Acidity-responsive nanocages as robust reactive oxygen species generators with butterfly effects for maximizing oxidative damage and enhancing cancer therapy

Advances in nanotherapeutics for tumor treatment by targeting calcium overload

Traditional antitumor strategies are facing challenges such as low therapeutic efficacy and high side effects, highlighting the significance of developing non-toxic or low-toxic alternative therapies. As a second messenger, calcium ion (Ca2+) plays an important role in cellular metabolism and communication. However, persistent Ca2+ overload leads to mitochondrial structural and functional dysfunction and ultimately induced apoptosis. Therefore, an antitumor strategy based on calcium overload is a promising alternative. Here, we first reviewed the classification of calcium-based nanoparticles (NPs) for exogenous Ca2+ overload, including calcium carbonate (CaCO3), calcium phosphate (CaP), calcium peroxide (CaO2), and hydroxyapatite (HA), calcium hydroxide, etc. Next, the current endogenous Ca2+ overload strategies were summarized, including regulation of Ca2+ channels, destruction of membrane integrity, induction of abnormal intracellular acidity and oxidative stress. Due to the specificity of the tumor microenvironment, it is difficult to completely suppress tumor development with monotherapy. Therefore, we reviewed the progress based on mitochondrial Ca2+ overload, which improved the treatment efficiency by combining photothermal therapy (PTT), photodynamic therapy (PDT), chemodynamic therapy (CDT), sonodynamic therapy (SDT), immunogenic cell death (ICD) and gas therapy. We further explored in detail the advantages and promising new targets of this combination antitumor strategies to better address future opportunities and challenges.

Acidity-Responsive Fe-PDA@CaCO3 Nanoparticles for Photothermal-Enhanced Calcium-Overload- and Reactive-Oxygen-Species-Mediated Tumor Therapy

Calcium-overload-mediated tumor therapy has received considerable interest in oncology. However, its efficacy has been proven to be inadequate due to insufficient calcium ion concentration at the tumor site coupled with challenges in facilitating efficient calcium uptake by tumors, leading to unsatisfactory therapeutic outcomes. In the present study, calcium carbonate nanoshell mineralized ferric polydopamine nanoparticles (Fe-PDA@CaCO3 NPs) were prepared for achieving Ca2+-overload-mediated tumor therapy. Upon entering the tumor site, the pH-responsive CaCO3 layer, acting as a "Ca2+ storage pool", rapidly degraded and released high quantities of free Ca2+ within the weakly acidic environment. The Fe-PDA core, with its excellent photothermal conversion properties, could significantly increase the temperature upon exposure to near-infrared (NIR) light irradiation, thereby activating the TRPV1 channel and leading to a large influx of released Ca2+ into the cytoplasm. Furthermore, the exposed Fe-PDA core could react with the tumor-overexpressed hydrogen peroxide (H2O2) to efficiently produce hydroxyl radicals (•OH), significantly increasing intracellular reactive oxygen species (ROS) levels and thus inhibiting the activity of the Ca2+ efflux pump, resulting in a high intracellular Ca2+ concentration. Ultimately, the increase in calcium/ROS levels could disrupt mitochondrial homeostasis and activate the apoptosis pathway. The current work presents a promising approach for tumor therapy using photothermal-enhanced calcium-overload-mediated ion interference therapy and chemodynamic therapy.

MOF-derived cobalt-iron containing nanocomposite with cascade-catalytic activities for multimodal synergistic tumor therapy

Reactive oxygen species (ROS)-driven chemodynamic therapy has emerged as a promising anti-tumor strategy. However, the insufficient hydrogen peroxide (H2O2) supply in tumor microenvironment results in a low Fenton reaction rate and subsequently poor ROS production and therapeutic efficacy. Herein, we report on a new nanocomposite MIL-53@ZIF-67/S loaded with doxorubicin and glucose oxidase, which is decomposed under the acidic tumor microenvironment to release Fe3+, Co3+, glucose oxidase, and doxorubicin. The released content leads to synergistic anti-tumor effect through the following manners: 1) doxorubicin is directly used for chemotherapy; 2) Fe3+and Co3+ result in glutathione depletion and Fenton reaction activation through Fe2+ and Co2+ generation to achieve chemodynamic therapy; 3) glucose oxidase continuously catalyzes glucose consumption to induce starvation of the cancer cells, and 4) at the same time the produced gluconic acid and H2O2 significantly promote Fenton reaction and further boost chemodynamic therapy. This work not only demonstrates the high anti-tumor effect of the new nanocomposite, but also provides an innovative strategy for the development of a multi-in-one nanoplatform for cancer therapy.

