Molecular Engineering of pH-Responsive NIR Oxazine Assemblies for Evoking Tumor Ferroptosis via Triggering Lysosomal Dysfunction

An ATPase-Mimicking MXene nanozyme pharmacologically breaks the ironclad defense system for ferroptosis cancer therapy

Anticancer nanomedicines used for ferroptosis therapy generally rely on the direct delivery of Fenton catalysts to drive lipid peroxidation in cancer cells. However, the therapeutic efficacy is limited by the ferroptosis resistance caused by the intracellular anti-ferroptotic signals. Herein, we report the intrinsic ATPase-mimicking activity of a vanadium carbide MXene nanozyme (PVCMs) to pharmacologically modulate the nuclear factor erythroid 2-related factor 2 (Nrf2) program, which is the master anti-ferroptotic mediator in the ironclad defense system in triple-negative breast cancer (TNBC) cells. The PVCMs perform high ATPase-like activity that can effectively and selectively catalyze the dephosphorylation of ATP to generate ADP. Through a cascade mechanism initiated by falling energy status, PVCMs can powerfully hinder the Nrf2 program to selectively drive ferroptosis in TNBC cells in response to PVCMs-induced glutathione depletion. This study provides a paradigm for the use of pharmacologically active nanozymes to moderate specific cellular signals and elicit desirable pharmacological activities for therapeutic applications.

Photochemical and biological dual-effects enhance the inhibition of photosensitizers for tumour growth

Photosensitizers typically rely on a singular photochemical reaction to generate reactive oxygen species, which can then inhibit or eradicate lesions. However, photosensitizers often exhibit limited therapeutic efficiency due to their reliance on a single photochemical effect. Herein, we propose a new strategy that integrates the photochemical effect (type-I photochemical effect) with a biological effect (proton sponge effect). To test our strategy, we designed a series of photosensitizers (ZZ-sers) based on the naphthalimide molecule. ZZ-sers incorporate both a p-toluenesulfonyl moiety and weakly basic groups to activate the proton sponge effect while simultaneously strengthening the type-I photochemical effect, resulting in enhanced apoptosis and programmed cell death. Experiments confirmed near-complete eradication of the tumour burden after 14 days (Wlight/Wcontrol ≈ 0.18, W represents the tumour weight). These findings support the notion that the coupling of a type-I photochemical effect with a proton sponge effect can enhance the tumour inhibition by ZZ-sers, even if the basic molecular backbones of the photosensitizers exhibit nearly zero or minimal tumour inhibition ability. We anticipate that this strategy can be generalized to develop additional new photosensitizers with improved therapeutic efficacy while overcoming limitations associated with systems relying solely on single photochemical effects.

Emerging Chemodynamic Nanotherapeutics for Cancer Treatment

Chemodynamic therapy (CDT) has emerged as a transformative paradigm in the realm of reactive oxygen species -mediated cancer therapies, exhibiting its potential as a sophisticated strategy for precise and effective tumor treatment. CDT primarily relies on metal ions and hydrogen peroxide to initiate Fenton or Fenton-like reactions, generating cytotoxic hydroxyl radicals. Its notable advantages in cancer treatment are demonstrated, including tumor specificity, autonomy from external triggers, and a favorable side-effect profile. Recent advancements in nanomedicine are devoted to enhancing CDT, promising a comprehensive optimization of CDT efficacy. This review systematically elucidates cutting-edge achievements in chemodynamic nanotherapeutics, exploring strategies for enhanced Fenton or Fenton-like reactions, improved tumor microenvironment modulation, and precise regulation in energy metabolism. Moreover, a detailed analysis of diverse CDT-mediated combination therapies is provided. Finally, the review concludes with a comprehensive discussion of the prospects and intrinsic challenges to the application of chemodynamic nanotherapeutics in the domain of cancer treatment.

