Radiotherapy Reduces N-Oxides for Prodrug Activation in Tumors

Progress of proteolysis-targeting chimeras (PROTACs) delivery system in tumor treatment

Proteolysis targeting chimeras (PROTACs) can use the intrinsic protein degradation system in cells to degrade pathogenic target proteins, and are currently a revolutionary frontier of development strategy for tumor treatment with small molecules. However, the poor water solubility, low cellular permeability, and off-target side effects of most PROTACs have prevented them from passing the preclinical research stage of drug development. This requires the use of appropriate delivery systems to overcome these challenging hurdles and ensure precise delivery of PROTACs towards the tumor site. Therefore, the combination of PROTACs and multifunctional delivery systems will open up new research directions for targeted degradation of tumor proteins. In this review, we systematically reviewed the design principles and the most recent advances of various PROTACs delivery systems. Moreover, the constructive strategies for developing multifunctional PROTACs delivery systems were proposed comprehensively. This review aims to deepen the understanding of PROTACs drugs and promote the further development of PROTACs delivery system.

Programmable melanoma-targeted radio-immunotherapy via fusogenic liposomes functionalized with multivariate-gated aptamer assemblies

Radio-immunotherapy exploits the immunostimulatory features of ionizing radiation (IR) to enhance antitumor effects and offers emerging opportunities for treating invasive tumor indications such as melanoma. However, insufficient dose deposition and immunosuppressive microenvironment (TME) of solid tumors limit its efficacy. Here we report a programmable sequential therapeutic strategy based on multifunctional fusogenic liposomes (Lip@AUR-ACP-aptPD-L1) to overcome the intrinsic radio-immunotherapeutic resistance of solid tumors. Specifically, fusogenic liposomes are loaded with gold-containing Auranofin (AUR) and inserted with multivariate-gated aptamer assemblies (ACP) and PD-L1 aptamers in the lipid membrane, potentiating melanoma-targeted AUR delivery while transferring ACP onto cell surface through selective membrane fusion. AUR amplifies IR-induced immunogenic death of melanoma cells to release antigens and damage-associated molecular patterns such as adenosine triphosphate (ATP) for triggering adaptive antitumor immunity. AUR-sensitized radiotherapy also upregulates matrix metalloproteinase-2 (MMP-2) expression that combined with released ATP to activate ACP through an "and" logic operation-like process (AND-gate), thus triggering the in-situ release of engineered cytosine-phosphate-guanine aptamer-based immunoadjuvants (eCpG) for stimulating dendritic cell-mediated T cell priming. Furthermore, AUR inhibits tumor-intrinsic vascular endothelial growth factor signaling to suppress infiltration of immunosuppressive cells for fostering an anti-tumorigenic TME. This study offers an approach for solid tumor treatment in the clinics.

Intercalating of AIEgens into MoS2 nanosheets to induce crystal phase transform for enhanced photothermal and photodynamic synergetic anti-tumor therapy

A MoS2-based nanotherapeutic platform was developed for synergetic photothermal and photodynamic anti-tumor therapy. AIEgens TFPy-SH molecules were intercalated into MoS2 nanosheets (MoS2 NSs) with S-deficiencies to give the nanocomposite MoS2-TFPy. The AIEgens intercalation expanded the interlayer spacing of MoS2 NSs and induced the transform of MoS2 crystal phase from 2H to 1T, offering MoS2-TFPy nanocomposite high molar absorption coefficient (5.65 L g-1 cm-1), excellent photothermal conversion efficiency under near-infrared (NIR) laser irradiation (38.3%), and favorable intracellular reactive oxygen species (ROS) generation capacity. The positively charged MoS2-TFPy were mainly distributed in mitochondria after cell up-taking, and achieved 1+1>2 anti-tumor effect attributed to its favorable photothermal and photodynamic properties. The high structure and physiological stability, favorable biocompatibility, excellent photothermal and photodynamic therapy effect make the MoS2-TFPy nanoplatform an promising candidate in biomedical clinical applications.

