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Abstract
Currently, there is a substantial research effort to develop near-infrared fluorescent polymethine cyanine dyes for biological imaging and sensing. In water, cyanine dyes with extended conjugation are known to cross over the "cyanine limit" and undergo a symmetry breaking Peierls transition that favors an unsymmetric distribution of π-electron density and produces a broad absorption profile and low fluorescence brightness. This study shows how supramolecular encapsulation of a newly designed series of cationic, cyanine dyes by cucurbit[7]uril (CB7) can be used to alter the π-electron distribution within the cyanine chromophore. For two sets of dyes, supramolecular location of the surrounding CB7 over the center of the dye favors a nonpolar ground state, with a symmetric π-electron distribution that produces a sharpened absorption band with enhanced fluorescence brightness. The opposite supramolecular effect (i.e., broadened absorption and partially quenched fluorescence) is observed with a third set of dyes because the surrounding CB7 is located at one end of the encapsulated cyanine chromophore. From the perspective of enhanced near-infrared bioimaging and sensing in water, the results show how that the principles of host/guest chemistry can be employed to mitigate the "cyanine limit" problem.
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Affiliation(s)
- Dong-Hao Li
- Department of Chemistry and Biochemistry, University of Notre Dame, 251 Nieuwland Science Hall, Notre Dame, Indiana 46556, United States
| | - Bradley D Smith
- Department of Chemistry and Biochemistry, University of Notre Dame, 251 Nieuwland Science Hall, Notre Dame, Indiana 46556, United States
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2
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Luna-Ixmatlahua RA, Carrasco-Ruiz A, Cervantes R, Vela A, Tiburcio J. An Anionic Ring Locked into an Anionic Axle: A Metastable Rotaxane with Chemically Activated Electrostatic Stoppers. Chemistry 2019; 25:14042-14047. [PMID: 31468580 DOI: 10.1002/chem.201902735] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2019] [Revised: 08/28/2019] [Indexed: 02/03/2023]
Abstract
The use of the electrostatic stoppers concept in the field of mechanically interlocked molecules is reported; these stoppers are chemically sensitive end groups on a linear guest molecule that allows for the conversion of a pseudo-rotaxane species into a rotaxane complex by a change in the medium acidity. The chemical stimulus causes the appearance of negative charges on both ends of the linear component, passing from cationic to anionic, and causing a significant ring-to-axle electrostatic repulsion. This phenomenon has two different and simultaneous effects: 1) destabilizes the complex as a consequence of confining an anionic ring into an anionic axle, and 2) increases the dissociation energy barrier, thus impeding ring extrusion. This newly formed metastable rotaxane species is resistant to solvent and temperature effects and performs as a two-state degenerated molecular shuttle in solution.
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Affiliation(s)
- Rubi A Luna-Ixmatlahua
- Department of Chemistry, Center for Research and Advanced Studies (Cinvestav), Avenida IPN 2508, Zacatenco, Mexico City, 07360, Mexico
| | - Anayeli Carrasco-Ruiz
- Department of Chemistry, Center for Research and Advanced Studies (Cinvestav), Avenida IPN 2508, Zacatenco, Mexico City, 07360, Mexico
| | - Ruy Cervantes
- Department of Chemistry, Center for Research and Advanced Studies (Cinvestav), Avenida IPN 2508, Zacatenco, Mexico City, 07360, Mexico
| | - Alberto Vela
- Department of Chemistry, Center for Research and Advanced Studies (Cinvestav), Avenida IPN 2508, Zacatenco, Mexico City, 07360, Mexico
| | - Jorge Tiburcio
- Department of Chemistry, Center for Research and Advanced Studies (Cinvestav), Avenida IPN 2508, Zacatenco, Mexico City, 07360, Mexico
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3
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Dempsey JM, Zhai C, McGarraugh HH, Schreiber CL, Stoffel SE, Johnson A, Smith BD. High affinity threading of a new tetralactam macrocycle in water by fluorescent deep-red and near-infrared squaraine dyes. Chem Commun (Camb) 2019; 55:12793-12796. [PMID: 31593200 PMCID: PMC6827183 DOI: 10.1039/c9cc05244e] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
A new tetralactam macrocycle was prepared and found to encapsulate deep-red and near-infrared squaraine and croconaine dyes in water with tunable threading kinetics. The new supramolecular paradigm of guest back-folding was used to increase macrocycle/squaraine affinity by 370-fold and achieve an association constant of 2.8 × 109 M-1.
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Affiliation(s)
- Janel M Dempsey
- Department of Chemistry and Biochemistry, University of Notre Dame, 236 Nieuwland Science Hall, Notre Dame, IN 46556, USA.
| | - Canjia Zhai
- Department of Chemistry and Biochemistry, University of Notre Dame, 236 Nieuwland Science Hall, Notre Dame, IN 46556, USA.
| | - Hannah H McGarraugh
- Department of Chemistry and Biochemistry, University of Notre Dame, 236 Nieuwland Science Hall, Notre Dame, IN 46556, USA.
| | - Cynthia L Schreiber
- Department of Chemistry and Biochemistry, University of Notre Dame, 236 Nieuwland Science Hall, Notre Dame, IN 46556, USA.
| | - Shannon E Stoffel
- Department of Chemistry and Biochemistry, University of Notre Dame, 236 Nieuwland Science Hall, Notre Dame, IN 46556, USA.
| | - Andrew Johnson
- Division of Science, Lindsey Wilson College, 317 Fugitte Science Center, Columbia, KY 42728, USA
| | - Bradley D Smith
- Department of Chemistry and Biochemistry, University of Notre Dame, 236 Nieuwland Science Hall, Notre Dame, IN 46556, USA.