A dynamic cascade DNA nanocomplex to synergistically disrupt the pyroptosis checkpoint and relieve tumor hypoxia for efficient pyroptosis cancer therapy

Pyroptosis has attracted widespread concerns in cancer therapy, while the therapeutic efficiency could be significantly restricted by using the crucial pyroptosis checkpoint of autophagy and tumor hypoxia. Herein, a DNA nanocomplex (DNFs@ZnMn), containing cascade DNAzymes, promoter-like ZnO2-Mn nanozymes and photosensitizers, was constructed in one pot through rolling circle amplification reactions to induce pyroptosis through disrupting autophagy. After targeting cancer cells with a high expression of H+ and glutathione, DNFs@ZnMn decomposed to expose DNAzymes and promoter-like ZnO2-Mn nanozymes. Then, sufficient metal ions and O2 were released to promote cascade DNA/RNA cleavage and relieving of tumor hypoxia. The released DNAzyme-1 self-cleaved long DNA strands with Zn2+ as the cofactor and simultaneously exposed DNAzyme-2 to cleave ATG-5 mRNA (with Mn2+ as the cofactor). This cascade DNAzyme-mediated gene regulation process induced downregulation of ATG-5 proteins to disrupt autophagy. Simultaneously, the released ZnO2 donated sufficient H2O2 to generate adequate O2 to relieve tumor hypoxia, obtaining highly cytotoxic 1O2 to trigger pyroptosis. By using dynamic cascade gene silencing to disrupt the pyroptosis checkpoint and synergistic relieving of hypoxia, this DNA nanocomplex significantly weakened cellular resistance to achieve efficient pyroptosis therapy both in vitro and in vivo.

Understanding the Novel Approach of Nanoferroptosis for Cancer Therapy

As a new form of regulated cell death, ferroptosis has unraveled the unsolicited theory of intrinsic apoptosis resistance by cancer cells. The molecular mechanism of ferroptosis depends on the induction of oxidative stress through excessive reactive oxygen species accumulation and glutathione depletion to damage the structural integrity of cells. Due to their high loading and structural tunability, nanocarriers can escort the delivery of ferro-therapeutics to the desired site through enhanced permeation or retention effect or by active targeting. This review shed light on the necessity of iron in cancer cell growth and the fascinating features of ferroptosis in regulating the cell cycle and metastasis. Additionally, we discussed the effect of ferroptosis-mediated therapy using nanoplatforms and their chemical basis in overcoming the barriers to cancer therapy.

A multi-mode Rhein-based nano-platform synergizing ferrotherapy/chemotherapy-induced immunotherapy for enhanced tumor therapy

Ferroptosis has emerged as a promising strategy for treating triple-negative breast cancer (TNBC) due to bypassing apoptosis and triggering immunogenic cell death (ICD) of tumor cells. However, the antitumor efficacy has been limited by the insufficient intracellular ferrous iron concentration required for ferroptosis and inadequate antitumor immune response. To address these limitations, we designed a multi-mode nano-platform (MP-FA@R-F NPs), which exhibited a synergistic effect of ferroptosis, apoptosis and induced immune response for enhanced antitumor therapy. MP-FA@R-F NPs target folate receptors, which are over-expressed on the tumor cell's surface to promote intracellular uptake. The cargoes, including Rhein and Fe3O4, would be released in intracellular acid, accelerating by NIR laser irradiation. The released Rhein induced apoptosis of tumor cells mediated by the caspase 3 signal pathway, while the released Fe3O4 triggered ferroptosis through the Fenton reaction and endowed the nanoplatform with magnetic resonance imaging (MRI) capabilities. In addition, ferroptosis-dying tumor cells could release damage-associated molecular patterns (DAMPs) to promote T cell activation and infiltration for immune response and induce immunogenic cell death (ICD) for tumor immunotherapy. Together, MP-FA@R-F NPs represent a potential synergistic ferro-/chemo-/immuno-therapy strategy with MRI guidance for enhanced antitumor therapy. STATEMENT OF SIGNIFICANCE: The massive strategies of cancer therapy based on ferroptosis have been emerging in recent years, which provided new insights into designing materials for cancer therapy. However, the antitumor efficacy of ferroptosis is still unsatisfactory, mainly due to insufficient intracellular pro-ferroptotic stimuli. In the current study, we designed a multi-mode nano-platform (MP-FA@R-F NPs), which represented a potential synergistic ferro-/chemo-/immuno-therapy strategy with MRI guidance for enhanced antitumor therapy.