Synergistic Brilliance: Engineered Bacteria and Nanomedicine Unite in Cancer Therapy

Engineered bacteria are widely used in cancer treatment because live facultative/obligate anaerobes can selectively proliferate at tumor sites and reach hypoxic regions, thereby causing nutritional competition, enhancing immune responses, and producing anticancer microbial agents in situ to suppress tumor growth. Despite the unique advantages of bacteria-based cancer biotherapy, the insufficient treatment efficiency limits its application in the complete ablation of malignant tumors. The combination of nanomedicine and engineered bacteria has attracted increasing attention owing to their striking synergistic effects in cancer treatment. Engineered bacteria that function as natural vehicles can effectively deliver nanomedicines to tumor sites. Moreover, bacteria provide an opportunity to enhance nanomedicines by modulating the TME and producing substrates to support nanomedicine-mediated anticancer reactions. Nanomedicine exhibits excellent optical, magnetic, acoustic, and catalytic properties, and plays an important role in promoting bacteria-mediated biotherapies. The synergistic anticancer effects of engineered bacteria and nanomedicines in cancer therapy are comprehensively summarized in this review. Attention is paid not only to the fabrication of nanobiohybrid composites, but also to the interpromotion mechanism between engineered bacteria and nanomedicine in cancer therapy. Additionally, recent advances in engineered bacteria-synergized multimodal cancer therapies are highlighted.

Medicinal Chemistry of Drugs with N-Oxide Functionalities

Molecules with N-oxide functionalities are omnipresent in nature and play an important role in Medicinal Chemistry. They are synthetic or biosynthetic intermediates, prodrugs, drugs, or polymers for applications in drug development and surface engineering. Typically, the N-oxide group is critical for biomedical applications of these molecules. It may provide water solubility or decrease membrane permeability or immunogenicity. In other cases, the N-oxide has a special redox reactivity which is important for drug targeting and/or cytotoxicity. Many of the underlying mechanisms have only recently been discovered, and the number of applications of N-oxides in the healthcare field is rapidly growing. This Perspective article gives a short summary of the properties of N-oxides and their synthesis. It also provides a discussion of current applications of N-oxides in the biomedical field and explains the basic molecular mechanisms responsible for their biological activity.

Radiotherapy activates picolinium prodrugs in tumours

Radiotherapy-induced prodrug activation provides an ideal solution to reduce the systemic toxicity of chemotherapy in cancer therapy, but the scope of the radiation-activated protecting groups is limited. Here we present that the well-established photoinduced electron transfer chemistry may pave the way for developing versatile radiation-removable protecting groups. Using a functional reporter assay, N-alkyl-4-picolinium (NAP) was identified as a caging group that efficiently responds to radiation by releasing a client molecule. When evaluated in a competition experiment, the NAP moiety is more efficient than other radiation-removable protecting groups discovered so far. Leveraging this property, we developed a NAP-derived carbamate linker that releases fluorophores and toxins on radiation, which we incorporated into antibody-drug conjugates (ADCs). These designed ADCs were active in living cells and tumour-bearing mice, highlighting the potential to use such a radiation-removable protecting group for the development of next-generation ADCs with improved stability and therapeutic effects.

Theoretical Design and Synthesis of Caged Compounds Using X-Ray-Triggered Azo Bond Cleavage

Caged compounds are frequently used in life science research. However, the light used to activate them is commonly absorbed and scattered by biological materials, limiting their use to basic research in cells or small animals. In contrast, hard X-rays exhibit high bio-permeability due to the difficulty of interacting with biological molecules. With the main goal of developing X-ray activatable caged compounds, azo compounds are designed and synthesized with a positive charge and long π-conjugated system to increase the reaction efficiency with hydrated electrons. The azo bonds in the designed compounds are selectively cleaved by X-ray, and the fluorescent substance Diethyl Rhodamine is released. Based on the results of experiments and quantum chemical calculations, azo bond cleavage is assumed to occur via a two-step process: a two-electron reduction of the azo bond followed by N─N bond cleavage. Cellular experiments also demonstrate that the azo bonds can be cleaved intracellularly. Thus, caged compounds that can be activated by an azo bond cleavage reaction promoted by X-ray are successfully generated.

