Sono-Driven STING Activation using Semiconducting Polymeric Nanoagonists for Precision Sono-Immunotherapy of Head and Neck Squamous Cell Carcinoma

Photochemical bomb: Precision nuclear targeting to activate cGAS-STING pathway for enhanced bladder cancer immunotherapy

Activating the cGAS-STING pathway presents a promising strategy to enhance the innate immunity and combat the immunosuppressive tumor microenvironment. One key mechanism for triggering this pathway involves the release of damaged DNA fragments caused by nuclear DNA damage. However, conventional cGAS-STING agonists often suffer from limited nucleus-targeting efficiency and potential biotoxicity. In this study, we develop a novel nucleus-targeting theranostic nanoplatform designed to synergistically activate the cGAS-STING pathway through the combination of photodynamic therapy (PDT) and cisplatin chemotherapy for orthotopic bladder cancer treatment. The nanoplatform integrates a new high-performance type-I photosensitizer with near-infrared-II emission, a TATSA peptide for enhanced nuclear targeting, and a biosafe platinum (IV) cisplatin prodrug. Upon NIR laser irradiation, the nanoagent delivers synergistic nucleus-targeted PDT and chemotherapy, causing substantial DNA damage and the release of double-stranded DNA, which subsequently activates the cGAS-STING pathway and triggers potent immunomodulation. This activation promotes dendritic cells maturation, enhances cytotoxic T infiltration, and facilitates the formation of memory T cells, leading to immune microenvironment remodeling, and long-lasting immune memory, thus effectively inhibiting orthotopic bladder tumors and reducing the risk of metastasis. These findings highlight the substantial potential of this strategy to overcome the limitations of current immunotherapies by leveraging nucleus-targeted PDT to activate the cGAS-STING pathway for cancer treatment.

Conjugated STING agonists

An innate immune system is the first line of defense and prevents the host from infection and attacks the invading pathogens. Stimulator of interferon genes (STING) plays a vital role in the innate immune system. STING activation by STING agonists leads to phosphorylation of TANK-binding kinase 1 (TBK1) and interferon regulatory factor 3 (IRF3) with the release of type I interferons and proinflammatory cytokines, further promoting the adaptive immune response and activating T cells by increased antigen presentation. Natural STING agonist cyclic dinucleotides (CDNs) encounter many defects such as high polarity by negative charges, low stability and circulative half-life, off-target systemic toxicity, and low response efficacy in clinical trials. To overcome these challenges, massive efforts have addressed chemical modifications of CDNs, development of non-CDN STING agonists, and delivery of these STING agonists either by conjugation or liposomes/nanoparticles. Considering there have been a great number of reports regarding nanosystem-aided delivery, here, we examine the development of STING agonists, especially for non-CDNs and their delivery specifically by conjugation strategy, with a focus on the STING agonists in clinical trials and current challenges of their potential in cancer immunotherapy.

Non-central symmetric 2D bismuth-based perovskites for piezoelectric-enhanced sonodynamic immunotherapy

Sonodynamic therapy (SDT), an emerging treatment modality, exhibits great potential in cancer therapy owing to its excellent tissue penetration, immune activation ability, and relatively low side effects. The lattice distortion of inorganic perovskite is challenging to control, which leads to an unsatisfactory SDT effect. This study presents a two-dimensional bismuth-based halide perovskite material, MA3Bi2Cl9-PEG (MBCP), with favorable piezoelectric properties, being first applied to tumor sonodynamic immunotherapy. By introducing methylamine cations, the central symmetry of MBC is effectively disrupted, resulting in a non-centrosymmetric crystal structure. This structural modification remarkably enhances the piezoelectric performance, enabling more robust charge separation effects under ultrasound excitation and thus facilitating the efficient generation of reactive oxygen species (ROS). Moreover, the generated ROS triggers immunogenic cell death in tumor cells, through the depletion of excessive glutathione and the inhibition of glutathione peroxidase 4, induces ferroptosis. The combined therapeutic strategy substantially enhances the anti-tumor efficacy and effectively suppresses lung metastasis. This research offers a promising example of the application of perovskite piezoelectric materials in sonodynamic immunotherapy.

Amplifying the Antitumor Effect of STING Agonist MSA-2 by Phospholipid Nanoparticles Delivering STING mRNA and Copper-Modified MSA-2 Combination

STING activation is a promising application therapeutic strategy for cancer immunotherapy. In particular, MSA-2 as an oral STING agonist is discovered to have antitumor activity. However, how to improve the antitumor effect of MSA-2 is a very valuable contribution to cancer immunotherapy. Here, we use two strategies to amplify the antitumor effect of MSA-2 by phospholipid nanoparticles delivering STING mRNA and copper-modified MSA-2. We synthesized a new series of ionizable phospholipid nanoparticles and optimized a phospholipid nanoparticle (1AP24) for delivering STING mRNA, increasing the expression of STING protein to bind more MSA-2. Second, we synthesized copper-modified MSA-2 (MSA-2-Cu), which induced cell death by Cu2+ toxicity. Combining 1AP24@STING mRNA and MSA-2-Cu can crucially decrease tumor growth and increase a mouse's survival. It is a new treatment strategy through amplifying the STING pathway.