Peptide-Driven Proton Sponge Nano-Assembly for Imaging and Triggering Lysosome-Regulated Immunogenic Cancer Cell Death

Triggering lysosome-regulated immunogenic cell death (ICD, e.g., pyroptosis and necroptosis) with nanomedicines is an emerging approach for turning an "immune-cold" tumor "hot"-a key challenge faced by cancer immunotherapies. Proton sponge such as high-molecular-weight branched polyethylenimine (PEI) is excellent at rupturing lysosomes, but its therapeutic application is hindered by uncontrollable toxicity due to fixed charge density and poor understanding of resulted cell death mechanism. Here, a series of proton sponge nano-assemblies (PSNAs) with self-assembly controllable surface charge density and cell cytotoxicity are created. Such PSNAs are constructed via low-molecular-weight branched PEI covalently bound to self-assembling peptides carrying tetraphenylethene pyridinium (PyTPE, an aggregation-induced emission-based luminogen). Assembly of PEI assisted by the self-assembling peptide-PyTPE leads to enhanced surface positive charges and cell cytotoxicity of PSNA. The self-assembly tendency of PSNAs is further optimized by tuning hydrophilic and hydrophobic components within the peptide, thus resulting in the PSNA with the highest fluorescence, positive surface charge density, cell uptake, and cancer cell cytotoxicity. Systematic cell death mechanistic studies reveal that the lysosome rupturing-regulated pyroptosis and necroptosis are at least two causes of cell death. Tumor cells undergoing PSNA-triggered ICD activate immune cells, suggesting the great potential of PSNAs to trigger anticancer immunity.

Bimetallic DNAsome Decorated with G4-DNA as a Nanozyme for Targeted and Enhanced Chemo/Chemodynamic Cancer Therapy

Cancer is indisputably one of the major threats to mankind, and hence the design of new approaches for the improvement of existing therapeutic strategies is always wanted. Herein, the design of a tumor microenvironment-responsive, DNA-based chemodynamic therapy (CDT) nanoagent with dual Fenton reaction centers for targeted cancer therapy is reported. Self-assembly of DNA amphiphile containing copper complex as the hydrophobic Fenton reaction center results in the formation of CDT-active DNAsome with Cu2+-based Fenton catalytic site as the hydrophobic core and hydrophilic ssDNA protrude on the surface. DNA-based surface addressability of the DNAsome is then used for the integration of second Fenton reaction center, which is a peroxidase-mimicking DNAzyme noncovalently loaded with Hemin and Doxorubicin, via DNA hybridization to give a CDT agent having dual Fenton reaction centers. Targeted internalization of the CDT nanoagent and selective generation of •OH inside HeLa cell are also shown. Excellent therapeutic efficiency is observed for the CDT nanoagent both in vitro and in vivo, and the enhanced efficacy is attributed to the combined and synergetic action of CDT and chemotherapy.

Multienzyme-Like Polyoxometalate-Based Single-Atom Enzymes for Cancer-Specific Therapy Through Acid-Triggered Nontoxicity-to-Toxicity Transition

Single-atom enzymes (SAzymes) exhibit great potential for chemodynamic therapy (CDT); while, general application is still challenged by their instability and unavoidable side effects during delivery. Herein, a manganese-based polyoxometalate single-atom enzyme (Mn-POM SAE) is first introduced into tumor-specific CDT, which exhibits tumor microenvironment (TME)-activated transition of nontoxicity-to-toxicity. Different from traditional POM materials, the aggregates of low-toxic Mn-POM SAE nanospheres are obtained at neutral conditions, facilitating efficient delivery and avoiding toxicity problems in normal tissues. Under acid TME conditions, these nanospheres are degraded into smaller units of toxic Mn(II)-PW11; thus, initiating cancer cell-specific therapy. The released active units of Mn(II)-PW11 exhibit excellent multienzyme-like activities (including peroxidase (POD)-like, oxidase (OXD)-like, catalase (CAT)-like, and glutathione peroxidase (Gpx)-like activities) for the synergistic cancer therapy due to the stabilized high valence Mn species (MnIII/MnIV). As demonstrated by both intracellular evaluations and in vivo experiments, ROS is generated to cause damage to lysosome membranes, further facilitating acidification and impaired autophagy to enhance cancer therapy. This study provides a detailed investigation on the acid-triggered releasing of active units and the electron transfer in multienzyme-mimic-like therapy, further enlarging the application of POMs from catalytical engineering into cancer therapy.

