Ultrasound-Based Micro-/Nanosystems for Biomedical Applications

Due to the intrinsic non-invasive nature, cost-effectiveness, high safety, and real-time capabilities, besides diagnostic imaging, ultrasound as a typical mechanical wave has been extensively developed as a physical tool for versatile biomedical applications. Especially, the prosperity of nanotechnology and nanomedicine invigorates the landscape of ultrasound-based medicine. The unprecedented surge in research enthusiasm and dedicated efforts have led to a mass of multifunctional micro-/nanosystems being applied in ultrasound biomedicine, facilitating precise diagnosis, effective treatment, and personalized theranostics. The effective deployment of versatile ultrasound-based micro-/nanosystems in biomedical applications is rooted in a profound understanding of the relationship among composition, structure, property, bioactivity, application, and performance. In this comprehensive review, we elaborate on the general principles regarding the design, synthesis, functionalization, and optimization of ultrasound-based micro-/nanosystems for abundant biomedical applications. In particular, recent advancements in ultrasound-based micro-/nanosystems for diagnostic imaging are meticulously summarized. Furthermore, we systematically elucidate state-of-the-art studies concerning recent progress in ultrasound-based micro-/nanosystems for therapeutic applications targeting various pathological abnormalities including cancer, bacterial infection, brain diseases, cardiovascular diseases, and metabolic diseases. Finally, we conclude and provide an outlook on this research field with an in-depth discussion of the challenges faced and future developments for further extensive clinical translation and application.

Application of Nanomaterial-Based Sonodynamic Therapy in Tumor Therapy

Sonodynamic therapy (SDT) has attracted significant attention in recent years as it is an innovative approach to tumor treatment. It involves the utilization of sound waves or ultrasound (US) to activate acoustic sensitizers, enabling targeted drug release for precise tumor treatment. This review aims to provide a comprehensive overview of SDT, encompassing its underlying principles and therapeutic mechanisms, the applications of nanomaterials, and potential synergies with combination therapies. The review begins by introducing the fundamental principle of SDT and delving into the intricate mechanisms through which it facilitates tumor treatment. A detailed analysis is presented, outlining how SDT effectively destroys tumor cells by modulating drug release mechanisms. Subsequently, this review explores the diverse range of nanomaterials utilized in SDT applications and highlights their specific contributions to enhancing treatment outcomes. Furthermore, the potential to combine SDT with other therapeutic modalities such as photothermal therapy (PTT) and chemotherapy is discussed. These combined approaches aim to synergistically improve therapeutic efficacy while mitigating side effects. In conclusion, SDT emerges as a promising frontier in tumor treatment that offers personalized and effective treatment options with the potential to revolutionize patient care. As research progresses, SDT is poised to play a pivotal role in shaping the future landscape of oncology by providing patients with a broader spectrum of efficacious and tailored treatment options.

Magnetically actuated sonodynamic nanorobot collectives for potentiated ovarian cancer therapy

Ovarian cancer presents a substantial challenge due to its high mortality and recurrence rates among gynecological tumors. Existing clinical chemotherapy treatments are notably limited by drug resistance and systemic toxic side effects caused by off target drugs. Sonodynamic therapy (SDT) has emerged as a promising approach in cancer treatment, motivating researchers to explore synergistic combinations with other therapies for enhanced efficacy. In this study, we developed magnetic sonodynamic nanorobot (Fe3O4@SiO2-Ce6, FSC) by applying a SiO2 coating onto Fe3O4 nanoparticle, followed by coupling with the sonosensitizer Ce6. The magnetic FSC nanorobot collectives could gather at fixed point and actively move to target site regulated by magnetic field. In vitro experiments revealed that the magnetic FSC nanorobot collectives enabled directional navigation to the tumor cell area under guidance. Furthermore, under low-intensity ultrasonic stimulation, FSC nanorobot collectives mediated sonodynamic therapy exhibited remarkable anti-tumor performance. These findings suggest that magnetically actuated sonodynamic nanorobot collectives hold promising potential for application in target cancer therapy.

Multifunctional nanoparticles for enhanced sonodynamic-chemodynamic immunotherapy with glutathione depletion

Aim: This study aimed to develop a sonodynamic-chemodynamic nanoparticle functioning on glutathione depletion in tumor immunotherapy. Materials & methods: The liposome-encapsulated 2,2-azobis[2-(2-imidazolin-2-yl) propane] dihydrochloride (AIPH) and copper-cysteine nanoparticles, AIPH/Cu-Cys@Lipo, were synthesized with a one-pot method. 4T1 cells were injected into female BALB/c mice for modeling. Results: AIPH/Cu-Cys@Lipo was well synthesized. It generated alkyl radicals upon ultrasound stimulation. AIPH/Cu-Cys@Lipo promoted the generation of -OH via a Fenton-like reaction. Both in vitro and in vivo experiments verified that AIPH/Cu-Cys@Lipo significantly inhibited tumor development by decreasing mitochondrial membrane potential, activating CD4+ and CD8+ T cells and promoting the expression of IL-2 and TNF-α. Conclusion: AIPH/Cu-Cys@Lipo provides high-quality strategies for safe and effective tumor immunotherapy.

