Supramolecular Crystal Networks Constructed from Cucurbit[8]uril with Two Naphthyl Groups
Ontology highlight
ABSTRACT:
SUBMITTER: Gao Z
PROVIDER: S-EPMC9822147 | biostudies-literature | 2022 Dec
REPOSITORIES: biostudies-literature
Similar Datasets
Project description:Conspectus This Account focuses on stimuli responsive systems that function in aqueous solution using examples drawn from the work of the Isaacs group using cucurbit[n]uril (CB[n]) molecular containers as key recognition elements. Our entry into the area of stimuli responsive systems began with the preparation of glycoluril derived molecular clips that efficiently distinguish between self and nonself by H-bonds and π-π interactions even within complex mixtures and therefore undergo self-sorting. We concluded that the selectivity of a wide variety of H-bonded supramolecular assemblies was higher than previously appreciated and that self-sorting is not exceptional behavior. This lead us to examine self-sorting within the context of CB[n] host-guest chemistry in water. We discovered that CB[n] homologues (CB[7] and CB[8]) display remarkably high binding affinity (Ka up to 10(17) M(-1)) and selectivity (ΔΔG) toward their guests, which renders CB[n]s prime components for the construction of stimuli responsive host-guest systems. The CB[7]·adamantaneammonium ion complex, which is particularly privileged (Ka = 4.2 × 10(12) M(-1)), was introduced by us as a stimulus to trigger constitutional changes in multicomponent self-sorting systems. For example, we describe how the free energy associated with the formation of host-guest complexes of CB[n]-type receptors can drive conformational changes of included guests like triazene-arylene foldamers and cationic calix[4]arenes, as well as induced conformational changes (e.g., ammonium guest size dependent homotropic allostery, metal ion triggered folding, and heterochiral dimerization) of the hosts themselves. Many guests display large pKa shifts within their CB[n]-guest complexes, which we used to promote pH controlled guest swapping and thermal trans-to-cis isomerization of azobenzene derivatives. We also used the high affinity and selectivity of CB[7] toward its guests to outcompete an enzyme (bovine carbonic anhydrase) for a two-faced inhibitor, which allowed stimuli responsive regulation of enzymatic activity. These results prompted us to examine the use of CB[n]-type receptors in both in vitro and in vivo biological systems. We demonstrated that adamantaneammonium ion can be used to intracellularly sequester CB[7] from gold nanoparticles passivated with hexanediammonium ion·CB[7] complexes and thereby trigger cytotoxicity. CB[7] derivatives bearing a biotin targeting group enhance the cytotoxicity of encapsulated oxaliplatin toward L1210FR cells. Finally, acyclic CB[n]-type receptors function as solubilizing excipients for insoluble drugs for drug delivery purposes and as a broad spectrum reversal agent for the neuromuscular blocking agents rocuronium, vecuronium, and cis-atracurium in rats. The work highlights the great potential for integration of CB[n]-type receptors with biological systems.
| S-EPMC4100796 | biostudies-other
Project description:The binding of imidazolium salts to cucurbit[8]uril, CB[8], triggers a stepwise self-assembly process with semiflexible polymer chains and crystalline nanostructures as early- and late-stage species, respectively. In such a process, which involves the crystallization of the host-guest complexes, the guest plays a critical role in directing self-assembly toward desirable morphologies. These include platelet-like aggregates and two-dimensional (2D) fibers, which, moreover, exhibit viscoelastic and lyotropic properties. Our observations provide a deeper understanding of the self-assembly of CB[8] complexes, with fundamental implications in the design of functional 2D systems and crystalline materials.