Rational design of a lysosome-targeted fluorescent probe for monitoring the generation of hydroxyl radicals in ferroptosis pathways

Ferroptosis is a newly discovered iron-dependent form of regulated cell death associated with high levels of hydroxyl radical (˙OH) production. Meanwhile, lysosome dysfunction has been shown to be one of the causes of ferroptosis. Although a variety of ˙OH-responsive fluorescent probes have been developed for detecting intracellular ˙OH in living cells, there are still only few lysosome-targeted probes to monitor the variation in lysosomal ˙OH levels during ferroptosis. Herein, we report a novel ˙OH-specific fluorescent probe HCy-Lyso, which is composed of the hydrocyanine and morpholine moiety. Upon treatment with ˙OH, its hydrocyanine unit was converted to the corresponding cyanine group, thus leading to a large π-conjugation extension of HCy-Lyso, accompanied by a significant fluorescence off-on response. Moreover, after reacting with ˙OH in an acidic environment, the protonation product of HCy-Lyso exhibits a higher fluorescence enhancement, which is suitable for detecting lysosomal ˙OH variation. HCy-Lyso has been utilized for imaging endogenous ˙OH in living cells under phorbol myristate acetate (PMA) stimuli and monitoring the changes in lysosomal ˙OH levels during ferroptosis. Thus, our study proposes a new strategy to design lysosome-targeted and ˙OH-responsive fluorescent probes to investigate the relationship between lysosomes and ferroptosis.

Mitochondria-Targeted Prodrug Nanoassemblies for Efficient Ferroptosis-Based Therapy via Devastating Ferroptosis Defense Systems

Ferroptosis is a form of regulated cell death accompanied by lipid reactive oxygen species (ROS) accumulation in an iron-dependent manner. However, the efficiency of tumorous ferroptosis was seriously restricted by intracellular ferroptosis defense systems, the glutathione peroxidase 4 (GPX4) system, and the ubiquinol (CoQH2) system. Inspired by the crucial role of mitochondria in the ferroptosis process, we reported a prodrug nanoassembly capable of unleashing potent mitochondrial lipid peroxidation and ferroptotic cell death. Dihydroorotate dehydrogenase (DHODH) inhibitor (QA) was combined with triphenylphosphonium moiety through a disulfide-containing linker to engineer well-defined nanoassemblies (QSSP) within a single-molecular framework. After being trapped in cancer cells, the acidic condition provoked the structural disassembly of QSSP to liberate free prodrug molecules. The mitochondrial membrane-potential-driven accumulation of the lipophilic cation prodrug was delivered explicitly into the mitochondria. Afterward, the thiol-disulfide exchange would occur accompanied by downregulation of reduced glutathione levels, thus resulting in mitochondria-localized GPX4 inactivation for ferroptosis. Simultaneously, the released QA from the hydrolysis reaction of the adjacent ester bond could further devastate mitochondrial defense and evoke robust ferroptosis via the DHODH-CoQH2 system. This subcellular targeted nanoassembly provides a reference for designing ferroptosis-based strategy for efficient cancer therapy through interfering antiferroptosis systems.

A Lysosome-Targeted Magnetic Nanotorquer Mechanically Triggers Ferroptosis for Breast Cancer Treatment

