Structure-Activity Relationship Studies Leading to the Discovery of Highly Water-Soluble and Biocompatible Acyclic Cucurbit[n]uril FY-3451 as a Universal Antagonist That Rapidly Reverses Neuromuscular Blocking Agents In Vivo.

The development of a reversal agent that can rapidly reverse clinically used nondepolarizing neuromuscular blocking agents (NMBAs) has long been a challenge. Here, we report the synthesis of a series of highly water-soluble acyclic cucurbit[n]urils (acCBs). Systematic structure-activity relationship studies reveal that introducing two propylidene units on the peripheral benzene rings not only remarkably improves the activity of the corresponding derivative acCB6 (FY 3451) in reversing the neuromuscular block of rocuronium, cisatracurium, vecuronium, and pancuronium, the four clinically used NMBAs, through stable inclusion, but also allows for high water-solubility as well as a maximum tolerated dose (2000 mg/kg on rats). In vivo experiments with rats show that, at the identical dose of 25 mg/kg, for rocuronium, vecuronium, and pancuronium, acCB6 can achieve a recovery time shorter than that of sugammadex for rocuronium and, at the dose of 100 mg/kg, realize comparably rapid reversal for cisatracurium.

Caltrop-like Small-Molecule Antidotes That Neutralize Unfractionated Heparin and Low-Molecular-Weight Heparin In Vivo.

Unfractionated heparin (UFH) and low-molecular-weight heparins (LMWHs) are widely applied for surgical procedures and extracorporeal therapies, which, however, suffer bleeding risk. Protamine, the only clinically approved antidote, can completely neutralize UFH, but only partially neutralizes LMWHs, and also has a number of safety drawbacks. Here, we show that caltrop-like multicationic small molecules can completely neutralize both UFH and LMWHs. In vitro and ex vivo assays with plasma and whole blood and in vivo assays with mice and rats support that the lead compound is not only superior to protamine by displaying higher neutralization activity and broader therapeutic windows but also biocompatible. The effective neutralization dose and the maximum tolerated dose of the lead compound are determined to be 0.4 and 25 mg/kg in mice, respectively, suggesting good promise for further preclinical studies.

Macrocycles and Acyclic Cucurbit[n]urils as Pseudo[2]catenane Partners for Long-Acting Neuromuscular Blocks and Rapid Reversal In Vivo.

Long-acting neuromuscular blocks followed by rapid reversal may provide prolonged surgeries with improved conditions by omitting repetitive or continuous administration of the neuromuscular blocking agent (NMBA), eliminating residual neuromuscular block and minimizing postoperative recovery, which, however, is not clinically available. Here, we demonstrate that imidazolium-based macrocycles (IMCs) and acyclic cucurbit[n]urils (ACBs) can form such partners by functioning as long-acting NMBAs and rapid reversal agents through a pseudo[2]catenation mechanism based on stable complexation with Ka values of over 109 M-1. In vivo experiments with rats reveal that, at the dose of 2- and 3-fold ED90, one IMC attains a duration of action corresponding to 158 or 442 min for human adults, covering most of prolonged surgeries. The block can be reversed by one ACB with recovery time significantly shorter than that achieved by sugammadex for reversing the block of rocuronium, the clinically most widely used intermediate-acting NMBA.

Bioinspired Self-Assembly of Metalloporphyrins and Polyelectrolytes into Hierarchical Supramolecular Nanostructures for Enhanced Photocatalytic H2 Production in Water.

