Acid‐Labile Acyclic Cucurbit[ n ]uril Molecular Containers for Controlled Release

Preparation and Characterization of Insecticide/Calix[4]arene Complexes and Their Enhanced Insecticidal Activities against Plutella xylostella

Applications of supramolecular materials in plant protection have attracted significant interest in recent years. To develop a feasible method to improve the efficacy and reduce the usage of chemical pesticides, the effect of calix[4]arene (C4A) inclusion on enhancing the insecticidal activity of commercial insecticides was investigated. Results showed that all three tested insecticides (chlorfenapyr, indoxacarb, and abamectin) with distinct molecular sizes and modes of action were able to form stable 1:1 host-guest complexes with C4A through simple preparation steps. The insecticidal activities of the complexes against Plutella xylostella were effectively enhanced compared to the guest molecule, with the synergism ratio being up to 3.05 (for indoxacarb). An obvious correlation was found between the enhanced insecticidal activity and the high binding affinity between insecticide and C4A, while the improvement in water solubility may not be a determining factor. The work would provide hints for the further development of functional supramolecular hosts as synergists in pesticide formulations.

A heat-controlled release system of ethyl vanillin based on acyclic cucurbit[n]urils

Ethyl vanillin (EVA) is one of the most popular spices in the world, but it is unstable and is prone to lose its aroma. Host–Guest encapsulation by supramolecular hosts can improve stability of fragrance molecules and endow them with excellent heat-controlled release properties to satisfy requirements in food, cosmetic and tobacco, etc. Herein, two acyclic cucurbit[n]urils (ACBs, M1 and M2) inclusion complexes of EVA were prepared. Their binding behaviors were investigated by 1H NMR, SEM, XRD, FT-IR and TGA. The stoichiometric ratio was 1:1 by Job’s plot and the binding constant was determined by fluorescence titration. The intermolecular interaction between host and guest was studied by 2D-ROESY NMR and the inclusion mode was proposed. Finally, the heat-controlled release experiment indicated that the inclusion complexes of ACBs/EVA possess less volatilization at higher temperature, longer retention time and heat-controlled release. This study provides theoretical and technical guidance for expanding the application of EVA.

Recent Updates on Supramolecular-Based Drug Delivery - Macrocycles and Supramolecular Gels

Supramolecules-based drug delivery has attracted significant recent research attention as it could enhance drug solubility, retention time, targeting, and stimuli responsiveness. Among the different supramolecules and assemblies, the macrocycles and the supramolecular hydrogels are the two important categories investigated to a greater extent. Here, we provide the most recent advancements in these categories. Under macrocycles, reports on drug delivery by cyclodextrins, cucurbiturils, calixarenes/pillararenes, crown ethers and porphyrins are detailed. The second category discusses the supramolecular hydrogels of macrocycles/polymers and low molecular weight gelators. The updated information provided could be helpful to advance R & D in this vital area.

Anti-MicroRNA-21 Oligonucleotide Loaded Spermine-Modified Acetalated Dextran Nanoparticles for B1 Receptor-Targeted Gene Therapy and Antiangiogenesis Therapy

The use of nanoparticles (NPs) to deliver small inhibiting microRNAs (miRNAs) has shown great promise for treating cancer. However, constructing a miRNA delivery system that targets brain cancers, such as glioblastoma multiforme (GBM), remains technically challenging due to the existence of the blood-tumor barrier (BTB). In this work, a novel targeted antisense miRNA-21 oligonucleotide (ATMO-21) delivery system is developed for GBM treatment. Bradykinin ligand agonist-decorated spermine-modified acetalated dextran NPs (SpAcDex NPs) could temporarily open the BTB by activating G-protein-coupled receptors that are expressed in tumor blood vessels and tumor cells, which increase transportation to and accumulation in tumor sites. ATMO-21 achieves high loading in the SpAcDex NPs (over 90%) and undergoes gradual controlled release with the degradation of the NPs in acidic lysosomal compartments. This allows for cell apoptosis and inhibition of the expression of vascular endothelial growth factor by downregulating hypoxia-inducible factor (HIF-1α) protein. An in vivo orthotopic U87MG glioma model confirms that the released ATMO-21 shows significant therapeutic efficacy in inhibiting tumor growth and angiogenesis, demonstrating that agonist-modified SpAcDex NPs represent a promising strategy for GBM treatment combining targeted gene therapy and antiangiogenic therapy.

