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1.
Chemistry ; 2020 Jul 14.
Artigo em Inglês | MEDLINE | ID: mdl-32663350

RESUMO

Nanothermometry is the study of temperature at the submicron scale with a broad range of potential applications such as cellular studies or electronics. Molecular luminescent based nanothermometers offer a non-contact means to record these temperatures with high spatial resolution and thermal sensitivity. A luminescent based molecular thermometer comprised of visible-emitting Ga3+/Tb3+ and Ga3+/Sm3+ metallacrowns (MCs) achieved remarkable relative thermal sensitivity associated with very low temperature uncertainty of Sr = 1.9 % K-1 and δT < 0.045 K, respectively, at 328 K, as an aqueous suspension of polystyrene nanobeads loaded with the corresponding MCs. They are so far the ratiometric molecular nanothermometers offering the highest level of sensitivity in the physiologically relevant temperature range.

2.
Chemistry ; 2020 Jul 01.
Artigo em Inglês | MEDLINE | ID: mdl-32608532

RESUMO

The interest for ratiometric luminescent probes that detect and quantify a specific analyte is growing. Due to their special luminescence properties, lanthanide(III) cations offer attractive opportunities for the design of dual-color ratiometric probes. Here, we describe the design principle of hetero-bis-lanthanide peptide conjugates using native chemical ligation for a perfect control of the localization of each lanthanide cation within the molecule. Two zinc-responsive probes, r-LZF1Tb|Cs124|Eu and r-LZF1Eu|Cs124|Tb are described on the basis of a zinc finger peptide and two DOTA complexes of terbium and europium. Both display dual-color ratiometric emission responding to the presence of Zn2+. Using a screening approach, anthracene was identified for the sensitization of the luminescence of two near infrared-emitting lanthanides, Yb3+ and Nd3+. Thus, two novel zinc-responsive hetero-bis-lanthanide probes, r-LZF3Yb|Anthra|Nd and r-LZF3Nd|Anthra|Yb were assembled, the former offering a neat ratiometric response to Zn2+ with emission in the near-infrared around 1000 nm, which is unprecedented.

3.
Chemistry ; 2020 Jun 05.
Artigo em Inglês | MEDLINE | ID: mdl-32501589

RESUMO

Herein we describe the design, synthesis and characterization of a phenhomazine ligand with six pendant acetate arms designed for the combined coordination of copper(II) and lanthanide(III) ions, with the perspective of the development of a "turn-off" copper sensor. The key step for the ligand preparation was the one-step endomethylene bridge fission of a diamino Tröger's base with a concomitant alkylation. Fluorescence and absorption spectroscopies as well as nuclear magnetic resonance (NMR) experiments were performed in order to analyze and understand the coordination properties of the ligand. Transition metal coordination was driven by the synergistic effect of the free nitrogen atoms of the diazocinic core and the two central acetate arms attached to those nitrogens, whereas lanthanide coordination is performed by external acetate arms, presumably forming a self-assembled 2:2 metallosupramolecular structure. The terbium complex shows the typical green emission with narrow bands and long luminescence lifetimes. The luminescence quenching produced by the presence of copper(II) ions was analyzed. This work sets therefore a starting point for the development of a phenhomazine-based "turn-off" copper(II) sensor.

4.
Int J Mol Sci ; 21(10)2020 May 14.
Artigo em Inglês | MEDLINE | ID: mdl-32423053

RESUMO

Galactofuranose is a rare form of the well-known galactose sugar, and its occurrence in numerous pathogenic micro-organisms makes the enzymes responsible for its biosynthesis interesting targets. Herein, we review the role of these carbohydrate-related proteins with a special emphasis on the galactofuranosidases we recently characterized as an efficient recombinant biocatalyst.

