A Mn(III)-Sealed Metal-Organic Framework Nanosystem for Redox-Unlocked Tumor Theranostics

Metal-Organic Framework Derived Multicomponent Nanoagent as a Reactive Oxygen Species Amplifier for Enhanced Photodynamic Therapy

Intracellular antioxidants such as glutathione (GSH) play a critical role in protecting malignant tumor cells from apoptosis induced by reactive oxygen species (ROS) and in mechanisms of multidrug and radiation resistance. Herein, we rationally design two multicomponent self-assembled photodynamic therapy (PDT) nanoagents, that is, Glup-MFi-c and Glud-MFo-c, which consist of respective GSH-passivation and GSH-depletion linkers in metal-organic frameworks encapsulated with photosensitizers for a deeply comprehensive understanding of GSH-based tumor PDT. Multicomponent coordination, π-π stacking, and electrostatic interactions among metal ions, photosensitizers, and bridging linkers under the protection of a biocompatible polymer generate homogeneous nanoparticles with satisfied size, good colloid stability, and ultrahigh loading capacity. Compared to the GSH-passivated Glup-MFi-c, the GSH-depleted Glud-MFo-c shows pH-responsive release of photosensitizer and [Fe^III(CN)₆] linker in tumor cells to efficiently deplete intracellular GSH, thus amplifying the cell-killing efficiency of ROS and suppressing the tumor growth in vivo. This study demonstrates that Glud-MFo-c acts as a ROS amplifier, providing a useful strategy to deeply understand the role of GSH in combating cancer.

Regulation of redox balance using a biocompatible nanoplatform enhances phototherapy efficacy and suppresses tumor metastasis

Many cancer treatments including photodynamic therapy (PDT) utilize reactive oxygen species (ROS) to kill tumor cells. However, elevated antioxidant defense systems in cancer cells result in resistance to the therapy involving ROS. Here we describe a highly effective phototherapy through regulation of redox homeostasis with a biocompatible and versatile nanotherapeutic to inhibit tumor growth and metastasis. We systematically explore and exploit methylene blue adsorbed polydopamine nanoparticles as a targeted and precise nanocarrier, oxidative stress amplifier, photodynamic/photothermal agent, and multimodal probe for fluorescence, photothermal and photoacoustic imaging to enhance anti-tumor efficacy. Remarkably, following the glutathione-stimulated photosensitizer release to generate exogenous ROS, polydopamine eliminates the endogenous ROS scavenging system through depleting the primary antioxidant, thus amplifying the phototherapy and effectively suppressing tumor growth in vitro and in vivo. Furthermore, this approach enables a robust inhibition against breast cancer metastasis, as oxidative stress is a vital impediment to distant metastasis in tumor cells. Innovative, safe and effective nanotherapeutics via regulation of redox balance may provide a clinically relevant approach for cancer treatment.

Targeted GSH-exhausting and hydroxyl radical self-producing manganese-silica nanomissiles for MRI guided ferroptotic cancer therapy

Ferroptosis, a cell death path induced by the generation of reactive oxygen species (ROS), will cause the accumulation of lipid peroxides (PL-PUFA-OOH) and achieve potent tumor-regression. However, glutathione (GSH)-dependent glutathione peroxidase 4 (GPx4) can reduce PL-PUFA-OOH and antagonize the ferroptosis inducing effect of ROS. Herein, folate-PEG modified dihydroartemisinin (DHA) loaded manganese doped mesoporous silica nanoparticles (described as nanomissiles) were constructed for integrating the effect of GSH exhaustion and ROS generation. After endocytosis by tumor cells, intracellular GSH triggered the degradation of nanomissiles, which allowed the simultaneous release of DHA and Fenton catalytic Mn2+ due to the redox reaction between the manganese-oxygen bonds and GSH. The degradation would lead to GSH exhaustion, activation of Mn2+-based magnetic resonance imaging (MRI), and DHA-driven ˙OH generation. The GSH-free environment inhibited the activity of GPx4 and enhanced the accumulation of PL-PUFA-OOH oxidized by ˙OH. Furthermore, the cooperative effects suppressed tumor metastasis by destroying the structure of polyunsaturated fatty acids in the cell membranes and showed potent antitumor activity. This innovative ferroptotic therapy integrating the GSH exhaustion and ROS generation will be a promising strategy for cancer therapy.

