. [283] , [284] , [285] Therefore, improving the targeting of US-mediated NMs in the treatment of inflammatory diseases is also a future direction to explore. At present, there are several methods available to increase the targeting of NMs, including employing highly expressed factors, ions, or proteins in the target environment; [286] , [287] , [288] employing external factors such as light, heat, radiation, magnetic fields, microwaves, and US; [121] , [289] and decorating materials with macrophage membranes, platelet membranes, or erythrocyte membranes. [290] , [291] , [292] , [293] Furthermore, combining the above strategies is a good idea. [294] However, these methods are not necessarily suitable for every nanomedicine, nor are they all necessarily suitable for treating inflammatory diseases. Therefore, efforts should be made to explore ways to increase nanomedicine targeting for treating inflammatory diseases. While different inflammatory environments exhibit many similarities, they also possess distinct characteristics at the cellular and molecular levels. These differences can be leveraged to develop NMs targeted at specific inflammatory diseases. In certain diseases, specific molecules are expressed at elevated levels, allowing for targeted suppression of their expression to control inflammation. For instance, in drug or IR-induced hepatitis hepatitis, various adhesion molecules such as ICAM-1 are highly expressed on HECs. Designing NMs that target ICAM-1 to reduce its levels presents a promising anti-inflammatory strategy. [202] Similarly, macrophage foam cells play a critical role in atherosclerosis, indicating that designing NMs to target these cells, reducing their functionality or promoting their apoptosis, could be significantly beneficial in treating atherosclerosis. [168] , [169] In the treatment of infections causing inflammation, designing specialized NMs tailored to the characteristics of different bacteria to eliminate them is also a promising approach. For example, many bacteria form biofilms, complicating their removal. Therefore, when addressing inflammation caused by these bacteria, it is crucial to design NMs capable of disrupting their biofilms to achieve effective treatment. [30] , [237] , [295] Additionally, certain bacteria, such as MRSA, have the ability to secretes toxins at the infection site, which can further harm the host. Developing NMs that simultaneously inhibit MRSA growth and neutralize its toxins could lead to improved therapeutic outcomes. [224] , [226] In summary, when treating various inflammatory diseases, it is essential to thoroughly understand the characteristics of the inflammatory microenvironment to facilitate the targeted design and development of NMs. The efficacy of therapeutic US significantly depends on key parameters, such as frequency and intensity, and lacks uniformity across different studies, which requires optimization and standardized criteria. There is also a need for further development of equipment specialized for US therapy. Advancements in capacitive micromachined ultrasonic transducers and integrated systems have enhanced the effectiveness and safety of therapeutic US devices. Furthermore, the integration of artificial intelligence and big data augments the intelligence of therapeutic US devices, which will propel therapeutic US toward clinical translation. To date, US-mediated treatments have been applied across a variety of diseases, with some applications entering clinical use and receiving approval from the US Food and Drug Administration and the European Union, while many others remain under investigation. [296] , [297] US enhances drug delivery and controls drug release. Recently, US-responsive drug delivery systems have gained considerable attention for their non-invasive nature, robust tissue penetration, and precise spatiotemporal controllability, showcasing significant potential for clinical translation. [298] Furthermore, representative clinical trials related to US and their key findings are as follows. Regarding HIFU, substantial research documents its high therapeutic performance in fields such as aesthetics, prostate ablation, breast cancer treatment, bone tumors, liver cancer, renal cancer, uterine fibroids, adenomyosis, benign thyroid nodules, and essential tremor. [299] , [300] , [301] , [302] , [303] , [304] , [305] , [306] , [307] , [308] , [309] , [310] Low-intensity pulsed ultrasound has demonstrated efficacy in promoting fracture healing, [311] , [312] and its regulatory effects on the nervous system suggest potential applications in Alzheimer’s disease, Parkinson’s disease, depression, schizophrenia, anxiety disorders, and substance use disorders. [313] , [314] In lithotripsy, ultrasound is utilized to facilitate the fragmentation of calculi in the kidneys, ureters, bladder, and pancreas, exhibiting satisfactory therapeutic effect. [315] , [316] , [317] It is noteworthy that the role of US in immunotherapy is becoming increasingly prominent. Tumor immunotherapy primarily works by reactivating and maintaining the tumor immune cycle to suppress or kill tumor cells. By adjusting various parameters, US can precisely focus on tumor sites and selectively activate sonosensitizers, thereby selectively killing tumor cells. [318] There are four modes of US: HIFU, LIFU, UTMD, and SDT, which can enhance the body's immune response to tumors, thereby improving cancer treatment outcomes, overcoming immune tolerance, and effectively preventing tumor recurrence and metastasis. [319] Among these, Chimeric Antigen Receptor (CAR) T-cell therapy is a rapidly evolving cancer immunotherapy in which T cells are genetically engineered to possess redirected specificity against malignant cells. Recent studies have identified inducible CAR T cells that can be directly controlled by FUS without the need for any exogenous auxiliary factors. [320] Compared to standard CAR T cells, short-pulse FUS stimulation can activate engineered T cells at the desired time and location, thereby inhibiting tumor growth in vivo with improved safety. Additionally, FUS-clustered regularly interspaced short palindromic repeats (CRISPR)-mediated telomere disruption primes solid tumors for CAR T cell therapy. The FUS-CRISPR toolbox allows for non-invasive and spatiotemporal control of