Activating Tumor-Selective Liquid Metal Nanomedicine through Galvanic Replacement

Advanced chemotherapeutic strategies including prodrug and nanocatalytic medicine have significantly advanced tumor-selective theranostics, but delicate prodrug screening, tedious synthesis, low degradability/biocompatibility of inorganic components, and unsatisfied reaction activity complicate treatment efficacies. Here, the intrinsic anticancer bioactivity of liquid metal nanodroplets (LMNDs) is explored through galvanic replacement. By utilizing a mechano-degradable ligand, the resultant size of the aqueous LMND is unexpectedly controlled as small as ≈20 nm (LMND20). It is demonstrated that LMND20 presents excellent tumor penetration and biocompatibility and activates tumor-selective carrier-to-drug conversion, synchronously depleting Cu2+ ions and producing Ga3+ ions through galvanic replacement. Together with abundant generation of reactive oxygen species, multiple anticancer pathways lead to selective apoptosis and anti-angiogenesis of breast cancer cells. Compared to the preclinical/clinical anticancer drugs of tetrathiomolybdate and Ga(NO3 )3 , LMND20 administration significantly improves the therapeutic efficacy and survival in a BCap-37 xenograft mouse model, yet without obvious side effects.

Reactive Reductive Species Participating Photodynamic Therapy for Cancer Treatment

Although the development of oxidative photodynamic therapy (O-PDT) based on reactive oxygen species (ROS) has led to great progress in cancer treatment, tumor hypoxia, cellular adaptation and intrinsic antioxidant defenses are still obstacles at this stage. Fortunately, with the discovery and development of reactive reductive species (RRS) in the PDT process, reductive PDT (R-PDT) is receiving increasing research interest. R-PDT with oxygen-independence is an effective reduction therapy that promises excellent therapeutic efficacy in extremely hypoxic or even anaerobic environments. In the concept, we introduce representative strategies to boost the type-I photosensitizing pathway, and then focus on the most recent R-PDT involving hydrogen radical (H⋅) and the single electron transfer (SET) process.

Bioorthogonal Bond Cleavage Chemistry for On-demand Prodrug Activation: Opportunities and Challenges

Time- and space-resolved drug delivery is highly demanded for cancer treatment, which, however, can barely be achieved with a traditional prodrug strategy. In recent years, the prodrug strategy based on a bioorthogonal bond cleavage chemistry has emerged with the advantages of high temporospatial resolution over drug activation and homogeneous activation irrespective of individual heterogeneity. In the past five years, tremendous progress has been witnessed in this field with one such bioorthogonal prodrug entering Phase II clinical trials. This Perspective aims to highlight these new advances (2019-2023) and critically discuss their pros and cons. In addition, the remaining challenges and potential strategic directions for future progress will also be included.

A Bioorthogonal Decaging Chemistry of N-Oxide and Silylborane for Prodrug Activation both In Vitro and In Vivo

Bioorthogonal decaging chemistry with both fast kinetics and high efficiency is highly demanded for in vivo applications but remains very sporadic. Herein, we describe a new bioorthogonal decaging chemistry between N-oxide and silylborane. A simple replacement of "C" in boronic acid with "Si" was able to substantially accelerate the N-oxide decaging kinetics by 106 fold (k2: up to 103 M-1 s-1). Moreover, a new N-oxide-masked self-immolative spacer was developed for the traceless release of various payloads upon clicking with silylborane with fast kinetics and high efficiency (>90%). Impressively, one such N-oxide-based self-assembled bioorthogonal nano-prodrug in combination with silylborane led to significantly enhanced tumor suppression effects as compared to the parent drug in a 4T1 mouse breast tumor model. In aggregate, this new bioorthogonal click-and-release chemistry is featured with fast kinetics and high efficiency and is perceived to find widespread applications in chemical biology and drug delivery.