DNA adsorption on nanoscale zeolitic imidazolate framework-8 enabling rational design of a DNA-based nanoprobe for gene detection and regulation in living cells

DNA functionalized nanomaterials have attracted tremendous attention for bioanalytical applications. Owing to exceptional fluorescence quenching ability, most DNA-based nanoprobes were designed with turn-on signals for target gene detection, while only a few of them could simultaneously achieve gene detection and regulation in one system. In this study, we explored the use of nanoscale zeolitic imidazolate framework-8 (ZIF-8) as a building block to construct a DNA-based nanoprobe. We found ZIF-8 could stably adsorb DNA to resist the dissociation by various biological ligands, enabling potential biological applications. However, ZIF-8 was not a nano-quencher to turn off the fluorophore labeling on the adsorbed DNA. We therefore designed a DNAzyme embedded molecular beacon (DMB) to functionalize ZIF-8. After endocytosis, ZIF-8 was disintegrated to release DMB for target mRNA detection, and the co-released Zn2+ acted as an effective cofactor to activate the embedded DNAzyme for mRNA regulation. This study provides a versatile nano-platform to realize multiple functions inside cells by using functional nucleic acids, which holds great promise for theranostic applications.

Biocompatible Fe-Hematoporphyrin coordination nanoplatforms with efficient sonodynamic-chemo effects on deep-seated tumors

Sonodynamic therapy (SDT) utilizing semiconductors or organic sonosensitizers has attracted increasing attention as a noninvasive treatment for deep-seated tumors, but its practical applications are still limited due to unsatisfactory therapeutical effects. To address the issue, we reported a metal-organic nanosonosensitizer by assembling clinical drug hematoporphyrin monomethyl ether (HMME) with Fe(III) ions through covalently coordination. The Fe-HMME coordination particles (FeCPs) had the average size of ~70 nm, and they were surface-modified with phospholipids to confer high hydrophilicity and stability. Upon ultrasound irradiation, they efficiently produced ¹O₂ to destroy cancer cells coated without or with tissue-barriers (1-3 cm). Importantly, the porous structure of FeCPs facilitated high loading capacity (31.3%) of anticancer drug doxorubicin (DOX), and the DOX@FeCPs exhibited pH-sensitive and ultrasound-enhanced releasing behavior that was favorable to the acidic microenvironment of tumors. When the lipids-coated FeCPs were intravenously injected into tumor-bearing mouse, they could passively accumulate within tumors, leading to the magnetic resonance imaging of tumors. Importantly, as deep-seated tumor model, tumors covered with barrier were exposed to ultrasound and thereafter their growth was significantly inhibited by SDT of FeCPs. The inhibition effects could be further enhanced by DOX@FeCPs due to the SDT-chemo combined therapy. Therefore, the DOX@FeCPs have achieved good therapeutical performances on deep-seated tumor and would supply some insights on the design of other metal-organic nanoplatforms.

Developing a Novel Nanoscale Porphyrinic Metal-Organic Framework: A Bifunctional Platform with Sensitive Fluorescent Detection and Elimination of Nitenpyram in Agricultural Environment

Developing a rapid sensing platform with effective pesticide degradation capabilities integrated into a single structure and realistic application is an imminent challenge to ensure sustainable agriculture and food safety. Here, we described establishment of a bifunctional nanoscale porphyrinic metal-organic framework (MOF) probe serving as a sensor for detection of trace nitenpyram and as a photocatalyst to facilitate the pesticide degradation. Based on the signal turned "on-off", the strong fluorescence of the probe was quenched by the target, leading to the sensing range from 0.05 to 10.0 μg mL^-1 and a detection limit of 0.03 μg mL^-1. Given the versatile design by which the porphyrin photosensitizers were isolated subtly in the MOF to avoid self-quenching, the probe was endowed with sustainable and efficient pesticide photodegradation activity with a degradation rate of ∼95% for nitenpyram. Our work represents powerful all-in-one MOF-derived materials jointly for sensing and degrading pesticide residues in agricultural soils and other pesticide-contaminated environments.

