Radio- and Photosensitizing Os(II)-Based Nanocage for Combined Radio-/Chemo-/X-ray-Induced Photodynamic Therapies, NIR Imaging, and Drug Delivery

Harnessing Porous Coordination Cages for Sonodynamic Therapy: Enhanced Efficacy Through Atomic Precision and Immune Activation

Sonodynamic therapy (SDT) has emerged as a promising non-invasive approach for immunotherapy. However, its broad applicability is often limited by the inefficiency of sonosensitizers. Here, we introduce a novel series of porous coordination cages (PCCs) specifically engineered to enhance sonodynamic therapeutic performance for the first time. These PCCs incorporate energy harvesting and conversion components, with variations in bandgap, electrical conductivity, and redox activity. Characterized by atomically precise compositions and well-defined structures, the PCCs enable strategic manipulation of functionalized moieties and metal centers, allowing for precise control over their sonodynamic efficiency. Their small particle size enhances penetration through dense tumor extracellular matrices, significantly improving tumor permeability. Upon ultrasound stimulation, the PCCs exhibit robust sonodynamic effects, resulting in increased reactive oxygen species (ROS) levels in tumor cells, which triggers apoptosis and antigens release. Notably, PCC-1 demonstrates metal-mediated catalytic activity, converting endogenous hydrogen peroxide into additional ROS, synergistically enhancing SDT efficacy and activating the cyclic GMP-AMP synthase-stimulator of interferon genes (cGAS-STING) pathway in dendritic cells. In tumor model, PCCs effectively inhibited tumor growth and activated immune responses both locally and systemically. Collectively, these findings underscore the exceptional sonodynamic-immunotherapeutic potential of PCCs, paving the way for innovative strategies in tumor treatment.

Activating Metal-Organic Cages by Incorporating Functional M(ImPhen)3 Metalloligands: From Structural Design to Applications

ConspectusThe emulation of ingenious biofunctions has been a research focus for several decades. Metal-organic cages (MOCs), as a type of discrete supramolecular assembly with well-defined shapes and cavities, have aroused great interest in chemists to imitate natural protein cages or enzymes. However, to genuinely achieve tailored functionalities or reactivities of enzymes, the design of cage structures combining both the confined microenvironment and the active site is a prerequisite. Therefore, the integration of functionalized motifs into MOCs is expected to provide a feasible approach to construct biofunctional confined nanospaces, which not only allows the modulation of cage properties for applications such as molecular recognition, transport, and catalysis but also creates unique microenvironments that promote enzymatic effects for special reactivities and selectivities, thereby providing a versatile platform to achieve exceptional biomimetic functions and beyond.In this Account, we specifically focus on our research toward engineering active confined-nanospaces in MOCs via incorporation of M(ImPhen)3 metalloligands, a typical tris-chelate coordination moiety comprising imidazophenanthroline ligands and variable metal ions, as the principle functional units for stepwise assembly of active-MOCs. Starting from their structure design and merits, we describe the versatility of M(ImPhen)3 centers for multifunctionalization of the confined cage-nanospaces. By integrating different metal ions like Ru, Os, Fe, Co, Ni, Zn, the metal ion inherent properties, e.g., redox activity of Fe/Co-centers, chirality, and photoactivity of Ru-centers, and dynamics of Co/Zn-centers, could be integrated and tailored on the cages as isostructural nanosized containers or reactors. Changing the Pd or Pt cage vertices to organic clips could remarkably enhance acid-base stability and endow cages with flexibility and allostery. Utilization of ImPhen organic ligands containing imidazole groups introduces proton transfer capability, which can couple with the high-positive charges on the cage to create amphoteric microenvironments in the porous open-cage solution. Moreover, the nonplanar stereoconfiguration of M(ImPhen)3 confers multiple peripheral pockets on the cage, which render multisite, high-order, and dynamics guest binding for the benefit of applications such as drug delivery, molecular separation, and catalytic turnover.The construction of active-MOCs from tailorable M(ImPhen)3 metalloligands provides us with a new perspective on their structural design and functionalities. Merging the cage confinement with distinct physicochemical properties on a supramolecular level makes it practical to realize synergistic and cooperative effects for functionality enhancement beyond molecular components or the reactivity different from the bulky solution, which could largely expand the potential of MOCs as a multirole platform to wide application scenarios such as artificial photosynthesis, unconventional catalysis, and theranostic nanomedicine.