Ultrasound-Energized OX40L-Expressing Biohybrid for Multidimensional Mobilization of Sustained T Cell-Mediated Antitumor Immunity and Potent Sono-Immunotherapy

Harnessing immunostimulation to reinvigorate antitumor effector immune cells represents a promising strategy for tumor eradication. However, achieving durable clinical outcomes necessitates multidimensional activation to sustain robust immune responses. Here, we present an ultrasound-empowered living biohybrid that strategically mobilizes T-cell-mediated immunity for potent tumor sono-immunotherapy. Through synthetic biology, we engineer bacteria to express a fusion protein encoding the costimulatory OX40 ligand (OX40L), and further functionalize them with a high-performance polymer sonosensitizer tethered via a reactive oxygen species-cleavable linker. Upon ultrasound irradiation, the sono-activated nanocargoes detach from the bacterial surface, facilitating cellular entry and exposing immune-stimulating OX40L. The potent sonodynamic effects, coupled with the native immunogenicity of bacteria, promotes tumor-associated antigen release, fosters a proinflammatory microenvironment, and drives dendritic cell maturation, thereby priming cytotoxic T-cell activation. The OX40L expressed by the engineered bacteria amplifies and sustains T-cell activity, orchestrating a robust and durable antitumor response. This cascade-amplified immune activation effectively suppresses tumor growth, induces long-lasting immune memory, and provides protection against tumor metastasis and recurrence, significantly enhancing survival outcomes. By integrating ultrasound-energized nanoadjuvants with costimulatory immune boosters, this hybrid living biotherapeutic platform offers a versatile and powerful strategy for multidimensional immune activation, advancing the frontier of cancer sono-immunotherapy.

Albumin-targeted oxaliplatin(iv) prodrugs bearing STING agonists

The anticancer platinum complex oxaliplatin exerts its activity through DNA damage and immune-stimulatory mechanisms, but is associated with adverse treatment side effects. Platinum(iv) complexes represent a promising prodrug strategy to improve tolerability and to enhance antitumor efficacy via attachment of additional bioactive ligands or tumor-targeting moieties. In the present study, oxaliplatin(iv) complexes containing immune-stimulatory STING agonists SR-717 or MSA-2 were synthesized and their biological properties were studied. Whereas the Pt-SR-717 compound was fast reduced, Pt-MSA-2 complexes displayed significantly higher reductive stability reflected by low in vitro cytotoxicity. Although the platinum(iv) complexes activated interferon regulatory factor (IRF) and NF-κB signaling pathways less effectively compared to the free STING agonists, reducing conditions elevated cytotoxicity and STING downstream signaling, particularly for MSA-2-containing prodrugs. Rapid albumin binding of a maleimide-containing Pt-MSA-2 derivative resulted in elevated plasma levels, prolonged blood circulation, and enhanced tumor accumulation of platinum in CT-26 tumor-bearing mice. The Pt-MSA-2 complexes triggered immune activation and cytokine secretion without hematotoxicity usually associated with free oxaliplatin. The albumin-targeted Pt-MSA-2 drug significantly inhibited tumor growth after intravenous application, while the non-maleimide complex was effective only when applied peritumorally. However, the effects were not enhanced compared to mono-treatment with oxaliplatin or MSA-2, indicating a lack of synergism between the two simultaneously released agents. Our results demonstrate that oxaliplatin(iv) complexes represent a valuable strategy for enhanced tumor-targeting and adverse effect reduction, but question the simultaneous release of STING agonists and free oxaliplatin as a potent strategy towards synergistic antineoplastic activity.

A precision intelligent nanomissile for inhibiting tumor metastasis, boosting energy deprivation and immunotherapy

The epithelial-mesenchymal transition (EMT), tumor stroma and local metabolic alterations cooperate to establish a unique tumor microenvironment (TME) that fosters tumor progression and metastasis. To tackle this challenge, a precision intelligent nanomissile named HA@AT-Pd has been designed for dual-pronged cancer-associated fibroblast (CAF) transformation and tumor cell elimination. It is observed that HA@AT-Pd inhibits the production of cancer stem cells (CSCs) by blocking the TGF-β/Smad signaling pathway-mediated EMT and reversing activated CAFs to quiescence. Notably, HA@AT-Pd induces energy depletion in breast cancer cells through simultaneously suppressing cellular oxidative phosphorylation and glycolysis. The inhibition of glycolysis results in reduced lactic acid production, thereby converting an immunosuppressive TME into an immune-activating environment. Furthermore, the photothermal effect generated by HA@AT-Pd evokes immunogenic cell death, which can further enhance the anti-tumor immune response. Overall, this multifunctional combination strategy unveils potential therapeutic avenues to inhibit tumor progression and metastasis.