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4
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Li DH, Smith BD. Molecular recognition using tetralactam macrocycles with parallel aromatic sidewalls. Beilstein J Org Chem 2019; 15:1086-1095. [PMID: 31164945 PMCID: PMC6541352 DOI: 10.3762/bjoc.15.105] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2019] [Accepted: 05/02/2019] [Indexed: 01/16/2023] Open
Abstract
This review summarizes the supramolecular properties of tetralactam macrocycles that have parallel aromatic sidewalls and four NH residues directed into the macrocyclic cavity. These macrocycles are versatile hosts for a large number of different guest structures in water and organic solvents, and they are well-suited for a range of supramolecular applications. The macrocyclic cavity contains a mixture of polar functional groups and non-polar surfaces which is reminiscent of the amphiphilic binding pockets within many proteins. In water, the aromatic surfaces in the tetralactam cavity drive high affinity due the hydrophobic effect and the NH groups provide secondary interactions that induce binding selectivity. In organic solvents, the supramolecular factors are reversed; the polar NH groups drive high affinity and the aromatic surfaces provide the secondary interactions. In addition to an amphiphilic cavity, macrocyclic tetralactams exhibit conformational flexibility, and the combination of properties enables them to be effective hosts for a wide range of guest molecules including organic biscarbonyl derivatives, near-infrared dyes, acenes, precious metal halide complexes, trimethylammonium ion-pairs, and saccharides.
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Affiliation(s)
- Dong-Hao Li
- Department of Chemistry and Biochemistry, University of Notre Dame, 236 Nieuwland Science Hall, Notre Dame, Indiana 46556, United States
| | - Bradley D Smith
- Department of Chemistry and Biochemistry, University of Notre Dame, 236 Nieuwland Science Hall, Notre Dame, Indiana 46556, United States
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5
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Abstract
Molecular conjugation refers to methods used in biomedicine, advanced materials and nanotechnology to link two partners - from small molecules to large and sometimes functionally complex biopolymers. The methods ideally have a broad structural scope, proceed under very mild conditions (including in H2O), occur at a rapid rate and in quantitative yield with no by-products, enable bioorthogonal reactivity and have zero toxicity. Over the past two decades, the field of click chemistry has emerged to afford us new and efficient methods of molecular conjugation. These methods are based on chemical reactions that produce permanently linked conjugates, and we refer to this field here as covalent click chemistry. Alternatively, if molecular conjugation is undertaken using a pair of complementary molecular recognition partners that associate strongly and selectively to form a thermodynamically stable non-covalent complex, then we refer to this strategy as non-covalent click chemistry. This Perspective is concerned with this latter approach and highlights two distinct applications of non-covalent click chemistry in molecular conjugation: the pre-assembly of molecular conjugates or surface-coated nanoparticles and the in situ capture of tagged biomolecular targets for imaging or analysis.
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Affiliation(s)
- Cynthia L Schreiber
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN, USA
| | - Bradley D Smith
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN, USA
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6
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Zeng J, Wang X, Qi Y, Yu Y, Zeng X, Zhang X. Structural Transformation in Metal–Organic Frameworks for Reversible Binding of Oxygen. Angew Chem Int Ed Engl 2019. [DOI: 10.1002/ange.201902810] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Affiliation(s)
- Jin‐Yue Zeng
- Key Laboratory of Biomedical Polymers of Ministry of Education & Department of ChemistryWuhan University Wuhan 430072 China
| | - Xiao‐Shuang Wang
- Key Laboratory of Biomedical Polymers of Ministry of Education & Department of ChemistryWuhan University Wuhan 430072 China
| | - Yong‐Dan Qi
- Key Laboratory of Biomedical Polymers of Ministry of Education & Department of ChemistryWuhan University Wuhan 430072 China
| | - Yun Yu
- Key Laboratory of Biomedical Polymers of Ministry of Education & Department of ChemistryWuhan University Wuhan 430072 China
| | - Xuan Zeng
- Key Laboratory of Biomedical Polymers of Ministry of Education & Department of ChemistryWuhan University Wuhan 430072 China
| | - Xian‐Zheng Zhang
- Key Laboratory of Biomedical Polymers of Ministry of Education & Department of ChemistryWuhan University Wuhan 430072 China
- The Institute for Advanced StudiesWuhan University Wuhan 430072 China
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7
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Zeng JY, Wang XS, Qi YD, Yu Y, Zeng X, Zhang XZ. Structural Transformation in Metal-Organic Frameworks for Reversible Binding of Oxygen. Angew Chem Int Ed Engl 2019; 58:5692-5696. [PMID: 30848514 DOI: 10.1002/anie.201902810] [Citation(s) in RCA: 33] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2019] [Indexed: 01/14/2023]
Abstract
Polycyclic aromatic derivatives can trap 1 O2 to form endoperoxides (EPOs) for O2 storage and as sources of reactive oxygen species. However, these materials suffer from structural amorphism, which limit both practical applications and fundamental studies on their structural optimization for O2 capture and release. Metal-organic frameworks (MOFs) offer advantages in O2 binding, such as clear structure-performance relationships and precise controllability. Herein, we report the reversible binding of O2 is realized via the chemical transformation between anthracene-based and the corresponding EPO-based MOF. It is shown that anthracene-based MOF, the framework featuring linkers with polycyclic aromatic structure, can rapidly trap 1 O2 to form EPOs and can be restored upon UV irradiation or heating to release O2 . Furthermore, we confirm that photosensitizer-incorporated anthracene-based MOF are promising candidates for reversible O2 carriers controlled by switching Vis/UV irradiation.
