Sonodynamic Therapy with Metal Complexes: A New Promise in Cancer Therapy

Sonodynamic Cancer Therapy by Mn(I)-tricarbonyl Complexes via Ultrasound-triggered CO Release and ROS Generation

A novel ferrocene conjugated Mn(I)-tricarbonyl complex viz [Mn(Fc-tpy)(CO)3Br] (Mn2) where, Fc-tpy=4'-ferrocenyl-2,2':6',2''-terpyridine was synthesized and fully characterized along with its non-ferrocene analog [Mn(Ph-tpy)(CO)3Br] Ph-tpy=4'-phenyl-2,2':6',2''-terpyridine (Mn1) for ultrasound (US) activated anticancer applications. The X-ray structure of Mn2 confirmed its distorted octahedral geometry. Mn1 and Mn2, for the first time, showed US-triggered release of CO and ROS generation (1O2 and ⋅OH) in an aqueous solution from any Mn(I)-tricarbonyl complexes, indicating its potential for synergetic CO gas therapy and sonodynamic therapy. The above-mentioned in-solution chemistry was successfully translated into in vitro cellular models. These complexes showed unprecedented US-triggered toxicity against T-cell lymphoma and human breast cancer cells (IC50 for Mn2<1 μM) while were minimally toxic without US or against normal spleen and human embryonic kidney cells. Mn2 was ca. 12 fold more anticancer active than Mn1, indicating that the ferrocene conjugation augmented the US sensitivity. The apoptotic sonotoxicity of Mn2 was due to US-promoted mitochondrial depolarization via ROS generation and CO release. The apoptosis was triggered by caspase 3 activation. This is the first report of Mn(I)-tricarbonyl-based sonosensitizers for cancer SDT. Overall, this study, for the first time, establishes the effectiveness of 3d metal carbonyls in SDT.

Recent Advances and Future Directions in Sonodynamic Therapy for Cancer Treatment

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

Layer-by-Layer Nanoparticles for Calcium Overload in situ Enhanced Reactive Oxygen Oncotherapy

Background

Challenges such as poor drug selectivity, non-target reactivity, and the development of drug resistance continue to pose significant obstacles in the clinical application of cancer therapeutic drugs. To overcome the limitations of drug resistance in chemotherapy, a viable treatment strategy involves designing multifunctional nano-platforms that exploit the unique physicochemical properties of tumor microenvironment (TME).

Methods

Herein, layer-by-layer nanoparticles with polyporous CuS as delivery vehicles, loaded with a sonosensitizer (tetra-(4-aminophenyl) porphyrin, TAPP) and sequentially functionalized with pH-responsive CaCO3, targeting group hyaluronic acid (HA) were designed and synthesized for synergistic treatment involving chemodynamic therapy (CDT), sonodynamic therapy (SDT), photothermal therapy (PTT), and calcium overload. Upon cleavage in an acidic environment, CaCO3 nanoparticles released TAPP and Ca2+, with TAPP generating 1O2 under ultrasound trigger. Exposed CuS produced highly cytotoxic ·OH in response to H2O2 and also exhibited a strong PTT effect.

Results

CuS@TAPP-CaCO3/HA (CTCH) delivered an enhanced ability to release more Ca2+ under acidic conditions with a pH value of 6.5, which in situ causes damage to HeLa mitochondria. In vitro and in vivo experiments both demonstrated that mitochondrial dysfunction greatly amplified the damage caused by reactive oxygen species (ROS) to tumor, which strongly confirms the synergistic effect between calcium overload and reactive oxygen therapy.

Conclusion

Collectively, the development of CTCH presents a novel therapeutic strategy for tumor treatment by effectively responding to the acidic TME, thus holding significant clinical implications.