A syringeable immunotherapeutic hydrogel enhances T cell immunity via in-situ activation of STING pathway for advanced breast cancer postoperative therapy

Complete surgical resection of advanced breast cancer is highly challenging and often leaves behind microscopic tumor foci, leading to inevitable relapse. Postoperative formation of the immunosuppressive tumor microenvironment (TME) reduces the efficacy of immunotherapies against residual tumors. Although cytotoxic chemotherapeutics exert the capacity to intensify cancer immunotherapy via immunogenic cell death (ICD) effects, systemically administered chemo agents often cannot access residual tumor sites, and fail to elicit antitumor immune responses. Herein, we present a novel syringeable immunotherapeutic hydrogel (SiGel@SN38/aOX40) loaded with the DNA-targeting chemotherapeutic 7-ethyl-10-hydroxycamptothecin (SN38) and the anti-OX40 agonist antibody (aOX40). The sustained in-site release of SN38 and aOX40 activate the stimulator of interferon genes (STING) pathway, intensify type I interferons expression, synergistically facilitate dendritic cell (DC) activation, and initiate persistent T cell mediated immune responses within the surgical resection bed that eliminate residual tumors with no tumor recurrence in 120 days. Collectively, our designed SiGel@SN38/aOX40 induces robust and long-lasting tumoricidal immunity following breast cancer resection and exhibit immense potential for clinical translation.

A Single-Atom Mn/MoO3- x Nanoagonist for Cascade cGAS/STING Activation in Tumor-Specific Catalytic Metalloimmunotherapy

The cyclic GMP-AMP synthase (cGAS)/stimulator of interferon genes (STING) pathway plays a crucial role in initiating anti-tumor immunity. Despite the development of various STING agonists, their effectiveness is often limited by suboptimal activation efficiency and poor sustainability. To address this, a Mn/MoO3- x nanoagonist featuring Mn single-atom sites is presented, designed for cascade cGAS/STING activation in tumor-specific catalytic metalloimmunotherapy. The single-atom nanoagonist (SANA) is meticulously crafted by doping Mn atoms into defective molybdenum oxide (MoO3- x), enabling robust peroxidase-mimicking catalysis and inducing severe double-stranded DNA (dsDNA) damage in tumors. Of note, Mn2+ and MoO4 2- can be responsively released from Mn/MoO3- x SANA and enhance the sensitivity of cGAS to dsDNA. Importantly, MoO4 2- with a relatively slow-release profile and facile cellular accumulation compensates for Mn2+ that has poor cellular accumulation due to continuous efflux, thus continuatively triggering the secretion of type I interferon for beyond 72 h. Remarkably, Mn/MoO3- x SANA significantly inhibits tumor growth and metastasis without supplementary STING agonists or external stimulation. This study offers a promising cascade cGAS/STING activation approach to enhance the efficacy and sustainability of catalytic metalloimmunotherapy.

A pH-Responsive and Guanidinium-Rich Nanoadjuvant Efficiently Delivers STING Agonist for Cancer Immunotherapy

As natural agonists of the stimulator of interferon genes (STING), cyclic dinucleotides (CDNs) have been identified as promising immunotherapies that trigger a potent immune response against tumors. However, the low stability, rapid clearance, inadequate cellular uptake, and inefficient cytosol localization heavily hinder the therapeutic efficacy of the hydrophilic and negatively charged 2', 3'-cyclic-GMP-AMP (cGAMP). How to efficiently deliver cGAMP into the endoplasmic reticulum (ER) to activate STING for immune priming remains challenging. Here, we report a pH-responsive and guanidinium-rich STING nanoagonist (nPGSA) for cytosol delivery of cGAMP. Compared with free cGAMP, nPGSA achieves up to a 37.4-fold enhancement of cellular internalization. The pH-sensitive and guanidinium-functional design facilitates quick release and endosome escape, thus enabling precise ER targeting of cGAMP and 33.9-fold amplification of STING sensibilization. Furthermore, through the modulation of tumor-associated macrophage (TAM) polarization, nPGSA elicits a potent antigen-specific cellular immune response and sustained tumor regression in melanoma- and neuroblastoma-bearing mice. Our study provides a promising strategy for the delivery of cGAMP, and it offers insights into the function of cGAMP in modulating the tumor immune microenvironment for cancer immunotherapy.

Cascaded immunotherapy with implantable dual-drug depots sequentially releasing STING agonists and apoptosis inducers

Non-nucleotide stimulators of interferon gene (STING) agonists hold promise as immunotherapeutic agents for postsurgical adjuvant treatment of tumors. However, their limited effect duration hampers therapeutic effectiveness, necessitating prolonged administration of multiple doses that heightens infection risk and impacts patient compliance. Here, we develop an implantable dual-drug depot in a sandwich-like configuration, with a non-nucleotide STING agonist (MSA-2) in the outer layers of 3D-printed scaffolds and an immunogenic apoptosis inducer (doxorubicin, DOX) in the inner layer of electrospun fibers. We discover that MSA-2 can elicit endoplasmic reticulum stress-mediated and general immunogenic apoptosis of cancer cells. The stimulations with tumor-associated antigens and damage-associated molecular patterns from cancer cells, along with proinflammatory factors secreted by matured dendritic cells and M1-polarized macrophages, can depolymerize intracellular microtubules guiding activated STING trafficking towards lysosomes for degradation. Collectively, the dual-drug depots can initiate a long-lasting cascaded immunotherapy and chemotherapy, suppressing postsurgical tumor recurrence and metastasis.