An ultrasound-controllable ROS-responsive nanoplatform for O2 and NO generation to enhance sonodynamic therapy against multidrug-resistant bacterial infections

Antimicrobial sonodynamic therapy (SDT) has broad application potential in the eradication of multidrug-resistant (MDR) bacterial infections due to its non-invasiveness, absence of resistance concern, and high cytotoxicity. However, the hypoxic infection microenvironment and the rapid depletion of O2 during SDT severely limit the therapeutic efficacy of SDT. Herein, an ultrasound-controllable ROS-responsive nanoplatform (FOT/Fe3O4@Lipo-ICG) was constructed and prepared by encapsulating FOT and Fe3O4 nanoparticles (Fe3O4 NPs) within sonosensitiser ICG-modified liposomes. Both in vitro and in vivo, we observed that ICG conjugation on the surface of liposomes could effectively maintain good dispersion and prevent ICG aggregates in complex biological matrices. In addition, liposomes could significantly block the catalytic activity of Fe3O4 NPs, as well as the release of FOT, whereas upon US irradiation, the catalytic activity of Fe3O4 NPs was recovered to catalyse the decomposition of endogenous H2O2 into O2 and ˙OH. Meanwhile, the FOT was successfully released to react with endogenous glutathione to sequentially produce NO. Based on the aforementioned advantages, the FOT/Fe3O4@Lipo-ICG demonstrated potent efficacy in eradicating methicillin-resistant Staphylococcus aureus-induced local infection and sepsis resulting from local infection. Thus, the developed US-controllable nanoplatform offers a promising strategy for enhancing SDT for eradicating MDR bacterial infections.

Ultrasound Sonosensitizers for Tumor Sonodynamic Therapy and Imaging: A New Direction with Clinical Translation

With the rapid development of sonodynamic therapy (SDT), sonosensitizers have evolved from traditional treatments to comprehensive diagnostics and therapies. Sonosensitizers play a crucial role in the integration of ultrasound imaging (USI), X-ray computed tomography (CT), and magnetic resonance imaging (MRI) diagnostics while also playing a therapeutic role. This review was based on recent articles on multifunctional sonosensitizers that were used in SDT for the treatment of cancer and have the potential for clinical USI, CT, and MRI applications. Next, some of the shortcomings of the clinical examination and the results of sonosensitizers in animal imaging were described. Finally, this paper attempted to inform the future development of sonosensitizers in the field of integrative diagnostics and therapeutics and to point out current problems and prospects for their application.

Perfluorocarbons: A perspective of theranostic applications and challenges

Perfluorocarbon (PFC) are biocompatible compounds, chemically and biologically inert, and lacks toxicity as oxygen carriers. PFCs nanoemulsions and nanoparticles (NPs) are highly used in diagnostic imaging and enable novel imaging technology in clinical imaging modalities to notice and image pathological and physiological alterations. Therapeutics with PFCs such as the innovative approach to preventing thrombus formation, PFC nanodroplets utilized in ultrasonic medication delivery in arthritis, or PFC-based NPs such as Perfluortributylamine (PFTBA), Pentafluorophenyl (PFP), Perfluorohexan (PFH), Perfluorooctyl bromide (PFOB), and others, recently become renowned for oxygenating tumors and enhancing the effects of anticancer treatments as oxygen carriers for tumor hypoxia. In this review, we will discuss the recent advancements that have been made in PFC's applications in theranostic (therapeutics and diagnostics) as well as assess the benefits and drawbacks of these applications.

Spotlight on porphyrins: Classifications, mechanisms and medical applications

Photodynamic therapy (PDT) and sonodynamic therapy (SDT) are non-invasive treatment methods with obvious inhibitory effect on tumors and have few side effects, which have been widely concerned and explored by researchers. Sensitizer is the main factor in determining the therapeutic effect of PDT and SDT. Porphyrins, a group of organic compounds widespread in nature, can be activated by light or ultrasound and produce reactive oxygen species. Therefore, porphyrins as sensitizers in PDT have been widely explored and investigated for many years. Herein, we summarize the classical porphyrin compounds and their applications and mechanisms in PDT and SDT. The application of porphyrin in clinical diagnosis and imaging is also discussed. In conclusion, porphyrins have good application prospects in disease treatment as an important part of PDT or SDT, and in clinical diagnosis and imaging.

Metal-Organic Frameworks (MOF)-Assisted Sonodynamic Therapy in Anticancer Applications

Sonodynamic therapy (SDT) has emerged as a promising therapeutic modality for anticancer treatments and is becoming a cutting-edge interdisciplinary research field. This review starts with the latest developments of SDT and provides a brief comprehensive discussion on ultrasonic cavitation, sonodynamic effect, and sonosensitizers in order to popularize the basic principles and probable mechanisms of SDT. Then the recent progress of MOF-based sonosensitizers is overviewed, and the preparation methods and properties (e.g., morphology, structure, and size) of products are presented in a fundamental perspective. More importantly, many deep observations and understanding toward MOF-assisted SDT strategies were described in anticancer applications, aiming to highlight the advantages and improvements of MOF-augmented SDT and synergistic therapies. Last but not least, the review also pointed out the probable challenges and technological potential of MOF-assisted SDT for the future advance. In all, the discussions and summaries of MOF-based sonosensitizers and SDT strategies will promote the fast development of anticancer nanodrugs and biotechnologies.