Facile synthesis of a hydrazone-based zinc(ii) complex for ferroptosis-augmented sonodynamic therapy

Sonodynamic therapy (SDT), as a novel non-invasive cancer treatment modality derived from photodynamic therapy (PDT), has drawn much attention due to its unique advantages for the treatment of deep tumors. Zinc-based complexes have shown great clinical prospect in PDT due to their excellent photodynamic activity and biosafety. However, their application in SDT has lagged seriously behind. Exploring efficient zinc-based complexes as sono-sensitizers remains an appealing but significantly challenging task. Herein, we develop a hydrazone ligand-based zinc complex (ZnAMTC) for SDT of tumors in vitro and in vivo. ZnAMTC was facilely synthesized via a two-step reaction from low-cost raw materials without tedious purification. It shows negligible dark toxicity and can produce singlet oxygen (1O2) under ultrasound (US) irradiation, exhibiting high sono-cytotoxicity to various cancer cells. Mechanism studies show that ZnAMTC can effectively reduce the levels of glutathione (GSH) and glutathione peroxidase 4 (GPX4) under US irradiation and later cause ferroptosis of cancer cells. In vivo studies further demonstrate that ZnAMTC exhibits efficient tumor growth inhibition under US irradiation and has good biosafety. This work provides useful insights into the design of first-row transition metal complexes for SDT application.

Nanomedicine for T-Cell Mediated Immunotherapy

T-cell immunotherapy offers outstanding advantages in the treatment of various diseases, and with the selection of appropriate targets, efficient disease treatment can be achieved. T-cell immunotherapy has made great progress, but clinical results show that only a small proportion of patients can benefit from T-cell immunotherapy. The extensive mechanistic work outlines a blueprint for using T cells as a new option for immunotherapy, but also presents new challenges, including the balance between different fractions of T cells, the inherent T-cell suppression patterns in the disease microenvironment, the acquired loss of targets, and the decline of T-cell viability. The diversity, flexibility, and intelligence of nanomedicines give them great potential for enhancing T-cell immunotherapy. Here, how T-cell immunotherapy strategies can be adapted with different nanomaterials to enhance therapeutic efficacy is discussed. For two different pathological states, immunosuppression and immune activation, recent advances in nanomedicines for T-cell immunotherapy in diseases such as cancers, rheumatoid arthritis, systemic lupus erythematosus, ulcerative colitis, and diabetes are summarized. With a focus on T-cell immunotherapy, this review highlights the outstanding advantages of nanomedicines in disease treatment, and helps advance one's understanding of the use of nanotechnology to enhance T-cell immunotherapy.

De Novo Designed Ru(II) Metallacycle as a Microenvironment-Adaptive Sonosensitizer and Sonocatalyst for Multidrug-Resistant Biofilms Eradication

Albeit sonodynamic therapy (SDT) has achieved encouraging progress in microbial sterilization, the scarcity of guidelines for designing highly effective sonosensitizers and the intricate biofilm microenvironment (BME), substantially hamper the therapeutic efficacy against biofilm infections. To address the bottlenecks, we innovatively design a Ru(II) metallacycle-based sonosensitizer/sonocatalyst (named Ru-A3-TTD) to enhance the potency of sonotherapy by employing molecular engineering strategies tailored to BME. Our approach involves augmenting Ru-A3-TTD's production of ultrasonic-triggered reactive oxygen species (ROS), surpassing the performance of commercial sonosensitizers, through a straightforward but potent π-expansion approach. Within the BME, Ru-A3-TTD synergistically amplifies sonotherapeutic efficacy via triple-modulated approaches: (i) effective alleviation of hypoxia, leading to increased ROS generation, (ii) disruption of the antioxidant defense system, which shields ROS from glutathione consumption, and (iii) enhanced biofilm penetration, enabling ROS production in deep sites. Notably, Ru-A3-TTD sono-catalytically oxidizes NADPH, a critical coenzyme involved in antioxidant defenses. Consequently, Ru-A3-TTD demonstrates superior biofilm eradication potency against multidrug-resistant Escherichia coli compared to conventional clinical antibiotics, both in vitro and in vivo. To our knowledge, this study represents the pioneering instance of a supramolecular sonosensitizer/sonocatalyst. It provides valuable insights into the structure-activity relationship of sonosensitizers and paves a promising pathway for the treatment of biofilm infections.