Polypeptides, as natural polyelectrolytes, are assembled into tailored proteins to integrate chromophores and catalytic sites for photosynthesis. Mimicking nature to create the water-soluble nanoassemblies from synthetic polyelectrolytes and photocatalytic molecular species for artificial photosynthesis is still rare. Here, we report the enhancement of the full-spectrum solar-light-driven H2 production within a supramolecular system built by the co-assembly of anionic metalloporphyrins with cationic polyelectrolytes in water. This supramolecular photocatalytic system achieves a H2 production rate of 793 and 685 µmol h-1 g-1 over 24 h with a combination of Mg or Zn porphyrin as photosensitizers and Cu porphyrin as a catalyst, which is more than 23 times higher than that of free molecular controls. With a photosensitizer to catalyst ratio of 10000 : 1, the highest H2 production rate of >51,700 µmol h-1 g-1 with a turnover number (TON) of >1,290 per molecular catalyst was achieved over 24 h irradiation. The hierarchical self-assembly not only enhances photostability through forming ordered stackings of the metalloporphyrins but also facilitates both energy and electron transfer from antenna molecules to catalysts, and therefore promotes the photocatalysis. This study provides structural and mechanistic insights into the self-assembly enhanced photostability and catalytic performance of supramolecular photocatalytic systems.

Host-guest binding of tetracationic cyclophanes to photodynamic agents inhibits posttreatment phototoxicity and maintains antitumour efficacy.

In the past two decades, photodynamic therapy (PDT) has become an effective method for the treatment of cancer. However, the posttreatment residue of photodynamic agents (PDAs) causes long-term skin phototoxicity. Here, we apply naphthalene-derived, box-like tetracationic cyclophanes, named NpBoxes, to bind to clinically used porphyrin-based PDAs to alleviate their posttreatment phototoxicity by reducing their free content in skin tissues and 1O2 quantum yield. We show that one of the cyclophanes, 2,6-NpBox, could include the PDAs to efficiently suppress their photosensitivity for the generation of reactive oxygen species. A tumour-bearing mouse model study revealed that, when Photofrin, the most widely used PDA in clinic, was administrated at a dose corresponding to the clinical one, 2,6-NpBox of the same dose could significantly suppress its posttreatment phototoxicity on the skin induced by simulated sunlight irradiation, without imposing a negative influence on its PDT efficacy.

Highly Water-Soluble Cucurbit[8]uril Derivative as a Broad-Spectrum Neuromuscular Block Reversal Agent.

Broad-spectrum agents for the reversal of residual curarization induced by neuromuscular blocking agents are of great significance. Here, we report a highly water-soluble cucurbit[8]uril (CB[8]) derivative as a broad-spectrum neuromuscular block reversal agent induced by both benzylisquinolinium and aminosteroid neuromuscular block agents by the supramolecular sequestration strategy. The UV/Vis competition titration assays suggest the high binding affinity of the CB[8] derivative toward both benzylisquinolinium-type cisatracurium besylate and aminosteroid-type rocuronium, vecuronium, and pancuronium, at the level of 107 M-1. In vivo studies demonstrate that the administration of the CB[8] derivative could significantly accelerate the recovery time compared to the placebo or neostigmine groups. The reversal activity of the CB[8] derivative is comparable to or higher than that of clinically approved sugammadex. Acute toxicity evaluations reveal that the CB[8]-derivative displays outstanding biocompatibility, with the maximum tolerance dose as high as 960 mg kg-1.

Flexible organic frameworks sequester neuromuscular blocking agents in vitro and reverse neuromuscular block in vivo.

Supramolecular sequestration and reversal of neuromuscular block (NMB) have great clinical applications. Water-soluble flexible organic frameworks (FOFs) cross-linked by disulfide bonds are designed and prepared. Different linker lengths are introduced to FOFs to give them varied pore sizes. FOFs are anionic nanoscale polymers and capable of encapsulating cationic neuromuscular blocking agents (NMBAs), including rocuronium (Roc), vecuronium (Vec), pancuronium (Panc) and cisatracurium (Cis). A host-guest study confirms that FOFs bind NMBAs in water. The multivalency interaction between FOFs and NMBAs is able to sequester NMBAs, and prevent them from escaping. These FOFs are non-toxic and biocompatible. Animal studies show that FOFs are effective for the reversal of NMB induced by Roc, Vec and Cis, which shorten the time to a train-of-four ratio of 0.9 by 2.6, 3.8 and 5.7-fold compared to a placebo, respectively.

Supramolecular Organic Frameworks: Exploring Water-Soluble, Regular Nanopores for Biomedical Applications.