Bioorthogonal chemistry for prodrug activation in vivo

Prodrugs have emerged as a major strategy for addressing clinical challenges by improving drug pharmacokinetics, reducing toxicity, and enhancing treatment efficacy. The emergence of new bioorthogonal chemistry has greatly facilitated the development of prodrug strategies, enabling their activation through chemical and physical stimuli. This "on-demand" activation using bioorthogonal chemistry has revolutionized the research and development of prodrugs. Consequently, prodrug activation has garnered significant attention and emerged as an exciting field of translational research. This review summarizes the latest advancements in prodrug activation by utilizing bioorthogonal chemistry and mainly focuses on the activation of small-molecule prodrugs and antibody-drug conjugates. In addition, this review also discusses the opportunities and challenges of translating these advancements into clinical practice.

X-Ray-Induced Drug Release for Cancer Therapy

Drug delivery systems (DDSs) are designed to deliver therapeutic agents to specific target sites while minimizing systemic toxicity. Recent developments in drug-loaded DDSs have demonstrated promising characteristics and paved new pathways for cancer treatment. Light, a prevalent external stimulus, is widely utilized to trigger drug release. However, conventional light sources primarily concentrate on the ultraviolet (UV) and visible light regions, which suffer from limited biological tissue penetration. This limitation hinders applications for deep-tissue tumor drug release. Given their deep tissue penetration and well-established application technology, X-rays have recently received attention for the pursuit of controlled drug release. With precise spatiotemporal and dosage controllability, X-rays stand as an ideal stimulus for achieving controlled drug release in deep-tissue cancer therapy. This article explores the recent advancements in using X-rays for stimulus-triggered drug release in DDSs and delves into their action mechanisms.

Stimuli-Responsive Prodrug Chemistries for Cancer Therapy

Prodrugs are pharmacologically inactive, chemically modified derivatives of active drugs, which, following in vivo administration, are converted to the parent drugs through chemical or enzymatic cleavage. The prodrug approach holds tremendous potential to create the enhanced version of an existing pharmacological agent and leverage those improvements to augment the drug molecules' bioavailability, targeting ability, therapeutic efficacy, safety, and marketability. Especially in cancer therapy, prodrug application has received substantial attention. A prodrug can effectively broaden the therapeutic window of its parent drug by enhancing its release at targeted tumor sites while reducing its access to healthy cells. The spatiotemporally controlled release can be achieved by manipulating the chemical, physical, or biological stimuli present at the targeted tumor site. The critical strategy comprises drug-carrier linkages that respond to physiological or biochemical stimuli in the tumor milieu to yield the active drug form. This review will focus on the recent advancements in the development of various fluorophore-drug conjugates that are widely used for real-time monitoring of drug delivery. The use of different stimuli-cleavable linkers and the mechanisms of linker cleavage will be discussed. Finally, the review will conclude with a critical discussion of the prospects and challenges that might impede the future development of such prodrugs.

Nanoscale Metal-Organic Framework with an X-ray Triggerable Prodrug for Synergistic Radiotherapy and Chemotherapy

As heavy-metal-based nanoscale metal-organic frameworks (nMOFs) are excellent radiosensitizers for radiotherapy via enhanced energy deposition and reactive oxygen species (ROS) generation, we hypothesize that nMOFs with covalently conjugated and X-ray triggerable prodrugs can harness the ROS for on-demand release of chemotherapeutics for chemoradiotherapy. Herein, we report the design of a novel nMOF, Hf-TP-SN, with an X-ray-triggerable 7-ethyl-10-hydroxycamptothecin (SN38) prodrug for synergistic radiotherapy and chemotherapy. Upon X-ray irradiation, electron-dense Hf12 secondary building units serve as radiosensitizers to enhance hydroxyl radical generation for the triggered release of SN38 via hydroxylation of the 3,5-dimethoxylbenzyl carbonate followed by 1,4-elimination, leading to 5-fold higher release of SN38 from Hf-TP-SN than its molecular counterpart. As a result, Hf-TP-SN plus radiation induces significant cytotoxicity to cancer cells and efficiently inhibits tumor growth in colon and breast cancer mouse models.