Protective effect of the newly synthesized and characterized charge transfer (CT) complex against arecoline induced toxicity in third-instar larvae of transgenic Drosophila melanogaster (hsp70-lacZ)Bg9: experimental and theoretical mechanistic insights

Agents that suppress the toxic effect of arecoline (a chemical present in the Areca nut fruit) have become a need of the hour owing to its several harmful effects on human beings. Although some drug molecules have been developed for this purpose, yet, simple, easy to prepare, and economical molecules with remarkable potency are still a challenge to design. The present work thus becomes important as it involves the synthesis of a new charge transfer complex (CTC) material, which has, for the first time, been screened to investigate its effect on the toxic effects of arecoline. The newly designed material (CL), which is generated from the reaction between 2,4,6-trinitrophenol (TNP) and pyrazole (PYZ), has been crystallized by a slow evaporation method and characterized by employing spectral studies including single crystal X-ray crystallography. Spectrophotometry studies with the inclusion of the Benesi-Hildebrand equation reveal 1 : 1 stoichiometry and physical parameters of CL. Assays were used for determining the protective effect of CL against arecoline. CL was found to (dose-dependently) decrease β-galactosidase activity, damage in tissue and DNA damage caused by arecoline (80 μM) in the third-instar larvae of the transgenic Drosophila melanogaster (hsp70-lacZ)Bg⁹. The possible mechanism of this effect was explored through fluorescence and UV-vis spectroscopy. The possibility of suppression of arecoline action on the muscarinic acetylcholine receptor 1-G11 protein complex (found in the cell membrane) in the presence of CL was studied theoretically by molecular docking. Density functional theory (DFT) also theoretically supported various aspects of the designed material concerning the energy profile of the orbitals (HOMO-LUMO) as well as the energy minimized structure. Furthermore, time dependent (TD) DFT corroborated the electronic properties of the designed material.

Enhanced Photodynamic Therapy: A Review of Combined Energy Sources

Photodynamic therapy (PDT) has been used in recent years as a non-invasive treatment for cancer, due to the side effects of traditional treatments such as surgery, radiotherapy, and chemotherapy. This therapeutic technique requires a photosensitizer, light energy, and oxygen to produce reactive oxygen species (ROS) which mediate cellular toxicity. PDT is a useful non-invasive therapy for cancer treatment, but it has some limitations that need to be overcome, such as low-light-penetration depths, non-targeting photosensitizers, and tumor hypoxia. This review focuses on the latest innovative strategies based on the synergistic use of other energy sources, such as non-visible radiation of the electromagnetic spectrum (microwaves, infrared, and X-rays), ultrasound, and electric/magnetic fields, to overcome PDT limitations and enhance the therapeutic effect of PDT. The main principles, mechanisms, and crucial elements of PDT are also addressed.

Newly developed gas-assisted sonodynamic therapy in cancer treatment

Sonodynamic therapy (SDT) is an emerging noninvasive treatment modality that utilizes low-frequency and low-intensity ultrasound (US) to trigger sensitizers to kill tumor cells with reactive oxygen species (ROS). Although SDT has attracted much attention for its properties including high tumor specificity and deep tissue penetration, its anticancer efficacy is still far from satisfactory. As a result, new strategies such as gas-assisted therapy have been proposed to further promote the effectiveness of SDT. In this review, the mechanisms of SDT and gas-assisted SDT are first summarized. Then, the applications of gas-assisted SDT for cancer therapy are introduced and categorized by gas types. Next, therapeutic systems for SDT that can realize real-time imaging are further presented. Finally, the challenges and perspectives of gas-assisted SDT for future clinical applications are discussed.

Recent developments of sonodynamic therapy in antibacterial application

The rapid emergence of pathogenic bacteria poses a serious threat to global health. Notably, traditional antibiotic therapies suffer from the risk of strengthening bacterial drug resistance. Sonodynamic therapy (SDT) combining sonosensitizers and low-intensity ultrasound (US) has broadened the way towards treating drug-resistant bacteria. The allure of this therapy emerges from the capacity to focus the US energy on bacterial infection sites buried deep in tissues, locally activating the sonosensitizers to produce cytotoxic reactive oxygen species (ROS) with the ability to induce bacterial death. The past decade has witnessed the rapid development of antibacterial SDT owing to their excellent penetration, favorable biocompatibility and specific targeting ability. This review summarizes available sonosensitizers for antibacterial SDT, and digs into innovative biotechnologies to improve SDT efficiency, such as enhancing the targeting ability of sonosensitizers, image-guided assisted SDT, improvement of hypoxia and combination of SDT with other therapies. Finally, we conclude with the present challenges and provide insights into the future research of antibacterial SDT.

Defect Engineering Triggers Exceptional Sonodynamic Activity of Manganese Oxide Nanoparticles for Cancer Therapy

Sonodynamic therapy (SDT) has received increasing interest in cancer treatment, but its clinical application is still constrained by the low activity of sonosensitizers and their unclear mechanism. Herein, a kind of oxygen-deficient manganese oxide (MnOx) nanoparticles with greatly enhanced sonodynamic activity and good biocompatibility is developed as an advanced sonosensitizer. The introduced oxygen defects can remarkably enhance the electrical conductivity of manganese oxide (MnO) nanoparticles and serve as charge trapping sites to prohibit the electron-hole pair recombination upon ultrasound (US) irradiation. Such distinct merits promote the generation of reactive oxygen species (ROS), making MnOx as a decent sonosensitizer for SDT, and thus endowing MnOx with higher ROS production under US irradiation. As a demonstration, the MnOx nanoparticles decorated by 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-[methoxy(polyethylene glycol)-2000] (MnOx-DSPE-PEG), a biocompatible coverage to enhance the dispersion ability, achieve a superior tumor killing efficiency of 96%, substantially higher than the MnO-DSPE-PEG counterpart (9%). Our experimental results also reveal that MnOx-DSPE-PEG nanoparticles induce the death of tumor cells by targeting polyunsaturated fatty acids in their membrane with US-triggered ROS. Furthermore, the as-designed sonosensitizers exhibit negligible toxicity toward the treated mice.