genomic/epigenomic reprogramming in cancer treatment and can be applied to synergistic cancer immunotherapy. [321] The precise mechanisms of US-mediated NMs in disease therapy remain contentious and require thorough clarification. Although most studies illustrate that US and NMs can play an anti-inflammatory role in the treatment of disease, there are a few more cases of US and/or NMs triggering inflammation. In the treatment of neurological diseases, US may induce a sterile inflammatory response while opening the BBB, and it was found that several factors can influence this event. [322] , [323] , [324] , [325] , [326] Besides, some studies have indicated that applying NMs may induce or enhance inflammatory responses caused by other factors. [327] , [328] , [329] , [330] , [331] , [332] These studies demonstrate that US and NMs can also trigger inflammation in certain situations. It is important to avoid these circumstances during their therapeutic use to avoid unexpected patient harm. Further research is required to explore the mechanisms of US and NMs in inflammation treatment, which will guide the manufacturing of these materials and their clinical application. Although US-mediated NMs have been utilized in many inflammatory diseases, their therapeutic role in some inflammatory diseases has not been deeply explored, such as digestive tract inflammation. Inflammatory diseases of the digestive tract, such as inflammatory bowel disease, have a great impact on the quality of life of patients. [333] , [334] However, to the best of our knowledge, there are few reports on the use of NMs and US combined for inflammatory and antibacterial therapy in the field of the digestive tract. Only a few researchers have explored the application of SDT in treating Helicobacter pylori and Fusobacterium nucleatum . [335] , [336] , [337] However, there are many combined applications of US and NMs for treating gastrointestinal cancers, such as colorectal cancer. Inflammation and cancer have some commonalities. Therefore, treating gastrointestinal cancer can also provide insights into managing inflammatory diseases. For example, oral administration of drugs is the most popular and feasible method for treating colorectal cancer. However, an acidic environment, digestive enzymes, and mucus barriers in the digestive tract always affect the therapeutic effectiveness of oral administration. In fact, not only the treatment of cancer but also inflammatory diseases of the digestive tract face this problem. Therefore, studies on reducing the loss of oral drugs during delivery in cancer treatment can provide insights for future research aimed at reducing drug losses during delivery to the gastrointestinal tract during the treatment of inflammatory diseases. This can potentially lower treatment costs and improve therapeutic efficacy. In addition to gastrointestinal inflammatory diseases, US-mediated NMs have potential applications in various inflammatory conditions, including those associated with fungal infections. Recently, some inflammatory diseases caused by fungal infections can also be treated using US-mediated NMs, such as vulvovaginal candidiasis caused by Candida albicans. [338] It is hoped that further research will be conducted in the field of inflammation. Research on nano-sensitizers and therapeutic US necessitates deeper interdisciplinary collaboration among chemists, biologists, material scientists, and clinical practitioners. In terms of therapeutic approach, SDT can be combined with PDT, CDT, immunotherapy, and other therapies to achieve a more comprehensive treatment effect. With the collective advancement of multiple disciplines, these innovations will ultimately be applied to diagnosing and treating diseases. This review provides a comprehensive overview of US-mediated NMs for treating inflammatory diseases. Furthermore, US-mediated nanotherapy is crucial for several other diseases. For instance, in the realm of cancer treatment, US-mediated NMs have been extensively researched and applied. [33] , [339] Notably, in the treatment of liver and breast cancer, these nanomaterials are favored for their excellent targeting capabilities and therapeutic efficacy. [340] , [341] , [342] Additionally, in the management of cardiovascular diseases, US-mediated NMs can aid in treating ischemic heart disease by inhibiting while promoting their regression. [168] , [169] , [173] Moreover, in the treatment of conditions such as hypertension and hypercholesterolemia, NMs can also play a significant role. [343] , [344] , [345] , [346] The strategies for enhancing the targeting of US-mediated NMs and reducing their side effects in cancer and cardiovascular diseases treatment can also be referenced in the applications of inflammatory disease therapy. Similarly, any innovative advancements in materials technology within the field of inflammation treatment could benefit cancer and cardiovascular diseases therapy. Therefore, this review may serve as a stepping stone for enhancing the treatment efficacy of inflammatory diseases and improving therapeutic outcomes across various other diseases. Kai Zhang: Writing – original draft, Supervision, Resources, Funding acquisition, Conceptualization. Tingting Wang: Writing – original draft, Investigation, Conceptualization. Xingyong Huang: Writing – original draft, Investigation. Peng Wu: Writing – original draft, Resources. Lufan Shen: Resources. Yuanyuan Yang: Resources. Wenyu Wan: Writing – original draft, Validation, Supervision, Investigation. Siyu Sun: Writing – review & editing, Validation, Supervision, Resources. Zhan Zhang: Writing – review & editing, Supervision, Funding acquisition, Conceptualization.