X-ray-responsive prodrugs and polymeric nanocarriers for multimodal cancer therapy

Radiotherapy as one of the most important cancer treatment modalities has been widely used in the therapy of various cancers. The clinically used radiation (e.g. X-ray) for radiotherapy has the advantages of precise spatiotemporal controllability and deep tissue penetration. However, traditional radiotherapy is frequently limited by the high side effects and tumor hypoxia. The combination of radiotherapy and other cancer treatment modalities may overcome the disadvantages of radiotherapy and improve the final therapeutic efficacy. In recent years, X-ray-activable prodrugs and polymeric nanocarriers have been extensively explored to introduce other treatment modalities in the precise position during radiotherapy, which can reduce the side toxicity of the drugs and improve the combination therapeutic efficacy. In this review, we focus on recent advances in X-ray-activable prodrugs and polymeric nanocarriers to boost X-ray-based multimodal synergistic therapy with reduced toxicity. The design strategies of prodrugs and polymeric nanocarriers are highlighted. Finally, challenges and outlooks of X-ray-activable prodrugs and polymeric nanocarriers are discussed.

A MOF-Based Potent Ferroptosis Inducer for Enhanced Radiotherapy of Triple Negative Breast Cancer

Radiotherapy (RT) is one of the important clinical treatments for local control of triple-negative breast cancer (TNBC), but radioresistance still exists. Ferroptosis has been recognized as a natural barrier for cancer progression and represents a significant role of RT-mediated anticancer effects, while the simultaneous activation of ferroptosis defensive system during RT limits the synergistic effect between RT and ferroptosis. Herein, we engineered a tumor microenvironment (TME) degradable nanohybrid with a dual radiosensitization manner to combine ferroptosis induction and high-Z effect based on metal-organic frameworks for ferroptosis-augmented RT of TNBC. The encapsulated l-buthionine-sulfoximine (BSO) could inhibit glutathione (GSH) biosynthesis for glutathione peroxidase 4 (GPX4) inactivation to break down the ferroptosis defensive system, and the delivered ferrous ions could act as a powerful ferroptosis executor via triggering the Fenton reaction; the combination of them induces potent ferroptosis, which could synergize with the surface decorated Gold (Au) NPs-mediated radiosensitization to improve RT efficacy. In vivo antitumor results revealed that the nanohybrid could significantly improve the therapeutic efficacy and antimetastasis efficiency based on the combinational mechanism between ferroptosis and RT. This work thus demonstrated that combining RT with efficient ferroptosis induction through nanotechnology was a feasible and promising strategy for TNBC treatment.

Renal Clearable Mo-Based Polyoxometalate Nanoclusters: A Promising Radioprotectant against Ionizing Irradiation

In response to diffused ionizing radiation damage throughout the body caused by nuclear leaks and inaccurate radiotherapy, radioprotectants with considerable free radical scavenging capacities, along with negligible adverse effects, are highly regarded. Herein, unlike being performed as toxic chemotherapeutic drug candidates, molybdenum-based polyoxometalate nanoclusters (Mo-POM NCs) were developed as a non-toxic potent radioprotectant with impressive free radical scavenging capacities for ionizing radiation protection. In comparison to the clinically used radioprotectant drug amifostine (AM), the as-prepared Mo-POM NCs exhibited effective shielding capacity by virtue of their antioxidant properties resulting from a valence shift of molybdenum ions, alleviating not only ionizing radiation-induced DNA damage but also disruption of the radiation-sensitive hematopoietic system. More encouragingly, without trouble with long-term retention in the body, ultra-small sized Mo-POM NCs prepared by the mimetic Folin-Ciocalteu assay can be removed from the body through the renal-urinary pathway and the hepato-enteral excretory system after completing the mission of radiation protection. This work broadened the biological applications of metal-based POM chemotherapeutic drugs to act as a neozoic radioprotectant.

Recent Progress in Carrier-Free Nanomedicine for Tumor Phototherapy

Safe and effective strategies are urgently needed to fight against the life-threatening diseases of various cancers. However, traditional therapeutic modalities, such as radiotherapy, chemotherapy and surgery, exhibit suboptimal efficacy for malignant tumors owing to the serious side effects, drug resistance and even relapse. Phototherapies, including photodynamic therapy (PDT) and photothermal therapy (PTT), are emerging therapeutic strategies for localized tumor inhibition, which can produce a large amount of reactive oxygen species (ROS) or elevate the temperature to initiate cell death by non-invasive irradiation. In consideration of the poor bioavailability of phototherapy agents (PTAs), lots of drug delivery systems have been developed to enhance the tumor targeted delivery. Nevertheless, the carriers of drug delivery systems inevitably bring biosafety concerns on account of their metabolism, degradation, and accumulation. Of note, carrier-free nanomedicine attracts great attention for clinical translation with synergistic antitumor effect, which is characterized by high drug loading, simplified synthetic method and good biocompatibility. In this review, the latest advances of phototherapy with various carrier-free nanomedicines are summarized, which may provide a new paradigm for the future development of nanomedicine and tumor precision therapy.