Targeting ferroptosis has attracted exponential attention to eradicate cancer cells with high iron-dependent growth. Increasing the level of intracellular labile iron pool via small molecules and iron-containing nanomaterials is an effective approach to induce ferroptosis but often faces insufficient efficacy due to the fast drug metabolism and toxicity issues on normal tissues. Therefore, developing a long-acting and selective approach to regulate ferroptosis is highly demanded in cancer treatment. Herein, a lysosome-targeted magnetic nanotorquer (T7-MNT) is proposed as the mechanical tool to dynamically induce the endogenous Fe2+ pool outbreak for ferroptosis of breast cancer. T7-MNTs target lysosomes via the transferrin receptor-mediated endocytosis in breast cancer cells. Under the programmed rotating magnetic field, T7-MNTs generate torques to trigger endogenous Fe2+ release by disrupting the lysosomal membrane. This magneto-mechanical manipulation can induce oxidative damage and antioxidant defense imbalance to boost frequency- and time-dependent lipid peroxidization. Importantly, in vivo studies show that T7-MNTs can efficiently trigger ferroptosis under the magnetic field and play as a long-acting physical inducer to boost ferrotherapy efficacy in combination with RSL3. It is anticipated that this dynamic targeted strategy can be coupled with current ferroptosis inducers to achieve enhanced efficacy and inspire the design of mechanical-based ferroptosis inducers for cancer treatment.

Ferroptosis: Potential opportunities for natural products in cancer therapy

Cancer cells often exhibit defects in the execution of cell death, resulting in poor clinical outcomes for patients with many cancer types. Ferroptosis is a newly discovered form of programmed cell death characterized by intracellular iron overload and lipid peroxidation in the cell membrane. Increasing evidence suggests that ferroptosis is closely associated with a wide variety of physiological and pathological processes, particularly in cancer. Notably, various bioactive natural products have been shown to induce the initiation and execution of ferroptosis in cancer cells, thereby exerting anticancer effects. In this review, we summarize the core regulatory mechanisms of ferroptosis and the multifaceted roles of ferroptosis in cancer. Importantly, we focus on natural products that regulate ferroptosis in cancer cells, such as terpenoids, polyphenols, alkaloids, steroids, quinones, and polysaccharides. The clinical efficacy, adverse effects, and drug-drug interactions of these natural products need to be evaluated in further high-quality studies to accelerate their application in cancer treatment.

High Contrast Bioimaging of Tumor and Inflammation with a Bicyclic Dioxetane Chemiluminescent Probe

The link between inflammation and the evolution of cancer is well established. Visualizing and tracking both tumor proliferation and the associated inflammatory response within a living organism are vital for dissecting the nexus between these two processes and for crafting precise treatment modalities. We report the creation and synthesis of an advanced NIR chemiluminescence probe that stands out for its exceptional selectivity, extraordinary sensitivity at nanomolar concentrations, swift detection capabilities, and broad application prospects. Crucially, this probe has been successfully utilized to image endogenous ONOO- across different inflammation models, including abdominal inflammation triggered by LPS, subcutaneous inflammatory conditions, and tumors grafted onto mice. These findings highlight the significant promise of chemiluminescence imaging in enhancing our grasp of the intricate interplay between cancer and inflammation and in steering the development of potent, targeted therapeutic strategies.

Cascade Catalytic Nanoparticles Selectively Alkalize Cancerous Lysosomes to Suppress Cancer Progression and Metastasis

Lysosomes are critical in modulating the progression and metastasis for various cancers. There is currently an unmet need for lysosomal alkalizers that can selectively and safely alter the pH and inhibit the function of cancer lysosomes. Here an effective, selective, and safe lysosomal alkalizer is reported that can inhibit autophagy and suppress tumors in mice. The lysosomal alkalizer consists of an iron oxide core that generates hydroxyl radicals (•OH) in the presence of excessive H+ and hydrogen peroxide inside cancer lysosomes and cerium oxide satellites that capture and convert •OH into hydroxide ions. Alkalized lysosomes, which display impaired enzyme activity and autophagy, lead to cancer cell apoptosis. It is shown that the alkalizer effectively inhibits both local and systemic tumor growth and metastasis in mice. This work demonstrates that the intrinsic properties of nanoparticles can be harnessed to build effective lysosomal alkalizers that are both selective and safe.