In past decades, regular porous architectures have received a great amount of attention because of their versatile functions and applications derived from their efficient adsorption of various guests. However, most reported porous architectures exist only in the solid state. Therefore, their applications as biomaterials may face several challenges, such as phase separation, slow degradation, and long-term accumulation in the body. This Account summarizes our efforts with respect to the development and biomedical applications of water-soluble 3D diamondoid supramolecular organic frameworks (dSOFs), a family of supramolecular polymers that possess intrinsic regular nanoscale porosity.dSOFs have been constructed from tetratopic components and cucurbit[8]uril (CB[8]) through hydrophobically driven encapsulation by CB[8] for intermolecular dimers formed by peripheral aromatic subunits of the tetratopic components in water. All dSOFs exhibit porosity regularity or periodicity in aqueous solution, which is confirmed by solution-phase synchrotron SAXS and XRD experiments. Dynamic light scattering (DLS) reveals that their sizes range from 50 to 150 nm, depending on the concentrations of the components. As nonequilibrium supramolecular architectures, dSOFs can maintain their nanoscale sizes at micromolar concentrations for dozens of hours. Their diamondoid pores have aperture sizes ranging from 2.1 to 3.6 nm, whereas their water solubility and porosity regularity allow them to rapidly include discrete guests driven by ion-pair electrostatic attraction, hydrophobicity, or a combination of the two interactions. The guests may be small molecule or large macromolecular drugs, photodynamic agents (PDAs), or DNA.The rapid inclusion of bioactive guests into dSOFs has led to two important biofunctions. The first is to function as antidotes through including residual drugs. For heparins, the inclusion results in full neutralization of their anticoagulant activity. For clinically used porphyrin PDAs, the inclusion can alleviate their long-term posttreatment phototoxicity but does not reduce their photodynamic efficacy. The second is to function as in situ loading carriers for the intracellular delivery of antitumor drugs or DNA. Their nanoscale sizes bring out their ability to overcome the multidrug resistance of tumor cells, which leads to a remarkable enhancement of the bioactivity of the included drugs. By conjugating aldoxorubicin to tetrahedral components, albumin-mimicking prodrugs have also been constructed, which conspicuously improves the efficacy of aldoxorubicin toward multi-drug-resistant tumors through the delivery of the frameworks. As new supramolecular drugs and carriers, dSOFs are generally biocompatible. Thus, further efforts might lead to medical benefits in the future.

Conjugating aldoxorubicin to supramolecular organic frameworks: polymeric prodrugs with enhanced therapeutic efficacy and safety.

Phase I-III clinical studies show that aldoxorubicin (AlDox), a prodrug of doxorubicin (Dox), displays reduced cardiotoxicity compared to Dox, but does not demonstrate an overall survival benefit in patients. Here we report that three-dimensional supramolecular organic frameworks (SOFs) can conjugate AlDox through quantitative thiol-maleimide addition to afford two polymeric prodrugs of Dox. The previously established ability of SOFs in overcoming the multidrug resistance of tumor cells is utilized to achieve efficient intracellular delivery of the conjugated AlDox, which releases Dox as an active agent through acid-responsive hydrolysis of the hydrazone bond of AlDox within tumor cells. In vitro and in vivo experiments show that conjugation to SOF significantly improves the antitumor efficacy of AlDox as compared with free AlDox of the identical dose. Moreover, the SOF prodrugs do not show cardiotoxicity, the major superiority of AlDox over Dox. Since free AlDox is conjugated to endogenous albumin in the blood through thiol-maleimide addition to achieve enhanced intracellular delivery and Dox release through acid-responsive hydrazone hydrolysis, SOF conjugation provides a surrogate strategy for prodrug design to gain improved efficacy.

Porous Polymers as Universal Reversal Agents for Heparin Anticoagulants through an Inclusion-Sequestration Mechanism.