A Lactate-Depleting metal organic framework-based nanocatalyst reinforces intratumoral T cell response to boost anti-PD1 immunotherapy

Infiltration and activation of intratumoral T lymphocytes are critical for immune checkpoint blockade (ICB) therapy. Unfortunately, the low tumor immunogenicity and immunosuppressive tumor microenvironment (TME) induced by tumor metabolic reprogramming cooperatively hinder the ICB efficacy. Herein, we engineered a lactate-depleting MOF-based catalytic nanoplatform (LOX@ZIF-8@MPN), encapsulating lactate oxidase (LOX) within zeolitic imidazolate framework-8 (ZIF-8) coupled with a coating of metal polyphenol network (MPN) to reinforce T cell response based on a "two birds with one stone" strategy. LOX could catalyze the degradation of the immunosuppressive lactate to promote vascular normalization, facilitating T cell infiltration. On the other hand, hydrogen peroxide (H2O2) produced during lactate depletion can be transformed into anti-tumor hydroxyl radical (•OH) by the autocatalytic MPN-based Fenton nanosystem to trigger immunogenic cell death (ICD), which largely improved the tumor immunogenicity. The combination of ICD and vascular normalization presents a better synergistic immunopotentiation with anti-PD1, inducing robust anti-tumor immunity in primary tumors and recurrent malignancies. Collectively, our results demonstrate that the concurrent depletion of lactate to reverse the immunosuppressive TME and utilization of the by-product from lactate degradation via cascade catalysis promotes T cell response and thus improves the effectiveness of ICB therapy.

Immunoantitumor Activity and Oxygenation Effect Based on Iron-Copper-Doped Folic Acid Carbon Dots

Cancer metastasis and recurrence are closely associated with immunosuppression and a hypoxic tumor microenvironment. Chemodynamic therapy (CDT) and photothermodynamic therapy (PTT) have been shown to induce immunogenic cell death (ICD), effectively inhibiting cancer metastasis and recurrence when combined with immune adjuvants. However, the limited efficacy of Fenton's reaction and suboptimal photothermal effect present significant challenges for successfully inducing ICD through CDT and PTT. This paper described the synthesis and immunoantitumor activity of the novel iron-copper-doped folic acid carbon dots (CFCFB). Copper-doped folic acid carbon dots (Cu-FACDs) were initially synthesized via a hydrothermal method, using folic acid and copper gluconate as precursors. Subsequently, the nanoparticles CFCFB were obtained through cross-linking and self-assembly of Cu-FACDs with ferrocene dicarboxylic acid (FeDA) and 3-bromopyruvic acid (3BP). The catalytic effect of carbon dots in CFCFB enhanced the activity of the Fenton reaction, thereby promoting CDT-induced ICD and increasing the intracellular oxygen concentration. Additionally, 3BP inhibited cellular respiration, further amplifying the oxygen concentration. The photothermal conversion efficiency of CFCFB reached 55.8%, which significantly enhanced its antitumor efficacy through photothermal therapy. Immunofluorescence assay revealed that treatment with CFCFB led to an increased expression of ICD markers, including calreticulin (CRT) and ATP, as well as extracellular release of HMGB-1, indicating the induction of ICD by CFCFB. Moreover, the observed downregulation of ARG1 expression indicates a transition in the tumor microenvironment from an immunosuppressive state to an antitumor state following treatment with CFCFB. The upregulation of IL-2 and CD8 expression facilitated the differentiation of effector T cells, resulting in an augmented population of CD8+ T cells, thereby indicating the activation of systemic immune response.

Calcium Carbonate-Based Nanoplatforms for Cancer Therapeutics: Current State of Art and Future Breakthroughs

With the rapid development of nanotechnology, nanomaterials have shown immense potential for antitumor applications. Nanosized calcium carbonate (CaCO3) materials exhibit excellent biocompatibility and degradability, and have been utilized to develop platform technologies for cancer therapy. These materials can be engineered to carry anticancer drugs and functional groups that specifically target cancer cells and tissues, thereby enhancing therapeutic efficacy. Additionally, their physicochemical properties can be tailored to enable stimuli-responsive therapy and precision drug delivery. This Review consolidates recent literatures focusing on the synthesis, physicochemical properties, and multimodal antitumor therapies of CaCO3-based nanoplatforms (CBN). We also explore the current challenges and potential breakthroughs in the development of CBN for antitumor applications, providing a valuable reference for researchers in the field.