Tumor-Targeted Fluorescent/Photoacoustic Imaging of Legumain Activity In Vivo

Legumain has been identified as a target for diagnosis and treatment of associated cancers. Therefore, real-time imaging of legumain activity in vivo is helpful in diagnosing and evaluating therapeutic efficacy of associated cancers. Fluorescent/photoacoustic (FL/PA) dual-modal imaging developed rapidly because of its good sensitivity and spatial resolution. As far as we know, a tumor-targeted probe for FL/PA imaging of legumain activity in vivo has not been reported. Hence, we intended to develop a tumor-targeted hemicyanine (HCy) probe (HCy-AAN-Bio) for FL/PA imaging of legumain in vivo. The control probe HCy-AAN does not have tumor-targeting ability. Legumain can specifically cleave HCy-AAN-Bio or HCy-AAN with the generation of FL/PA signal while more HCy-AAN-Bio could be recognized by legumain than HCy-AAN with higher sensitivity in vitro. Due to the tumor-targeting ability, HCy-AAN-Bio could image 4T1 cells with an additional 1.3-fold FL enhancement and 1.9-fold PA enhancement than HCy-AAN. In addition, HCy-AAN-Bio could image legumain activity in vivo with an additional 1.5-fold FL enhancement and 1.9-fold PA enhancement than HCy-AAN. We expected that HCy-AAN-Bio will be a powerful tool for early diagnosis of associated cancer.

Superoxide Anion-Mediated Afterglow Mechanism-Based Water-Soluble Zwitterion Dye Achieving Renal-Failure Mice Detection

Afterglow materials-based biological imaging has promising application prospects, due to negligible background. However, currently available afterglow materials mainly include inorganic materials as well as some organic nanoparticles, which are difficult to translate to the clinic, resulting from non-negligible metabolic toxicity and even leakage risk of inorganic heavy metals. Although building small organic molecules could solve such obstacles, organic small molecules with afterglow ability are extremely scarce, especially with a sufficient renal metabolic capacity. To address these issues, herein, we designed water-soluble zwitterion Cy5-NF with renal metabolic capacity and afterglow luminescence, which relied on an intramolecular cascade reaction between superoxide anion (O2•-, instead of 1O2) and Cy5-NF to release afterglow luminescence. Of note, compared with different reference contrast agents, zwitterion Cy5-NF not only had excellent afterglow properties but also had a rapid renal metabolism rate (half-life period, t1/2, around 10 min) and good biocompatibility. Unlike prior afterglow nanosystems possessing a large size, for the first time, zwitterion Cy5-NF has achieved the construction of water-soluble renal metabolic afterglow contrast agents, which showed higher sensitivity and signal-to-background ratio in afterglow imaging than fluorescence imaging for the kidney. Moreover, zwitterion Cy5-NF had a longer kidney retention time in renal-failure mice (t1/2 more than 15 min). More importantly, zwitterion Cy5-NF can be metabolized very quickly even in severe renal-failure mice (t1/2 around 25-30 min), which greatly improved biosecurity. Therefore, we are optimistic that the O2•--mediated afterglow mechanism-based water-soluble zwitterion Cy5-NF is very promising for clinical application, especially rapid detection of kidney failure.

Rational Design of Tunable Near-Infrared Oxazine Probe with Large Stokes Shift for Leucine Aminopeptidase Detection and Imaging

Near-Infrared (NIR) fluorescence imaging with the advantages of deep tissue penetration and minimum background, has been widely employed and developed in the study of biological applications. However, small Stokes shifts, difficulty in optical tuning, and pH sensitivity are still the major limitations faced by current NIR dyes. To solve these problems, we rationally designed a pH insensitive amino-tunable NIR oxazine fluorophore DQF-NH2 , which exhibited large Stokes shift (125 nm) accompanied with NIR excitation/emission due to the introduction an asymmetrical alternating vibronic feature. By benefiting from the excellent photophysical properties of DQF-NH2 , we have successfully constructed the probe DQF-NH2 -LAP with the ability to detect endogenous LAP. Bioimaging assays demonstrated that DQF-NH2 -LAP can not only effectively detect LAP in living cells, but also was successfully applied to image tumor tissue in vivo. We anticipate that the functionalizable dye DQF-NH2 may be a potential new NIR dye platform with an optically tunable group for the development of future desirable probes for bioimaging.