Combined photothermal and sonodynamic therapy using a 2D black phosphorus nanosheets loaded coating for efficient bacterial inhibition and bone-implant integration

Surgical site infection (SSI) remains a major threat for implant failure in orthopedics. Herein, we report a dual-functional coating on Ti implants (named Ti/PDA/BP) with the integration of two-dimensional (2D) photo-sono sensitive black phosphorus nanosheets (BPNSs) and polydopamine (PDA) for efficient bacterial inhibition and bone-implant integration. For the first time, we employ BPNSs as generators of reactive radicals (ROS) under ultrasound (US) stimuli for implant associated infection. Additionally, the application of PDA improves the stability of BPNSs, the biocompatibility and photothermal performance of this hybrid coating. The as-prepared Ti/PDA/BP coating exhibits superior biocompatibility, bioactivity, photothermal and sonodynamic conversion abilities. Owing to the synergistic effect of hyperthermia and ·OH, Ti/PDA/BP damages the membrane and antioxidant system of Staphylococcus aureus, reaching a high antibacterial activity of 96.6% in vitro and 97.3% in vivo with rapid 10 min NIR irradiation and 20 min US treatment. In addition, we firstly unveil the significant effect of Ti/PDA/BP-based sonodynamic therapy (SDT) on bacterial membrane and oxidative stress at the transcriptome level. Moreover, the Ti/PDA/BP coating remarkably promotes osteogenesis in vitro and bone-implant osseointegration in vivo. Overall, development of Ti/PDA/BP bioactive coating provides a new strategy for combating the implant associated infection.

Amplifying the efficacy of ALA-based prodrugs for photodynamic therapy using nanotechnology

5-aminolevulinic acid (ALA) is a clinically approved prodrug involved in intracellular Heme biosynthesis to produce the natural photosensitizer (PS) Protoporphyrin IX (PpIX). ALA based photodynamic therapy (PDT) has been used to treat various malignant and non-malignant diseases. However, natural ALA has disadvantages such as weak lipophilicity, low stability and poor bioavailability, greatly reducing its clinical performance. The emerging nanotechnology is expected to address these limitations and thus improve the therapeutic outcomes. Herein, we summarized important recent advances in the design of ALA-based prodrugs using nanotechnology to improve the efficacy of PDT. The potential limitations and future perspectives of ALA-based nanomedicines are also briefly presented and discussed.

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.

A Two-In-One Nanoprodrug for Photoacoustic Imaging-Guided Enhanced Sonodynamic Therapy

Sonodynamic therapy (SDT) is garnering considerable attention in cancer treatment due to its non-invasive nature and the potential of spatiotemporal control. However, the high level of glutathione (GSH) in cancer cells can alleviate the SDT-mediated ROS-damages, resulting in a reduced SDT effect. Here, a two-in-one nano-prodrug for photoacoustic imaging-guided enhanced SDT against skin cancers is synthesized. A dual-prodrug molecule (DOA) of sulfide dioxide (SO₂ ) and 5-aminolevulinic acid (ALA) is first synthesized and then co-assembled with methoxyl poly(ethylene glycol)-b-poly(l-lysine) (mPEG-b-PLL) to generate the two-in-one prodrug nanoparticles (P-DOA NPs). The P-DOA NPs simultaneously released ALA and SO₂ in response to the overexpressed GSH in tumor cells. The released ALA is metabolically converted into protoporphyrin IX (PpIX) in tumor cells for SDT and photoacoustic imaging. Meanwhile, the released SO₂ , together with the consumption of GSH based on the reaction of DOA in P-DOA NPs with intracellular GSH, can significantly increase the intracellular ROS content, leading to enhanced SDT. As a result, the P-DOA NPs significantly inhibited the growth of melanoma and squamous cell carcinoma xenografts in mouse models under the guidance of real-time photoacoustic imaging. Therefore, this novel two-in-one nano-prodrug is promising for effective SDT against skin cancers.