Palladium-based multifunctional nanoparticles for combined chemodynamic/photothermal and calcium overload therapy of tumors

Due to the high mortality and incidence rates associated with tumors and the specificity of the tumor microenvironment (TME), it is difficult to achieve a complete cure for tumors using a single therapy. In this study, calcium carbonate-modified palladium hydride nanoparticles (PdH@CaCO3) were prepared and utilized for the combined treatment of tumors through chemodynamic therapy (CDT)/photothermal therapy (PTT) and calcium overload therapy. After entering tumor cells, PdH@CaCO3 releases calcium ions (Ca2+) and PdH once it reaches the TME due to the pH reactivity of the calcium carbonate coating. The mitochondrial membrane potential is lowered by the Ca2+, leading to irreversible cell damage. Meanwhile, PdH reacts with excessive hydrogen peroxide (H2O2) in the TME via the Fenton reaction, generating hydroxyl radicals (·OH). Moreover, PdH is an excellent photothermal agent that can kill tumor cells under laser irradiation, leading to significant anti-tumor effects. In vitro and in vivo studies have demonstrated that PdH@CaCO3 could combine CDT/PTT and calcium overload therapy, exhibiting great clinical potential in the treatment of tumors.

RuCu Nanosheets with Ultrahigh Nanozyme Activity for Chemodynamic Therapy

Nanoenzymes have been widely explored for chemodynamic therapy (CDT) in cancer treatment. However, poor catalytic efficiency of nanoenzymes, especially in the tumor microenvironment with insufficient H2 O2 and mild acidity, limits the effect of CDT. Herein, a new ultrathin RuCu nanosheet (NS) based nanoenzyme which has a large specific surface area and abundant channels and defects is developed. The RuCu NSs show superb catalytic efficiency for the oxidation of peroxidase substrate H2 O2 at a wide range of pH and their catalytic efficiency (kcat /Km = 177.2 m-1  s-1 ) is about 14.9 times higher than that of the single-atom catalyst FeN3 P. Besides being an efficient nanozyme as peroxidase, the RuCu NSs possess other two enzyme activities, not only disproportionating superoxide anion to produce H2 O2 but also consuming glutathione to keep a high concentration of H2 O2 in the tumor microenvironment for Fenton reaction. With these advantages, the RuCu NSs exhibit good performance to kill cancer cells and inhibit tumor growth in mice, demonstrating a promising potential as new CDT reagent.

Manganese oxide-modified bismuth oxychloride piezoelectric nanoplatform with multiple enzyme-like activities for cancer sonodynamic therapy

Sonodynamic therapy (SDT) is considered as a new-rising strategy for cancer therapeutics, but the inefficient production of reactive oxygen species (ROS) by current sonosensitizers seriously hinders its further applications. Herein, a piezoelectric nanoplatform is fabricated for enhancing SDT against cancer, in which manganese oxide (MnO_x) with multiple enzyme-like activities is loaded on the surface of piezoelectric bismuth oxychloride nanosheets (BiOCl NSs) to form a heterojunction. When exposed to ultrasound (US) irradiation, piezotronic effect can remarkably promote the separation and transport of US-induced free charges, and further enhance ROS generation in SDT. Meanwhile, the nanoplatform shows multiple enzyme-like activities from MnO_x, which can not only downregulate the intracellular glutathione (GSH) level, but also disintegrate endogenous hydrogen peroxide (H₂O₂) to generate oxygen (O₂) and hydroxyl radicals (•OH). As a result, the anticancer nanoplatform substantially boosts ROS generation and reverses tumor hypoxia. Ultimately, it reveals remarkable biocompatibility and tumor suppression in a murine model of 4 T1 breast cancer under US irradiation. This work provides a feasible pathway for improving SDT using piezoelectric platforms.

Migration inhibition and selective cytotoxicity of cobalt hydroxide nanosheets on different cancer cell lines

5 nm-thick cobalt hydroxide nanosheets exhibited concentration-dependent selective antitumor activity and cell migration inhibition against a variety of cancer cells.