Fusiform-Like Copper(II)-Based Metal-Organic Framework through Relief Hypoxia and GSH-Depletion Co-Enhanced Starvation and Chemodynamic Synergetic Cancer Therapy

The therapeutic effect of traditional chemodynamic therapy (CDT) agents is severely restricted by their weakly acidic pH and glutathione (GSH) overexpression in the tumor microenvironment. Here, fusiform-like copper(II)-based tetrakis(4-carboxy phenyl)porphyrin (TCPP) nanoscale metal-organic frameworks (nMOFs) were designed and constructed for the first time (named PCN-224(Cu)-GOD@MnO₂). The coated MnO₂ layer can not only avoid conjugation of glucose oxidase (GOD) to damage normal cells but also catalyzes the generation of O₂ from H₂O₂ to enhance the oxidation of glucose (Glu) by GOD, which also provides abundant H₂O₂ for the subsequent Cu⁺-based Fenton-like reaction. Meanwhile, the Cu²⁺ chelated to the TCPP ligand is converted to Cu⁺ by the excess GSH in the tumor, which reduces the tumor antioxidant activity to improve the CDT effect. Next, the Cu⁺ reacts with the plentiful H₂O₂ by enzyme catalysis to produce a toxic hydroxyl radical (^•OH), and singlet oxygen (¹O₂) is synchronously generated from combination with Cu⁺, O₂, and H₂O via the Russell mechanism. Furthermore, the nanoplatform can be used for both TCPP-based in vivo fluorescence imaging and Mn²⁺-induced T₁-weighted magnetic resonance imaging. In conclusion, fusiform-like PCN-224(Cu)-GOD@MnO₂ nMOFs facilitate the therapeutic efficiency of chemodynamic and starvation therapy via combination with relief hypoxia and GSH depletion after acting as an accurate imaging guide.

A promising anticancer drug: a photosensitizer based on the porphyrin skeleton

Photodynamic therapy (PDT) is a minimally invasive combination of treatments that treat tumors and other diseases by using photosensitizers, light and oxygen to produce cytotoxic reactive oxygen species (ROS) inducing tumor cell apoptosis. Photosensitizers are the key part of PDT for clinical application and experimental research, and most of them are porphyrin compounds at present. Due to their unique affinity for tumor tissues, porphyrins are not only excellent photosensitizers, but also good carriers to transport other active drugs into tumor tissues, which can exert synergistic anticancer effects of PDT and chemotherapy. This article reviews the clinical development of porphyrin photosensitizers and the research status of porphyrin containing bioactive groups. Finally, future perspectives and the current challenges of photosensitizers based on the porphyrin skeleton are discussed.

Epitope Molecularly Imprinted Polymer Nanoparticles for Chemo-/Photodynamic Synergistic Cancer Therapy Guided by Targeted Fluorescence Imaging

It is a still tough task to precisely target cancer cells and efficiently improve the therapeutic efficacy of various therapies at the same time. Here, dual-template imprinting polymer nanoparticles (MIPs) with a core-shell structure were prepared, in which fluorescent silica nanoparticles (FSiO₂) were the core and the imprinted polymer layers were the outermost shell. The imprinted layer was designed and constructed via free-radical precipitation approach on the surface of FSiO₂, which simultaneously encapsulated gadolinium-doped silicon quantum dots and photosensitizers (Ce6). During the polymerization process, two template molecules were introduced into the mixtures, one was the epitope of CD59 protein (YNCPNPTADCK), which was overexpressed on the surface of a great deal of the solid cancers, and the other was antitumor agent doxorubicin (DOX) to be used for chemotherapy. Furthermore, the embedded Ce6 could generate toxic ¹O₂ under 655 nm laser irradiation to kill cancer cells, combining with the loaded-DOX to obtain a synergistic cancer therapy. Moreover, owing to the introduction of gadolinium-doped silicon quantum dots, Ce6, and DOX, the MIPs were endowed with targeted fluorescence imaging (FI) and MR imaging (MRI). In vitro and in vivo experiments had been conducted to demonstrate the excellent targeting ability and desirable treatment effect with negligible toxicity to healthy tissues and organs. As a consequence, the designed MIPs can promote the development of targeted recognition against biomarkers and precise treatment guided with cell imaging tools.