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Affiliation(s)
- Jin-Yue Zeng
- Key Laboratory of Biomedical Polymers of Ministry of Education & Department of Chemistry, Wuhan University, Wuhan, 430072, China
| | - Xiao-Shuang Wang
- Key Laboratory of Biomedical Polymers of Ministry of Education & Department of Chemistry, Wuhan University, Wuhan, 430072, China
| | - Yong-Dan Qi
- Key Laboratory of Biomedical Polymers of Ministry of Education & Department of Chemistry, Wuhan University, Wuhan, 430072, China
| | - Yun Yu
- Key Laboratory of Biomedical Polymers of Ministry of Education & Department of Chemistry, Wuhan University, Wuhan, 430072, China
| | - Xuan Zeng
- Key Laboratory of Biomedical Polymers of Ministry of Education & Department of Chemistry, Wuhan University, Wuhan, 430072, China
| | - Xian-Zheng Zhang
- Key Laboratory of Biomedical Polymers of Ministry of Education & Department of Chemistry, Wuhan University, Wuhan, 430072, China.,The Institute for Advanced Studies, Wuhan University, Wuhan, 430072, China
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8
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Jarvis TS, Smith BD. Macrocycle threading using solvatochromic squaraine dyes. Supramol Chem 2019. [DOI: 10.1080/10610278.2019.1568433] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Affiliation(s)
- Tia S. Jarvis
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN, USA
| | - Bradley D. Smith
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN, USA
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9
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Sun T, Zhang G, Wang Q, Guo Z, Chen Q, Chen X, Lu Y, Zhang Y, Zhang Y, Guo Q, Gao X, Cheng Y, Jiang C. Pre-blocked molecular shuttle as an in-situ real-time theranostics. Biomaterials 2019; 204:46-58. [PMID: 30878796 DOI: 10.1016/j.biomaterials.2019.02.019] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2018] [Revised: 01/23/2019] [Accepted: 02/19/2019] [Indexed: 02/05/2023]
Abstract
Real-time monitor of drug-release from drug formulations in a noninvasive way can provide spatio-temporal information for drug activation and guide further clinical rational administration. In this work, a molecular shuttle, as a typical nanosized artificial molecular machine, was managed to act as a conceptually-new nanotheranostics for oxaliplatin. A post-recognition strategy was utilized, where a default supramolecular-dye couple was pre-blocked. The rational design, synthesis, characterization and proof-of-concept of this strategy were described in detail. The drug-release upon reducing environment can be translated into near-infrared (NIR) fluorescence signal (OFF-to-ON), allowing to track the drug-release procedure by multi-modal images including IVIS, FLECT and photoacoustic imaging. The versatile nanotheranostics system can target to triple negative breast tumor via conjugated F3 peptide, and show an improved anti-tumor efficacy with much lower side effect. The intelligent nanotheranostics system based on molecular shuttle provides new reference for precision medicine in preclinical trial and postclinical evaluation.
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Affiliation(s)
- Tao Sun
- Key Laboratory of Smart Drug Delivery (Ministry of Education), State Key Laboratory of Medical Neurobiology, Department of Pharmaceutics, School of Pharmacy, Fudan University, 826 Zhangheng Road, Shanghai, 201203, PR China
| | - Guangping Zhang
- Shandong Province Key Laboratory of Medical Physics and Image Processing Technology, School of Physics and Electronics & Institute of Materials and Clean Energy, Shandong Normal University, 1 University Road, Jinan, 250358, PR China
| | - Qingbing Wang
- Department of Interventional Radiology, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, 197 Ruijin Er Road, Shanghai, 200025, PR China
| | - Zhongyuan Guo
- Key Laboratory of Smart Drug Delivery (Ministry of Education), State Key Laboratory of Medical Neurobiology, Department of Pharmaceutics, School of Pharmacy, Fudan University, 826 Zhangheng Road, Shanghai, 201203, PR China
| | - Qinjun Chen
- Key Laboratory of Smart Drug Delivery (Ministry of Education), State Key Laboratory of Medical Neurobiology, Department of Pharmaceutics, School of Pharmacy, Fudan University, 826 Zhangheng Road, Shanghai, 201203, PR China
| | - Xinli Chen
- Key Laboratory of Smart Drug Delivery (Ministry of Education), State Key Laboratory of Medical Neurobiology, Department of Pharmaceutics, School of Pharmacy, Fudan University, 826 Zhangheng Road, Shanghai, 201203, PR China
| | - Yifei Lu
- Key Laboratory of Smart Drug Delivery (Ministry of Education), State Key Laboratory of Medical Neurobiology, Department of Pharmaceutics, School of Pharmacy, Fudan University, 826 Zhangheng Road, Shanghai, 201203, PR China
| | - Yu Zhang
- Key Laboratory of Smart Drug Delivery (Ministry of Education), State Key Laboratory of Medical Neurobiology, Department of Pharmaceutics, School of Pharmacy, Fudan University, 826 Zhangheng Road, Shanghai, 201203, PR China
| | - Yujie Zhang
- Key Laboratory of Smart Drug Delivery (Ministry of Education), State Key Laboratory of Medical Neurobiology, Department of Pharmaceutics, School of Pharmacy, Fudan University, 826 Zhangheng Road, Shanghai, 201203, PR China
| | - Qin Guo
- Key Laboratory of Smart Drug Delivery (Ministry of Education), State Key Laboratory of Medical Neurobiology, Department of Pharmaceutics, School of Pharmacy, Fudan University, 826 Zhangheng Road, Shanghai, 201203, PR China
| | - Xiang Gao
- Department of Neurosurgery and Institute of Neurosurgery, State Key Laboratory of Biotherapy West China Hospital, West China Medical School, Sichuan University/Collaborative Innovation Center for Biotherapy, 24 Renmin Nan Road, Chengdu, 610041, PR China
| | - Yongzhong Cheng
- Department of Neurosurgery and Institute of Neurosurgery, State Key Laboratory of Biotherapy West China Hospital, West China Medical School, Sichuan University/Collaborative Innovation Center for Biotherapy, 24 Renmin Nan Road, Chengdu, 610041, PR China
| | - Chen Jiang
- Key Laboratory of Smart Drug Delivery (Ministry of Education), State Key Laboratory of Medical Neurobiology, Department of Pharmaceutics, School of Pharmacy, Fudan University, 826 Zhangheng Road, Shanghai, 201203, PR China.