5.
J Am Chem Soc ; 142(19): 8776-8781, 2020 May 13.
Artigo em Inglês | MEDLINE | ID: mdl-32311264

RESUMO

While metal-organic frameworks (MOFs) have been identified as promising materials for sensitizing near-infrared emitting lanthanide ions (Ln3+) for biological imaging, long-wavelength excitation of such materials requires large, highly delocalized organic linkers or guest-chromophores. Incorporation of such species generally coincides with fewer Ln3+ emitters per unit volume. Herein, the excitation bands of ytterbium-based MOFs are extended to 800 nm via the postsynthetic coupling of acetylene units to form a high density of conjugated π-systems throughout MOF pores. The resulting long wavelength excitation/absorption bands are a synergistic property of the composite material as they are not observed in the individual organic components after disassociation of the MOFs, thus circumventing the need for large organic chromophores. We demonstrate that the long wavelength excitation and emission properties of these modified MOFs are maintained in the biological conditions of cell culture (aqueous environment, salts, heating), pointing toward their promising use for biological imaging applications.

6.
Chemistry ; 26(6): 1274-1277, 2020 Jan 27.
Artigo em Inglês | MEDLINE | ID: mdl-31808971

RESUMO

Multimodal probes capable of combining imaging modalities within a single molecule are in high demand today as they can provide information at both molecular and anatomical levels. Herein, a study was conducted on a series of gallium(III)/lanthanide(III) bis(12-MC-4) metallacrowns (MCs) with the general composition {Ln[12-MCGa III N(shi) -4]}2 (iph)4 (Ln-Ix , x=0, 4, 8, 12), where shi and iph are salicylhydroximate and isophthalate ligands, respectively, or their iodinated derivatives. For Yb-Ix , the attenuation in X-ray computed tomography (XCT) imaging and near-infrared (NIR) luminescence properties can be finely tuned by controlled structural modifications based on iodo groups. Solutions of Yb-Ix appear to be 22-40 times more efficient as XCT agents in comparison to the commercially available iobitridol, while providing an intense emission signal in the NIR range with total quantum yields up to 8.6 %, which are among the highest values reported so far. Therefore, these molecules are promising potential bimodal agents for combined NIR luminescence and XCT imaging.

7.
Chem Commun (Camb) ; 55(54): 7776-7779, 2019 Jul 02.
Artigo em Inglês | MEDLINE | ID: mdl-31210218

RESUMO

An unusual class, compact in size, of fluorescent probes based on pyridazino-1,3a,6a-triazapentalene scaffolds exhibits promising fluorescent properties (quantum yield values up to 73%, large Stokes shifts, emission wavelengths located in the green-yellow range, excellent solubility) with good photostability suitable for optical imaging applications.


Assuntos
Corantes Fluorescentes/química , Compostos Heterocíclicos com 3 Anéis/química , Fluorescência , Corantes Fluorescentes/síntese química , Células HeLa , Compostos Heterocíclicos com 3 Anéis/síntese química , Humanos , Microscopia de Fluorescência/métodos , Imagem Óptica/métodos , Fotodegradação
8.
Carbohydr Res ; 480: 35-41, 2019 Jul 01.
Artigo em Inglês | MEDLINE | ID: mdl-31174175

RESUMO

Despite the crucial role of the rare galactofuranose (Galf) in many pathogenic micro-organisms and our increased knowledge of its metabolism, there is still a lack of recombinant and efficient galactofuranoside hydrolase available for chemo-enzymatic synthetic purposes of specific galactofuranosyl-conjugates. Subcloning of the Galf-ase from JHA 19 Streptomyces sp. and its further overexpression lead us to the production of this enzyme with a yield of 0.5 mg/L of culture. It exhibits substrate specificity exclusively towards pNP ß-d-Galf, giving a KM value of 250 µM, and the highest enzymatic efficiency ever observed of 14 mM-1  s-1. It proved to be stable to temperature up to 60 °C and to at least 4 freeze-thaw's cycles. Thus, Galf-ase demonstrated to be an efficient and stable biocatalyst with greatly improved specificity toward the galactofuranosyl entity, thus paving the way to the further development of transglycosylation and thioligation reactions.