Infection is the process by which pathogenic microorganisms such as bacteria, viruses, fungi, etc. invade the human body and proliferate, causing local tissue and systemic inflammatory reactions, which remain a formidable public health enemy. Infections caused by pathogenic bacteria are common in daily life and can cause diseases ranging from minor skin infections to severe sepsis. [208] , [209] Even though the use of antibiotics has achieved success in slowing down the progress of bacterial infections, the overuse of antibiotics has increased the appearance of multidrug-resistant (MDR) species and greatly reduced the efficacy of antibiotics in treating bacterial infectious diseases. [210] The challenge is further exacerbated by the formation of bacterial biofilms, which are usually encapsulated with extracellular polymeric substances. [211] With less potential for inducing resistance and toxicity, physical methods such as light, US, and temperature have become novel alternatives. Among them, US wave-driven aSDT is becoming a highly promising approach for infection eradiation. [212] Sonosensitizers play a significant role in SDT. [213] With the action of sonosensitizers driven by low frequency ultrasonic waves, SDT can convert O 2 into toxic ROS, such as •OH and 1 O 2 , causing non-selective damage to the bacterial structures. [214] However, traditional sonosensitizers exhibit problems such as low targeting ability, low bioavailability, and a short duration of action, showing insufficient efficiency in the use of US energy to generate sufficient ROS for bacterial inactivation. The rapid development of nanotechnology has brought opportunities to the treatment of infection. Nano-sonosensitizers refer to NPs loaded with small molecule sonosensitizers or NMs with acoustic sensitization, which can enhance the cavitation effect and effectively promote the efficiency of aSDT. [215] Of note, SDT has been found to be more effective in combination with other strategies for destroying bacteria and their biofilms. CDT utilizes Fenton catalysts to eradicate bacteria by promoting the generation of highly toxic •OH from hydrogen peroxide (H 2 O 2 ). [29] A combined modality of sonoactivated chemodynamic therapy (SCDT) has been proposed. Recently, Liang et al. engineered copper peroxide (CuO 2 ) nanoclusters on the surface of titanium oxide (TiO 2 ) nanosheets, which endowed the Fenton catalytic activity for SCDT, demonstrating an elimination rate > 99.9999 % against MDR pathogens in 5 min ( Fig. 13 A ). [216] In PTT, solar energy is able to be transferred into heat. He and co-workers developed a Molybdenum (Mo) based sonosensitizer to achieve multimodal therapy by combing SDT and PTT, which was proposed as a novel strategy for NIR-II photo-amplified SDT ( Fig. 13 B ). [217] Moreover, antibacterial photodynamic therapy (aPDT) is considered an effective therapy that can quickly eradicate pathogens via ROS production under light irradiation. [218] Cheng et al. reported dual-responsive nanocomposites for synergistic antibacterial application when exposed to combined stimulation of NIR and US, which exerted PDT/PTT/SDT functions via the mesoporous TiO 2 @Polydopamine NPs. This simple structure nanoplatform can achieve effective sterilization with low-energy stimulation ( Fig. 13 C ). [219] Fig. 13 A) The sonodynamically promoted ROS production mechanism of CuO 2 /TiO 2 . [216] Copyright 2022, Elsevier Ltd. B) Schematic illustration of the preparation of oxygen vacancy and wide interlayer gap sodium molybdenum bronze nanoplatform, and NIR-II-mediated ROS production for increasing SDT efficacy against subcutaneous S. aureus infection. [217] Copyright 2022, Wiley‐VCH. C) Schematic illustration of NIR/US stimulated mTiO 2 @PDA for PDT/PTT/SDT synergistic antibacterial effect. [219] Copyright 2023, Wiley‐VCH. A) The sonodynamically promoted ROS production mechanism of CuO 2 /TiO 2 . [216] Copyright 2022, Elsevier Ltd. B) Schematic illustration of the preparation of oxygen vacancy and wide interlayer gap sodium molybdenum bronze nanoplatform, and NIR-II-mediated ROS production for increasing SDT efficacy against subcutaneous S. aureus infection. [217] Copyright 2022, Wiley‐VCH. C) Schematic illustration of NIR/US stimulated mTiO 2 @PDA for PDT/PTT/SDT synergistic antibacterial effect. [219] Copyright 2023, Wiley‐VCH. Osteomyelitis, a difficult-to-treat bone disease triggered by bacterial infection, can induce serious inflammation, permanent disability, and fatal sepsis, which is a life-threatening challenge. [220] Clinically, such infection is often treated by the lasting and high-dose antibiotics administration as well as invasive debridement. However, these treatment approaches have failure rates of up to 30 %, accompanied by notable problems like antibiotic resistance and tissue disfigurement. [221] PDT and PTT are mature in dealing with bacterial infection; however, the insufficient penetration depth of light limits the effectiveness of these therapies. [222] Instead, the US is advantageous owing to its safety and strong ability for tissue penetration. aSDT represents an advanced method for treating drug-resistant bacterial infections. Under US irradiation, sonosensitizers could generate toxic ROS, which can cause cellular oxidative stress, lipid peroxidation, DNA damage, and eventually bacterial death. [223] Rapid, dynamic clearance of concurrent bacteria and residual toxins is needed, given that the marrow cavity has a blood flow environment. Yu and colleagues construct a multifunctional system for SDT in treating osteomyelitis caused by methicillin-resistant Staphylococcus aureus (MRSA), which has excellent single-atom sonocatalytic and dynamic detoxifying capabilities. [224] They enhanced the sonocatalytic property by immobilizing Pt single atoms in a zirconium-based porphyrin metal–organic framework (HNTM) and realized the dynamic movement ability by loading Au nanorods (Au NRs) on the surface of HNTM-Pt, which also increased ultrasonic, cavitation, and electron transfer efficiency, thus giving the sonosensitizer ideal antibacterial properties. The sonocatalytic mechanism is that Au NRs, as a US-responsive actuator, can boost the ultrasonic cavitation and enhance the ultrasonic energy absorption, thus promoting the generation of 1 O 2 ; moreover, Au NRs and Pt single atoms served as electron acceptors to facilitate the transfer of electrons produced from HNTM, increasing the separation efficiency of electron-hole pairs ( Fig. 14 A ). Besides, the team improved the biocompatibility and enabled toxin neutralization ability by coating HNTM-Pt@Au with rat red blood cell (RBC) membrane. Thus, the RBC-HNTM-Pt@Au had a powerful US propelled ability to dynamically neutralize the toxins secreted by MRSA and provided an achievable method for in situ and rapid management of osteomyelitis. Fig. 14 A) Preparation of the RBC-HNTM-Pt@Au and its sonocatalytic