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The use of aromatic organic macrocycles as supramolecular hosts for non-covalent energy transfer is reported herein. These macrocycles lead to stronger binding and more efficient energy transfer compared to commercially available γ-cyclodextrin. This energy transfer was particularly efficient for the highly toxic benzo[a]pyrene with a fluorescent B...
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... System design BODIPY was chosen as the fluorophore for this experiment due to its known efficacy in fluorescence-based detection systems, which has been reported both by our group (Radaram, Potvin, and Levine 2013) and others (Baruah et al. 2005;Thakare et al. 2018); its ability to interact with b-cyclodextrin (Shi et al. 2013) and its derivatives (Li, Mintzer, and Bittman 2006;Holtta-Vuori et al. 2008); and its high-quantum yield (0.96 in tetrahydrofuran) (Zhang, Chen, and Jian 2016). b-Cyclodextrin (b-CD) was chosen as the supramolecular host for this experiment because of its known ability to interact with hGH (Otzen et al. 2002), with the derivatives 2-hydroxypropyl-b-cyclodextrin (2-HP-b-CD) and methyl-b-cyclodextrin (Me-b-CD) included for comparison. ...
The ability to detect human growth hormone (hGH) via sensitive, selective, and easy-to-use methods is a high priority research area from a variety of public health, law enforcement, and scientific objectives. Reported herein is the use of cyclodextrin-promoted fluorescence modulation of a high-quantum yield BODIPY fluorophore in the presence of low concentrations of hGH, leading to a system that can detect hGH in concentrations as low as 0.279 µM and with a 96% accuracy in distinguishing different hGH concentrations.
... In addition to investigating the dependency of the pyrene emission spectra on the concentration of pyrene, the dependency on the concentration of the cyclodextrin host was also investigated (Fig. 4). For concentrations of β-cyclodextrin ranging from 0.2 mM to 10 mM and a constant pyrene concentration, the fluorescence intensity of pyrene increased dramatically, in line with reports that report a decrease in nonradiative decay pathways and increase in fluorescence upon macrocycle encapsulation [34], but no excimer emission appeared (Fig. 4a). In contrast, excimer emission of pyrene in γcyclodextrin solutions appeared at 4 mM of γ-cyclodextrin, with the intensity of the excimer emission band increasing until 6 mM and then remaining roughly constant between 6 (Fig. 4b). ...
Although significant effort has been expended to analyze the binding of pyrene in β-cyclodextrin and γ-cyclodextrin, little has been published on the binding of this guest in β-cyclodextrin derivatives (methyl-β-cyclodextrin and 2-hydroxypropyl-β-cyclodextrin) or in mixtures of such derivatives, despite the fact that these derivatives are known to have different supramolecular properties that facilitate unique modes of complexation. Reported herein is a detailed spectroscopic investigation of the binding of pyrene in β-cyclodextrin derivatives and in binary mixtures of cyclodextrins. Py values, defined as the ratio of representative vibronic bands in the fluorescence emission of pyrene, were used to measure changes in the pyrene microenvironment in the presence of the cyclodextrin hosts, and indicated that unmodified β-cyclodextrin is unique in providing a fully hydrophobic environment for pyrene through the use of two cyclodextrins to bind a single pyrene guest. By comparison, both γ-cyclodextrin and modified β-cyclodextrin analogues bind pyrene in a less hydrophobic environment through 1:1 binding stoichiometries that allow for continued interactions between the incompletely encapsulated pyrene guest and the aqueous solvent system. Binary mixtures of cyclodextrins were also explored and reinforce the unique properties of the unmodified β-cyclodextrin host.
The unique binding geometries of pyrene in beta-cyclodextrin and its derivatives leads to measurable fluorescence emission signals, whose information can be used to elucidate the highly structurally dependent binding geometries and stoichiometries
... Previous work from our research groups has reported extensive results using cyclodextrin-based systems for highly effective toxicant detection and medical imaging applications (10)(11)(12). Some work in synthetically modified cyclodextrins (13,14), modified cucurbiturils (15), and fully synthetic all-organic macrocycles (16,17), has also been reported, but the utility of such materials in small molecule binding and sequestration has not been fully explored. The highly efficient removal of micropollutants using insoluble cyclodextrin polymers cross-linked with rigid aromatic groups has been reported by Dichtel and co-workers (18,19). ...
The ability to bind and detect analytes with high levels of selectivity, sensitivity and broad applicability for a variety of analytes is an essential goal, with applications in public health and environmental remediation. Methods to achieve effective binding and detection include electrochemical, and spectroscopic methods. The use of supramolecular chemistry to accomplish such detection, by binding a target in a host and transducing that binding into a measurable signal, has advantages, including tunability of the sensor and the ability to rationally design hosts through an understanding of non-covalent interactions. Reported herein is the design and use of pillar[5]arenes to accomplish precisely such detection. Water-soluble pillar[5]arenes containing 10 cationic linker arms on their periphery bound toxicants in their hydrophobic cores with association constants of 10⁵–10⁶M⁻¹. With the use of cationic exchange resins, the pillar[5]arene hosts were removed from solution with their encapsulated guests, allowing for effective toxicant removal.