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10
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Abstract
The photophysical properties of a deep-red fluorescent squaraine dye can be improved by encapsulating it within a tetralactam macrocycle. Three new tetralactams are described with different substituents (methyl, methoxy, methylenedioxy) on the macrocycle aromatic sidewalls. The capability of each tetralactam to encapsulate a squaraine dye in chloroform solution was determined experimentally using absorption, fluorescence, and NMR spectroscopy. Two of the tetralactams were found to thread a squaraine dye with association constants on the order of 106 M-1, while a third macrocycle exhibited no squaraine affinity. An X-ray crystal structure of the third tetralactam showed that the substituents sterically blocked squaraine association. Of the two tetralactams that encapsulate a squaraine, one induces an increase in squaraine fluorescence quantum yield, while the other quenches the squaraine fluorescence. The results suggest that these new squaraine binding systems will be useful for biological imaging and diagnostics applications.
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Affiliation(s)
- Janel M Dempsey
- Department of Chemistry and Biochemistry, 236 Nieuwland Science Hall, University of Notre Dame, Notre Dame, IN 46556, USA.
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11
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Shaw SK, Liu W, Gómez Durán CFA, Schreiber CL, Betancourt Mendiola MDL, Zhai C, Roland FM, Padanilam SJ, Smith BD. Non-Covalently Pre-Assembled High-Performance Near-Infrared Fluorescent Molecular Probes for Cancer Imaging. Chemistry 2018; 24:13821-13829. [PMID: 30022552 PMCID: PMC6415912 DOI: 10.1002/chem.201801825] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2018] [Revised: 07/05/2018] [Indexed: 12/15/2022]
Abstract
New fluorescent molecular probes, which can selectively target specific cell surface receptors, are needed for microscopy, in vivo imaging, and image guided surgery. The preparation of multivalent probes using standard synthetic chemistry can be a laborious process due to low reaction yields caused by steric effects. In this study, fluorescent molecular probes were prepared by a programmed non-covalent pre-assembly process that used a near-infrared fluorescent squaraine dye to thread a macrocycle bearing a cyclic arginine-glycine-aspartate peptide antagonist (cRGDfK) as a cancer targeting unit. Cell microscopy studies using OVCAR-4 (ovarian cancer) and A549 (lung cancer) cells that express high levels of the integrin αvβ3 or αvβ5 receptors, respectively, revealed a multivalent cell targeting effect. That is, there was comparatively more cell uptake of a pre-assembled probe equipped with two copies of the cRGDfK antagonist than a pre-assembled probe with only one appended cRGDfK antagonist. The remarkably high photostability and low phototoxicity of these near-infrared probes allowed for acquisition of long-term fluorescence movies showing endosome trafficking in living cells. In vivo near-infrared fluorescence imaging experiments compared the biodistribution of a targeted and untargeted probe in a xenograft mouse tumor model. The average tumor-to-muscle ratio for the pre-assembled targeted probe was 3.6 which matches the tumor targeting performance reported for analogous cRGDfK-based probes that were prepared entirely by covalent synthesis. The capability to excite these pre-assembled near-infrared fluorescent probes with blue or deep-red excitation light makes it possible to determine if a target site is located superficially or buried in tissue, a probe performance feature that is likely to be very helpful for eventual applications such as fluorescence guided surgery.
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Affiliation(s)
- Scott K Shaw
- Department of Chemistry & Biochemistry, University of Notre Dame, 236 Nieuwland Science Hall, Notre Dame, IN, 46545, USA
| | - Wenqi Liu
- Department of Chemistry & Biochemistry, University of Notre Dame, 236 Nieuwland Science Hall, Notre Dame, IN, 46545, USA
| | | | - Cynthia L Schreiber
- Department of Chemistry & Biochemistry, University of Notre Dame, 236 Nieuwland Science Hall, Notre Dame, IN, 46545, USA
| | | | - Canjia Zhai
- Department of Chemistry & Biochemistry, University of Notre Dame, 236 Nieuwland Science Hall, Notre Dame, IN, 46545, USA
| | - Felicia M Roland
- Department of Chemistry & Biochemistry, University of Notre Dame, 236 Nieuwland Science Hall, Notre Dame, IN, 46545, USA
| | - Simon J Padanilam
- Department of Chemistry & Biochemistry, University of Notre Dame, 236 Nieuwland Science Hall, Notre Dame, IN, 46545, USA
| | - Bradley D Smith
- Department of Chemistry & Biochemistry, University of Notre Dame, 236 Nieuwland Science Hall, Notre Dame, IN, 46545, USA
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12
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Fluorescent Thienothiophene-Containing Squaraine Dyes and Threaded Supramolecular Complexes with Tunable Wavelengths between 600⁻800 nm. Molecules 2018; 23:molecules23092229. [PMID: 30200488 PMCID: PMC6225225 DOI: 10.3390/molecules23092229] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2018] [Revised: 08/28/2018] [Accepted: 08/31/2018] [Indexed: 12/13/2022] Open
Abstract
A new family of fluorescent thiophene and thienothiophene-containing squaraine dyes is described with tunable wavelengths that cover the absorption/emission range of 600–800 nm. The deep-red and near-infrared fluorescent compounds were easily prepared by simple synthesis and purification methods. Spectral studies showed that each squaraine was rapidly encapsulated by a tetralactam macrocycle, with nanomolar affinity in water, to produce a threaded supramolecular complex with high chemical stability, increased fluorescence quantum yield, and decreased fluorescence quenching upon dye self-aggregation. Energy transfer within the supramolecular complex permitted multiplex emission. That is, two separate dyes with fluorescence emission bands that match the popular Cy5 and Cy7 channels, could be simultaneously excited with a beam of 375 nm light. A broad range of practical applications is envisioned in healthcare diagnostics, microscopy, molecular imaging, and fluorescence-guided surgery.