In Vitro and In Vivo Sequestration of Methamphetamine by a Sulfated Acyclic CB[n]-Type Receptor

We report the synthesis of two new acyclic sulfated acyclic CB[n]-type receptors (TriM0 and Me4 TetM0) and investigations of their binding properties toward a panel of drugs of abuse (1-13) by a combination of 1 H NMR spectroscopy and isothermal titration calorimetry. TetM0 is the most potent receptor with Ka ≥106  M-1 toward methamphetamine, fentanyl, MDMA and mephedrone. TetM0 is not cytotoxic toward HepG2 and HEK 293 cells below 100 μM according to MTS metabolic and adenylate kinase release assays and is well tolerated in vivo when dosed at 46 mg kg-1 . TetM0 does not inhibit the hERG ion channel and is not mutagenic based on the Ames fluctuation test. Finally, in vivo efficacy studies show that the hyperlocomotion of mice treated with methamphetamine can be greatly reduced by treatment with TetM0 up to 5 minutes later. TetM0 has potential as a broad spectrum in vivo sequestrant for drugs of abuse.

In Vitro and In Vivo Sequestration of Phencyclidine by Me4 Cucurbit[8]uril*

We report investigations of the use of cucurbit[8]uril (CB[8]) macrocycles as an antidote to counteract the in vivo biological effects of phencyclidine. We investigate the binding of CB[8] and its derivative Me4 CB[8] toward ten drugs of abuse (3-9, 12-14) by a combination of 1 H NMR spectroscopy and isothermal titration calorimetry in phosphate buffered water. We find that the cavity of CB[8] and Me4 CB[8] are able to encapsulate the 1-amino-1-aryl-cyclohexane ring system of phencyclidine (PCP) and ketamine as well as the morphinan skeleton of morphine and hydromorphone with Kd values ≤50 nm. In vitro cytotoxicity (MTS metabolic and adenylate kinase cell death assays in HEK293 and HEPG2 cells) and in vivo maximum tolerated dose studies (Swiss Webster mice) which were performed for Me4 CB[8] indicated good tolerability. The tightest host⋅guest pair (Me4 CB[8]⋅PCP; Kd =2 nm) was advanced to in vivo efficacy studies. The results of open field tests demonstrate that pretreatment of mice with Me4 CB[8] prevents subsequent hyperlocomotion induction by PCP and also that treatment of animals previously dosed with PCP with Me4 CB[8] significantly reduces the locomotion levels.

Acyclic Cucurbit[n]uril-Type Receptors: Aromatic Wall Extension Enhances Binding Affinity, Delivers Helical Chirality, and Enables Fluorescence Sensing

We report the linear extension from M1 to M2 to anthracene walled M3 which adopts a helical conformation (X-ray) to avoid unfavorable interactions between sidewalls. M3 is water soluble (=30 mm) and displays enhanced optical properties (ϵ=1.28×105  m-1  cm-1 , λmax =370 nm) relative to M2. The binding properties of M3 toward guests 1-29 were examined by 1 H NMR and ITC. The M3⋅guest complexes are stronger than the analogous complexes of M2 and M1. The enhanced binding of M3 toward neuromuscular blockers 25, 27-29 suggests that M3 holds significant promise as an in vivo reversal agent. The changes in fluorescence observed for M3⋅guest complexes are a function of the relative orientation of the anthracene sidewalls, guest concentration, Ka , and guest electronics which rendered M3 a superb component of a fluorescence sensing array. The work establishes M3 as a next generation sequestering agent and a versatile component of fluorescence sensors.

Supramolecular Container-Mediated Surface Engineering Approach for Regulating the Biological Targeting Effect of Nanoparticles

Surface chemistry is essential for the biomedical applications of functional nanomaterials. Here, a supramolecular container-based surface engineering approach is designed to impart excellent water dispersibility and precisely control the orientation of surface targeting ligands of the nanoparticles. An acyclic cucurbituril (aCB) molecular container is used as a chemical bridge to incorporate nanoparticles and targeting ligands via a bilateral host-guest complexation, enabling the bioactive moieties of targeting ligands to be fully exposed and faced outward to facilitate biological targeting. The enhanced biological targeting effect as well as targeted imaging performance of aCB-engineered nanoparticles are demonstrated in vitro and in vivo. Molecular dynamic simulations illustrate a tight binding of targeting ligand to the relevant receptor with the assistance of the aCB molecular container for the enhanced targeting efficiency, representing an attractive extension of supramolecular chemistry-based technology for nanoparticle surface engineering and supramolecularly regulated biological targeting.