Assuntos
Glicosídeo Hidrolases/genética , Glicosídeo Hidrolases/metabolismo , Streptomyces/enzimologia , Streptomyces/genética , Biocatálise , Clonagem Molecular , Estabilidade Enzimática , Glicosídeo Hidrolases/química , Concentração de Íons de Hidrogênio , Cinética , Especificidade por Substrato , Temperatura
9.
Inorg Chem ; 58(20): 13619-13630, 2019 Oct 21.
Artigo em Inglês | MEDLINE | ID: mdl-31136161

RESUMO

Thanks to their versatile magnetic and luminescence features, lanthanide complexes have gained a central position in biomedical imaging as magnetic resonance imaging (MRI) contrast agents and optical imaging probes. In addition, appropriate chemical design allows modification of the magnetic relaxation properties of GdIII complexes and the optical properties of visible- or near-infrared (NIR)-emitting lanthanide chelates upon interaction with various biomarkers, which makes them ideal candidates for the creation of responsive agents. In this Forum Article, we demonstrate such design principles as well as the difficulties encountered in the context of neurotransmitter (NT) detection. Lanthanide(III) complexes of a macrocyclic ligand incorporating a benzophenone chromophore and a monoazacrown ether (LnL3) have been synthesized as responsive probes to monitor amino acid NTs either in MRI (Ln = Gd) or in NIR optical detection (Ln = Nd or Yb). The parameters characterizing the water exchange and rotational dynamics of the gadolinium(III) complex were assessed by 17O NMR and 1H NMRD. In the presence of zwitterionic NTs, the inner-sphere water molecule is replaced by the carboxylate function of the NTs in the gadolinium(III) complex, leading to a decrease of the longitudinal relaxivity from 6.7 to 2-2.5 mM-1 s-1 (300 MHz and 37 °C). The apparent affinity constants range from Ka = 35 for γ-aminobutyric acid (GABA) to 80 M-1 for glycine and glutamate, and there is no selectivity with respect to hydrogen carbonate (Ka = 232; pH 7.4). The gadolinium(III) complex interacts with human serum albumin (HSA), resulting in a 60% increase in the relaxivity (20 MHz, 37 °C) in the absence of NTs. The HSA-bound complex, however, was revealed to be less responsive to NTs because of displacement of the GdIII-bound water by HSA, which was confirmed by the hydration number calculated from luminescence lifetimes of the HSA-bound europium(III) complex. The creation of an imaging agent suitable for NIR detection of NTs for an enhanced sensitivity in biological systems using the benzophenone (BP) moiety as the sensitizer of lanthanide luminescence was also attempted. Upon excitation at 300 nm of the BP chromophore in aqueous solutions of NdL3 and YbL3, characteristic NIR emissions of NdIII and YbIII were observed because of 4F3/2 → 4IJ (J = 9/2-13/2) and 2F5/2 → 2F7/2 transitions, respectively, indicating that this chromophore is a suitable antenna. Despite these promising results, luminescence titrations of NdIII and YbIII complexes with NTs were not conclusive because of chemical conversion of the ligand triggered by light, preventing quantitative analysis. The observed photochemical reaction of the ligand is strongly dependent on the nature of the lanthanide chelated; it is considerably slowed down in the presence of NdIII and EuIII.

10.
Chem Sci ; 9(42): 8099-8102, 2018 Nov 14.
Artigo em Inglês | MEDLINE | ID: mdl-30542559

RESUMO

We successfully demonstrate that metal-organic frameworks (MOFs) can be designed to be excited and emit within the biological diagnostic window (650-1450 nm). An isoreticular series of anionic rare earth MOFs with fcu topology was synthesized using 10 different rare earth elements (Y3+, Eu3+, Gd3+, Tb3+, Dy3+, Ho3+, Er3+, Tm3+, Yb3+, Lu3+) and common linear ditopic ligands. Five different cationic dye molecules were incorporated into the MOFs via ion exchange. When LDS 750, which exhibits low-energy absorption in the range 450-770 nm, is loaded into an Yb3+-MOF, it can be used as an antenna to sensitize the near-infrared (NIR) emission of Yb3+ centred at 980 nm.