... 9 Previous research in our group introduced a fundamentally new approach for the detection of PAHs, that relies on using the PAHs as energy donors in combination with high quantum yield fluorophore acceptors including BODIPY (compound 10) and Rhodamine 6G (compound 11) ( Figure 1). [10][11][12][13][14] Energy transfer from the PAH to the fluorophore occurs when both are bound in the cavity of commercially available, non-toxic γ-cyclodextrin, leading to a new, brightly fluorescent signal in the presence of the PAH of interest ( Figure 2). This energy transfer based detection has been used in complex biological fluids 14 and with PAHs that have been extracted from crude oil samples. ...
... Previous results from our research group demonstrated highly efficient cyclodextrin-promoted energy transfer for a wide range of toxicants and fluorophores, with greater than 100% energy transfer efficiencies observed in several cases. [10][11][12][13][14] These energy transfer efficiencies were particularly efficient for pyrene and benzo[a]pyrene, as well as for highly toxic aromatic amines such as 2-aminofluorene, 2-acetylaminofluorene, and benzidine, in combination with fluorophores 10 and 11. Attempts to extend this cyclodextrin-promoted energy transfer to analytes 4-9 resulted in highly efficient energy transfer in several cases (Table 1), in particular for analytes 4, 6, and 8 in combination with fluorophore 10 ( Figure 3). ...
... They undergo intramolecular conformational changes in the excited state that give rise to a reshaping of the fluorescence spectrum on the nanosecond timescale. A recent example of complexation of anthracene by an organic macrocycle led to significant changes in the energy transfer rates due to orientation of donor and acceptors [38]. ...
... Previous results from our research group demonstrated highly efficient cyclodextrinpromoted energy transfer for a wide range of toxicants and fluorophores, with greater than 100% energy transfer efficiencies observed in several cases (10)(11)(12)(13)(14). These energy transfer efficiencies were particularly efficient for pyrene and benzo[a]pyrene, as well as for highly toxic aromatic amines such as 2-aminofluorene (23), 2-acetylaminofluorene (23), and benzidine (24), in combination with fluorophores 10 and 11. ...
Reported herein is the use of proximity-induced non-covalent energy transfer for the detection of medium-sized polycyclic aromatic hydrocarbons (PAHs). This energy transfer occurs within the cavity of γ-cyclodextrin in various aqueous environments, including human plasma and coconut water. Highly efficient energy transfer was observed, and the efficiency of the energy transfer is independent of the concentration of γ-cyclodextrin used, demonstrating the importance of hydrophobic binding in facilitating such energy transfer. Low limits of detection were also observed for many of the PAHs investigated, which is promising for the development of fluorescence-based detection schemes.
There is great need for stand-alone luminescence-based chemosensors that exemplify selectivity, sensitivity, and applicability and that overcome the challenges that arise from complex, real-world media. Discussed herein are recent developments toward these goals in the field of supramolecular luminescent chemosensors, including macrocycles, polymers, and nanomaterials. Specific focus is placed on the development of new macrocycle hosts since 2010, coupled with considerations of the underlying principles of supramolecular chemistry as well as analytes of interest and common luminophores. State-of-the-art developments in the fields of polymer and nanomaterial sensors are also examined, and some remaining unsolved challenges in the area of chemosensors are discussed.
Two new star-shaped phenyl- and triazine-core based donor-acceptor (D-A) type conjugated molecules bearing triphenylamine end-capped arms were synthesized and characterized as imminent organic optoelectronic materials. Photophysical properties of the compounds were explored systematically via spectroscopic and theoretical methods. Because of the presence of donor-acceptor interactions, these luminogens display multifunctional properties, for instance, high extinction coefficient, large stokes shift, and pronounced solvatochromic effect. The compounds also exhibited phenomenon known as aggregation-induced emission on formation of nano-aggregates in the tetrahydrofuran-water mixture. The aggregate formation was confirmed by transmission electron microscopy, scanning electron microscopy, and dynamic light scattering analyses. Moreover, by controlling the electron withdrawing ability of the acceptor, complementary emissive fluorophores (blue and yellow) were achieved. These two complementary colors together span the entire range of visible spectrum (400-800 nm) and therefore when mixed in a requisite proportion generate white light in solution phase. These findings have potential for the progress of new organic white light radiating materials for applications in lighting and display devices.
Macrocycle-based amphiphiles, including macrocyclic amphiphiles and macrocyclic host-based supra-amphiphiles, are a class of amphiphiles which are capable of self-assembling to multidimensional assemblies with defined nanostructures. By involving host−guest recognition, these amphiphiles can be tailored to fabricate new topological structures and fulfill multiple applications. Compared with covalent-bonded traditional amphiphiles and polymeric amphiphiles, the introduction of host−guest interactions faciliates the design, synthesis and controlability of these amphiphilic systems. Moreover, host−guest interactions usually possess stimuli-responsive properties, which futher endow self-assemblies of macrocycle-based amphiphiles with fantastic functions. In this review, we summarize recent progress in macrocyclic amphiphiles and macrocyclic host-based supra-amphiphiles, with a focus on novel functions and applications of self-assemblies of these amphiphiles.