Heparins are widely used anticoagulants for surgical procedures and extracorporeal therapies. However, all of them have bleeding risks. Protamine sulfate, the only clinically approved antidote for unfractionated heparin (UFH), has adverse effects. Moreover, protamine can only partially neutralize low-molecular-weight heparins (LMWHs) and is not effective for fondaparinux. Here, an inclusion-sequestration strategy for efficient neutralization of heparin anticoagulants by cationic porous supramolecular organic frameworks (SOFs) and porous organic polymers (POPs) is reported. Isothermal titration calorimetric and fluorescence experiments show strong binding affinities of these porous polymers toward heparins, whereas dynamic light scattering and zeta potential analysis confirm that the heparin sequences are adsorbed into the interior of the porous hosts. Activated partial thromboplastin time, anti-FXa, and thromboelastography assays indicate that their neutralization efficacies are higher than or as high as that of protamine for UFH and generally superior to protamine for LMWHs and fondaparinux, which is further confirmed by tail-transection model in mice and ex vivo aPTT or anti-FXa analysis in rats. Acute toxicity evaluations reveal that one of the SOFs displays outstanding biocompatibility. This work suggests that porous polymers can supply safe and rapid reversal of clinically used heparins, as protamine surrogates, providing an improved approach for their neutralization.

Two-Dimensional Covalent and Supramolecular Polymers: From Monolayer to Bilayer and the Thicker.

Selective preparation of two-dimensional polymers (2DPs) and supramolecular polymers (2DSPs) with defined thickness is crucially important for controlling and maximizing their functions, yet it has remained as a synthetic challenge. In the past decade, several approaches have been developed to allow selective preparation of discrete monolayer 2DPs and 2DSPs. Recently, crystal exfoliation and self-assembly strategies have been employed to successfully prepare bilayer 2DP and 2DSP, which represent the first step towards the controlled "growth" of 2D polymers from the thinnest monolayers to thicker few-layers along the third dimension. This Concept review discusses the concept of accurate synthesis of 2D polymers with defined layers. Advances in this research area will pave the way to rational synthetic strategies for 2D polymers with controlled thickness.

Porous dynamic covalent polymers as promising reversal agents for heparin anticoagulants.

Heparins are natural and partially degraded polyelectrolytes that consist of sulfated polysaccharide backbones. However, as clinically used anticoagulants, heparins are associated with clinical bleeding risks and thus require rapid neutralization. Protamine sulfate is the only clinically approved antidote for unfractionated heparin (UFH), which not only may cause severe adverse reactions in patients, but also is only partially effective against low molecular weight heparins (LMWHs). We here present the facile synthesis of four porous multicationic dynamic covalent polymers (DCPs) from the condensation of tritopic aldehyde and acylhydrazine precursors. We show that, as new water-soluble polymeric antidotes, the new DCPs can effectively include both UFH and LMWHs and thus reverse their anticoagulating activity, which is confirmed by the activated partial thromboplastin time and thromboelastographic assays as well as mouse tail transection assay (bleeding model). The neutralization activities of two of the DCPs were found to be overall superior to that of protamine and have wider concentration windows and good biocompatibility. This pore-inclusion neutralization strategy paves the way for the development of water-soluble polymers as universal heparin binding agents.

Water-soluble and dispersible porous organic polymers: preparation, functions and applications.

Porous organic polymers (POPs) have attracted increasing attention and emerged as a new research area in polymer chemistry. During the past decade, the intense desirability for application in aqueous scenarios has spawned the development of a specific class of POPs, i.e., water-soluble or dispersible porous organic polymers (WS-POPs) that can allow the implementation of porosity-based functions in aqueous media. In this Tutorial Review, aiming at providing a practical guide to this area, we will discuss recent advances in the preparation of WS-POPs through covalent/dynamic covalent, coordination and supramolecular approaches. As a result of their intrinsic and well-defined porosity, diverse topological architectures as well as unique water-processable features, many water-soluble/dispersible POPs have been demonstrated to exhibit potential for various applications, which include drug, DNA and protein delivery, bioimaging, photocatalysis, explosive detection and membrane separation. We will also highlight the related function of the representative structures. Finally, we provide our perspective for the future research, with a focus on the development of new structures and biofunctions.

Self-Assembly of a Bilayer 2D Supramolecular Organic Framework in Water.