11.
J Am Chem Soc ; 140(34): 10820-10828, 2018 08 29.
Artigo em Inglês | MEDLINE | ID: mdl-30109926

RESUMO

We have designed a rigid photocleavable dianthracene-based ligand that reacts with ytterbium as coordination metal ion for the creation of a class of tridimensional light-degradable metal-organic framework (MOF). We demonstrated that we can obtain a high level of control on the disassembly of the MOF formed with this ligand which can be triggered either through light irradiation or temperature increase. The reversible 4π-4π photodimerization is the intrinsic chemical mechanism ruling the ligand and MOF cleavage. In the fields of biology and medicine, MOFs have sparked a strong interest as highly porous vehicles for drug release but have only been explored so far through the passive leakage of their payloads. The designed light-degradable MOFs can potentially overcome this limitation and serve as prototypes for drug delivery and corresponding therapeutic applications.

12.
Chemistry ; 24(50): 13158-13169, 2018 Sep 06.
Artigo em Inglês | MEDLINE | ID: mdl-30016559

RESUMO

Intrigued by the unexpected room-temperature dual visible/near-infrared (NIR) luminescence observed for fast-relaxing erbium complexes embedded in triple-stranded helicates, in this contribution, we explore a series of six tridentate N-donor receptors L4-L9 with variable aromaticities and alkyl substituents to extricate the stereoelectronic features responsible for such scarce optical signatures. Detailed solid-state (X-ray diffraction, differential scanning calorimetry, optical spectroscopy) and solution (speciations and thermodynamic stabilities, spectrophotometry, NMR and optical spectroscopy) studies of mononuclear unsaturated [Er(Lk)2 ]3+ and saturated triple-helical [Er(Lk)3 ]3+ model complexes reveal that the stereoelectronic changes induced by the organic ligands affect inter- and intramolecular interactions to such an extent that 1) melting temperatures in solids, 2) the affinity for trivalent erbium in solution, and 3) optical properties in luminescent complexes can be rationally varied and controlled. With this toolkit in hand, mononuclear erbium complexes with low stabilities displaying only NIR emission can be transformed into molecular-based dual Er-centered visible/NIR emitters operating at room temperature in both solid and solution states.

13.
Chemistry ; 24(42): 10773-10783, 2018 Jul 25.
Artigo em Inglês | MEDLINE | ID: mdl-29770506

RESUMO

A new family of [3.3.1] metallacryptates with the general composition [LnGa6 (H2 shi)(Hshi)(shi)7 (C5 H5 N)] (Ln-1; shi3- =salicylhydroximate; Ln = Pr, Nd, Sm-Yb) has been synthesized and characterized. Ln-1 display both interesting magnetic and luminescent properties. Sm-1 has sharp emission bands in the visible and the near-infrared (NIR) regions with quantum yield values (QSmL ) of 1.64(9) and 5.5(2). 10-2 %, respectively. Tb-1 exhibits a weak green emission (QTbL =1.89(3). 10-1 %) while Pr-1, Nd-1, Ho-1, Er-1, and Yb-1 possess emission bands in the NIR range with QPrL =3.7(2). 10-3 %, QNdL =1.71(5). 10-1 %, QHoL =1.1(2). 10-3 %, QErL =7.1(2). 10-3 % and QYbL =0.65(3) %. Nd-1, Dy-1, and Yb-1 display slow magnetization relaxation in an applied field, where only Dy-1 has been observed to follow an Orbach process (Ueff =12.7 K). The combination of NIR emission with magnetic properties makes Nd-1 and Yb-1 attractive candidates as smart materials addressable in two manners.

14.
Chem Sci ; 9(2): 325-335, 2018 Jan 14.
Artigo em Inglês | MEDLINE | ID: mdl-29629101

RESUMO

Metal-containing (bio)organic polymers are materials of continuously increasing importance for applications in energy storage and conversion, drug delivery, shape-memory items, supported catalysts, organic conductors and smart photonic devices. The embodiment of luminescent components provides a revolution in lighting and signaling with the ever-increasing development of polymeric light-emitting devices. Despite the unique properties expected from the introduction of optically and magnetically active lanthanides into organic polymers, the deficient control of the metal loading currently limits their design to empirical and poorly reproducible materials. We show here that the synthetic efforts required for producing soluble multi-site host systems Lk are largely overcome by the virtue of reversible thermodynamics for mastering the metal loading with the help of only two parameters: (1) the affinity of the luminescent lanthanide container for a single binding site and (2) the cooperative effect which modulates the successive fixation of metallic units to adjacent sites. When unsymmetrical perfluorobenzene-trifluoroacetylacetonate co-ligands (pbta-) are selected for balancing the charge of the trivalent lanthanide cations, Ln3+, in six-coordinate [Ln(pbta)3] containers, the explored anti-cooperative complexation processes induce nearest-neighbor intermetallic interactions twice as large as thermal energy at room temperature (RT = 2.5 kJ mol-1). These values have no precedent when using standard symmetrical containers and they pave the way for programming metal alternation in luminescent lanthanidopolymers.