mechanism. Reproduced with permission. [224] Copyright 2021, American Chemical Society. B) The development and therapeutic mechanism of the Au/TNT@PG nanostructure for effective osteomyelitis treatment. Reproduced with permission. [30] Copyright 2022, Wiley‐VCH. A) Preparation of the RBC-HNTM-Pt@Au and its sonocatalytic mechanism. Reproduced with permission. [224] Copyright 2021, American Chemical Society. B) The development and therapeutic mechanism of the Au/TNT@PG nanostructure for effective osteomyelitis treatment. Reproduced with permission. [30] Copyright 2022, Wiley‐VCH. Cheng et al. constructed a robust sonosensitizer for synergistic sonodynamic-catalytic therapy for the control of osteomyelitis caused by MRSA, which can produce large amounts of ROS and has high biosafety. [30] The sonosensitizer uses gold-doped titanate nanotubes (Au/TNTs) as the sonodynamic-catalytic backbone and is conjugated with a potent guanidinium-rich polymer (PG). Au/TNTs have high US absorption capacity and exhibit peroxidase-like functionality activated by an infected microenvironment that rapidly degrades endogenous H 2 O 2 to generate adequate ROS, especially •OH, which is the most toxic one to bacterial biofilm. PG shows an excellent affinity for matrix rich in negatively charged components, demonstrating better penetration of biofilms to remove physical barriers, thus supporting the sonodynamic-catalytic clearance of bacterial biofilms. Meanwhile, US has a deep and safe tissue penetration ability, nanostructure Au/TNT@PG sensed and responded to endogenous and exogenous triggers, showing superior bacterial anchorage and bacterial biofilm matrix penetration to trigger “collapse inside biofilm” ( Fig. 14 B ). Other high efficiency sonosensitizers provide multiple strategies for treating bone infections. Feng et al. developed a bifunctional sonosensitizer, which consists of porphyrin-like Zn single-atom catalysts (g-ZnN 4 ) and MoS 2 quantum dots. [225] Benefiting from the construction of heterogeneous interfaces, the g-ZnN 4 -MoS 2 fully allowed more generation of 1 O 2 . Within 20 min of US irradiation, the generated 1 O 2 can kill MRSA with an efficiency of 99.58 %; meanwhile, it can achieve steady release for 28 days, ensuring great biologic function, which is a successful treatment of MRSA-infected osteomyelitis ( Fig. 15 A ). Its sonocatalytic and osteogenic abilities have been proven to be excellent both in vitro and in vivo. Of note, the same research team reported another efficient sonosensitizer, RBC-HNTM-MoS 2 , through piezoelectric-assisted sonocatalysis. [226] MoS 2 nanosheets have a piezoelectric effect, which piezoelectric polarization induced by US, leading to effective charge transfer in the heterointerface of HNTM-MoS 2 , promoting ROS generation ( Fig. 15 B ). The sonosensitizer has powerful US-propelling ability to manage MRSA-infected osteomyelitis by producing ROS and excellent mechanical force, which can eradicate MRSA with an efficiency of 98.5 % under 15 min of US irradiation, combined with the toxin neutralization ability. Recently, Wang et al. developed a sonosensitizer, HNTM, modified by Ti 3 C2 nanosheets (HN-Ti 3 C 2 ), which is a distinctive nanocomposite that can be used in eliminating infection and promoting bone repair under low-intensity US. [227] Ti 3 C 2 efficiently improved the acoustic catalytic performance and generated large amounts of ROS under US irradiation, demonstrating great 99.75 % antibacterial effectiveness in a MRSA-infected rat osteomyelitis model ( Fig. 15 C ). Fig. 15 A) The effective use of sonodynamic ion therapy in the treatment of osteomyelitis by sonocatalytic mechanism. [226] Copyright 2022, Wiley‐VCH. B) Sonocatalytic mechanism of HNTM-MoS 2 . [225] Copyright 2022, American Chemical Society. C) Schematic diagram of SDT for osteomyelitis using HN-Ti 3 C 2 in vivo. [227] Copyright 2023, Ivyspring International Publisher . D) Schematic illustration of various functions of PtCu-PEG NPs in the control of inflammation and wound healing processes. [228] Copyright 2023, Wiley‐VCH. A) The effective use of sonodynamic ion therapy in the treatment of osteomyelitis by sonocatalytic mechanism. [226] Copyright 2022, Wiley‐VCH. B) Sonocatalytic mechanism of HNTM-MoS 2 . [225] Copyright 2022, American Chemical Society. C) Schematic diagram of SDT for osteomyelitis using HN-Ti 3 C 2 in vivo. [227] Copyright 2023, Ivyspring International Publisher . D) Schematic illustration of various functions of PtCu-PEG NPs in the control of inflammation and wound healing processes. [228] Copyright 2023, Wiley‐VCH. Moreover, it has been found that sonosensitizers can modulate the inflammatory environment. Cheng and co-workers synthesized ultrasmall platinum-copper alloy nanoparticles (PtCu NPs), which can generate high 1 O 2 under US irradiation. [228] Experiments show that PtCu NPs promote cell migration and angiogenesis by up-regulating HIF-1α and CD31. Meanwhile, PtCu NPs effectively eliminated staphylococcus aureus ( S. aureus ) and inhibited S. aureus- induced osteomyelitis in the wound model ( Fig. 15 D ). Periodontitis is a chronic disease induced by bacteria with uncontrolled bacterial overgrowth and progressive tooth supporting tissue destruction, eventually leading to tooth loss or even systemic diseases. [229] Major clinical treatment strategies, such as antibiotic therapy and mechanical debridement, have some limitations, including bacterial resistance or invasive methods, which will cause side effects and panic in patients. [230] Xin et al. developed an innovative nano-sonosensitizer for efficient ROS generation by combining SDT and CDT under US stimulation, which can treat periodontitis efficiently and noninvasively. [231] The multifunctional nanoplatform was prepared by growing TiO 2 on dendritic large pore mesoporous silica nanoparticles (DLMSNs), subsequent to Ag deposition (DT-Ag), and decorating it with quaternary ammonium chitosan (CS + ). The obtained DT-Ag-CS + exhibited excellent SDT and CDT performances, owing to Ag deposition, and the highly positive-charged CS + on the surface of DT-Ag makes it easy to penetrate into bacterial cells. They investigated the in vitro antibacterial effects of DT-Ag-CS + against Porphyromonas gingivalis ( P. gingivalis) and evaluated the in vivo anti-periodontitis