Recent Progress Toward Imaging Application of Multifunction Sonosensitizers in Sonodynamic Therapy

Sonodynamic therapy (SDT) is a rapidly developing non-surgical therapy that initiates sensitizers’ catalytic reaction using ultrasound, showing great potential for cancer treatment due to its high safety and non-invasive nature. In addition, recent research has found that using different diagnostic and therapeutic methods in tandem can lead to better anticancer outcomes. Therefore, as essential components of SDT, sonosensitizers have been extensively explored to optimize their functions and integrate multiple medical fields. The review is based on five years of articles evaluating the combined use of SDT and imaging in treating cancer. By developing multifunctional sonosensitive particles that combine imaging and sonodynamic therapy, we have integrated diagnosis into the treatment of precision medicine applications, improving SDT cell uptake and antitumor efficacy utilizing different tumour models. This paper describes the imaging principle and the results of cellular and animal imaging of the multifunctional sonosensitizers. Efforts are made in this paper to provide data and design references for future SDT combined imaging research and clinical application development and to provide offer suggestions.

Recent advances in smart nanoplatforms for tumor non-interventional embolization therapy

Tumor embolization therapy has attracted great attention due to its high efficiency in inhibiting tumor growth by cutting off tumor nutrition and oxygen supply by the embolic agent. Although transcatheter arterial embolization (TAE) is the mainstream technique in the clinic, there are still some limitations to be considered, especially the existence of high risks and complications. Recently, nanomaterials have drawn wide attention in disease diagnosis, drug delivery, and new types of therapies, such as photothermal therapy and photodynamic therapy, owing to their unique optical, thermal, convertible and in vivo transport properties. Furthermore, the utilization of nanoplatforms in tumor non-interventional embolization therapy has attracted the attention of researchers. Herein, the recent advances in this area are summarized in this review, which revealed three different types of nanoparticle strategies: (1) nanoparticles with active targeting effects or stimuli responsiveness (ultrasound and photothermal) for the safe delivery and responsive release of thrombin; (2) tumor microenvironment (copper and phosphate, acidity and GSH/H₂O₂)-responsive nanoparticles for embolization therapy with high specificity; and (3) peptide-based nanoparticles with mimic functions and excellent biocompatibility for tumor embolization therapy. The benefits and limitations of each kind of nanoparticle in tumor non-interventional embolization therapy will be highlighted. Investigations of nanoplatforms are undoubtedly of great significance, and some advanced nanoplatform systems have arrived at a new height and show potential applications in practical applications.

Red Blood Cell Inspired Strategies for Drug Delivery: Emerging Concepts and New Advances

In the past five decades, red blood cells (RBCs) have been extensively explored as drug delivery systems due to their distinguishing potential in modulating the pharmacokinetic, pharmacodynamics, and biological activity of carried payloads. The extensive interests in RBC-mediated drug delivery technologies are in part derived from RBCs' unique biological features such as long circulation time, wide access to many tissues in the body, and low immunogenicity. Owing to these outstanding properties, a large body of efforts have led to the development of various RBC-inspired strategies to enable precise drug delivery with enhanced therapeutic efficacy and reduced off-target toxicity. In this review, we discuss emerging concepts and new advances in such RBC-inspired strategies, including native RBCs, ghost RBCs, RBC-mimetic nanoparticles, and RBC-derived extracellular vesicles, for drug delivery.

Ultrasound triggered organic mechanoluminescence materials

Ultrasound induced organic mechanoluminescence materials have become one of the focal topics in wireless light sources since they exhibit high spatiotemporal resolution, biocompatibility and excellent tissue penetration depth. These properties promote great potential in ultrahigh sensitive bioimaging with no background noise and noninvasive nanodevices. Recent advances in chemistry, nanotechnology and biomedical research are revolutionizing ultrasound induced organic mechanoluminescence. Herein, we try to summarize some recent researches in ultrasound induced mechanoluminescence that use various materials design strategies based on the molecular conformational changes and cycloreversion reaction. Practical applications, like noninvasive bioimaging and noninvasive optogenetics, are also presented and prospected.

Photoresponsive prodrug‐dye nanoassembly for in‐situ monitorable cancer therapy

Photocleavable prodrugs enable controllable drug delivery to target sites modulated by light irradiation. However, the in vivo utility is usually hindered by their insolubility and inefficient delivery. In this study, we report a simple strategy of co‐assembling boron‐dipyrromethene‐chlorambucil prodrug and near‐infrared dye IR783 to fabricate photoresponsive nanoassemblies, which achieved both high prodrug loading capacity (~99%) and efficient light‐triggered prodrug activation. The incorporated IR783 dye not only stabilized the nanoparticles and contributed tumor targeting as usual, but also exhibited degradation after light irradiation and in‐situ monitoring of nanoparticle dissociation by fluorescent imaging. Systemic administration of the nanoparticles and localized light irradiation at tumor sites enabled monitorable and efficient drug release in vivo. Our results demonstrate that such prodrug‐dye co‐assembled nanomedicine is a promising formulation for photoresponsive drug delivery, which would advance the translation of photoresponsive nanomedicines.

Ultrasound-activated nanomaterials for sonodynamic cancer theranostics

Despite intensive efforts to develop diagnostic and therapeutic tools, the successful treatment of cancer is still hampered by the obscure boundary between cancerous cells and normal cells, recurrence of the cancer, and the development of drug resistance during chemotherapy. In recent years, sonodynamic therapy (SDT), employing therapeutic ultrasound with sonosensitizers, has attracted attention as a potentially promising approach for cancer therapy. This review describes the current understanding of the mechanisms and the preclinical and clinical efficacy of SDT-based applications in tumors, providing an insight into the therapeutic potential offered by SDT. The limitations and future directions of this emerging treatment are also discussed.