Photothermal-reinforced and glutathione-triggered in Situ cascaded nanocatalytic therapy

Tumor microenvironment (TME)-responsive nanoformulations that catalyze a cascade of intracellular redox reactions showed promise for tumor treatment with high specificity and efficiency. In this study, we report Cu²⁺-doped zeolitic imidazolate frameworks-coated polydopamine nanoparticles (PDA@Cu/ZIF-8 NPs) for glutathione-triggered and photothermal-reinforced sequential catalytic therapy against breast cancer. In the TME, the PDA@Cu/ZIF-8 NPs could initially react with antioxidant glutathione (GSH), inducing GSH depletion and Cu⁺ generation. Whereafter, the generated Cu⁺ would catalyze local H₂O₂ to produce highly toxic hydroxyl radicals (·OH) through an efficient Fenton-like reaction even in weakly acidity. Importantly, the PDA could exert excellent photothermal conversion effect to simultaneously accelerate GSH consumption and improve the Fenton-like reaction for further expanding the intracellular oxidative stress, which innovatively achieves a synergistic photothermal-chemodynamic therapy for highly efficient anticancer treatment.

Green Layer-by-Layer Assembly of Porphyrin/G-Quadruplex-Based Near-Infrared Nanocomposite Photosensitizer with High Biocompatibility and Bioavailability

A simple and green layer-by-layer assembly strategy is developed for the preparation of a highly bioavailable nanocomposite photosensitizer by assembling near-infrared (NIR) light-sensitive porphyrin/G-quadruplex complexes on the surface of a highly biocompatible nanoparticle that is prepared via Zn²⁺-assisted coordination self-assembly of an amphiphilic amino acid. After being efficiently delivered to the target site and internalized into tumor cells via enhanced permeability and retention effect and interactions between aptamers and tumor markers, the as-prepared nanoassembly can be directly used as an NIR light-responsive photosensitizer for tumor photodynamic therapy (PDT) since the porphyrin/G-quadruplex complexes are exposed on the nanoassembly surface and kept in an active state. It can also disassemble under the synergistic stimuli of an acidic pH environment and overexpressed glutathione, leasing more efficient porphyrin/G-quadruplex composite photosensitizers while reducing the interference caused by glutathione-dependent ¹O₂ consumption. Since the nanoassembly can work no matter if it is disassembled or not, the compulsory requirement for in vivo photosensitizer release is eliminated, thus resulting in the great improvement of the bioavailability of the photosensitizer. The PDT applications of the nanoassembly were well demonstrated in both in vitro cell and in vivo animal experiments.

Novel triorganotin complexes based on phosphonic acid ligands: Syntheses, structures and in vitro cytostatic activity