Prolonging Treatment Window of Photodynamic Therapy with Self-Amplified H2 O2 -Activated Photodynamic/Chemo Combination Therapeutic Nanomedicines

Photodynamic therapy (PDT) is a promising approach to cancer therapy. However, the relatively short tumor retention time of photosensitizers (PSs) makes it difficult to catch the optimal treatment time and restricts multiple PDT within a single injection. In this study, a tumor-specific phototheranostic nanomedicine (DPPa NP) is developed for photodynamic/chemo combination therapy with a prolonged PDT treatment window. DPPa NP is prepared via encapsulating a hydrophobic oxidized bovine serum albumin (BSA-SOH)-conjugatable PS DPPa with amphiphilic H2 O2 -activatable chlorambucil (CL) prodrug mPEG-TK-CL. The released CL under H2 O2 treatment can not only kill tumor cells but also upregulate reactive oxygen species levels within tumor cells, leading to the almost full release of cargoes. The released DPPa may conjugate with overexpressed BSA-SOH, which results in the recovery of the fluorescence signal and photodynamic effect. More importantly, such conjugation transfers DPPa from a small molecule PS into a macromolecular PS with a long tumor retention time and treatment window of PDT, which enables multiple PDT. This study thus provides an effective strategy to prolong the treatment window of PDT and enables tumor-specific fluorescence imaging-guided combination therapy.

Small molecules and conjugates as theranostic agents

Theranostics, the integration of therapy and diagnostics into a single entity for the purpose of monitoring disease progression and treatment response. Diagnostics involves identifying specific characteristics of a disease, while therapeutics refers to the treatment of the disease based on this identification. Advancements in medicinal chemistry and technology have led to the development of drug modalities that provide targeted therapeutic effects while also providing real-time updates on disease progression and treatment. The inclusion of imaging in therapy has significantly improved the prognosis of devastating diseases such as cancer and neurodegeneration. Currently, theranostic treatment approaches are based on nuclear medicine, while nanomedicine and a wide diversity of macromolecular systems such as gels, polymers, aptamers, and dendrimer-based agents are being developed for the purpose. Theranostic agents have significant roles to play in both early-stage drug development and clinical-stage therapeutic-containing drug candidates. This review will briefly outline the pros and cons of existing and evolving theranostic approaches before comprehensively discussing the role of small molecules and their conjugates.

Synergistically remodulating H+/Ca2+ gradients to induce mitochondrial depolarization for enhanced synergistic cancer therapy

The remodulation of H+/Ca2+ gradients in the mitochondria matrix could be effective to induce mitochondria depolarization for the enhancement of cancer therapy. However, it is still challenged by H+ homeostasis, insufficient Ca2+, uncoordinated regulations, and inefficient loading/delivery strategies. Herein, a supramolecular DNA nanocomplex (Ca@DNA-MF) was prepared to synergistically remodulate H+/Ca2+ gradients for mitochondrial depolarization. Upon targeted functionalization and TME-triggered delivery, multiple reagents were released in cancer cells for synergistic three-channel mitochondrial depolarization: the gene reagent of siMCT4 blocked the LA metabolism to induce mitochondrial acidification by downregulating monocarboxylate transporter 4 (MCT4); released Ca2+ disrupted Ca2+ homeostasis to facilitate Ca2+-based mitochondrial depolarization; specifically, TME-activated glutathione (GSH) depletion facilitated efficient generation of hydroxyl radicals (˙OH), further enhancing the mitochondrial depolarization. The remodulation not only triggered apoptosis but also led to ferroptosis to generate abundant ROS for efficient LPO-based apoptosis, providing a synergistic strategy for enhanced synergistic cancer therapy.