Low-intensity pulsed ultrasound-generated singlet oxygen induces telomere damage leading to glioma stem cell awakening from quiescence

Cancer stem cells, quiescent and drug resistant, have become a therapeutic target. Unlike high-intensity focused ultrasound directly killing tumor, low-intensity pulsed ultrasound (LIPUS), a new noninvasive physical device, promotes pluripotent stem cell differentiation and is primarily applied in tissue engineering but rarely in oncotherapy. We explored the effect and mechanism of LIPUS on glioma stem cell (GSC) expulsion from quiescence. Here, we observed that LIPUS led to attenuated expression of GSC biomarkers, promoted GSC escape from G0 quiescence, and significantly weakened the Wnt and Hh pathways. Of note, LIPUS transferred sonomechanical energy into cytochrome c and B5 proteins, which converted oxygen molecules into singlet oxygen, triggering telomere crisis. The in vivo and in vitro results confirmed that LIPUS enhanced the GSC sensitivity to temozolomide. These results demonstrated that LIPUS "waked up" GSCs to improve their sensitivity to chemotherapy, and importantly, we confirmed the direct targeted proteins of LIPUS in GSCs.

A novel hypocrellin-based assembly for sonodynamic therapy against glioblastoma

The non-invasive treatment of glioblastoma (GBM) is of great significance and can greatly reduce the complications of craniotomy. Sonodynamic therapy (SDT) is an emerging tumor therapeutic strategy that overcomes some fatal flaws of photodynamic therapy (PDT). Different from PDT, SDT has deep tissue penetration and can be applied in the non-invasive treatment of deep-seated tumors. However, effective sonosensitizers that can be used for SDT of GBM are still very rare. Herein, we have prepared a suitable assembly based on a hypocrellin derivative (CTHB) with good biocompatibility. Excitedly, the hypocrellin-based assembly (CTHB NPs) can effectively produce reactive oxygen species under ultrasound stimulation. The inherent fluorescence and photoacoustic imaging characteristics of the CTHB NPs are conducive to the precise positioning of the tumors. It has been proved both in subcutaneous and in intracranial tumor models that CTHB NPs can be used as an effective sonosensitizer to inhibit tumor growth under ultrasound irradiation. This hypocrellin-based assembly has a good clinical prospect in the non-invasive treatment of GBM.

2D Piezoelectric Bi2 MoO6 Nanoribbons for GSH-Enhanced Sonodynamic Therapy

Reducing the scavenging capacity of reactive oxygen species (ROS) and elevating ROS production are two primary goals of developing novel sonosensitizers for sonodynamic therapy (SDT). Hence, ultrathin 2D Bi₂ MoO₆ -poly(ethylene glycol) nanoribbons (BMO NRs) are designed as piezoelectric sonosensitizers for glutathione (GSH)-enhanced SDT. In cancer cells, BMO NRs can consume endogenous GSH to disrupt redox homeostasis, and the GSH-activated BMO NRs (GBMO) exhibit an oxygen-deficient structure, which can promote the separation of electron-hole pairs, thereby enhancing the efficiency of ROS production in SDT. The ultrathin GBMO NRs are piezoelectric, in which ultrasonic waves introduce mechanical strain to the nanoribbons, resulting in piezoelectric polarization and band tilting, thus accelerating toxic ROS production. The as-synthesized BMO NRs enable excellent computed tomography imaging of tumors and significant tumor suppression in vitro and in vivo. A piezoelectric Bi₂ MoO₆ sonosensitizer-mediated two-step enhancement SDT process, which is activated by endogenous GSH and amplified by exogenous ultrasound, is proposed. This process not only provides new options for improving SDT but also broadens the application of 2D piezoelectric materials as sonosensitizers in SDT.

Advanced biotechnology-assisted precise sonodynamic therapy

Despite significant advances, the therapeutic impact of photodynamic therapy is still substantially hampered by the restricted penetration depth of light and the reactive oxygen species (ROS)-mediated toxicity, which is impeded by the shorter effective half-life and radius of ROS produced during treatment. Sonodynamic therapy (SDT), on the other hand, provides unrivalled benefits in deep-seated tumour ablation due to its deep penetration depth and not totally ROS-dependent toxicity, exhibiting enormous preclinical and clinical potential. In this tutorial review, we highlight imaging-guided precise SDT, which allows choosing the best treatment option and monitoring the therapy response in real-time, as well as recent clinical trials based on SDT. Aside from that, the subtle design strategies of sonosensitizers based on tumour environment shaping and rational structure modification, as well as SDT combination treatment (chemotherapy, chemodynamic therapy, photodynamic therapy, photothermal therapy, gas therapy and immunotherapy), aimed at a more effective treatment outcome, are summarized. Finally, we discussed the future of SDT for personalized cancer and other disease treatments.

Synthesis of porphyrin-incorporating covalent organic frameworks for sonodynamic therapy

Porphyrin-incorporating covalent organic frameworks were synthesized at room temperature. The resulting products with uniform morphology and excellent crystallinity exhibited good singlet oxygen generation ability. Both in vitro and in vivo experiments demonstrated the significant antitumor efficiency via sonodynamic therapy.