Six novel organotin phosphonate complexes, [(Me₃Sn)₄(HL¹)₄]_n1, [(Me₃Sn)₂(HL²)₂]_n2, [(Me₃Sn)₂L³(H₂O)]_n3, [(Ph₃Sn)(HL¹)]₆4, [(Ph₃Sn)₂L²]_n5 and [(Ph₃Sn)₂L³]₆6, derived from phosphonic acid ligands [NaHL¹ = 1-C₁₀H₇OPO₂(OH)Na, H₂L² = 1-C₁₀H₇PO(OH)₂, H₂L³ = 2-C₁₀H₇PO(OH)₂], have been synthesized and characterized by elemental analysis, FT-IR, NMR (¹H, ¹³C, ³¹P and ¹¹⁹Sn) spectroscopy and X-ray crystallography. The structural analysis reveals that complexes 1 and 5 display 1D infinite zig-zag chain structures, and complex 2 shows 1D right-handed helical chain structure, while complex 3 displays 1D left-handed helical chain structure. Complexes 4 and 6 are 24-membered macrocyclic rings interconnected by P, O and Sn atoms. Additionally, the molecules of complexes 1 and 3 are further linked through intermolecular π···π and O-H···O interaction into supramolecular structures, respectively. Furthermore, we preliminarily estimated in vitro cytostatic activity of complexes 1-6 against the human cervix tumor cells (HeLa), human hepatocellular carcinoma cells (HepG-2) and human normal breast cells (HBL-100). Importantly, the anti-proliferative properties and possible pathway of complex 6 are investigated, and the results demonstrate that complex 6 could induce apoptotic cell death via an overload of intracellular reactive oxygen species (ROS) levels and the dysfunctional depolarization of mitochondrial membranes.

Mn-Porphyrin-Based Metal-Organic Framework with High Longitudinal Relaxivity for Magnetic Resonance Imaging Guidance and Oxygen Self-Supplementing Photodynamic Therapy

A nanoplatform for magnetic resonance imaging guidance and oxygen self-supplementing photodynamic therapy (PDT) was constructed on the basis of a porous metal-organic framework (PCN-222(Mn)), which was built by simple Mn-porphyrin ligands and biocompatible Zr⁴⁺ ions. Because of the good dispersibility of Mn³⁺ in the open framework and the high water affinity of the channel, PCN-222(Mn) exhibits a high longitudinal relaxivity of ∼35.3 mM^-1 s^-1 (1.0 T). In addition, it shows good catalytic activity for the conversion of endogenous hydrogen peroxide into oxygen, thereby improving tumor hypoxia during photodynamic therapy. The intravenous injection of PCN-222(Mn) into tumor-bearing mice mode provided good T₁-weighted contrast of the tumor site and effectively inhibited tumor growth upon a single-laser irradiation. The findings provide insights for the development of multifunctional theranostic nanoplatforms based on simple components.

Acid-Triggered Nanoexpansion Polymeric Micelles for Enhanced Photodynamic Therapy

Photodynamic therapy (PDT) as a noninvasive and selective treatment technology has presented great potential in cancer prevention and precision medicine, but its therapeutic efficacy is still greatly inhibited by the limitations of photosensitizers (PSs) in the microenvironment such as the aggregation caused quenching (ACQ) of PSs. Herein, we proposed an "acid-triggered nanoexpansion" method to further reduce the aggregation of photosensitizers by constructing acetal-based polymeric micelles. A pH-responsive amphiphilic block copolymer, POEGMA-b-[PTTMA-co-PTPPC6MA] was synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization and self-assembled into spherical micelles. In the normal physiological environment, the micelles were stable and had good biocompatibility. Upon entry into the acidic microenvironment of the tumor, the acid-responsive hydrophobic 2, 4, 6-trimethoxybenzaldehyde in the micelles hydrolyzed and generated a hydrophilic diol moiety. Although the hydrophility of the micellar core was increased, the assembled structure of block copolymers was not dissociated but expanded. The responsive expansion of the micelles could allow the photosensitizers to well-disperse in the core, whereas more tumor-dissolved oxygen entered the micelles. This phenomenon could provide a better nanoenvironment for photosensitizers to reduce the ACQ of the photosensitizers, leading to more singlet oxygen (¹O₂) produced under the laser irradiation (650 nm). Both in vitro and in vivo studies have demonstrated that the remarkable photodynamic therapeutic efficacy of acid-responsive micelles could be realized. Thus, the acid-triggered nanoexpansion method might provide more possibilities to develop efficient platforms for treating cancers.

Self-quenching synthesis of coordination polymer pre-drug nanoparticles for selective photodynamic therapy

A novel “pre-photodynamic” nanoparticles (Fe-IBDP NPs) with a tumor microenvironment (TME)-activatable PDT and good biodegradability were synthesized by self-quenching strategy.