| S-EPMC6772898 | biostudies-literature
Project description:This report describes cucurbit[7]uril (CB7) complexation of azobenzene dyes that have a 4-(N,N'-dimethylamino) or 4-amino substituent. Absorption and NMR data show that CB7 encapsulates the protonated form of the azobenzene and that the complexed dye exists as its azonium tautomer with a trans azo conformation and substantial quinoid resonance character. Because CB7 complexation stabilizes the dye conjugate acid, there is an upward shift in its pKa, and in one specific case, the pKa of the protonated azobenzene is increased from 3.09 to 4.47. Molecular modeling indicates that the CB7/azobenzene complex is stabilized by three major noncovalent factors: (i) ion-dipole interactions between the partially cationic 4-(N,N'-dimethylamino) or 4-amino group on the encapsulated protonated azobenzene and the electronegative carbonyl oxygens on CB7, (ii) inclusion of the upper aryl ring of the azobenzene within the hydrophobic CB7 cavity, and (iii) a hydrogen bond between the proton on the azo nitrogen and CB7 carbonyls. CB7 complexation enhances azobenzene stability and increases azobenzene hydrophilicity; thus, it is a promising way to improve azobenzene performance as a pigment or prodrug. In addition, the striking yellow/pink color change that accompanies CB7 complexation can be exploited to create azobenzene dye displacement assays with naked eye detection.
| S-EPMC10843849 | biostudies-literature
Project description:Porphyrins serve as photosensitizers (PS) in the realm of cancer photodynamic therapy (PDT). Upon excitation by laser light, porphyrins are capable of converting molecular oxygen into highly cytotoxic singlet oxygen (1O2). However, the rigid π-conjugated structure of porphyrins frequently results in the formation of aggregates in aqueous solutions, which leads to the self-quenching of the excited state. Cucurbit[n]urils exhibit the capacity to stably bind with porphyrins via host-guest interactions, effectively inhibiting their aggregation and potentially enhancing the therapeutic efficacy of PDT. In this study, water-soluble tetramethyl cucurbit[6]uril (TMeQ[6]) was selected as the host, while four propionic acid group-appended porphyrin cationic (TPPOR) was utilized as guests to construct a supramolecular photosensitizer (TPPOR-2TMeQ[6]) in a molar ratio of 2:1. Further experimental findings demonstrate that the presence of TMeQ[6] inhibits the aggregation of TPPOR through non-covalent interactions. This inhibition reduces the energy difference between the excited singlet and triplet states, thereby enhancing the conversion efficiency of 1O2. Moreover, TPPOR-2TMeQ[6] exhibits favorable biocompatibility and minimal dark toxicity against breast cancer cells (4T1). Upon intracellular excitation, the levels of reactive oxygen species (ROS) significantly increase, inducing oxidative stress in 4T1 cells and leading to apoptosis. Consequently, the findings of this study suggest that the enhanced photosensitization achieved through this supramolecular approach is likely to promote the anticancer therapeutic effects of PDT, thereby broadening the application prospects of porphyrins within PDT systems.
| S-EPMC11641528 | biostudies-literature
Project description:pH-dependent host-guest complexation of a monoamine neurotransmitter, Serotonin, with cucurbit[7]uril has been thoroughly investigated. The binding phenomena were explored using steady-state and time-resolved fluorescence spectroscopy at different pH values. At lower pH, i.e., protonated Serotonin, the binding affinity with cucurbit[7]uril was significantly higher compared to higher pH. Furthermore, detailed NMR titration experiments depicted the solution structure of the host-guest complex through the complexation induced chemical shift values. A competitive binding assay with cesium ions at pD 2.8 was subsequently performed for the further manifestation of the binding. Finally, the molecular docking studies provided well-documented proof of the 1:1 inclusion complex and the geometry of the complex. We believe that understanding from such studies can be important for pH-controlled delivery of serotonin for biological applications.