Hypoxia-Adapted Sono-chemodynamic Treatment of Orthotopic Pancreatic Carcinoma Using Copper Metal-Organic Frameworks Loaded with an Ultrasound-Induced Free Radical Initiator

The efficacy of sonodynamic therapy (SDT) is largely dependent upon oxygen availability to generate deleterious reactive oxygen species, and as such, hypoxic microenvironments greatly constrain the efficacy of SDT. Development of free radical generators that are not dependent on oxygen and related combination treatment strategies thus have the potential to enhance the antitumor potential of SDT. Combined treatment strategies are expected to improve the efficacy of sonodynamic antitumor therapy. As metal-organic framework (MOF) platforms are highly amenable to integration with other therapeutic approaches, we herein report the development of tumor microenvironment (TME)-responsive nanoparticles constructed by embedding the azo initiator 2,2'-azobis[2-(2-imidazolin-2-yl)propane]dihydrochloride (AIPH) into hypoxia-triggered copper metal-organic framework (Cu-MOF) nanovectors to achieve synergistic sono-chemodynamic therapy in an orthotopic murine pancreatic carcinoma model system. When exposed to hypoxic conditions within the TME, this Cu-MOF structure underwent degradation, leading to the release of Cu2+ and AIPH. Cu2+ was then able to deplete local glutathione stores, resulting in the reduction of Cu2+ to Cu+, which then reacts with endogenous H2O2 in a Fenton-like reaction to yield cytotoxic hydroxyl radicals (•OH) for chemodynamic therapy. When exposed to ultrasound irradiation, AIPH further degraded in an oxygen-independent manner to yield nitrogen bubbles and alkyl radicals, the former of which enhanced the ability of these nanoparticles to penetrate deeply into the tumor. The resultant radicals induced substantial DNA damage and apoptotic cell death within target tumors under different levels of oxygen availability. As such, this hypoxic TME-responsive synergistic sono-chemodynamic approach offers an ideal means of achieving oxygen-independent free radical generation and enhanced treatment efficacy.

A Robust Oxygen-Carrying Hemoglobin-Based Natural Sonosensitizer for Sonodynamic Cancer Therapy

The development of novel sonosensitizers with outstanding reactive oxygen (ROS) generation capacity and great biocompatibility poses a significant challenge for the clinical practice of sonodynamic therapy (SDT). In this work, hemoglobin (Hb) with natural metalloporphyrin was first shown to possess great potential as a sonosensitizer. Compared with traditional organic sonosensitizers, Hb had satisfactory sono-sensitizing efficiency because four the porphyrin molecules were separated by four polypeptide chains. This effectively avoided the problem of low ROS quantum yield caused by the stacking of hydrophobic porphyrins. Meanwhile, Hb is an efficient and safe oxygen carrier that may release O₂ at hypoxic tumors site, which improved tumor oxygenation and subsequently enhanced SDT efficacy. Therefore, Hb was integrated with zeolitic imidazolate framework 8 (ZIF-8) to form a nanoplatform that demonstrated a potent suppression effect on deep-seated tumors under ultrasound irradiation.

Nanoparticle-Assisted Sonosensitizers and Their Biomedical Applications

As a non-invasive strategy, sonodynamic therapy (SDT) which utilizes sonosensitizers to generate reactive oxygen species (ROS) has received significant interest over recent years due to its ability to break depth barrier. However, intrinsic limitations of traditional sonosensitizers hinder the widespread application of SDT. With the development of nanotechnology, various nanoparticles (NPs) have been designed and used to assist sonosensitizers for SDT. This review first summarizes the possible mechanisms of SDT, then classifies the NPs-assisted sonosensitizers and discusses their biomedical applications in ultrasonography, drug delivery, high intensity focused ultrasound and SDT-based combination treatment. Finally, some challenges and future perspectives of NPs-assisted SDT has also been discussed.

Dual ultrasound-activatable nanodroplets for highly-penetrative and efficient ovarian cancer theranostics

The selective delivery and deep intertumoral penetration of nanosensitizers remain challenging in the fabrication of sonodynamic therapy (SDT) platforms. In this work, we rationally constructed dual ultrasound (US)-activatable nanodroplets (NDs)/nanoliposomes/nanosensitizers with perfluoropentane (PFP) in the core, hematoporphyrin monomethyl ether (HMME) in the phospholipid shell and folate (FA)-conjugated to the surface (collectively termed FA-H@NDs). We aimed to validate the feasibility of these FA-H@NDs for FA receptor (FR)-overexpressed ovarian cancer theranostics. The ND formulations were based on PFP that can undergo acoustic droplet vaporization (ADV) when exposed to US irradiation. The ADV phenomenon disrupts the adjacent vasculature, and the resistance to drug diffusion within the tumor can be decreased, enabling nanosensitizers to more deeply penetrate into the inner tissue far from the intertumoral vasculature. These FA-H@NDs assisted by US irradiation can also induce the production of excess reactive oxygen species (ROS) and consequently trigger tumor cell/tissue apoptosis and necrosis. Furthermore, this therapeutic process can be guided and monitored by US/photoacoustic (PA) dual-modal imaging. This work established a new paradigm for highly efficient ovarian cancer theranostics based on the rational utilization of dual US-activatable NDs.

Urchin-Shaped Metal Organic/Hydrogen-Bonded Framework Nanocomposite as a Multifunctional Nanoreactor for Catalysis-Enhanced Synergetic Therapy

Ultrasound (US)-induced sonodynamic therapy (SDT) is an efficient and precise method against tumor, and the integration of multiple cancer therapies has been proved as a promising strategy for better therapeutic effects. Herein, for the first time, a multifunctional nanoreactor has been fabricated by integrating Fe-MIL-88B-NH₂, PFC-1, and glucose oxidase (GO_x) to form urchin-like Fe-MIL-88B-NH₂@PFC-1-GO_x (MPG) nanoparticles as Fenton's reagent, a sonosensitizer, and a tumor microenvironment (TME) modulator. In detail, MPG can generate ^•OH for chemodynamic therapy (CDT) and deplete glutathione (GSH) to alleviate the antioxidant ability of cancer cells. Moreover, catalase (CAT)-like MPG can react with H₂O₂ to generate O₂ for relieving hypoxia in TME, enhancing GO_x-catalyzed glucose oxidation to produce H₂O₂ and gluconic acid. Then, the regenerated H₂O₂ can promote the Fenton reaction to achieve GO_x catalysis-enhanced CDT. Owing to its large π-electron conjugated system, MPG also serves as an ideal sonosensitizer, realizing a burst generation of ¹O₂ under US irradiation for efficient SDT. Therefore, the tumor treatment will be notably enhanced by MPG-based synergetic CDT/SDT/starvation therapy via a series of cascade reactions. Overall, this work develops a versatile nanoreactor with improved tumor treatment effectiveness and broadens the application prospects of porous materials in the field of biomedical research.