Profile of STING agonist and inhibitor research: a bibliometric analysis

Background

STING is a core signaling hub molecule in the innate immune system, involved in various diseases, including infectious diseases, autoimmune diseases, tumors, aging, organ fibrosis, and neurodegenerative diseases. Its activation has shown great potential in anti-tumor and anti-infective therapies, with STING agonists emerging as a promising approach in cancer immunotherapy in recent years. This study identifies research trends and potential directions in the field by collecting and analyzing relevant literature.

Methods

A total of 527 publications regarding STING agonists and 107 about inhibitors were retrieved from the WOS Core Collection database. Bibliometric information was extracted with CiteSpace and VOSviewer software for visualization.

Results

It shows that research on both STING agonists and inhibitors is burgeoning rapidly. The United States and China are leading contributors in this field. Application of STING agonists primarily focuses on cancer immunotherapy, while STING inhibitors target inflammation, particularly neuroinflammation and acute lung injury.

Conclusion

Current research emphasizes optimizing STING agonists for permeability, efficacy, and safety, with nanotechnology and lipid nanoparticles being prominent delivery techniques. Future research is expected to focus on drug development and clinical applications. This comprehensive bibliometric analysis provides clinical insights and a guide for further investigation to STING agonist/inhibitor.

Enhanced antitumor efficacy of STING agonist MSA-2 by lipid nanoparticles delivering circular IL-23 mRNA and platinum-modified MSA-2 combination

A next-generation STING agonist MSA-2 is a promising tumor immunotherapy strategy. However, the methods for improving the anti-tumor efficacy of MSA-2 are a lot of effort. We have demonstrated antitumor effect of platinum-modified MSA-2 (MSA-2-Pt) was better than MSA-2. Here, we combined lipid nanoparticles delivering circular IL-23 mRNA (LNP@cIL-23) and MSA-2-Pt strategy, which showed good antitumor efficacy. Firstly, we synthesized a new series of ionizable phospholipids and formulated and optimized an LNP36 for delivering circular IL-23 mRNA. Then, the combination of LNP36@cIL-23 mRNA and MSA-2-Pt induced tumor cell death and immune activation in the tumor with a single i.t. injection. Finally, the combination of LNP36@cIL-23 mRNA and MSA-2-Pt significantly decreased the melanoma B16F10 tumor and prolonged the survival, demonstrating significant anti-tumor effects. This finding provides promising new avenues for STING activation strategies in tumor immunotherapy.

Advanced Polymeric Nanoparticles for Cancer Immunotherapy: Materials Engineering, Immunotherapeutic Mechanism and Clinical Translation

Cancer immunotherapy, which leverages immune system components to treat malignancies, has emerged as a cornerstone of contemporary therapeutic strategies. Yet, critical concerns about the efficacy and safety of cancer immunotherapies remain formidable. Nanotechnology, especially polymeric nanoparticles (PNPs), offers unparalleled flexibility in manipulation-from the chemical composition and physical properties to the precision control of nanoassemblies. PNPs provide an optimal platform to amplify the potency and minimize systematic toxicity in a broad spectrum of immunotherapeutic modalities. In this comprehensive review, the basics of polymer chemistry, and state-of-the-art designs of PNPs from a physicochemical standpoint for cancer immunotherapy, encompassing therapeutic cancer vaccines, in situ vaccination, adoptive T-cell therapies, tumor-infiltrating immune cell-targeted therapies, therapeutic antibodies, and cytokine therapies are delineated. Each immunotherapy necessitates distinctively tailored design strategies in polymeric nanoplatforms. The extensive applications of PNPs, and investigation of their mechanisms of action for enhanced efficacy are particularly focused on. The safety profiles of PNPs and clinical research progress are discussed. Additionally, forthcoming developments and emergent trends of polymeric nano-immunotherapeutics poised to transform cancer treatment paradigms into clinics are explored.

Semiconducting polymer nanoprodrugs enable tumor-specific therapy via sono-activatable ferroptosis

Ferroptosis, a recently identified form of cell death, holds promise for cancer therapy, but concerns persist regarding its uncontrolled actions and potential side effects. Here, we present a semiconducting polymer nanoprodrug (SPNpro) featuring an innovative ferroptosis prodrug (DHU-CBA7) to induce sono-activatable ferroptosis for tumor-specific therapy. DHU-CBA7 prodrug incorporate methylene blue, ferrocene and urea bond, which can selectively and specifically respond to singlet oxygen (1O2) to turn on ferroptosis action via rapidly cleaving the urea bonds. DHU-CBA7 prodrug and a semiconducting polymer are self-assembled with an amphiphilic polymer to construct SPNpro. Ultrasound irradiation of SPNpro leads to the production of 1O2 via sonodynamic therapy (SDT) of the semiconducting polymer, and the generated 1O2 activated DHU-CBA7 prodrug to achieve sono-activatable ferroptosis. Consequently, SPNpro combine SDT with the controlled ferroptosis to effectively cure 4T1 tumors covered by 2-cm tissue with a tumor inhibition efficacy as high as 100 %, and also completely restrain tumor metastases. This study introduces a novel sono-activatable prodrug strategy for regulating ferroptosis, allowing for precise cancer therapy.