| S-EPMC7645158 | biostudies-literature
Project description:Upon mixing of aqueous solutions of the freely soluble building blocks cucurbit[7]uril (Q[7]) and 4-sulfocalix[4]arene (SC[4]A), white microcrystals instantly separate in near-quantitative yield. The driving force for this assembly is suggested to be the outer-surface interaction of the Q[n]. Dynamic light scattering, scanning electron microscopy, and NMR (diffusion-ordered NMR spectroscopy) analyses have confirmed the supramolecular aggregation of Q[7] and SC[4]A. Titration 1H NMR spectroscopy and isothermal titration calorimetry have shown that the interaction ratio of Q[7] and SC[4]A is close to 3:1. Moreover, the Q[7]/SC[4]A-based supramolecular assembly can accommodate molecules of some volatile compounds or luminescent dyes. Thus, this work offers a simple and highly efficient means of preparing adsorbent or solid fluorescent materials.
| S-EPMC6644559 | biostudies-literature
Project description:Recent efforts to develop hydrogel biomaterials have focused on better recapitulating the dynamic properties of the native extracellular matrix. In hydrogel biomaterials, binding thermodynamics and cross-link kinetics directly affect numerous bulk dynamic properties such as strength, stress relaxation, and material clearance. However, despite the broad range of bulk dynamic properties observed in biological tissues, present strategies to incorporate dynamic linkages in cell-encapsulating hydrogels rely on a relatively small number of dynamic covalent chemical reactions and host-guest interactions. To expand this toolkit, we report the preparation of supramolecular gelatin hydrogels with cucurbit[8]uril (CB[8])-based cross-links that form on demand via thiol-ene reactions between preassembled CB[8]·FGGC peptide ternary complexes and grafted norbornenes. Human fibroblast cells encapsulated within these optically transparent, shear thinning, injectable hydrogels remained highly viable and exhibited a well-spread morphology in culture. These CB[8]-based gelatin hydrogels are anticipated to be useful in applications ranging from bioprinting to cell and drug delivery.
| S-EPMC7286610 | biostudies-literature
Project description:Chiral macromolecules have been widely used as synthetic pockets to mimic natural enzymes and promote asymmetric reactions. An achiral host, cucurbit[8]uril (CB[8]), was used for an asymmetric Lewis acid catalyzed Diels-Alder reaction. We achieved a remarkable increase in enantioselectivity and a large rate acceleration in the presence of the nanoreactor by using an amino acid as the chiral source. Mechanistic and computational studies revealed that both the amino acid-Cu2+ complex and the dienophile substrate are included inside the macrocyclic host cavity, suggesting that contiguity and conformational constraints are fundamental to the catalytic process and rate enhancement. These results pave the way towards new studies on asymmetric reactions catalyzed in confined achiral cavities.
| S-EPMC4955226 | biostudies-literature
Project description:Chiral macromolecules have been widely used as synthetic pockets to mimic natural enzymes and promote asymmetric reactions. An achiral host, cucurbit[8]uril (CB[8]), was used for an asymmetric Lewis acid catalyzed Diels-Alder reaction. We achieved a remarkable increase in enantioselectivity and a large rate acceleration in the presence of the nanoreactor by using an amino acid as the chiral source. Mechanistic and computational studies revealed that both the amino acid-Cu(2+) complex and the dienophile substrate are included inside the macrocyclic host cavity, suggesting that contiguity and conformational constraints are fundamental to the catalytic process and rate enhancement. These results pave the way towards new studies on asymmetric reactions catalyzed in confined achiral cavities.
| S-EPMC4643185 | biostudies-literature
Project description:Interaction of the lanthanide nitrates M(NO3)3 (M = Gd, Eu) with methylcucurbit[5]uril (Me10Q[5]) in the presence of transition metal chlorides (ZnCl2 and FeCl3) in acidic media resulted in the isolation of the complexes [Me10Q[5]Gd(H2O)2Cl Gd(H2O)6](ZnCl4)2∙Cl∙8.9H2O (1) and [Me10Q[5]Eu(H2O)3Cl(H3O)](FeCl4)3 (2). The molecular structures of 1 and 2 have been determined by single crystal X-ray crystallography, and reveal discrete complexes which are involved in dense stacking with adjacent Me10Q[5]s linked via H-bonding and/or metal anions resulting in a supramolecular assembly.
| S-EPMC11261008 | biostudies-literature