Accurate control of the layer number of orderly stacked 2D polymers has been an unsettled challenge in self-assembly. Herein we describe the fabrication of a bilayer 2D supramolecular organic framework from a monolayer 2D supramolecular organic framework in water by utilizing the cooperative coordination of a rod-like bipyridine ligands to zinc porphyrin subunits of the monolayer network. The monolayer supramolecular framework is prepared from the co-assembly of an octacationic zinc porphyrin monomer and cucurbit[8]uril (CB[8]) in water through CB[8]-encapsulation-promoted dimerization of 4-phenylpyridiunium subunits that the zinc porphyrin monomer bear. The bilayer 2D supramolecular organic framework exhibits structural regularity in both solution and the solid state, which is characterized by synchrotron small-angle X-ray scattering and high-resolution transmission electron microscopic techniques. Atomic force microscopic imaging confirms that the bilayer character of the 2D supramolecular organic framework can be realized selectively on the micrometer scale.

Enhancing Hydrogen Generation Through Nanoconfinement of Sensitizers and Catalysts in a Homogeneous Supramolecular Organic Framework.

Enrichment of molecular photosensitizers and catalysts in a confined nanospace is conducive for photocatalytic reactions due to improved photoexcited electron transfer from photosensitizers to catalysts. Herein, the self-assembly of a highly stable 3D supramolecular organic framework from a rigid bipyridine-derived tetrahedral monomer and cucurbit[8]uril in water, and its efficient and simultaneous intake of both [Ru(bpy)3 ]2+ -based photosensitizers and various polyoxometalates, that can take place at very low loading, are reported. The enrichment substantially increases the apparent concentration of both photosensitizer and catalyst in the interior of the framework, which leads to a recyclable, homogeneous, visible light-driven photocatalytic system with 110-fold increase of the turnover number for the hydrogen evolution reaction.

2:2 Complexes from Diphenylpyridiniums and Cucurbit[8]uril: Encapsulation-Promoted Dimerization of Electrostatically Repulsing Pyridiniums.

Rigid linear compounds G1 and G2, which contained two 4-phenylpyridinium (PhPy+ ) units, have been prepared to investigate their binding with cucurbit[8]uril (CB[8]). X-ray crystallographic structures revealed that in the solid state both compounds were included by CB[8], through antiparallel stacking, to form 2:2 quaternary complexes (G1)2 @(CB[8])2 and (G2)2 @(CB[8])2 . For the former complex, CB[8] entrapped G1 by holding two heterodimers of its Py+ and benzyl units, which were at opposite ends of the backbone. In contrast, for the first time, the second complex disclosed parallel stacking of two cationic Py+ units of G2 in the cavity of CB[8] in the solid state, despite the generation of important electrostatic repulsion. Isothermal titrations in water afforded high apparent association constants of 4.36×106 and 6.43×106 m-1 for 1:1 complexes G1@CB[8] and G2@CB[8], respectively, and 1 H NMR spectroscopy experiments in D2 O confirmed a similar stacking pattern to that observed in the solid state. A previous study and crystal structures of the 2:1 complexes formed between three new controls, G3-5, and CB[8] did not display such unusual stacking of the cationic Py+ unit; this may be attributed to the multivalency of the two CB[8] encapsulation interactions.

Postmodification of a supramolecular organic framework: visible-light-induced recyclable heterogeneous photocatalysis for the reduction of azides to amines.

We present the postmodification of a diamondoid 3D supramolecular organic framework (SOF) to append [Ru(BPY)3]2+ groups through the formation of a hydrazone bond. The resulting SOF works as an efficient recyclable heterogeneous catalyst for visible-light-induced reduction of aromatic azides to amines.

Morpholine or methylpiperazine and salicylaldimine based heteroleptic square planner platinum (II) complexes: In vitro anticancer study and growth retardation effect on E. coli.