Theoretical Prediction on a Novel Reduction-Responsive Nanoring Having a Disulfide Group for Facile Encapsulation and Release of Fullerenes C60 and C70

In this work, a novel reduction-responsive disulfide bond-containing cycloparaphenylene nanoring molecule (DSCPP) with a pyriform shape has been designed. In addition, the interactions between the designed nanoring (host) and fullerenes C₆₀ and C₇₀ (guests) were investigated theoretically at the M06-2X/6-31G(d,p) and M06-L/MIDI! levels of theory. By analyzing geometric characteristics and host-guest binding energies, it is revealed that the designed DSCPP is an ideal host molecule of guests C₆₀ and C₇₀. DSCPP presents excellent elastic deformation during the encapsulation of C₆₀ and C₇₀. The high binding energies suggest that both DSCPP⊃C₆₀ and DSCPP⊃C₇₀ (∼92 and 118 kJ·mol^-1 at the M06-2X/6-31G(d,p) level of theory) are stable host-guest complexes, and the guest C₇₀ is more strongly encapsulated than C₆₀ in the gas phase. The thermodynamic information indicates that the formation of the two host-guest complexes is thermodynamically spontaneous. In addition, the frontier molecular orbital (FMO) features and intermolecular weak interaction region between DSCPP and fullerenes gusts are discussed to further understand the structures and properties of the DSCPP⊃fullerene systems. Finally, the ring-opening mechanism of the DSCPP under reduction conditions is investigated.

Charge Conversional Biomimetic Nanocomplexes as a Multifunctional Platform for Boosting Orthotopic Glioblastoma RNAi Therapy

Nanotechnology-based RNA interference (RNAi) has shown great promise in overcoming the limitations of traditional clinical treatments for glioblastoma (GBM). However, because of the complexity of brain physiology, simple blood-brain barrier (BBB) penetration or tumor-targeting strategies cannot entirely meet the demanding requirements of different therapeutic delivery stages. Herein, we developed a charge conversional biomimetic nanoplatform with a three-layer core-shell structure to programmatically overcome persistent obstacles in siRNA delivery to GBM. The resulting nanocomplex presents good biocompatibility, prolonged blood circulation, high BBB transcytosis, effective tumor accumulation, and specific uptake by tumor cells in the brain. Moreover, red blood cell membrane (RBCm) disruption and effective siRNA release can be further triggered elegantly by charge conversion from negative to positive in the endo/lysosome (pH 5.0-6.5) of tumor cells, leading to highly potent target-gene silencing with a strong anti-GBM effect. Our study provides an intelligent biomimetic nanoplatform tailored for systemically siRNA delivery to GBM, leveraging Angiopep-2 peptide-modified, immune-free RBCm and charge conversional components. Improved therapeutic efficacy, higher survival rates, and minimized systemic side effects were achieved in orthotopic U87MG-luc human glioblastoma tumor-bearing nude mice.

Aptamer-Functionalized Exosomes: Elucidating the Cellular Uptake Mechanism and the Potential for Cancer-Targeted Chemotherapy

Exosomes (Exos) are nanoscale natural vehicles for transporting biomolecules to facilitate cell-to-cell communication, indicating a high potential of them for delivering therapeutics/diagnostics. To improve their delivery capacity, a simple, noninvasive, and efficient strategy for functionalizing Exos with effective targeting ligands as well as elucidation of the cellular uptake mechanism of these functionalized Exos was found be to necessary, but remained a challenge. In this work, we used diacyllipid-aptamer conjugates as the targeting ligand to develop an aptamer-functionalized Exos (Apt-Exos) nanoplatform for cell type-specific delivery of molecular therapeutics. The cellular uptake mechanism of Apt-Exos was investigated in details, and distinct behavior was observed in comparison to free Exos. By combining the excellent molecular recognition capability of aptamers and the superiority of Exos as natural vehicles, Apt-Exos can efficiently deliver molecular drugs/fluorophores to target cancer cells, providing a promising delivery platform for cancer theranostics.

Transformative Supramolecular Vesicles Based on Acid-Degradable Acyclic Cucurbit[n]uril and a Prodrug for Promoted Tumoral-Cell Uptake

Smart supramolecular vesicles constructed by host-guest interactions between "acid-degradable" acyclic cucurbit[n]uril (CB[n]) and a doxorubicin prodrug are reported. "Acid-degradable" acyclic CB[n] is a high-affinity host for several common antitumor drugs, and its degradation leads to a more dramatic decrease in binding affinity than that observed for "acid-sensitive" hosts. Supramolecular complexation between acid-degradable acyclic CB[n] and a doxorubicin prodrug resulted in the formation of negatively charged supramolecular vesicles. The prodrug strategy allowed doxorubicin to be conjugated to vesicles in a stable manner with a high drug-loading ratio of 20 %. The resulting supramolecular vesicles were responsive to tumor acidity (pH 6.5). Induced by mildly acidic conditions (pH 6.5-5.5), acid-degradable acyclic CB[n] could be degraded, and this led to a vesicle-to-micelle transition to form positively charged micelles. This transition resulted in a pH-dependent change in size and surface charge, which improved tumoral-cell uptake for doxorubicin.