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13
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Chaudhuri S, Verderame M, Mako TL, Bandara YMNDY, Fernando AI, Levine M. Synthetic β‐Cyclodextrin Dimers for Squaraine Binding: Effect of Host Architecture on Photophysical Properties, Aggregate Formation and Chemical Reactivity. European J Org Chem 2018. [DOI: 10.1002/ejoc.201800283] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- Sauradip Chaudhuri
- Department of Chemistry University of Rhode Island 140 Flagg Road 02881 Kingston RI USA
| | - Molly Verderame
- Department of Chemistry University of Rhode Island 140 Flagg Road 02881 Kingston RI USA
| | - Teresa L. Mako
- Department of Chemistry University of Rhode Island 140 Flagg Road 02881 Kingston RI USA
| | | | - Ashvin I. Fernando
- Department of Chemistry University of Rhode Island 140 Flagg Road 02881 Kingston RI USA
| | - Mindy Levine
- Department of Chemistry University of Rhode Island 140 Flagg Road 02881 Kingston RI USA
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14
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Liu W, Johnson A, Smith BD. Guest Back-Folding: A Molecular Design Strategy That Produces a Deep-Red Fluorescent Host/Guest Pair with Picomolar Affinity in Water. J Am Chem Soc 2018; 140:3361-3370. [PMID: 29439578 DOI: 10.1021/jacs.7b12991] [Citation(s) in RCA: 46] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
One of the major goals of modern supramolecular chemistry, with important practical relevance in many technical fields, is the development of synthetic host/guest partners with ultrahigh affinity and selectivity in water. Currently, most association pairs exhibit micromolar affinity or weaker, and there are very few host/guest systems with Ka > 109 M-1, apparently due to a barrier imposed by enthalpy/entropy compensation. This present study investigated the threading of a water-soluble tetralactam cyclophane by a deep-red fluorescent squaraine guest with flanking polyethylene glycol chains, an association process that is dominated by a highly favorable enthalpic driving force. A squaraine structure was rationally designed to permit guest back-folding as a strategy to greatly expand the hydrophobic surface area that could be buried upon complexation. Guided by computational modeling, an increasing number of N-benzyl groups were appended to the squaraine core, so that, after threading, the aromatic rings could fold back and stack against the cyclophane periphery. The final design iteration exhibited an impressive combination of fluorescence and supramolecular properties, including ratiometric change in deep-red emission, picomolar affinity ( Ka = 5.1 × 1010 M-1), and very rapid threading ( kon = 7.9 × 107 M-1 s-1) in water at 25 °C. Similar excellent behavior was observed in serum solution. A tangible outcome of this study is a new cyclophane/squaraine association pair that will be a versatile platform for many different types of fluorescence-based imaging and diagnostics applications. From a broader perspective, guest back-folding of aromatic groups is a promising new supramolecular stabilization strategy to overcome enthalpy/entropy compensation and produce ultrahigh affinity [2]pseudorotaxane complexes in water and biological media.
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Affiliation(s)
- Wenqi Liu
- Department of Chemistry and Biochemistry , University of Notre Dame , 236 Nieuwland Science Hall , Notre Dame , Indiana 46556 , United States
| | - Andrew Johnson
- Division of Science , Lindsey Wilson College , 317 Fugitte Science Center , Columbia , Kentucky 42728 , United States
| | - Bradley D Smith
- Department of Chemistry and Biochemistry , University of Notre Dame , 236 Nieuwland Science Hall , Notre Dame , Indiana 46556 , United States
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15
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Shaw SK, Liu W, Brennan SP, de Lourdes Betancourt-Mendiola M, Smith BD. Non-Covalent Assembly Method that Simultaneously Endows a Liposome Surface with Targeting Ligands, Protective PEG Chains, and Deep-Red Fluorescence Reporter Groups. Chemistry 2017; 23:12646-12654. [PMID: 28736857 DOI: 10.1002/chem.201702649] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2017] [Indexed: 12/28/2022]
Abstract
A new self-assembly method is used to rapidly functionalize the surface of liposomes without perturbing the membrane integrity or causing leakage of the aqueous contents. The key molecule is a cholesterol-squaraine-PEG conjugate with three important structural elements: a cholesterol membrane anchor, a fluorescent squaraine docking station that allows rapid and high-affinity macrocycle threading, and a long PEG-2000 chain to provide steric shielding of the decorated liposome. The two-step method involves spontaneous insertion of the conjugate into the outer leaflet of pre-formed liposomes followed by squaraine threading with a tetralactam macrocycle that has appended targeting ligands. A macrocycle with six carboxylates permitted immobilization of intact fluorescent liposomes on the surface of cationic polymer beads, whereas a macrocycle with six zinc(II)-dipicolylamine units enabled selective targeting of anionic membranes, including agglutination of bacteria in the presence of human cells.
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Affiliation(s)
- Scott K Shaw
- Department of Chemistry & Biochemistry, University of Notre Dame, 236 Nieuwland Science Hall, Notre Dame, IN., 46545, USA
| | - Wenqi Liu
- Department of Chemistry & Biochemistry, University of Notre Dame, 236 Nieuwland Science Hall, Notre Dame, IN., 46545, USA
| | - Seamus P Brennan
- Department of Chemistry & Biochemistry, University of Notre Dame, 236 Nieuwland Science Hall, Notre Dame, IN., 46545, USA
| | | | - Bradley D Smith
- Department of Chemistry & Biochemistry, University of Notre Dame, 236 Nieuwland Science Hall, Notre Dame, IN., 46545, USA
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16
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Gómez-Durán CFA, Liu W, Betancourt-Mendiola MDL, Smith BD. Structural Control of Kinetics for Macrocycle Threading by Fluorescent Squaraine Dye in Water. J Org Chem 2017; 82:8334-8341. [PMID: 28753022 DOI: 10.1021/acs.joc.7b01486] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
While the general concept of steric speed bumps has been demonstrated in rotaxane shuttles and macrocycle threading systems, the sensitivity of speed bump effects has not been evaluated as a function of structural geometry. Values of Ka and kon for macrocycle threading in water are reported for a series of homologous squaraine dyes with different substituents (speed bumps) on the flanking chains and two macrocycles with different cavity sizes. Sensitivity to a steric speed bump effect was found to depend on (a) structural location, being lowest when the speed bump was near the end of a flanking chain, and (b) macrocycle cavity size, which was enhanced when the cavity was constricted. This new insight is broadly applicable to many types of molecular threading systems.