Morpholine and methylpiperazine are among the most important structural parts of different drugs including organic chemotherapeutic agents. In the current study we incorporated these entities as co-ligand and a series of structurally related mono- and di-metallic square planner Pt(II) complexes (Pt(II)(salicylaldimine)(morpholine)Cl C1a-C3a, Pt(II)(salicylaldimine) (methylpiperazine)Cl C1b-C3b, di-metallic Pt(II)2(bis-salicylaldimine)(morpholine)2Cl2C4a and Pt(II)2(bis-salicylaldimine)(methylpiperazine)2Cl2C4b were prepared. These complexes were characterized by 1H, 13C, 19F, 2D NOESY NMR, HR ESI-MS and elemental analyses, while structures of C2a, C3a and C4b were determined by single crystal X-ray analysis. All these complexes were studied for their in vitro cytotoxic effect on breast (MCF-7), liver (HepG2) and lung (A549) cancer cell lines. All these complexes showed considerable cytotoxic effect on these tested cancer cell lines comparable to cisplatin. Moreover three complexes C1a, C4a and C1b were studied in details. Time- and dose-dependent study was performed for C1a, C4a and C1b. These complexes induced the expression of p53 that suppresses cancer cell growth. Induction of PUMA gene and repression of MYC oncogene suggested that these complexes targeted different genes to suppress cancer progression. TUNEL assay showed induction of apoptosis and invasion analysis showed reduction in invasion ability of breast cancer cells treated with C1a, C4a or C1b. Importantly, these novel complexes suppressed the expression of EMT and metastasis promoter genes. Similarly these complexes induced autophagy by enhancing the expression of autophagy related genes such as beclin, atg-5 and atg-7. The E. coli growth retardation study showed stronger growth inhibitory effects and subsequently resulted in filamentous morphology of bacterial cells. Gel electrophoresis study proved the interaction of these complexes with DNA. All these analysis revealed anticancer potencies of this class of complexes.

ent-Abietane diterpenoids with anti-neuroinflammatory activity from the rare Chloranthaceae plant Chloranthus oldhamii.

Twelve new ent-abietane diterpenoids, chlorabietins A-L (), were isolated from the roots of Chloranthus oldhamii. Their structures and absolute configurations were determined by extensive spectroscopic analyses, X-ray diffraction, and experimental/calculated electronic circular dichroism (ECD) spectroscopy. Among the new isolates, chlorabietins D () and E () are the first two naturally occurring 8-spiro-fused 9,10-seco-ent-abietanes containing an unexpected cis-fused A/B ring system. Chlorabietin F () is a rare chinane-type diterpenoid featuring a hitherto unknown C-ring cleavage between C-13 and C-14, which might be derived from a common precursor of the above spiro-diterpenoid epimers and , and their biosynthetic relationships are briefly discussed. Meanwhile, chlorabietin I () is the first representative of the abietane-type diterpenoids possessing a tetrahydrofurano function bridging C-6 and C-19. Chlorabietins B (), C (), F (), and G () showed anti-neuroinflammatory effects by inhibiting the nitric oxide (NO) production in lipopolysaccharide (LPS)-activated murine BV-2 microglial cells, with IC50 values ranging from 16.4 to 33.8 µM.

Full-Color Light-Emitting Carbon Dots with a Surface-State-Controlled Luminescence Mechanism.

Carbon dots (CDs) with tunable photoluminescence (PL) and a quantum yield of up to 35% in water were hydrothermally synthesized in one pot and separated via silica column chromatography. These separated CDs emitted bright and stable luminescence in gradient colors from blue to red under a single-wavelength UV light. They exhibited high optical uniformity; that is, every sample showed only one peak in the PL excitation spectrum, only one peak in the excitation-independent PL emission spectrum, and similar monoexponential fluorescence lifetimes. Although these samples had similar distributions of particle size and graphite structure in their carbon cores, the surface state gradually varied among the samples, especially the degree of oxidation. Therefore, the observed red shift in their emission peaks from 440 to 625 nm was ascribed to a gradual reduction in their band gaps with the increasing incorporation of oxygen species into their surface structures. These energy bands were found to depend on the surface groups and structures but not on the particle size, not as in traditional semiconductor quantum dots. In addition, because of their excellent PL properties and low cytotoxicity, these CDs could be used to image cells in different colors under a single-wavelength light source, and the red-emitting CDs could be used to image live mice because of the strong penetration capability of their fluorescence.