Ultrasound-Targeted Microbubble Destruction Enhances the Inhibitory Effect of Sonodynamic Therapy against Hepatocellular Carcinoma

Purpose: To assess the anticancer effect of microbubbles (MBs) in combination with sinoporphyrin sodium (DVDMS)-mediated sonodynamic therapy (SDT) for the in vitro and in vivo treatment of hepatocellular carcinoma (HCC). Methods: HepG2 cells were used for in vitro experiments. Reactive oxygen species (ROS) production was detected using 2',7'-dichlorodihydrofluorescein diacetate and singlet oxygen sensor green in vitro and in solution, respectively. Cytotoxicity was evaluated using a Cell Counting Kit 8 assay and the calcein AM/PI double-staining method. Annexin V-FITC/PI staining was employed to analyze the rate of cell apoptosis. Cell surface calreticulin exposure, high mobility group box 1 release, and adenosine triphosphate secretion were measured to detect immunogenic cell death (ICD). The anticancer effect of the combination therapy was further assessed in Hepa1-6 tumor-bearing mice. Results: Compared with SDT alone, ROS production in the MBs + SDT group was enhanced 1.2-fold (p < 0.0001). The cytotoxic effect of DVDMS-mediated SDT on HepG2 cells was concentration-dependent, and the additional application of MBs increased cytotoxicity. Additionally, MBs augmented the SDT-induced apoptosis rate from 33.26 ± 13.48 to 72.95 ± 7.95% (p < 0.01). Notably, our results demonstrated that MBs can enhance SDT-induced ICD. In in vivo experiments, SDT combined with MBs significantly reduced tumor volume, with negligible differences in mouse body weight. Furthermore, MBs effectively enhanced SDT-induced tumor tissue destruction. Conclusion: The present study indicates that MBs can markedly improve the anticancer effects of SDT in HCC.

Bifunctional black phosphorus quantum dots platform: Delivery and remarkable immunotherapy enhancement of STING agonist

Cancer immunotherapy has been developed to improve therapeutic effects for patients by activating the innate immune stimulator of interferon gene (STING) pathway. However, most patients cannot benefit from this therapy, mainly due to the problems of excessively low immune responses and lack of tumor specificity. Herein, we report a solution to these two problems by developing a bifunctional platform of black phosphorus quantum dots (BPQDs) for STING agonists. Specifically, BPQDs could connect targeted functional groups and regulate surface zeta potential by coordinating metal ions to increase loading (over 5 times) while maintaining high universality (7 STING agonists). The controlled release of STING agonists enabled specific interactions with their proteins, activating the STING pathway and stimulating the secretion release of immunosuppressive factors by phosphorylating TBK1 and IFN-IRF3 and secreting high levels of immunostimulatory cytokines, including IL-6, IFN-α, and IFN-β. Moreover, the immunotherapy was enhanced was enhanced mild photothermal therapy (PTT) of BPQDs platform, producing enough T cells to eliminate tumors and prevent tumor recurrence. This work facilitates further research on targeted delivery of small-molecule immune drugs to enhance the development of clinical immunotherapy.

Light/X-ray/ultrasound activated delayed photon emission of organic molecular probes for optical imaging: mechanisms, design strategies, and biomedical applications

Conventional optical imaging, particularly fluorescence imaging, often encounters significant background noise due to tissue autofluorescence under real-time light excitation. To address this issue, a novel optical imaging strategy that captures optical signals after light excitation has been developed. This approach relies on molecular probes designed to store photoenergy and release it gradually as photons, resulting in delayed photon emission that minimizes background noise during signal acquisition. These molecular probes undergo various photophysical processes to facilitate delayed photon emission, including (1) charge separation and recombination, (2) generation, stabilization, and conversion of the triplet excitons, and (3) generation and decomposition of chemical traps. Another challenge in optical imaging is the limited tissue penetration depth of light, which severely restricts the efficiency of energy delivery, leading to a reduced penetration depth for delayed photon emission. In contrast, X-ray and ultrasound serve as deep-tissue energy sources that facilitate the conversion of high-energy photons or mechanical waves into the potential energy of excitons or the chemical energy of intermediates. This review highlights recent advancements in organic molecular probes designed for delayed photon emission using various energy sources. We discuss distinct mechanisms, and molecular design strategies, and offer insights into the future development of organic molecular probes for enhanced delayed photon emission.

Nanosonosensitizer Optimization for Enhanced Sonodynamic Disease Treatment

Low-intensity ultrasound-mediated sonodynamic therapy (SDT), which, by design, integrates sonosensitizers and molecular oxygen to generate therapeutic substances (e.g., toxic hydroxyl radicals, superoxide anions, or singlet oxygen) at disease sites, has shown enormous potential for the effective treatment of a variety of diseases. Nanoscale sonosensitizers play a crucial role in the SDT process because their structural, compositional, physicochemical, and biological characteristics are key determinants of therapeutic efficacy. In particular, advances in materials science and nanotechnology have invigorated a series of optimization strategies for augmenting the therapeutic efficacy of nanosonosensitizers. This comprehensive review systematically summarizes, discusses, and highlights state-of-the-art studies on the current achievements of nanosonosensitizer optimization in enhanced sonodynamic disease treatment, with an emphasis on the general design principles of nanosonosensitizers and their optimization strategies, mainly including organic and inorganic nanosonosensitizers. Additionally, recent advancements in optimized nanosonosensitizers for therapeutic applications aimed at treating various diseases, such as cancer, bacterial infections, atherosclerosis, and autoimmune diseases, are clarified in detail. Furthermore, the biological effects of the improved nanosonosensitizers for versatile SDT applications are thoroughly discussed. The review concludes by highlighting the current challenges and future opportunities in this rapidly evolving research field to expedite its practical clinical translation and application.