effects via combating periodontitis in rats ( Fig. 16 A ). The findings revealed the DT-Ag-CS + group had the lowest relative bacterial survival rate with US irradiation (1 W/cm 2 , 1 MHz, 5 min), only 19.3 %; meanwhile, it effectively alleviated inflammatory responses. Fig. 16 A) Schematic illustration for the synthesis and the anti-periodontitis mechanism of DT-Ag-CS + NPs. [231] Copyright 2023, Elsevier B.V. B) Schematic diagram of in vivo studies of antibacterial performance. [236] Copyright 2023, Elsevier B.V. A) Schematic illustration for the synthesis and the anti-periodontitis mechanism of DT-Ag-CS + NPs. [231] Copyright 2023, Elsevier B.V. B) Schematic diagram of in vivo studies of antibacterial performance. [236] Copyright 2023, Elsevier B.V. Different from periodontitis in natural periodontal tissue, the tissue surrounding the implant is more vulnerable to bacterial invasion, resulting in infectious diseases such as peri -implantitis, namely, peri -implant infection. [232] The primary contributing factor to peri -implantitis is plaque biofilm composed of P. gingivalis and other anaerobic bacteria, whose main manifestation is peri -implant mucosal inflammation and finally implant failure. [233] Biofilm is a microbial community, and the biofilm microenvironment is hypoxic, providing an excellent environment for the colonization of more anaerobic bacteria, reducing antimicrobial efficiency. [234] In addition, the biofilm matrix protects bacteria and makes them resistant to typical treatments. [235] Therefore, the eradication of biofilm is decisive for the successful treatment of peri -implantitis. US-activated aSDT is an emerging method for the management of biofilm infections. Li et al. proposed an activatable nanoplatform (Au TNT) for eradicating biofilm and treating peri -implant infection. [236] This nanoplatform can be utilized as a sonosensitizer for aSDT, which can increase the quantum yield and the performance of SDT and has long-term antibacterial properties. Au TNT was prepared by forming TiO 2 nanotubes (TNT) on the surface of the Ti implant and depositing Au NP on the surface of the TNT. Under US irradiation, O 2 and ROS produced by Au TNT increased, which alleviated the hypoxic microenvironment of biofilms and effectively eradicated single- and multi-species pathogenic biofilms. In the rat peri -implantitis model, Au TNT decreased by 3 logs of colony-forming units compared with the control group, showing excellent antibacterial effect. Of note, the downregulation of inflammatory cytokines suggested that AU TNT also had an anti-inflammatory effect and promoted bone repair. Previously, Sun et al. developed an Au nanoparticles modified TiO 2 nanotube (AuNPs-TNT) to increase the therapeutic depth and enhance the antibacterial effect via SDT. [237] The experiments showed that, under ultrasonic treatment, AuNPs modified on the TNT surface induced the production of many ROS by preventing the rapid recombination of triggered electron holes, which could effectively inactivate P. gingivalis , one of the major pathogenic bacteria forming biofilms in vivo ( Fig. 16 B ). Enterococcus faecalis (E. faecalis) is a prominent contributor to dental root canal infection. [238] It is highly resistant to intra-canal irrigation and other disinfection treatments, which may lead to the failure of root canal treatment. [239] Mesoporous calcium silicon nanoparticles (MCSNs) are drug transport vehicles with excellent mesoporous, infiltrating, and releasing properties. Ag-MCSNs prepared by incorporating nanosilver into MCSNs can penetrate into dentin tubules after ultrasonic activation, thus persistently inhibiting the growth of E. faecalis and having an ideal antibacterial effect. Ag − MCSN prepared by Fan et al. by adsorption and the template method, was able to inhibit the colonization of E. faecalis . [240] Among them, Ag-MCSN-T prepared by the template method had lower cytotoxicity and was expected to become a novel root canal disinfectant. Studies have demonstrated that zinc ions can increase the antibacterial effect of silver ions. Further studies by Fan et al. indicated that the combination of silver and zinc exhibited the lowest cytotoxicity and the largest synergistic bactericidal effect when the ratio of silver to zinc atoms was more than 1:6. [241] Based on the above findings, Sun et al. developed silver–zinc-incorporated mesoporous calcium silicon nanoparticles (Ag-Zn MCSNs) with the optimal Ag-Zn ratio (1:12), and verified their great antibacterial effect in the animal tooth infection medal of beagle dogs, indicating their potential as an effective root canal disinfectant. [242] In addition, another team fabricated a synergistic nanoplatform based on mesoporous silica nanoparticles (MSNs) for Fenton reaction-enhanced aSDT for root canal disinfection. The fenton reaction refers to the catalytic conversion of H 2 O 2 to •OH. [243] The sonosensitizer loaded on MSNs was activated by ultrasonic irradiation to produce ROS. Meanwhile, the team further increased the production of ROS through a Fenton reaction mediated by metal ions, like iron, which realized efficient bactericidal action against E. faecalis and had good anti-biofilm activity. Tuberculosis is an infectious disease caused by Mycobacterium tuberculosis ( MTB ), posing a great threat to human health compared with other bacterial infections. The current regimen for MTB requires a duration of over 6 months, involving the use of multiple anti-tuberculosis drugs, which is time-consuming. Moreover, it can cause drug resistance and many side effects, leading to poor patient compliance. [244] The rapid development of efficient drug delivery strategies has aroused great attention in disease treatment. NPs, which are effective as drug carriers in achieving controlled release of drugs, have shown great potential to deliver therapeutic drugs or molecules to the site of infection, effectively improving anti-infection effects. [245] US-mediated drug delivery can be synergistic with NPs to trigger the release of drug-loaded NPs through the cavitation effect to achieve bactericidal efficacy. [246] Due to the high contagiousness and pathogenicity of MTB , experiments about MTB must be performed in laboratories that adhere to the requirements of National Biosafety Level 3 