Fluorescent dyes and their supramolecular host/guest complexes with macrocycles in aqueous solution

Photomodulated fluorescence of supramolecular assemblies of sulfonatocalixarenes and tetraphenylethene

Self-assembled fluorescent nanoparticles responding to specific stimuli are highly appealing for applications such as labels, probes, memory devices, and logic gates. However, organic analogues are challenging to prepare, due to unfavorable aggregation-caused quenching. We herein report the preparation of self-assembled fluorescent organic nanoparticles in water by means of calixarene-induced aggregation of a tetraphenylethene derivative (QA-TPE) mediated by p-sulfonatocalix[4]arenes. The self-assembled nanoparticles showed interesting photoswitching behaviors, and the fluorescence output of the generated nanoparticles was opposite to that of free QA-TPE both before and after irradiation. Free QA-TPE is nonfluorescent, owing to intramolecular rotations of the phenyl rings. In contrast, the self-assembled nanoparticles that formed upon complexation of QA-TPE with p-sulfonatocalix[4]arene exhibited aggregation-induced emission fluorescence (λ(em) = 480 nm, Φ = 14%), as a result of the inhibition of rotations. Upon UV light irradiation, free QA-TPE was cyclized to the corresponding diphenylphenanthrene, which showed typical fluorescence of a π-conjugated system (λ(em) = 385 nm, Φ = 9.3%), whereas the nanoparticles were nonfluorescent upon irradiation due to the aggregation-caused quenching. In effect, this system allows programmed modulation of TPE fluorescence at two different emission wavelengths by means of host-guest complexation and irradiation. Relative to a single-mode stimulus-responsive system, our new developed system of highly integrated modes into a single molecular unit that can exhibit modulation of fluorescence by multiple stimulus is expected to be more adaptable for practical applications and to show enhanced multifunctionality.

Kinetics and thermodynamics of berberine inclusion in cucurbit[7]uril

The kinetics and thermodynamics of berberine inclusion in cucurbit[7]uril was studied by stopped-flow method, fluorescence titrations, and isothermal calorimetry in neat water. The ~500-fold fluorescence intensity enhancement upon encapsulation was exploited to monitor the complex formation in real time at various temperatures. The increase in the fluorescence intensity could be fitted well by assuming a simple 1:1 binding equilibrium without any intermediate formation. For the rate constants of association and dissociation, (1.9 ± 0.1) × 10(7) M(-1) s(-1) and (0.81 ± 0.08) s(-1) were found at 298 K, respectively. The ingression into the cavity of CB7 had 32 ± 2 kJ mol(-1) activation enthalpy, implying a constrictive binding, whereas 69 ± 2 kJ mol(-1) was obtained for the activation enthalpy of the egression. Substantial structural change had to occur when berberine passed through the tight carbonyl-rimmed portal of the macrocycle to reach the transition state. An enthalpy-driven complexation took place with a slight entropy gain.

A supramolecular approach to fabricate highly emissive smart materials

The aromatic chromophores, for example, perylene diimides (PDIs) are well known for their desirable absorption and emission properties. However, their stacking nature hinders the exploitation of these properties and further applications. To fabricate emissive aggregates or solid-state materials, it has been common practice to decrease the degree of stacking of PDIs by incorporating substituents into the parent aromatic ring. However, such practice often involves difficultorganic synthesis with multiple steps. A supramolecular approach is established here to fabricate highly fluorescent and responsive soft materials, which has greatly decreases the number of required synthetic steps and also allows for a system with switchable photophysical properties. The highly fluorescent smart material exhibits great adaptivity and can be used as a supramolecular sensor for the rapid detection of spermine with high sensitivity and selectivity, which is crucial for the early diagnosis of malignant tumors.

Fluorescent cyclodextrin carriers for a water soluble ZnII pyrazinoporphyrazine octacation with photosensitizer potential

Novel, negatively charged, fluorescent cyclodextrin oligomers form highly stable complexes with a water soluble, octacationic porphyrazine photosensitizer in dimeric form.

Light harvesting of CdSe/CdS quantum dots coated with β-cyclodextrin based host–guest species through resonant energy transfer from the guests

Nano-hybrids based on red emitting QDs covered by β-cyclodextrin hosting a green emitting nitrobenzoxadiazole derivative show emission harvested by the host–guest organic system.