A Highly Charged Positive Cage Causes Simultaneous Enhancement of Type-II and O2-Independent-Type-I Photodynamic Therapy via One-/Two-Photon Stimulation and Tumor Immunotherapy via PANoptosis and Ferroptosis

To solve the oxygen dependence problem of photodynamic therapy (PDT), it is critical to explore photosensitizers that do not rely on O2 molecule to generate reactive oxygen species (ROS). Herein, a stable cationic metal-organic cage [Pd6(RuLoz 3)8](BF4)28 (MOC-88) that possesses high +28 charges is designed. The cage-confined positive microenvironment enables efficient generation of hydroxyl radicals and improved yield of the singlet oxygen under one-/two-photon excitation, showing excellent performance to concurrently enhance Type-II and O2-independent-Type-I PDT. Moreover, the effective ROS production and robust lipid peroxidation trigger a series of signaling pathways (inflammasome, cyclic guanosine monophosphate-adenosine monophosphate synthase stimulator of interferon genes, and NF-κB) to evoke PANoptosis and ferroptosis in tumor cells, enabling MOC-88 to simultaneously cause the loss of cell membrane integrity, release a series of inflammatory cytokines and damage-associated molecular patterns, stimulate the maturation and antigen presentation ability of dendritic cells, and ultimately activate T-cell-dependent adaptive immunity in vivo to inhibit tumor growth.

Modified frankincense resin stabilized gold nanoparticles for enhanced antioxidant and synergetic activity in in-vitro anticancer studies

For the first time, Frankincense resin (FR) has been carboxymethylated to produce CMFR - AuNPs and the conjugate was utilized for the Doxorubicin drug loading. The carboxymethylation of the carboxylic, phenolic, and hydroxyl functional groups of FR has been developed into carboxymethylated Frankincense resin (CMFR). A novel CMFR-AuNPs was synthesized using the developed CMFR as a stabilizing and reducing agent. The antibacterial, antioxidant, and in-vitro anticancer activities were investigated by using CMFR-AuNPs and CMFR - AuNPs@DOX. CMFR-AuNPs demonstrated antioxidative properties by quenching DPPH radicals effectively. CMFR-AuNPs and DOX@CMFR-AuNPs demonstrated strong antibacterial activity against K. pneumoniae, S. aureus, B. subtilis, and E. coli. The cell viability was tested for CMFR -AuNPs at various concentrations of Dox-loaded CMFR -AuNPs (CMFR-AuNPs + Dox1, CMFR-AuNPs + Dox 2, & CMFR-AuNPs + Dox 3). The highest inhibition was observed on MCF-7 and HeLa cell lines using CMFR-AuNPs + Dox 3, respectively. Various techniques such as UV, FTIR, TGA, XRD, SEM, EDAX and TEM were used to characterize the designed CMFR and CMFR-AuNPs. After carboxy methylation, the amorphous nature of FR changed to crystallinity, as reflected in the XRD spectra. The XRD spectrum of the CMFR- AuNPs showed FCC structure due to the involvement of hydroxyl and carboxylic functional groups of CMFR strongly bound with the AuNPs. TGA results revealed that the CMFR is thermally more stable than FR. TEM revealed that CMFR - AuNPs were well dispersed, spherical, and hexagonal with an average diameter of 7 to 10 nm, while the size of doxorubicin loaded (DOX@CMFR-AuNPs) AuNPs was 11 to 13 nm. Green CMFR-AuNPs have the potential to enhance the drug loading and anticancer efficacy of drugs.

A Redox-Active Phenothiazine-based Pd2L4-Type Coordination Cage and Its Isolable Crystalline Polyradical Cations

Polyradical cages are of great interest because they show very fascinating physical and chemical properties, but many challenges remain, especially for their synthesis and characterization. Herein, we present the synthesis of a polyradical cation cage 14⋅+ through post-synthetic oxidation of a redox-active phenothiazine-based Pd2L4-type coordination cage 1. It's worth noting that 1 exhibits excellent reversible electrochemical and chemical redox activity due to the introduction of a bulky 3,5-di-tert-butyl-4-methoxyphenyl substituent. The generation of 14⋅+ through reversible electrochemical oxidation is investigated by in situ UV/Vis-NIR and EPR spectroelectrochemistry. Meanwhile, chemical oxidation of 1 can also produce 14⋅+ which can be reversibly reduced back to the original cage 1, and the process is monitored by EPR and NMR spectroscopies. Eventually, we succeed in the isolation and single crystal X-ray diffraction analysis of 14⋅+, whose electronic structure and conformation are distinct to original 1. The magnetic susceptibility measurements indicate the predominantly antiferromagnetic interactions between the four phenothiazine radical cations in 14⋅+. We believe that our study including the facile synthesis methodology and in situ spectroelectrochemistry will shed some light on the synthesis and characterization of novel polyradical systems, opening more perspectives for developing functional supramolecular cages.