Safety. Therefore, homologous substitution models have become suitable choices for experiments, among which M. smegmatis and Bacille Calmette-Guerin ( BCG ) are commonly used MTB models. [247] , [248] In order to be more effective against MTB , Du's research team conducted a series of studies. In 2020, they developed PLGA NPs loaded with levofloxacin (LEV/LVFX), a typical anti-tuberculosis drug, and combined with low-frequency and low-intensity ultrasound (LFLIU) for the treatment of M. smegmatis in macrophages. [249] Experiments showed that US irradiation (0.13 W/cm 2 , 42 kHz, 10 min) promoted the release of LEV from NPs, increased the local concentration of the drug, played a combined bactericidal effect, and shortened the treatment period. Meanwhile, the combination of US and drug-loaded NPs can promote apoptosis of macrophages in vitro and induce the production of intracellular ROS, which further leads to bacterial damage. In 2021, the team demonstrated that the BM2-modified LVFX loaded PLGA-PEG (Polyethylene glycol) nanoparticles (BM2-LVFX NPs) have the ability to target BCG through both in vitro and in vitro experiments. [250] It can be used in the targeted treatment of BCG bacterial infections by sonodynamic antimicrobial chemotherapy (SACT). SACT produces ROS through the synergistic effect of low-frequency US (0.67 W/cm 2 , 42 kHz, 5 min) and NPs loaded with LEV sonosensitizers, effectively eradicating bacterial infection and inhibiting the growth of subcutaneous abscesses. The cellulose-containing biofilms formed by MTB make the treatment of tuberculosis more challenging. In 2023, the team developed a composite NP (CL@LEV-NPs) loaded with cellulase (CL) and LEV based on PLGA polymerized organic material, combined with low-frequency US (0.34 W/cm 2 , 42 kHz, 5 min). [110] US triggered the release of CL and LEV from the composite NPs, CL effectively triggered the destruction of BCG bacterial biofilms, and LEV effectively killed bacteria in biofilms. In addition, another mechanism of antimicrobial action may be associated with SCAT, where US-activated LEV sonosensitizers produce lots of ROS, leading to severe cellular injury. In vivo and in vitro assays have shown its significant removal and bacterial effect on biofilms. With the emergence of MDR bacteria, deep-tissue infectious diseases such as bacterial pneumonia induced by MDR bacteria are becoming a global health problem. [251] With the development of nanotechnology, scientists have committed to developing a variety of new antibiotic-alternative antimicrobial strategies, of which SDT has shown immense potential. Compared with laser lights, US has stronger tissue penetration and has obvious advantages in the treatment of deep-tissue diseases. [252] Pan et al. first reported the use of SDT for treating bacterial pneumonia by developing ZIF-8-derived carbon@TiO 2 nanoparticles (ZTNs) as a sonosensitizer that can be accurately delivered to infected tissue in the lung. [253] The metal–organic framework-derived NPs can be administered by pulmonary inhalation drug delivery, with high bioavailability compared to the oral administration route. In addition, compared with the typical inorganic sonosensitizer TiO 2 , ZTNs have a narrower bandgap and can produce a higher amount of ROS under US irradiation, mainly 1 O 2 and •OH, showing a good inhibition rate against a variety of Gram-negative MDR bacteria in vitro. Meanwhile, it can effectively clear MDR Klebsiella pneumoniae in mouse lung infection models ( Fig. 17 A ). Of note, the survival rate of NOD/SCID (severe immunodeficiency) mice is up to 100 %, which is safe and effective, showing a great prospect for the therapy of deep-tissue bacterial infections. Fig. 17 A) Scheme illustration of ZTN-based antibacterial SDT. [253] Copyright 2022, Wiley‐VCH. B) Scheme illustration of MLP18 nanoliposomes for diagnosis and clearance of MDR bacterial infection. [255] Copyright 2019, American Chemical Society. C) Sonocatalytic mechanism and the treatment of acne via an efficient sonodynamic ion therapy-based microneedle patch. [262] Copyright 2023, American Association for the Advancement of Science. A) Scheme illustration of ZTN-based antibacterial SDT. [253] Copyright 2022, Wiley‐VCH. B) Scheme illustration of MLP18 nanoliposomes for diagnosis and clearance of MDR bacterial infection. [255] Copyright 2019, American Chemical Society. C) Sonocatalytic mechanism and the treatment of acne via an efficient sonodynamic ion therapy-based microneedle patch. [262] Copyright 2023, American Association for the Advancement of Science. Myositis caused by bacterial infections usually presents as a focal muscle infection caused by spreading adjacent to the infected site. [254] MDR bacteria make the treatment of bacterial myositis even more challenging. Pan and co-workers developed a smart nanoliposome platform (MLP18) and demonstrated that MLP18-mediated SDT effectively eradicated inflammation and abscess in a MRSA-infected myositis mouse model. [255] The nanoliposomes were prepared by encapsulating a potent sonosensitizer purine 18 (P18) into a cholesterol and bacteria-responsive lipid compositions modified with maltohexaose, which enables the complete eradication of bacteria in vivo by cytotoxic ROS generated under US irradiation ( Fig. 17 B ). P18 has high sonodynamic activity, along with near infrared optical imaging capability, enabling controlled, effective bacterial internalization by infected microenvironment-triggered drug release. In addition, the maltohexaose and lipid compositions can help selectively target the identification of bacteria and achieve bacteria-activated sonosensitizer delivery, providing specific bacterial diagnostic functions that can accurately differentiate bacterial infection sites from sterile inflammation or cancer. Otitis media, commonly caused by bacterial infections such as S. aureus , can lead to hearing loss in young children and is currently commonly treated with antibiotics, although serious adverse reactions may occur. [256] , [257] SDT has a unique advantage, through the interaction between US and sonosensitizers, it generates ROS to destroy bacteria. Su et al. prepared an antibacterial nanocomposite (NC) consisting of Curcumin, Tanshinone IIA, and Chitosan, which has high solubility and strong electropositivity