Recent Progress in Photothermal, Photodynamic and Sonodynamic Cancer Therapy: Through the cGAS-STING Pathway to Efficacy-Enhancing Strategies

Photothermal, photodynamic and sonodynamic cancer therapies offer opportunities for precise tumor ablation and reduce side effects. The cyclic guanylate adenylate synthase-stimulator of interferon genes (cGAS-STING) pathway has been considered a potential target to stimulate the immune system in patients and achieve a sustained immune response. Combining photothermal, photodynamic and sonodynamic therapies with cGAS-STING agonists represents a newly developed cancer treatment demonstrating noticeable innovation in its impact on the immune system. Recent reviews have concentrated on diverse materials and their function in cancer therapy. In this review, we focus on the molecular mechanism of photothermal, photodynamic and sonodynamic cancer therapies and the connected role of cGAS-STING agonists in treating cancer.

Sono-Triggered Cascade Lactate Depletion by Semiconducting Polymer Nanoreactors for Cuproptosis-Immunotherapy of Pancreatic Cancer

The high level of lactate in tumor microenvironment not only promotes tumor development and metastasis, but also induces immune escape, which often leads to failures of various tumor therapy strategies. We here report a sono-triggered cascade lactate depletion strategy by using semiconducting polymer nanoreactors (SPNLCu) for cancer cuproptosis-immunotherapy. The SPNLCu mainly contain a semiconducting polymer as sonosensitizer, lactate oxidase (LOx) conjugated via a reactive oxygen species (ROS)-cleavable linker and chelated Cu2+. Upon ultrasound (US) irradiation, the semiconducting polymer generates singlet oxygen (1O2) to cut ROS-cleavable linker to allow the release of LOx that catalyzes lactate depletion to produce hydrogen peroxide (H2O2). The Cu2+ will be reduced to Cu+ in tumor microenvironment, which reacts with the produced H2O2 to obtain hydroxyl radical (⋅OH) that further improves LOx release via destroying ROS-cleavable linkers. As such, sono-triggered cascade release of LOx achieves effective lactate depletion, thus relieving immunosuppressive roles of lactate. Moreover, the toxic Cu+ induces cuproptosis to cause immunogenic cell death (ICD) for activating antitumor immunological effect. SPNLCu are used to treat both subcutaneous and deep-tissue orthotopic pancreatic cancer with observably enhanced efficacy in restricting the tumor growths. This study thus provides a precise and effective lactate depletion tactic for cancer therapy.

Membrane Disruption-Enhanced Photodynamic Therapy against Gram-Negative Bacteria by a Peptide-Photosensitizer Conjugate

Photodynamic therapy (PDT) emerges as a promising strategy for combating bacteria with minimal drug resistance. However, a significant hurdle lies in the ineffectiveness of most photosensitizers against Gram-negative bacteria, primarily attributable to their characteristic impermeable outer membrane (OM) barrier. To tackle this obstacle, we herein report an amphipathic peptide-photosensitizer conjugate (PPC) with intrinsic outer membrane disruption capability to enhance PDT efficiency against Gram-negative bacteria. PPC is constructed by conjugating a hydrophilic ultrashort cationic peptide to a hydrophobic photosensitizer. PPC could efficiently bind to the OM of Gram-negative bacteria through electrostatic adsorption, and subsequently disrupt the structural integrity of the OM. Mechanistic investigations revealed that PPC triggers membrane disruption by binding to both lipopolysaccharide (LPS) and phospholipid leaflet in the OM, enabling effective penetration of PPC into the Gram-negative bacteria interior. Upon light irradiation, PPC inside bacteria generates singlet oxygen not only to effectively decrease the survival of Gram-negative bacteria P. aeruginosa and E. coli to nearly zero in vitro, but also successfully cure the full-thickness skin infection and bacterial keratitis (BK) induced by P. aeruginosa in animal models. Thus, this study provides a broad-spectrum antibacterial phototherapeutic design strategy by the synergistic action of membrane disruption and PDT to combat Gram-negative bacteria.

A next-generation STING agonist MSA-2: From mechanism to application

The stimulator of interferon genes (STING) connects the innate and adaptive immune system and plays a significant role in antitumor immunity. Over the past decades, endogenous and CDN-derived STING agonists have been a hot topic in the research of cancer immunotherapies. However, these STING agonists are either in infancy with limited biological effects or have failed in clinical trials. In 2020, a non-nucleotide STING agonist MSA-2 was identified, which exhibited satisfactory antitumor effects in animal studies and is amenable to oral administration. Due to its distinctive binding mode and enhanced bioavailability, there have been accumulating interests and an array of studies on MSA-2 and its derivatives, spanning its structure-activity relationship, delivery systems, applications in combination therapies, etc. Here, we provide a comprehensive review of MSA-2 and interventional strategies based on this family of STING agonists to help more researchers extend the investigation on MSA-2 in the future.