Cyclodextrin Metal-Organic Framework as a Broad-Spectrum Potential Delivery Vehicle for the Gasotransmitters

The important role of gasotransmitters in physiology and pathophysiology suggest employing gasotransmitters for biomedical treatment. Unfortunately, the difficulty in storage and controlled delivery of these gaseous molecules hindered the development of effective gasotransmitters-based therapies. The design of a safe, facile, and wide-scale method to delivery multiple gasotransmitters is a great challenge. Herein, we use an ultrasonic assisted preparation γ-cyclodextrin metal organic framework (γ-CD-MOF) as a broad-spectrum delivery vehicle for various gasotransmitters, such as SO₂, NO, and H₂S. The release rate of gasotransmitters could be tuned by modifying the γ-CD-MOF with different Pluronics. The biological relevance of the exogenous gasotransmitters produced by this method is evidenced by the DNA cleavage ability and the anti-inflammatory effects. Furthermore, the γ-CD-MOF composed of food-grade γ-CD and nontoxic metal salts shows good biocompatibility and particle size (180 nm). Therefore, γ-CD-MOF is expected to be an excellent tool for the study of co-delivery and cooperative therapy of gasotransmitters.

Radiotherapy-Triggered Proteolysis Targeting Chimera Prodrug Activation in Tumors

Proteolysis targeting chimera (PROTAC) is an emerging protein degradation strategy, which shows excellent advantages in targeting those so-called "undruggable" proteins. However, the potential systemic toxicity of PROTACs caused by undesired off-tissue protein degradation may limit the application of PROTACs in clinical practice. Here we reported a radiotherapy-triggered PROTAC prodrug (RT-PROTAC) activation strategy to precisely and spatiotemporally control protein degradation through X-ray radiation. We demonstrated this concept by incorporating an X-ray inducible phenyl azide-cage to a bromodomain (BRD)-targeting PROTAC to form the first RT-PROTAC. The RT-PROTAC prodrug exhibits little activity but can be activated by X-ray radiation in vitro and in vivo. Activated RT-PROTAC degrades BRD4 and BRD2 with a comparable effect to the PROTAC degrader and shows a synergistic antitumor potency with radiotherapy in the MCF-7 xenograft model. Our work provides an alternative strategy to spatiotemporally control protein degradation in vivo and points to an avenue for reducing the undesired systemic toxicity of PROTACs.

Anticancer Effect of Chlorambucil Enhanced by Chiral Phthalidyl Promoiety

Phthalidyl promoiety has been used in several drugs, but they were all marketed in racemic form. The pharmaceutical effects of each enantiomer have not been clearly demonstrated. In this project, an anticancer chemotherapy drug, chlorambucil, was modified as enantiopure phthalidyl prodrugs. The enantiomers, together with phthalidyl unit and their racemic mixture, were then subject to the in vivo bioactivity tests against B16F10 melanoma cells. It was found that proper chirality within the promoiety had noticeably better in vivo pharmacological effects than the parent drug, the enantiomer and racemic mixture. This merit perhaps could be extended from the phthalidyl prodrugs to other chirality containing prodrugs.