and can capture bacteria through a spider-web-like effect generated by electrostatic interaction. [258] Meanwhile, in vivo experiments showed that SDT further enhanced the antibacterial and anti-inflammatory activities mediated by the nanocomposite through the generation of ROS and essentially had no bacterial resistance or toxicity, which shows the same efficacy as ofloxacin, a commonly used clinical antibacterial drug, suggesting that NC-mediated SDT is an effective treatment for bacterial otitis media. Acne is a chronic inflammatory disease primarily triggered by Propionibacterium acnes that can result in soreness, itching, and pain, leave scars on the skin, and even cause psychological problems. [208] , [259] Currently, the most commonly used treatments for acne include oral or topical antibiotics. [260] , [261] However, oral antibiotics may cause other side effects, while topical antibiotics may not have a good therapeutic performance due to the barrier effect of the skin. Applying potent antibacterial agents in situ is the most efficient approach for treating acne. Xiang's team constructed a sodium hyaluronate microneedle patch composed of a zinc porphyrin-based metal–organic framework and zinc oxide (ZnTCPP@ZnO). [262] Sodium hyaluronate made it easy for the ZnTCPP@ZnO to be delivered to diseased places. Under US irradiation, the composite material could generate a substantial amount of ROS to kill Propionibacterium acnes, thus decreasing the concentrations of proinflammatory factors such as TNF-α, IL-8, and MMP-2 ( Fig. 17 C ). Additionally, the patch enhanced the expression of genes involved in DNA replication and promoted fibroblastic proliferation, eventually favoring skin tissue repair. This study offers a highly effective approach to treating acne. In conclusion, in the treatment of infectious inflammation, most US-mediated NMs inhibit bacterial growth and kill bacteria through the generation of ROS ( Table 2 ). Therefore, identifying materials with high electron transfer efficiency to produce more ROS for bacterial eradication is a key strategy. Additionally, some materials can achieve antibacterial effects by reducing biofilm formation or disrupting existing biofilms. Furthermore, several US-mediated NMs can not only remove bacteria but also neutralize toxins produced by bacteria, which is vital for minimizing the damage caused by infectious inflammation to the body. Future research should focus on enhancing antibacterial efficacy without harming normal human cells and improving the effectiveness of neutralizing bacterial toxins. Table 2 US-mediated NMs for the treatment of infection-associated inflammatory diseases. Disease Ultrasound Ultrasound parameters Nanomaterials Effect Mechanism Ref. Osteomyelitis SDT (1 MHZ, 1.5 W/cm 2 ) 15 min Nanorod (RBC-HNTM-Pt@Au) Dynamically neutralize toxins secreted by MRSA As an ultrasonic response driver, Au nanorods can increase ultrasonic cavitation, promote electron transfer generated by HNTM, and impart biocompatibility to the red blood cell membrane [224] SDT (1 MHz, 1.5 W/ cm 2 ) 0, 2, 4, 6, 8 and 10 min Gold-doped titanate nanotubes (Au/TNTs) Eradicate bacterial biofilms and control osteomyelitis in MRSA infections The sonosensitizer has high ultrasonic absorption capacity and degrades H 2 0 2 to generate enough ROS to produce biofilm toxicity [30] US irradiation (1 MHz, 1.5 W/cm 2 )15 min RBC-HNTM-MoS 2 Kills MRSA and neutralizes toxins Ultrasonic propulsion capability, generating ROS and strong mechanical force [225] US irradiation (1 MHz, 1.5 W/cm 2 ) 20 min g-ZnN 4 -MoS 2 Treat MRSA infectious osteomyelitis Sonocatalytic ROS produces - 1 O 2 , which has a killing effect on MRSA [226] low intensity US (1 MHz, 1.5 W/cm 2 ) Nanosheets (HN-Ti 3 C 2 ) High antibacterial efficiency Improve sonocatalytic performance under ultrasonic irradiation and generate a large amount of ROS [227] US irradiation (40 KHz, 3 W/cm 2 ) 8 min PtCu NPs Regulate the inflammatory environment, eliminate Staphylococcus aureus and inhibit osteomyelitis Produces high 1 O 2 and upregulates HIF-1 to promote cell migration [228] Oral inflammatory diseases SDT + CDT (1 MHz, 1 W/cm 2 ) 5 min DT-Ag-CS+- Decreased bacterial survival rate and alleviated inflammatory response Combination therapy, improved permeability [231] ASDT (1 MHz, 1.5 W/cm 2 )20 min Au-TNT Relieve biofilm hypoxic microenvironment, eradicate biofilm, downregulate inflammatory cytokines, anti-inflammatory and promote bone repair Increased production of O 2 and ROS from nanoplatforms under ultrasonic irradiation [236] , [237] ASDT (1 MHz, 1.5 W/cm 2 ) 5 min MCSNs Highly effective sterilization Fenton reaction, sonosensitizer is activated under ultrasonic radiation and generates ROS [240] , [241] , [242] Tuberculosis LFLIU (42 kHz, 0.13 W/cm 2 ) 10 min LEV/ LVFX Bacterial damage US promotes drug release, combined with sterilization, induces macrophage apoptosis and ROS production [249] SACT (42 kHz, 0.67 W/cm 2 ) 5 min BM2-LVFX NPs Effectively eliminate bacterial infections Collaboratively generate ROS [250] Low frequency US (42 kHz, 0.34 W/cm 2 ) 5 min CL@LEV-NPs Bacterial biofilm destruction, cell damage US-triggered release of cellulase and levofloxacin from composite nanoparticles, and ROS generation [110] Pneumonia US irradiation (1 MHz, 1.5 W/cm 2 ) 8 min ZIF-8-derived carbon@TiO2 nanoparticles (ZTNs) High bacterial inhibition rate Higher ROS production and precise delivery of sonosensitizers to infected lung tissues [253] Myositis SDT (1 MHz, 0.97 W/ cm 2 )5 min Smart nanoliposomes platform (MLP18) Eradication of inflammation and abscesses in myositis models Generate toxic ROS, have sonodynamic activity, target bacterial recognition, and achieve bacterial-activated sonosensitizer delivery [255] Otitis media SDT (1 MHz, 3 W/ cm 2 ) 10 min Nanocomposite (NC) consisting of Curcumin Anti-inflammatory and antibacterial effect Spider-web-like effect captures bacteria, SDT generates ROS, enhances antibacterial and anti-inflammatory activities [258] Acne US-trigger (1 MHZ, 1.5 W/cm 2 )15 min ZnTCPP@ZnO Antibacterial effect and promotion of fibroblastic proliferation Rapidly produce a large number of ROS that kill P. acnes and decrease the level of proinflammatory factors [262] US-mediated NMs for the treatment of infection-associated inflammatory diseases.