The emergence of cancer sono-immunotherapy

Owing to its remarkable ease of use, ultrasound has recently been explored for stimulating or amplifying immune responses during cancer therapy, termed 'sono-immunotherapy'. Ultrasound can cause immunogenic cell death in cancer cells via thermal and nonthermal effects to regulate the tumor microenvironment, thereby priming anticancer immunity; by integrating well-designed biomaterials, novel sono-immunotherapy approaches with augmented efficacy can also be developed. Here, we review the advances in sono-immunotherapy for cancer treatment and summarize existing limitations along with potential trends. We offer emerging insights into this realm, which might prompt breakthroughs and expand its potential applications to other diseases.

Exosome-Inhibiting Polymeric Sonosensitizer for Tumor-Specific Sonodynamic Immunotherapy

Combination cancer immunotherapy based on electromagnetic energy and immunotherapy shows potent anti-cancer efficacy. However, as a factor that mediates tumor metastasis and immune suppression, the impact of tumor exosomes on therapy under electromagnetic energy stimulation remains unclear. Herein, findings indicate that sonodynamic therapy (SDT) increases serum exosome levels by inducing apoptotic exosomes and loosening the tumor extracellular matrix, promoting lung metastasis. To address this problem, an exosome-inhibiting polymeric sonosensitizer (EIPS) selectively inhibiting tumor exosome generation in response to the tumor biomarker is synthesized. EIPS consists of a semiconducting polymer backbone capable of inducing SDT and a poly(ethylene glycol) layer conjugated with a tumor-specific enzyme-responsive exosome inhibitor prodrug. After being cleaved by tumor Cathepsin B, EIPS releases active exosome inhibitors, preventing tumor exosome-mediated immune suppression and lung metastasis. As a result, EIPS elicits robust antitumor effects through the synergistic effect of SDT and tumor exosome inhibition, completely preventing lung metastasis and establishing a long-term immune memory effect. This is the first example showing that combining SDT with tumor-specific exosome inhibition can elicit a potent immune response without the help of typical immune agonists.

Dual-enzyme decorated semiconducting polymer nanoagents for second near-infrared photoactivatable ferroptosis-immunotherapy

Enzymes provide a class of potential options to treat cancer, while the precise regulation of enzyme activities for effective and safe therapeutic actions has been poorly reported. Dual-enzyme decorated semiconducting polymer nanoagents for second near-infrared (NIR-II) photoactivatable ferroptosis-immunotherapy are reported in this study. Such nanoagents (termed SPHGA) consist of hemoglobin (Hb)-based semiconducting polymer (SP@Hb), adenosine deaminase (ADA) and glucose oxidase (GOx) with loadings in a thermal-responsive nanoparticle shell. NIR-II photoactivation of SPHGA results in the generation of heat to trigger on-demand releases of two enzymes (ADA and GOx) via destroying the thermal-responsive nanoparticle shells. In the tumor microenvironment, GOx oxidizes glucose to form hydrogen peroxide (H2O2), which promotes the Fenton reaction of iron in SP@Hb, resulting in an enhanced ferroptosis effect and immunogenic cell death (ICD). In addition, ADA degrades high-level adenosine to reverse the immunosuppressive microenvironment, thus amplifying antitumor immune responses. Via NIR-II photoactivatable ferroptosis-immunotherapy, SPHGA shows an improved effect to absolutely remove bilateral tumors and effectively suppress tumor metastases in subcutaneous 4T1 breast cancer models. This study presents a dual-enzyme-based nanoagent with controllable therapeutic actions for effective and precise cancer therapy.

Ultrasound activated probe for disease imaging and therapy In-Vivo

Sonodynamic therapy (SDT) is the use of ultrasound (US) to excite sonosensitizers to produce reactive oxygen species (ROS) to induce tumor cell death, thereby achieving therapeutic purposes. Based on the strong tissue penetration ability of ultrasound, SDT can realize the treatment of deeper tumors, and it is targeted, can be specifically concentrated at the tumor site, and has little impact on surrounding normal tissues. It has broad clinical transformation prospects. Therefore, sonosensitizers are the key to SDT, and the exploration of sonosensitizers with excellent therapeutic performance has received great attention. We reviewed the development of ultrasound-inspired sound sensitizers for imaging and treatment. First, different types of sonosensitizers are introduced, the construction and performance of inorganic, organic and hybrid types of sonosensitizers are evaluated, followed by a review of different image-guided SDT, and finally the key problems and solutions in this field are discussed in detail.