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Affiliation(s)
- César F A Gómez-Durán
- Department of Chemistry and Biochemistry, University of Notre Dame , 236 Nieuwland Science Hall, South Bend, Indiana 46556, United States
| | - Wenqi Liu
- Department of Chemistry and Biochemistry, University of Notre Dame , 236 Nieuwland Science Hall, South Bend, Indiana 46556, United States
| | | | - Bradley D Smith
- Department of Chemistry and Biochemistry, University of Notre Dame , 236 Nieuwland Science Hall, South Bend, Indiana 46556, United States
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17
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Wang X, Wicher B, Ferrand Y, Huc I. Orchestrating Directional Molecular Motions: Kinetically Controlled Supramolecular Pathways of a Helical Host on Rodlike Guests. J Am Chem Soc 2017; 139:9350-9358. [DOI: 10.1021/jacs.7b04884] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Affiliation(s)
- Xiang Wang
- CBMN Laboratory, University of Bordeaux,
CNRS, IPB, Institut Européen de Chimie Biologie, 2 rue Escarpit 33607 Pessac, France
| | - Barbara Wicher
- CBMN Laboratory, University of Bordeaux,
CNRS, IPB, Institut Européen de Chimie Biologie, 2 rue Escarpit 33607 Pessac, France
| | - Yann Ferrand
- CBMN Laboratory, University of Bordeaux,
CNRS, IPB, Institut Européen de Chimie Biologie, 2 rue Escarpit 33607 Pessac, France
| | - Ivan Huc
- CBMN Laboratory, University of Bordeaux,
CNRS, IPB, Institut Européen de Chimie Biologie, 2 rue Escarpit 33607 Pessac, France
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18
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Jarvis TS, Collins CG, Dempsey JM, Oliver AG, Smith BD. Synthesis and Structure of 3,3-Dimethylindoline Squaraine Rotaxanes. J Org Chem 2017; 82:5819-5825. [DOI: 10.1021/acs.joc.7b00655] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Affiliation(s)
- Tia S. Jarvis
- Department of Chemistry and
Biochemistry, University of Notre Dame, 236 Nieuwland Science Hall, Notre Dame, Indiana 46556, United States
| | - Carleton G. Collins
- Department of Chemistry and
Biochemistry, University of Notre Dame, 236 Nieuwland Science Hall, Notre Dame, Indiana 46556, United States
| | - Janel M. Dempsey
- Department of Chemistry and
Biochemistry, University of Notre Dame, 236 Nieuwland Science Hall, Notre Dame, Indiana 46556, United States
| | - Allen G. Oliver
- Department of Chemistry and
Biochemistry, University of Notre Dame, 236 Nieuwland Science Hall, Notre Dame, Indiana 46556, United States
| | - Bradley D. Smith
- Department of Chemistry and
Biochemistry, University of Notre Dame, 236 Nieuwland Science Hall, Notre Dame, Indiana 46556, United States
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19
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Abstract
Biotin/(strept)avidin self-assembly is a powerful platform for nanoscale fabrication and capture with many different applications in science, medicine, and nanotechnology. However, biotin/(strept)avidin self-assembly has several well-recognized drawbacks that limit performance in certain technical areas and there is a need for synthetic mimics that can either become superior replacements or operational partners with bio-orthogonal recognition properties. The goal of this tutorial review is to describe the recent progress in making high affinity synthetic association partners that operate in water or biological media. The review starts with a background summary of biotin/(strept)avidin self-assembly and the current design rules for creating synthetic mimics. A series of case studies are presented that describe recent success using synthetic derivatives of cyclodextrins, cucurbiturils, and various organic cyclophanes such as calixarenes, deep cavitands, pillararenes, and tetralactams. In some cases, two complementary partners associate to produce a nanoscale complex and in other cases a ditopic host molecule is used to link two partners. The article concludes with a short discussion of future directions and likely challenges.
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Affiliation(s)
- Wenqi Liu
- Department of Chemistry and Biochemistry, 236 Nieuwland Science Hall, University of Notre Dame, Notre Dame, Indiana 46556, USA
| | - Soumen K. Samanta
- Department of Chemistry and Biochemistry, University of Maryland, College Park, Maryland 20742, USA
| | - Bradley D. Smith
- Department of Chemistry and Biochemistry, 236 Nieuwland Science Hall, University of Notre Dame, Notre Dame, Indiana 46556, USA
| | - Lyle Isaacs
- Department of Chemistry and Biochemistry, University of Maryland, College Park, Maryland 20742, USA
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20
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Liu W, Gómez-Durán CFA, Smith BD. Fluorescent Neuraminidase Assay Based on Supramolecular Dye Capture After Enzymatic Cleavage. J Am Chem Soc 2017; 139:6390-6395. [PMID: 28426220 DOI: 10.1021/jacs.7b01628] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
A conceptually new type of enzymatic cleavage assay is reported that utilizes in situ supramolecular capture of the fluorescent product. A squaraine-derived substrate with large blocking groups at each end of its structure cannot be threaded by a tetralactam macrocycle until the blocking groups are removed by enzyme cleavage. A prototype design responds to viral neuraminidase, an indicator of influenza infection, and also measures susceptibility of the sample to neuraminidase inhibitor drugs. The substrate structure incorporates three key features: (a) a bis(4-amino-3-hydroxyphenyl)squaraine core with bright deep-red fluorescence and excellent photostability, (b) an N-methyl group at each end of the squaraine core that ensures fast macrocycle threading kinetics, and (c) sialic acid blocking groups that prevent macrocycle threading until they are removed by viral neuraminidase. The enzyme assay can be conducted in aqueous solution where dramatic colorimetric and fluorescence changes are easily observed by the naked eye. Alternatively, affinity capture beads coated with macrocycle can be used to immobilize the liberated squaraine and enable a range of heterogeneous analysis options. With further optimization, this new type of neuraminidase assay may be useful in a point of care clinic to rapidly diagnose influenza infection and also determine which of the approved antiviral inhibitor drugs is likely to be the most effective treatment for an individual patient. The assay design is generalizable and can be readily modified to monitor virtually any type of enzyme-catalyzed cleavage reaction.