Ultrasmall Self-Cascade AuNP@FeS Nanozyme for H2S-Amplified Ferroptosis Therapy

Recently, nanozymes with peroxidase (POD)-like activity have shown great promise for ferroptosis-based tumor therapy, which are capable of transforming hydrogen peroxide (H2O2) to highly toxic hydroxyl radicals (•OH). However, the unsatisfactory therapeutic performance of nanozymes due to insufficient endogenous H2O2 and acidity at tumor sites has always been a conundrum. Herein, an ultrasmall gold (Au) @ ferrous sulfide (FeS) cascade nanozyme (AuNP@FeS) with H2S-releasing ability constructed with an Au nanoparticle (AuNP) and an FeS nanoparticle (FeSNP) is designed to increase the H2O2 level and acidity in tumor cells via the collaboration between cascade reactions of AuNP@FeS and the biological effects of released H2S, achieving enhanced •OH generation as well as effective ferroptosis for tumor therapy. The cascade reaction in tumor cells is activated by the glucose oxidase (GOD)-like activity of AuNP in AuNP@FeS to catalyze intratumoral glucose into H2O2 and gluconic acid; meanwhile, the released H2S from AuNP@FeS reduces H2O2 consumption by inhibiting intracellular catalase (CAT) activity and promotes lactic acid accumulation. The two pathways synergistically boost H2O2 and acidity in tumor cells, thus inducing a cascade to generate abundant •OH by catalyzing H2O2 through the POD-like activity of FeS in AuNP@FeS and ultimately causing amplified ferroptosis. In vitro and in vivo experiments demonstrated that AuNP@FeS presents a superior tumor therapeutic effect compared to that of AuNP or FeS alone. This strategy represents a simple but powerful method to amplify ferroptosis with H2S-releasing cascade nanozymes and will pave a new way for the development of tumor therapy.

Synergistic phototherapy of NIR wavelength xanthene-quinoline salt-based heavy-atom-free photosensitizers for tumor therapy

We propose a practical strategy to design a series of heavy-atom-free synergistic phototherapy agents (CSQs) with both photodynamic therapy (PDT) and photothermal therapy (PTT) under NIR wavelength excitation by simply replacing the indole salt of xanthene Changsha (CS) with quinoline salt.

Three Strategies in Engineering Nanomedicines for Tumor Microenvironment-Enabled Phototherapy

Canonical phototherapeutics have several limitations, including a lack of tumor selectivity, nondiscriminatory phototoxicity, and tumor hypoxia aggravation. The tumor microenvironment (TME) is characterized by hypoxia, acidic pH, and high levels of H2 O2 , GSH, and proteases. To overcome the shortcomings of canonical phototherapy and achieve optimal theranostic effects with minimal side effects, unique TME characteristics are employed in the development of phototherapeutic nanomedicines. In this review, the effectiveness of three strategies for developing advanced phototherapeutics based on various TME characteristics is examined. The first strategy involves targeted delivery of phototherapeutics to tumors with the assistance of TME-induced nanoparticle disassembly or surface modification. The second strategy involves near-infrared absorption increase-induced phototherapy activation triggered by TME factors. The third strategy involves enhancing therapeutic efficacy by ameliorating TME. The functionalities, working principles, and significance of the three strategies for various applications are highlighted. Finally, possible challenges and future perspectives for further development are discussed.

Versatile Switchable Targeted Polysiloxanes for High-Resolution Visualization of Mitochondrial and Lysosomal Interactions during Ferroptosis

Ferroptosis is an iron-dependent process that regulates cell death and is essential for maintaining normal cell and tissue survival. The explosion of reactive oxygen species characterizes ferroptosis in a significant way. Peroxynitrite (ONOO^-) is one of the endogenous reactive oxygen species. Abnormal ONOO^- concentrations cause damage to subcellular organelles and further interfere with organelle interactions. However, the proper conduct of organelle interactions is critical for cellular signaling and the maintenance of cellular homeostasis. Therefore, investigating the effect of ONOO^- on organelle interactions during ferroptosis is a highly attractive topic. To date, it has been challenging to visualize the full range of ONOO^- fluctuations in mitochondria and lysosomes during ferroptosis. In this paper, we constructed a switchable targeting polysiloxane platform. During the selective modification of NH₂ groups located in the side chain, the polysiloxane platform successfully constructed fluorescent probes targeting lysosomes and mitochondria (Si-Lyso-ONOO, Si-Mito-ONOO), respectively. Real-time detection of ONOO^- in lysosomes and mitochondria during ferroptosis was successfully achieved. Remarkably, the occurrence of autophagy during late ferroptosis and the interaction between mitochondria and lysosomes was observed via the differentiated responsive strategy. We expect that this switchable targeting polysiloxane functional platform will broaden the application of polymeric materials in bioimaging and provide a powerful tool for further deeper understanding of the ferroptosis process.