Antitumor Effect of Platinum-Modified STING Agonist MSA-2

The stimulator of interferon genes (STING)-activated innate immune pathway is strong and durable for tumor immunotherapy. MSA-2 is an available non-nucleotide human STING agonist that promotes the tumor immunotherapy of STING activation. However, strategies for remolding and improving the immunotherapy effects of MSA-2 are of value for clinical applications. Here, we synthesized the platinum salt-modified MSA-2 (MSA-2-Pt) due to platinum salt being a classic chemotherapeutic drug. We found that MSA-2-Pt could achieve double-effect antitumor immunotherapy, including inducing cell death by platinum and activating the STING pathway by MSA-2. In the colon carcinoma MC38 model (sensitive to immune checkpoint immunotherapy tumor) and melanoma B16F10 model (poorly immunogenic and highly aggressive tumor), the MSA-2-Pt had a good antitumor effect, which was a little better than MSA-2 with intratumor injections. The results present a promising strategy for STING activation in tumor immunotherapy and broadening platinum-based drugs.

Nanomaterial-encapsulated STING agonists for immune modulation in cancer therapy

The cGAS-STING signaling pathway has emerged as a critical mediator of innate immune responses, playing a crucial role in improving antitumor immunity through immune effector responses. Targeting the cGAS-STING pathway holds promise for overcoming immunosuppressive tumor microenvironments (TME) and promoting effective tumor elimination. However, systemic administration of current STING agonists faces challenges related to low bioavailability and potential adverse effects, thus limiting their clinical applicability. Recently, nanotechnology-based strategies have been developed to modulate TMEs for robust immunotherapeutic responses. The encapsulation and delivery of STING agonists within nanoparticles (STING-NPs) present an attractive avenue for antitumor immunotherapy. This review explores a range of nanoparticles designed to encapsulate STING agonists, highlighting their benefits, including favorable biocompatibility, improved tumor penetration, and efficient intracellular delivery of STING agonists. The review also summarizes the immunomodulatory impacts of STING-NPs on the TME, including enhanced secretion of pro-inflammatory cytokines and chemokines, dendritic cell activation, cytotoxic T cell priming, macrophage re-education, and vasculature normalization. Furthermore, the review offers insights into co-delivered nanoplatforms involving STING agonists alongside antitumor agents such as chemotherapeutic compounds, immune checkpoint inhibitors, antigen peptides, and other immune adjuvants. These platforms demonstrate remarkable versatility in inducing immunogenic responses within the TME, ultimately amplifying the potential for antitumor immunotherapy.

Leveraging Semiconducting Polymer Nanoparticles for Combination Cancer Immunotherapy

Cancer immunotherapy has become a promising method for cancer treatment, bringing hope to advanced cancer patients. However, immune-related adverse events caused by immunotherapy also bring heavy burden to patients. Semiconducting polymer nanoparticles (SPNs) as an emerging nanomaterial with high biocompatibility, can eliminate tumors and induce tumor immunogenic cell death through different therapeutic modalities, including photothermal therapy, photodynamic therapy, and sonodynamic therapy. In addition, SPNs can work as a functional nanocarrier to synergize with a variety of immunomodulators to amplify anti-tumor immune responses. In this review, SPNs-based combination cancer immunotherapy is comprehensively summarized according to the SPNs' therapeutic modalities and the type of loaded immunomodulators. The in-depth understanding of existing SPNs-based therapeutic modalities will hopefully inspire the design of more novel nanomaterials with potent anti-tumor immune effects, and ultimately promote their clinical translation.

Semiconducting Polymers for Cancer Immunotherapy

As a monumental breakthrough in cancer treatment, immunotherapy has attracted tremendous attention in recent years. However, one challenge faced by immunotherapy is the low response rate and the immune-related adverse events (irAEs). Therefore, it is important to explore new therapeutic strategies and platforms for boosting therapeutic benefits and decreasing the side effects of immunotherapy. In recent years, semiconducting polymer (SP), a category of organic materials with π-conjugated aromatic backbone, has been attracting considerable attention because of their outstanding characteristics such as excellent photophysical features, good biosafety, adjustable chemical flexibility, easy fabrication, and high stability. With these distinct advantages, SP is extensively explored for bioimaging and photo- or ultrasound-activated tumor therapy. Here, the recent advancements in SP-based nanomedicines are summarized for enhanced tumor immunotherapy. According to the photophysical properties of SPs, the cancer immunotherapies enabled by SPs with the photothermal, photodynamic, or sonodynamic functions are highlighted in detail, with a particular focus on the construction of combination immunotherapy and activatable nanoplatforms to maximize the benefits of cancer immunotherapy. Herein, new guidance and comprehensive insights are provided for the design of SPs with desired photophysical properties to realize maximized effectiveness of required biomedical applications.

Multistage Self-Assembled Nanomaterials for Cancer Immunotherapy

Advances in nanotechnology have brought innovations to cancer therapy. Nanoparticle-based anticancer drugs have achieved great success from bench to bedside. However, insufficient therapy efficacy due to various physiological barriers in the body remains a key challenge. To overcome these biological barriers and improve the therapeutic efficacy of cancers, multistage self-assembled nanomaterials with advantages of stimuli-responsiveness, programmable delivery, and immune modulations provide great opportunities. In this review, we describe the typical biological barriers for nanomedicines, discuss the recent achievements of multistage self-assembled nanomaterials for stimuli-responsive drug delivery, highlighting the programmable delivery nanomaterials, in situ transformable self-assembled nanomaterials, and immune-reprogramming nanomaterials. Ultimately, we perspective the future opportunities and challenges of multistage self-assembled nanomaterials for cancer immunotherapy.