Functionalized g-C3N4 nanosheets for potential use in magnetic resonance imaging-guided sonodynamic and nitric oxide combination therapy

The oxygen consumption-induced hypoxia and the high concentration of glutathione in tumor microenvironment limit the treatment outcomes of sonodynamic therapy (SDT). SDT needs to be combined with other treatment modalities to achieve the desired therapeutic efficiency. In this study, an oxidized g-C₃N₄ (OCN) nanosheet-based theranostic nanoplatform is developed for sonodynamic and nitric oxide (NO) combination therapy of cancer. The OCN nanosheets are successively modified with amino-terminated 6-armed polyethylene glycol, chlorin e6, and Gd³⁺ ions, and then the as-prepared OCN-PEG-(Ce6-Gd³⁺) nanosheets are loaded with the NO donor N,N'-di-sec-butyl-N,N'-dinitroso-1,4-phenylenediamine (BNN6). Upon ultrasound (US) irradiation, the OCN-PEG-(Ce6-Gd³⁺)/BNN6 nanocomposite can induce the generation of reactive oxygen species (ROS) and simultaneously release NO molecules to effectively kill the cancer cells, thereby significantly suppressing the tumor growth. Moreover, a good in vivo T₁-weighted magnetic resonance imaging (MRI) contrast effect is achieved after intravenous injection of OCN-PEG-(Ce6-Gd³⁺)/BNN6 due to remarkably enhanced contrast performance of the nanocomposite. Therefore, the OCN-PEG-(Ce6-Gd³⁺)/BNN6 formulation can serve as a promising theranostic agent for MRI-guided sonodynamic-NO combination therapy.

Design and application of inorganic nanoparticles for sonodynamic cancer therapy

This review focus on the recent developments in inorganic nanomaterials for tumor SDT.

Recent Advances in Nanomaterial-Assisted Combinational Sonodynamic Cancer Therapy

Ultrasound (US)-triggered sonodynamic therapy (SDT), as a promising noninvasive therapeutic modality, has received ever-increasing attention in recent years. Its specialized chemical agents, named sonosensitizers, are activated by low-intensity US to produce lethal reactive oxygen species (ROS) for oncotherapy. Compared with phototherapeutic strategies, SDT provides many noteworthy opportunities and benefits, such as deeper penetration depth, absence of phototoxicity, and fewer side effects. Nevertheless, previous studies have also demonstrated its intrinsic limitations. Thanks to the facile engineering nature of nanotechnology, numerous novel nanoplatforms are being applied in this emerging field to tackle these intrinsic barriers and achieve continuous innovations. In particular, the combination of SDT with other treatment strategies has demonstrated a superior efficacy in improving anticancer activity relative to that of monotherapies alone. Therefore, it is necessary to summarize the nanomaterial-assisted combinational sonodynamic cancer therapy applications. Herein, the design principles in achieving synergistic therapeutic effects based on nanomaterial engineering methods are highlighted. The ultimate goals are to stimulate the design of better-quality combined sonodynamic treatment schemes and provide innovative ideas for the perspectives of SDT in promoting its future transformation to clinical application.

Double security drug delivery system DDS constructed by multi-responsive (pH/redox/US) microgel

In this paper, the multi-responsive core-shell microgels were prepared for constructing a double-locked drug delivery system. The pH- sensitive poly(2-(diisopropylamino ethylmethacry-late)-block-poly(ethyleneimine) diblock copolymers (PDPA-b-PEI) were synthesized and used to prepare micelles through their self-assembly in neutral solution. Redox-responsive gel shells were formed by Michael addition of primary amine group of branched PEI using disulfide as a cross-linker, which was specifically cleaved by glutathione (GSH). Anticancer drug doxorubicin DOX and perfluorohexane (PFH) could be encapsulated in the core of microgel. The DOX was released sustainably only under the condition of pH and GSH were both right. For example, under neutral condition with GSH, DOX could not release swimmingly due to the core of microgels was in hydrophobic state and wrapped the DOX firmly, although the gel shells were collapsed by GSH. When exposed to ultrasound, the drug released abruptly and achieved a complete release instantly. Moreover, it was found that the structure of the microgels was not destroyed after the ultrasound stimulus but had undergone an expansion-recovery process. Finally, it was demonstrated that the microgel had a "double security" effect, ensuring the low drug leakage during the normal blood circulation and efficient drug release under the pH/redox/ultrasound stimulus. The multi-responsive microgels designed here, which combines the usage of both endogenous and exogenous stimuli, has the advantages of low side-effect, high spatiotemporal controllability and complete release.