Precise Post-Synthetic Modification of Heterometal-Organic Capsules for Selectively Encapsulating Tetrahedral Anions

Post-synthetic modification plays a crucial role in precisely adjusting the structure and functions of advanced materials. Herein, we report the self-assembly of a tubular heterometallic Pd3Cu6L16 capsule that incorporates Pd(II) and CuL1 metalloligands. This capsule undergoes further modification with two tridentate anionic ligands (L2) to afford a bicapped Pd3Cu6L16L22 capsule with an Edshammer polyhedral structure. By employing transition metal ions, acid, and oxidation agents, the bicapped capsule can be converted into an uncapped one. This uncapped form can then revert back to the bicapped structure on the addition of Br- ions and a base. Interestingly, introducing Ag+ ions leads to the removal of one L2 ligand from the bicapped capsule, yielding a mono-capped Pd3Cu6L16L2 structure. Furthermore, the size of the anions critically influences the precise control over the post-synthetic modifications of the capsules. It was demonstrated that these capsules selectively encapsulate tetrahedral anions, offering a novel approach for the design of intelligent molecular delivery systems.

Facile synthesis of an acid-responsive cinnamaldehyde-pendant polycarbonate for enhancing the anticancer efficacy of etoposide via glutathione depletion

Glutathione (GSH) is an important antioxidant that maintains cellular redox homeostasis and significantly contributes to resistance against various chemotherapeutic agents. To address the challenge of GSH-mediated drug resistance in etoposide (ETS), we developed a facile synthetic method to prepare a biocompatible acid-responsive polycarbonate (PEG-PCA) containing cinnamaldehyde (CA), a potent GSH-depleting agent, as a side chain using nontoxic raw materials. This polymer self-assembled in aqueous solutions to form nanoparticles (ETS@PCA) that encapsulated ETS, enhancing its water solubility and enabling tumor-targeted delivery. In vitro studies demonstrated that ETS@PCA could respond to the acidic tumor microenvironment, releasing CA to rapidly deplete GSH levels. Consequently, ETS@PCA exhibited superior cytotoxicity compared to free ETS. Furthermore, in vivo experiments corroborated the enhanced tumor inhibitory effects of ETS@PCA.

Dynamic Stereochemistry of M8 Pd6 Supramolecular Cages Based on Metal-Center Lability for Differential Chiral Induction, Resolution, and Recognition

A series of isostructural supramolecular cages with a rhombic dodecahedron shape have been assembled with distinct metal-coordination lability (M8 Pd6 -MOC-16, M=Ru2+ , Fe2+ , Ni2+ , Zn2+ ). The chirality transfer between metal centers generally imposes homochirality on individual cages to enable solvent-dependent spontaneous resolution of Δ8 /Λ8 -M8 Pd6 enantiomers; however, their distinguishable stereochemical dynamics manifests differential chiral phenomena governed by the cage stability following the order Ru8 Pd6 >Ni8 Pd6 >Fe8 Pd6 >Zn8 Pd6 . The highly labile Zn centers endow the Zn8 Pd6 cage with conformational flexibility and deformation, enabling intrigue chiral-Δ8 /Λ8 -Zn8 Pd6 to meso-Δ4 Λ4 -Zn8 Pd6 transition induced by anions. The cage stabilization effect differs from inert Ru2+ , metastable Fe2+ /Ni2+ , and labile Zn2+ , resulting in different chiral-guest induction. Strikingly, solvent-mediated host-guest interactions have been revealed for Δ8 /Λ8 -(Ru/Ni/Fe)8 Pd6 cages to discriminate the chiral recognition of the guests with opposite chirality. These results demonstrate a versatile procedure to control the stereochemistry of metal-organic cages based on the dynamic metal centers, thus providing guidance to maneuver cage chirality at a supramolecular level by virtue of the solvent, anion, and guest to benefit practical applications.