15.
Chem Commun (Camb) ; 54(50): 6816-6819, 2018 Jun 19.
Artigo em Inglês | MEDLINE | ID: mdl-29611584

RESUMO

We report here two isoreticular ytterbium (Yb) 2D metal-organic frameworks (MOFs) emitting near-infrared (NIR) luminescence with 1.26(2)% quantum yield values, which are among the highest values reported to date for MOFs incorporating NIR-emitting lanthanide cations. The excitation wavelength of the YbIII MOFs can be red-shifted to the visible range by introducing an amino group to the organic chromophore. Density functional theory (DFT) calculations were performed to gain insights into the photophysical properties of this new family of MOFs.

16.
Front Chem ; 6: 1, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-29441345

RESUMO

Self-aggregating calix[4]arenes carrying four DOTA ligands on the upper rim for stable complexation of paramagnetic GdIII-ions have already been proposed as MRI probes. In this work, we investigate the luminescence properties of TbIII-DOTA-calix[4]arene-4OPr containing four propyl-groups and compare them with those of the analog substituted with a phthalimide chromophore (TbIII-DOTA-calix[4]arene-3OPr-OPhth). We show that, given its four aromatic rings, the calix[4]arene core acts as an effective sensitizer of Tb-centered luminescence. Substituents on the lower rim can modulate the aggregation behavior, which in turn determines the luminescence properties of the compounds. In solid state, the quantum yield of the phthalimide derivative is almost three times as high as that of the propyl-functionalized analog demonstrating a beneficial role of the chromophore on Tb-luminescence. In solution, however, the effect of the phthalimide group vanishes, which we attribute to the large distance between the chromophore and the lanthanide, situated on the opposite rims of the calix[4]arene. Both quantum yields and luminescence lifetimes show clear concentration dependence in solution, related to the strong impact of aggregation on the luminescence behavior. We also evidence the variability in the values of the critical micelle concentration depending on the experimental technique. Such luminescent calix[4]arene platforms accommodating stable lanthanide complexes can be considered valuable building blocks for the design of dual MR/optical imaging probes.

17.
Dalton Trans ; 47(2): 596-607, 2018 Jan 02.
Artigo em Inglês | MEDLINE | ID: mdl-29239432

RESUMO

New functional coordination polymers based on the semi-flexible 9,10-di(1H-imidazol-1-yl)-anthracene ligand (L) with ZnII and CdII, namely {[Zn(µ2-L)2](ClO4)2·m(MeOH)·n(DCM)}n (1), {[Zn(µ2-L)2](BF4)2·m(MeOH)·n(DCM)}n (2), {[Zn(µ2-L)2(p-Tos)2]·m(DCM)·n(MeOH)}n (3), {[Cd(µ2-L)2(p-Tos)2]·m(DCM)}n (4) {[Cd(µ2-L)2(p-Tos)2]·m(MeOH)·n(Dioxane)}n (5) and {[Zn(µ2-L)2(CF3CO2)2]·2(Dioxane)}n (6), were obtained. Dissolving L in polar solvent mixtures MeOH-DCM (4 : 1) or MeOH-dioxane (1 : 1) with ZnII and CdII salts resulted in the formation of complexes 1, 2, and 5 adopting a cis-conformation of the imidazole groups with respect to anthracene. In less polar mixtures of solvents such as MeOH-DCM (1 : 4) trans-L is observed, leading to the coordination polymers 3-4 with ZnII and CdII. In an intermediate solvent mixture such as MeOH-dioxane (1 : 4), the cis- and trans-conformation coexist as exemplified in complex 6 with ZnII. In the solid state, complexes 1-5 assemble as supramolecular 2-D coordination polymers with a (4,4) topology, while 6 forms a tridimensional porous network with a cds topology. All compounds reveal strong blue emission in the solid state at room temperature.