Inflammation is defined as a response to microbial infection or sterile injury characterized by pathological manifestations, including redness, swelling, heat, and pain, which represent a significant milestone and lay the foundation for the pathophysiology of inflammation. [1] , [2] Inflammation can be classified into infection-associated inflammation and sterile inflammation based on the inflammatory triggers. [3] Both types collectively involve the activation of a cascade of signals, which may lead to the recruitment of inflammatory cells such as neutrophils and macrophages, along with the production of chemotactic factors and pro-inflammatory cytokines. [4] Infection-associated inflammation is typically caused by bacteria, viruses, fungi, and other pathogens. [5] Sterile inflammation is triggered by various sterile stimuli, including mechanical trauma, stress, ischemia, and environmental factors. [6] It occurs without any pathogen, promotes tissue repair during acute inflammation, and aids in preventing pathogen colonization. [7] Prolonged unresolved inflammatory processes can lead to detrimental chronic inflammation, contributing to sterile inflammatory diseases such as atherosclerosis, neurodegenerative diseases, and autoimmune diseases. [8] To treat inflammation, the optimal response requires achieving maximal efficacy (pathogen clearance) while minimizing associated damage. [9] Regulating infection-associated inflammation primarily involves eradicating pathogens. For sterile inflammation, tissue repair is essential, facilitating the cessation of inflammatory responses and the transition toward a steady state. Conventional drug therapy is a widely utilized clinical strategy for the treatment of inflammatory diseases. Despite certain drawbacks, traditional medications still play an important role in the current treatment of inflammatory diseases. Non-steroidal anti-inflammatory drugs (NSAIDs) as well as corticosteroids remain integral to the management of many inflammatory rheumatic diseases due to their ability to alleviate disease progression and their relatively low economic burden on patients, making them foundational treatment options. [10] , [11] , [12] , [13] Although bacterial resistance affects the use of antibiotics, they are still the first choice for most patients with infectious disorders because of their effective bactericidal properties, broad mechanisms of action, and diverse range of antibacterial agents. [14] , [15] However, conventional medications may lead to some side effects, such as gastrointestinal discomfort and kidney damage, and potentially affects the normal function of the immune system, thereby increasing the risk of infection in non-infectious diseases. [16] Additionally, for certain local inflammations, delivering drugs to the specific site is challenging. Inflammation often involves increased vascular permeability, tissue edema, and other changes that can impact the distribution and concentration of drugs at the site of inflammation, thereby limiting the effectiveness of treating inflammatory diseases. [17] To enhance drug delivery efficiency and therapeutic performance at sites of inflammation, researchers are striving to design superior targeted and inflammation-modulating therapies. Nanomaterials (NMs) possessing excellent physical and chemical properties have drawn great attention in biomedicine. NMs with small size can passively accumulate in inflamed tissues, resulting in favorable therapeutic outcomes through enhanced permeability and retention (EPR) effects. [18] , [19] Nevertheless, relying solely on the EPR effect to enhance the accumulation of NMs is sometimes not satisfactory. In order to obtain more precise delivery and better therapeutic effects, NMs can be designed as various stimulus-responsive delivery systems. [20] Currently, numerous stimuli can influence NMs to enhance their therapeutic efficacy, including US, light, and magnetic fields. Compared to light, which has limited penetration depth, and magnetic fields, which are relatively costly, US stands out as an excellent stimulus due to its deeper penetration, lower cost, and, most importantly, its non-invasive nature. [21] As a mechanical wave capable of transmitting energy, US can induce changes in tissue permeability, facilitating better entry of NMs. [22] , [23] Furthermore, once NMs reach the target tissue, US can promote the release of drugs loaded within the NMs. [24] Whether enhancing tissue permeability or facilitating drug release, US significantly improves the targeting capability of NMs, thereby reducing off-target side effects and enhancing therapeutic outcomes. Moreover, US has the potential to treat inflammatory diseases by significantly reducing the expression of pro-inflammatory cytokines. [25] In recent years, US-triggered nanotherapy has been widely studied as an effective therapeutic strategy. [26] Researchers achieved precise temporal and spatial control over treatment and accurately modulated energy and tissue penetration depth. [27] Extensive research indicates that US-triggered nanotherapy offers unique advantages in treating inflammatory diseases, such as excellent bactericidal rates, eradication of bacterial biofilms, maximizing anti-inflammatory efficacy and minimizing detrimental effects. [28] , [29] , [30] , [31] , [32] This review aims to provide an overview of the anti-inflammatory effects of US-mediated NMs, offer therapeutic strategies for inflammatory diseases, and guide their treatment. We introduce the biomedical applications of US and common classifications of therapeutic US, summarize the characteristics and superiority of NMs, and outline US-mediated NMs in inflammation control. Subsequently, the latest advances in the use of US-mediated NMs for sterile and infectious inflammatory diseases are discussed in detail. Finally, the current challenges faced in the clinical translation of US-mediated NMs are discussed, and possible future perspectives are outlined ( Fig. 1 ). Fig. 1 The application of US-mediated NMs in anti-inflammatory and antibacterial therapies. Created with BioRender.com . The application of US-mediated NMs in anti-inflammatory and antibacterial therapies. Created with BioRender.com .

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.