Ultrasound-Activated Sensitizers and Applications

Modalities for photo-triggered anticancer therapy are usually limited by their low penetrative depth. Sonotheranostics especially sonodynamic therapy (SDT), which is different from photodynamic therapy (PDT) by the use of highly penetrating acoustic waves to activate a class of sound-responsive materials called sonosensitizers, has gained significant interest in recent years. The effect of SDT is closely related to the structural and physicochemical properties of the sonosensitizers, which has led to the development of new sound-activated materials as sonosensitizers for various biomedical applications. This Review provides a summary and discussion of the types of novel sonosensitizers developed in the last few years and outlines their specific designs and the potential challenges. The applications of sonosensitizers with various functions such as for imaging and drug delivery as well as in combination with other treatment modalities would provide new strategies for disease therapy.

Multifunctional sonosensitizers in sonodynamic cancer therapy

Phototherapy, including photodynamic therapy and photothermal therapy, has the potential to treat several types of cancer.

Recent progress in the augmentation of reactive species with nanoplatforms for cancer therapy

Reactive species (RS), mainly including reactive oxygen species (ROS) and reactive nitrogen species (RNS), are indispensable in a wide variety of biological processes. RS often have elevated levels in cancer cells and tumor microenvironments. They also have a dual effect on cancer: on the one hand, they promote pro-tumorigenic signaling to facilitate tumor survival and on the other hand, they promote antitumorigenic pathways to induce cell death. Excessive RS would disrupt the cellular redox homeostasis balance and show partiality as oxidants, which would cause irreversible damage to the adjacent biomolecules such as lipids, proteins and nucleic acids. The altered redox environment and the corresponding increased antioxidant capacity in cancer cells render the cells susceptible to RS-manipulated therapies, especially the augmentation of RS. With the rapid development of nanotechnology and nanomedicine, a large number of cancer therapeutic nanoplatforms have been developed to trigger RS overproduction by exogenous and/or endogenous stimulation. In this review, we highlighted the latest progress in the nanoplatforms designed for the augmentation of RS in cancer therapy. Nanoplatforms based on strategies including disabling the antioxidant defense system, photodynamic therapy (PDT), sonodynamic therapy (SDT), and chemodynamic therapy (CDT) were introduced. The crucial obstacles involved in these strategies, such as the light penetration limitation of PDT, relatively low RS release by SDT, and strict conditions of Fenton reaction-mediated CDT, were also discussed, and feasible solutions for improvement were proposed. Furthermore, synergistic therapies among individual therapeutic modalities such as chemotherapy, photothermal therapy, and RS-based dynamic therapies were overviewed, which contributed to achieving more optimal anticancer efficacy than linear addition. This review sheds light on the development of non-invasive cancer therapy based on RS manipulation and provides guidance for establishing promising cancer therapeutic platforms in clinical settings.

Multifunctional two-dimensional nanocomposites for photothermal-based combined cancer therapy

Two-dimensional (2D) nanocomposites have been widely used in biomedical applications during the past few years due to their extraordinary physicochemical properties, which has proved their importance in the field of nanomedicine. Benefiting from the excellent optical absorption in the near-infrared window and large specific surface area, many efforts have been devoted to fabricating 2D nanomaterial-based multifunctional nanoplatforms to realize photothermal therapy (PTT)-based or chemotherapy-based synergistic treatment, which exhibits obvious anti-tumor effects and significantly enhances the therapeutic efficiency of cancer compared with monotherapy. In particular, 2D nanocomposites are usually fabricated as intelligent nanoplatforms for stimuli-responsive nanocarriers, whose therapeutic effects could be specifically activated by the tumor microenvironment (TME). In addition, different fluorescent probes and functional inorganic nanomaterials could be absorbed on the surface of 2D nanomaterials to fabricate multifunctional hybrid nanomaterials with satisfactory magnetic, optical, or other properties that are widely used for multimodal imaging-guided cancer therapy. In this review, the latest development of multifunctional 2D nanocomposites for combination therapy is systematically summarized, mainly focusing on PTT-based synergistic cancer therapy, and the other forms and potential forms of synergistic cancer therapy are also simply summarized. Furthermore, the design principles of 2D nanocomposites are particularly emphasized, and the current challenges and future prospects of 2D nanocomposites for cancer theranostics are discussed simultaneously.

Biodegradable Natural Product-Based Nanoparticles for Near-Infrared Fluorescence Imaging-Guided Sonodynamic Therapy

Natural products show high potential for clinical translation because of their specific biological activities and molecular structure diversities. Sonosensitizers that originate from natural products play a crucial role as anti-inflammatory and anticancer agents. Herein, hypocrellin-derivative nanoparticles (APHB NPs) were constructed for synchronous near-infrared fluorescence (NIR FL) imaging and sonodynamic therapy (SDT) for deep-seated tumors in vivo. The prepared APHB NPs exhibit excellent water solubility, FL in the NIR region, and effective reactive oxygen species generation under ultrasound stimulation. Furthermore, the APHB NPs show excellent biocompatibility, suitable biodegradation rate, and enhanced tumor accumulation. Therefore, the APHB NPs exhibit promising clinical potential as novel safe and precise NIR FL imaging and SDT agents for deep-seated tumor therapy.

Development of an interactive tumor vascular suppression strategy to inhibit multidrug resistance and metastasis with pH/H2O2 responsive and oxygen-producing nanohybrids

An ideal cancer therapeutic strategy should not only reverse multidrug resistance (MDR), but also prevent cancer metastasis. In this study, we address these cancer treatment challenges through an interactive vascular suppression strategy.

Ultrasound-triggered perfluorocarbon-derived nanobombs for targeted therapies of rheumatoid arthritis

The targeted US-triggered PFC-based “nanobombs” with US used to treat the RA in this work would offer a new treatment strategy and have a great potential for the application in the areas of theranostic agent and nanomedicine treatment.