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Affiliation(s)
- Wenqi Liu
- Department of Chemistry and Biochemistry, University of Notre Dame , 236 Nieuwland Science Hall, Notre Dame, Indiana 46556, United States
| | - César F A Gómez-Durán
- Department of Chemistry and Biochemistry, University of Notre Dame , 236 Nieuwland Science Hall, Notre Dame, Indiana 46556, United States
| | - Bradley D Smith
- Department of Chemistry and Biochemistry, University of Notre Dame , 236 Nieuwland Science Hall, Notre Dame, Indiana 46556, United States
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21
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Roland FM, Peck EM, Rice DR, Smith BD. Preassembled Fluorescent Multivalent Probes for the Imaging of Anionic Membranes. Bioconjug Chem 2017; 28:1093-1101. [PMID: 28125214 DOI: 10.1021/acs.bioconjchem.7b00012] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
A new self-assembly process known as Synthavidin (synthetic avidin) technology was used to prepare targeted probes for near-infrared fluorescence imaging of anionic membranes and cell surfaces, a hallmark of many different types of disease. The probes were preassembled by threading a tetralactam macrocycle with six appended zinc-dipicolylamine (ZnDPA) targeting units onto a linear scaffold with one or two squaraine docking stations to produce hexavalent or dodecavalent fluorescent probes. A series of liposome titration experiments showed that multivalency promoted stronger membrane binding by the dodecavalent probe. In addition, the dodecavalent probe exhibited turn-on fluorescence due to probe unfolding during fluorescence microscopy at the membrane surface. However, the dodecavalent probe also had a higher tendency to self-aggregate after membrane binding, leading to probe self-quenching under certain conditions. This self-quenching effect was apparent during fluorescence microscopy experiments that recorded low fluorescence intensity from anionic dead and dying mammalian cells that were saturated with the dodecavalent probe. Conversely, probe self-quenching was not a factor with anionic microbial surfaces, where there was intense fluorescence staining by the dodecavalent probe. A successful set of rat tumor imaging experiments confirmed that the preassembled probes have sufficient mechanical stability for effective in vivo imaging. The results demonstrate the feasibility of this general class of preassembled fluorescent probes for multivalent targeting, but fluorescence imaging performance depends on the specific physical attributes of the biomarker target, such as the spatial distance between different copies of the biomarker and the propensity of the probe-biomarker complex to self-aggregate.
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Affiliation(s)
- Felicia M Roland
- Department of Chemistry and Biochemistry, University of Notre Dame , 236 Nieuwland Science Hall, Notre Dame, Indiana 46556, United States
| | - Evan M Peck
- Department of Chemistry and Biochemistry, University of Notre Dame , 236 Nieuwland Science Hall, Notre Dame, Indiana 46556, United States
| | - Douglas R Rice
- Department of Chemistry and Biochemistry, University of Notre Dame , 236 Nieuwland Science Hall, Notre Dame, Indiana 46556, United States
| | - Bradley D Smith
- Department of Chemistry and Biochemistry, University of Notre Dame , 236 Nieuwland Science Hall, Notre Dame, Indiana 46556, United States
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22
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Yi X, Zhang J, Yan F, Lu Z, Huang J, Pan C, Yuan J, Zheng W, Zhang K, Wei D, He W, Yuan J. Synthesis of IR-780 dye-conjugated abiraterone for prostate cancer imaging and therapy. Int J Oncol 2016; 49:1911-1920. [DOI: 10.3892/ijo.2016.3693] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2016] [Accepted: 06/29/2016] [Indexed: 11/06/2022] Open
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23
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Nagai H, Suzaki Y, Osakada K. Chemical Modification of a [2]Rotaxane Composed of Dithiacrown Ether and Dialkylammonium with Organic and Inorganic Compounds. CHEM LETT 2016. [DOI: 10.1246/cl.160345] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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24
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Maltese V, Cospito S, Beneduci A, De Simone BC, Russo N, Chidichimo G, Janssen RAJ. Electro-optical Properties of Neutral and Radical Ion Thienosquaraines. Chemistry 2016; 22:10179-86. [PMID: 27334359 DOI: 10.1002/chem.201601281] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2016] [Indexed: 01/01/2023]
Abstract
Thienosquaraines are an interesting class of electroactive dyes that are useful for applications in organic electronics. Herein, the redox chemistry and electrochromic response of a few newly synthesized thienosquaraines are presented. These properties are compared to those of the commercial 2,4-bis[4-(N,N-diisobutylamino)-2,6-dihydroxyphenyl]squaraine. The stability of the radical ions formed in electrochemical processes strongly affects these properties, as shown by cyclic voltammetry, in situ spectroelectrochemistry, and quantum chemical calculations. Furthermore, all of the dyes show aggregation tendency resulting in panchromatic absorption covering the whole UV/Vis spectral range.