NIR-II Light Leveraged Dual Drug Synthesis for Orthotopic Combination Therapy

Pd-catalyzed bioorthogonal bond cleavage reactions are widely used and frequently reported. It is circumscribed by low reaction efficiency, which may encumber the therapeutic outcome when applied to physiological environments. Herein, an NIR-II light promoted integrated catalyst (CuS@PDA/Pd) (PDA - polydopamine) is designed to accelerate the reaction efficiency and achieve a dual bioorthogonal reaction for combination therapy. As NIR-II light can penetrate deeply into tissue, the Pd-mediated cleavage reaction can be promoted both in vitro and in vivo by the photothermal properties of CuS, beneficial to orthotopic 4T1 tumor treatment. In addition, CuS also catalyzes the synthesis of active resveratrol analogs by the CuAAC reaction. These simultaneously produced anticancer agents result in enhanced antitumor cytotoxicity in comparison to the single treatments. This is a fascinating study to devise an integrated catalyst boosted by NIR-II light for dual bioorthogonal catalysis, which may provide the impetus for efficient bioorthogonal combination therapy in vivo.

In Situ Formed Z-Scheme Graphdiyne Heterojunction Realizes NIR-Photocatalytic Oxygen Evolution and Selective Radiosensitization for Hypoxic Tumors

Photon radiotherapy is a common tool in the armory against tumors, but it is limited by hypoxia-related radioresistance of tumors and radiotoxicity to normal tissues. Here, we constructed a spatiotemporally controlled synergistic therapy platform based on the heterostructured CuO@Graphdiyne (CuO@GDY) nanocatalyst for simultaneously addressing the two key problems above in radiotherapy. First, the in situ formed Z-scheme CuO@GDY heterojunction performs highly efficient and controlled photocatalytic O₂ evolution upon near-infrared (NIR) laser stimulation for tumor hypoxia alleviation. Subsequently, the CuO@GDY nanocatalyst with X-ray-stimulated Cu⁺ active sites can accelerate Fenton-like catalysis of ·OH production by responding to endogenous H₂O₂ for the selective killing of tumor cells rather than normal cells. In this way, the sequential combination of NIR-triggered photocatalytic O₂ production and X-ray-accelerated Fenton-like reaction can lead to a comprehensive radiosensitization. Overall, this synergism underscores a controllable and precise therapy modality for simultaneously unlocking the hypoxia and non-selectivity in radiotherapy.

Monte Carlo Simulation-Guided Design of a Thorium-Based Metal-Organic Framework for Efficient Radiotherapy-Radiodynamic Therapy

High-Z metal-based nanoscale metal-organic frameworks (nMOFs) with photosensitizing ligands can enhance radiation damage to tumors via a unique radiotherapy-radiodynamic therapy (RT-RDT) process. Here we report Monte Carlo (MC) simulation-guided design of a Th-based nMOF built from Th6 -oxo secondary building units and 5,15-di(p-benzoato)porphyrin (DBP) ligands, Th-DBP, for enhanced RT-RDT. MC simulations revealed that the Th-lattice outperformed the Hf-lattice in radiation dose enhancement owing to its higher mass attenuation coefficient. Upon X-ray or γ-ray radiation, Th-DBP enhanced energy deposition, generated more reactive oxygen species, and induced significantly higher cytotoxicity to cancer cells over the previously reported Hf-DBP nMOF. With low-dose X-ray irradiation, Th-DBP suppressed tumor growth by 88 % in a colon cancer and 97 % in a pancreatic cancer mouse model.

External stimuli-responsive gasotransmitter prodrugs: Chemistry and spatiotemporal release

Gasotransmitters like nitric oxide, carbon monoxide, and hydrogen sulfide with unique pleiotropic pharmacological effects in mammals are an emerging therapeutic modality for different human diseases including cancer, infection, ischemia-reperfusion injuries, and inflammation; however, their clinical translation is hampered by the lack of a reliable delivery form, which delivers such gasotransmitters to the action site with precisely controlled dosage. The external stimuli-responsive prodrug strategy has shown tremendous potential in developing gasotransmitter prodrugs, which affords precise temporospatial control and better dose control compared with endogenous stimuli-sensitive prodrugs. The promising external stimuli employed for gasotransmitter activation range from photo, ultrasound, and bioorthogonal click chemistry to exogenous enzymes. Herein, we highlight the recent development of external stimuli-mediated decaging chemistry for the temporospatial delivery of gasotransmitters including nitric oxide, carbon monoxide, hydrogen sulfide and sulfur dioxide, and discuss the pros and cons of different designs.