18.
Chemistry ; 24(5): 1031-1035, 2018 Jan 24.
Artigo em Inglês | MEDLINE | ID: mdl-28960536

RESUMO

A family of dimeric LnIII [12-MCGa(III)N(shi) -4] metallacrowns (MCs) (LnIII =Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, and Yb) was synthesized using the isophthalate group (ip2- ) as a linker. The [LnGa4 ]2 complexes exhibit remarkable photophysical properties, with large molar absorptivities of ≈4×104 m-1 cm-1 , high quantum yields and long luminescence lifetimes with values of (i) 31.2(2)% and 1.410(1) ms, respectively for the visible-emitting [TbGa4 ]2 complex and (ii) 2.43(6)% and 30.5(1) µs for the near-infrared (NIR) emitting [YbGa4 ]2 in the solid state. The NIR emission was obtained not only from Yb, Nd, and Er complexes but also from the less frequently observed emitters such as Pr and Ho. In addition, emission in both visible and NIR domains could be detected for Dy and Sm MCs. ESI-MS and UV/Vis data revealed that the complexes are highly stable in dimethylsulfoxide (DMSO) solution with the 1 H- and COSY-NMR spectra of the diamagnetic [YGa4 ]2 analogue providing evidence for long-term solution stability. This new approach allows one to construct a basis for highly luminescent MCs that may be further modified to be adapted for applications such as optical imaging.

19.
Chem Sci ; 8(9): 6042-6050, 2017 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-28989634

RESUMO

Cell fixation is an essential approach for preserving cell morphology, allowing the targeting and labelling of biomolecules with fluorescent probes. One of the key requirements for more efficient fluorescent labelling is the preservation of cell morphology, which usually requires a combination of several fixation techniques. In addition, the use of a counter stain is often essential to improve the contrast of the fluorescent probes. Current agents possess significant limitations, such as low resistance toward photobleaching and sensitivity to changes in the microenvironment. Luminescent Ln3+ 'encapsulated sandwich' metallacrowns (MCs) overcome these drawbacks and offer complementary advantages. In particular, they emit sharp emission bands, possess a large difference between excitation and emission wavelengths and do not photobleach. Herein, MCs formed with pyrazinehydroxamic acid (Ln3+[Zn(ii)MCpyzHA], Ln3+ = Yb, Nd) were used, combined with near-infrared (NIR) counter staining and fixation agents for HeLa cells upon an initial five minute exposure to UV-A light. The validity and quality of the cell fixation were assessed with Raman spectroscopy. Analysis of the NIR luminescence properties of these MCs was performed under different experimental conditions, including in a suspension of stained cells. Moreover, the high emission intensity of Ln3+[Zn(ii)MCpyzHA] in the NIR region allows these MCs to be used for imaging with standard CCD cameras installed on routine fluorescence microscopes. Finally, the NIR-emitting Ln3+[Zn(ii)MCpyzHA] compounds combine, within a single molecule, features such as cell fixation and staining abilities, good photostability and minimal sensitivity of the emission bands to the local microenvironment, and they are highly promising for establishing the next generation of imaging agents with a single biodistribution.

20.
Chemistry ; 23(46): 10992-10996, 2017 Aug 16.
Artigo em Inglês | MEDLINE | ID: mdl-28759142

RESUMO

Responsive luminescent probes emitting in the near-infrared (NIR) are in high demand today for biological applications as they allow for the easy and unambiguous discrimination of autofluorescence. Due to their luminescence properties, lanthanide ions offer an interesting alternative to classical organic fluorescent dyes. This has stimulated the development of lanthanide-based responsive probes. Nevertheless, responsive probes that can operate in water with NIR-emitting lanthanide ions are scarce. In this communication, zinc fingers are shown to be versatile scaffolds to elaborate a variety of Zn2+ -responsive probes based on lanthanide emission and featuring desirable properties for the selective detection of Zn2+ in experimental conditions close to cellular. Of special interest is a NIR-emitting probe relying on Nd3+ emission.

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