Chemical designs of functional photoactive molecular assemblies

Molecular assemblies with defined structures capable of photo-induced electron transfer or photochemical reactions are reviewed, emphasizing their supramolecular features.

Interaction of a hemicyanine dye and its derivative with DNA and cucurbit[7]uril

A ternary complex among D2, DNA and CB[7] can be formed.

Sequential inclusion of two berberine cations in cucurbit[8]uril cavity: kinetic and thermodynamic studies

The formation and dissociation kinetics of 1 : 1 and 2 : 1 inclusion of berberine in the cucurbit[8]uril cavity is revealed.

Multi-responsive drug release from hydrogen-bonding multilayers containing PEGylated nanoparticles and azobenzenes

We report the design of a platform that is assembled within hydrogen-bonding nanoparticle/azobenzene multilayer films for multi-responsive drug release.

Cucurbit[n]uril type hosts for the reversal of steroidal neuromuscular blocking agents

The ideal neuromuscular blocking agent (NMBA) is regarded as being a non-depolarizing equivalent of succinylcholine, having a rapid onset and short duration of action, with minimal side effects. In the absence of a single drug, the administration of an aminosteroid NMBA, such as rocuronium, followed by reversal using an acetylcholinesterase inhibitor, such as neostigmine, is commonly employed. A different and safer approach to rapidly reversing the action of the NMBA, by encapsulating it with a macrocyclic or acyclic host molecule, such as the cyclodextrin sugammadex or more recently, cucurbituril-type hosts such as cyclic cucurbit[7]uril and the acyclic glycoluril tetramer calabadion 1, is described.

Cucurbit[n]uril-based coordination chemistry: from simple coordination complexes to novel poly-dimensional coordination polymers

Cucurbit[n]urils are a family of molecular container hosts bearing a rigid hydrophobic cavity and two identical carbonyl fringed portals. They have attracted much attention in supramolecular chemistry because of their superior molecular recognition properties in aqueous media. This review highlights the recent advances and challenges in the field of cucurbit[n]uril-based coordination chemistry. It not only presents progress in the knowledge of such macrocyclic compounds, which range from simple to complicated architectures, but also presents new routes of synthesis and their advantages in hybrid porous solids. The concept of structure "inducer" for their structural design to achieve predictable structures and controlled pores is described. The large pore sizes and hydrophobic cavities of these compounds that lead to unprecedented properties and potential applications are also discussed.

Host-guest supramolecular nanosystems for cancer diagnostics and therapeutics

Extensive efforts have been devoted to the construction of functional supramolecular nanosystems for applications in catalysis, energy conversion, sensing and biomedicine. The applications of supramolecular nanosystems such as liposomes, micelles, inorganic nanoparticles, carbon materials for cancer diagnostics and therapeutics have been reviewed by other groups. Here, we will focus on the recent momentous advances in the implementation of typical supramolecular hosts (i.e., cyclodextrins, calixarenes, cucurbiturils and metallo-hosts) and their nanosystems in cancer diagnostics and therapeutics. We discuss the evolutive process of supramolecular nanosystems from the structural control and characterization to their diagnostic and therapeutic function exploitation and even the future potentials for clinical translation.

Reversible near-infrared fluorescent probe introducing tellurium to mimetic glutathione peroxidase for monitoring the redox cycles between peroxynitrite and glutathione in vivo

The redox homeostasis between peroxynitrite and glutathione is closely associated with the physiological and pathological processes, e.g. vascular tissue prolonged relaxation and smooth muscle preparations, attenuation hepatic necrosis, and activation matrix metalloproteinase-2. We report a near-infrared fluorescent probe based on heptamethine cyanine, which integrates with telluroenzyme mimics for monitoring the changes of ONOO(-)/GSH levels in cells and in vivo. The probe can reversibly respond to ONOO(-) and GSH and exhibits high selectivity, sensitivity, and mitochondrial target. It is successfully applied to visualize the changes of redox cycles during the outbreak of ONOO(-) and the antioxidant GSH repair in cells and animal. The probe would provide a significant advance on the redox events involved in the cellular redox regulation.