cucurbit(8)uril and azobenzene

A 2D supramolecular organic framework (SOF) based on synthetic macrocycles has been constructed in water by a self-assembly strategy. Two new organic monomers of this SOF, possessing viologen and azobenzene functional groups, form a stimuli-responsive host-guest system upon cooperatively binding with cucurbit[8]uril rings. The reversible formation and dissociation of 2D SOF can be realized by the isomerization of azobenzene under ultraviolet and visible light. The light-responsive property of the SOF is highly reversible and stable for up to four cycles. Moreover, azoreductase produced by Escherichia coli can reduce the N=N double bond of azobenzene entities, resulting in fluorescence recovery of the system. As an excellent and effective fluorescent probe, the SOF can detect azoreductase activity for real-time monitoring of the growth process of Escherichia coli. The dual-stimuli responsive 2D SOF is envisioned to drive the development of responsive devices with complex functions.

Topics: Azo Compounds; Bridged-Ring Compounds; Escherichia coli; Imidazoles; Isomerism; Light; Macromolecular Substances; NADH, NADPH Oxidoreductases; Nitroreductases; Recombinant Proteins; Spectrometry, Fluorescence

A supramolecular nanocapsule was constructed by the ternary host-guest complexation of azobenzene (Azo) and methylviologen (MV) to cucurbit[8]uril (CB[8]) and the subsequent self-assembly. The supramolecular nanocapsule with both glutathione peroxidase (GPx) and superoxide dismutase (SOD) activities can mimic the intracellular enzymatic reactive oxygen species (ROS) defense system.

Topics: 3T3 Cells; Animals; Antioxidants; Azo Compounds; Biocompatible Materials; Bridged-Ring Compounds; Cell Survival; Glutathione Peroxidase; Imidazoles; Mice; Microscopy, Confocal; Nanocapsules; Paraquat; Reactive Oxygen Species; Superoxide Dismutase

A photoresponsive hydrolase model was constructed through the spatial organization of histidine/arginine-containing peptide supra-amphiphiles that are held together by cucurbit[8]uril (CB[8]) methylviologen (MV) azobenzene (Azo) ternary complexation and subsequently self-assemble into highly uniform giant vesicles. The reversible morphological transition of the vesicular structures to non-assembled peptide fragments was triggered by azobenzene photoisomerization. This enables the assembly/disassembly of its enzyme-like active site to cause a dramatic change in hydrolytic activity. The dynamic process can be directly monitored to determine the supramolecular structure-related enzymatic parameters, which may help to understand how the regulation of enzyme activity is coupled to the aggregation behaviors of natural enzymes.

Topics: A549 Cells; Azo Compounds; Biocompatible Materials; Bridged-Ring Compounds; Catalytic Domain; Cell Survival; Humans; Hydrolases; Imidazoles; Isomerism; Kinetics; Microscopy, Confocal; Models, Molecular; Peptides; Ultraviolet Rays

Supramolecular building blocks, such as cucurbit[n]uril (CB[n])-based host-guest complexes, have been extensively studied at the nano- and microscale as adhesion promoters. Herein, we exploit a new class of CB[n]-threaded highly branched polyrotaxanes (HBP-CB[n]) as aqueous adhesives to macroscopically bond two wet surfaces, including biological tissue, through the formation of CB[8] heteroternary complexes. The dynamic nature of these complexes gives rise to adhesion with remarkable toughness, displaying recovery and reversible adhesion upon mechanical failure at the interface. Incorporation of functional guests, such as azobenzene moieties, allows for stimuli-activated on-demand adhesion/de-adhesion. Macroscopic interfacial adhesion through dynamic host-guest molecular recognition represents an innovative strategy for designing the next generation of functional interfaces, biomedical devices, tissue adhesives, and wound dressings.

Topics: Azo Compounds; Bandages; Bridged-Ring Compounds; Cyclodextrins; Hydrogels; Imidazoles; Poloxamer; Rotaxanes; Tissue Adhesives; Water; Wettability

Cucurbit[8]uril (CB[8])-mediated complexation of a dicationic azobenzene in water allows for the light-controlled encapsulation of a variety of second guest compounds, including amino acids, dyes, and fragrance molecules. Such controlled guest sequestration inside the cavity of CB[8] enables the regulation of the thermally induced phase transition of poly(N-isopropylacrylamide)-which is not photosensitive-thus demonstrating the robustness and relevancy of the light-regulated CB[8] complexation.

Topics: Acrylamides; Acrylic Resins; Algorithms; Amino Acids; Azo Compounds; Bridged-Ring Compounds; Coloring Agents; Imidazoles; Light; Magnetic Resonance Spectroscopy; Models, Molecular; Molecular Conformation; Perfume; Polymers; Ultraviolet Rays; Water

A systematic study of the ternary complex formation process for aromatic amino acids using ucurbit[8]uril (CB[8]) and a viologen amphiphile shows that the affinity of the amino acid needs to be higher or in a comparable range to that of CB[8] for the amphiphile in order to form the ternary complex. Based on these observations, a supramolecular peptide amphiphile and its corresponding vesicle are prepared using a peptide containing an azobenzene moiety. The azobenzene group at the N-terminus of the peptide served as the second guest for CB[8]. The vesicles obtained from this peptide amphiphile show response to a number of external triggers. The trans-cis isomerization of the azobenzene group upon irradiation with UV-light of 365 nm leads to the breakdown of the ternary complex and eventually to the disruption of the vesicle. The deformation-reformation of the vesicle can be controlled by illuminating the disrupted solution with light of 420 nm as it facilitates the cis-trans isomerization. Thus, the vesicle showed a controlled and reversible response to UV-light with the ability for manipulation of the formation-deformation of the vesicle by the choice of an appropriate wavelength. The vesicle showed response to a stronger guest (1-adamantylamine) for CB[8], which displaces both the guests from the CB[8] cavity and consequently ruptures the vesicle structure. 2,6-Dihydroxynaphthalene acts as a competitive guest and thereby behaves as another external trigger for replacing the peptide from the CB[8] cavity by self-inclusion to form the ternary complex. Henceforth, it allows retaining the vesicle structure and results in the release of the peptide from the vesicle.

Topics: Azo Compounds; Bridged-Ring Compounds; Imidazoles; Liposomes; Naphthols; Peptides; Surface-Active Agents; Ultraviolet Rays; Viologens

In this study, a novel UV-responsive drug carrier based on mesoporous silica nanoparticles (MSNs) has been designed. A 'self' peptide was introduced onto the MSN surface through a supramolecular photoswitchable heteroternary complexation of cucurbit[8]uril, azobenzene and 4,4'-dipyridyl derivative. The light-induced isomerization of azobenzene contributed to the formation of intelligent cucurbit[8]uril based self-preserving MSNs (CSMSNs). In vitro studies demonstrated that the CSMSNs were effectively shielded against macrophages by the peptide protective layer. Doxorubicin hydrochloride (DOX·HCl) could be well encapsulated in the CSMSNs and exhibit low toxicity without UV-irradiation. After reaching the tumor tissue, the peptide camouflage was removed upon UV-irradiation, which enabled the target ligand mediated cell uptake of the drug carrier and the accelerated drug release.

Topics: Antibiotics, Antineoplastic; Azo Compounds; Bridged-Ring Compounds; Cell Line, Tumor; Delayed-Action Preparations; Doxorubicin; Humans; Imidazoles; Peptides; Porosity; Pyridines; Silicon Dioxide; Ultraviolet Rays