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Affiliation(s)
- Vito Maltese
- Department of Chemistry and Chemical Technologies, University of Calabria, Via P. Bucci, Arcavacata di Rende (CS), 87036, Italy. .,Molecular Materials and Nanosystems, Institute for Complex Molecular Systems, Eindhoven University of Technology, P. O. Box 513, 5600 MB, Eindhoven, The Netherlands.
| | - Sante Cospito
- Department of Chemistry and Chemical Technologies, University of Calabria, Via P. Bucci, Arcavacata di Rende (CS), 87036, Italy
| | - Amerigo Beneduci
- Department of Chemistry and Chemical Technologies, University of Calabria, Via P. Bucci, Arcavacata di Rende (CS), 87036, Italy.
| | - Bruna Clara De Simone
- Department of Chemistry and Chemical Technologies, University of Calabria, Via P. Bucci, Arcavacata di Rende (CS), 87036, Italy
| | - Nino Russo
- Department of Chemistry and Chemical Technologies, University of Calabria, Via P. Bucci, Arcavacata di Rende (CS), 87036, Italy
| | - Giuseppe Chidichimo
- Department of Chemistry and Chemical Technologies, University of Calabria, Via P. Bucci, Arcavacata di Rende (CS), 87036, Italy
| | - René A J Janssen
- Molecular Materials and Nanosystems, Institute for Complex Molecular Systems, Eindhoven University of Technology, P. O. Box 513, 5600 MB, Eindhoven, The Netherlands
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25
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Peck EM, Battles PM, Rice DR, Roland FM, Norquest KA, Smith BD. Pre-Assembly of Near-Infrared Fluorescent Multivalent Molecular Probes for Biological Imaging. Bioconjug Chem 2016; 27:1400-10. [PMID: 27088305 DOI: 10.1021/acs.bioconjchem.6b00173] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
A programmable pre-assembly method is described and shown to produce near-infrared fluorescent molecular probes with tunable multivalent binding properties. The modular assembly process threads one or two copies of a tetralactam macrocycle onto a fluorescent PEGylated squaraine scaffold containing a complementary number of docking stations. Appended to the macrocycle periphery are multiple copies of a ligand that is known to target a biomarker. The structure and high purity of each threaded complex was determined by independent spectrometric methods and also by gel electrophoresis. Especially helpful were diagnostic red-shift and energy transfer features in the absorption and fluorescence spectra. The threaded complexes were found to be effective multivalent molecular probes for fluorescence microscopy and in vivo fluorescence imaging of living subjects. Two multivalent probes were prepared and tested for targeting of bone in mice. A pre-assembled probe with 12 bone-targeting iminodiacetate ligands produced more bone accumulation than an analogous pre-assembled probe with six iminodiacetate ligands. Notably, there was no loss in probe fluorescence at the bone target site after 24 h in the living animal, indicating that the pre-assembled fluorescent probe maintained very high mechanical and chemical stability on the skeletal surface. The study shows how this versatile pre-assembly method can be used in a parallel combinatorial manner to produce libraries of near-infrared fluorescent multivalent molecular probes for different types of imaging and diagnostic applications, with incremental structural changes in the number of targeting groups, linker lengths, linker flexibility, and degree of PEGylation.
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Affiliation(s)
- Evan M Peck
- Department of Chemistry and Biochemistry, 236 Nieuwland Science Hall, University of Notre Dame , Notre Dame, Indiana 46556, United States
| | - Paul M Battles
- Department of Chemistry and Biochemistry, 236 Nieuwland Science Hall, University of Notre Dame , Notre Dame, Indiana 46556, United States
| | - Douglas R Rice
- Department of Chemistry and Biochemistry, 236 Nieuwland Science Hall, University of Notre Dame , Notre Dame, Indiana 46556, United States
| | - Felicia M Roland
- Department of Chemistry and Biochemistry, 236 Nieuwland Science Hall, University of Notre Dame , Notre Dame, Indiana 46556, United States
| | - Kathryn A Norquest
- Department of Chemistry and Biochemistry, 236 Nieuwland Science Hall, University of Notre Dame , Notre Dame, Indiana 46556, United States
| | - Bradley D Smith
- Department of Chemistry and Biochemistry, 236 Nieuwland Science Hall, University of Notre Dame , Notre Dame, Indiana 46556, United States
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26
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Liu W, Peck EM, Smith BD. High Affinity Macrocycle Threading by a Near-Infrared Croconaine Dye with Flanking Polymer Chains. J Phys Chem B 2016; 120:995-1001. [PMID: 26807599 DOI: 10.1021/acs.jpcb.5b11961] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Croconaine dyes have narrow and intense absorption bands at ∼800 nm, very weak fluorescence, and high photostabilities, which combine to make them very attractive chromophores for absorption-based imaging or laser heating technologies. The physical supramolecular properties of croconaine dyes have rarely been investigated, especially in water. This study focuses on a molecular threading process that encapsulates a croconaine dye inside a tetralactam macrocycle in organic or aqueous solvent. Macrocycle association and rate constant data are reported for a series of croconaine structures with different substituents attached to the ends of the dye. The association constants were highest in water (Ka ∼ 10(9) M(-1)), and the threading rate constants (kon) increased in the solvent order H2O > MeOH > CHCl3. Systematic variation of croconaine substituents located just outside the croconaine/macrocycle complexation interface hardly changed Ka but had a strong influence on kon. A croconaine dye with N-propyl groups at each end of the structure exhibited a desirable mixture of macrocycle threading properties; that is, there was rapid and quantitative croconaine/macrocycle complexation at relatively high concentrations in water, and no dissociation of the preassembled complex when it was diluted into a solution of fetal bovine serum, even after laser-induced photothermal heating of the solution. The combination of favorable near-infrared absorption properties and tunable mechanical stability makes threaded croconaine/macrocycle complexes very attractive as molecular probes or as supramolecular composites for various applications in absorption-based imaging or photothermal therapy.
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Affiliation(s)
- Wenqi Liu
- Department of Chemistry and Biochemistry, University of Notre Dame , 236 Nieuwland Science Hall, Notre Dame, Indiana 46556, United States
| | - Evan M Peck
- Department of Chemistry and Biochemistry, University of Notre Dame , 236 Nieuwland Science Hall, Notre Dame, Indiana 46556, United States
| | - Bradley D Smith
- Department of Chemistry and Biochemistry, University of Notre Dame , 236 Nieuwland Science Hall, Notre Dame, Indiana 46556, United States
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