Publications by authors named "Chantal Andraud"

93 Publications

Effective π-electron number and symmetry perturbation effect on the two-photon absorption of oligofluorenes.

Phys Chem Chem Phys 2021 Sep 17;23(34):18602-18609. Epub 2021 Aug 17.

Photonics Group, Instituto de Física de São Carlos, Universidade de São Paulo, CP 369, 13560-970 São Carlos, SP, Brazil.

Fluorene-based molecules exhibit significant nonlinear optical responses and multiphoton absorption in the visible region, which, combined with the high fluorescence quantum yield in organic solvents, could make this class of materials potentially engaging in diverse photonics applications. Thus, herein, we have determined the two-photon absorption (2PA) of oligofluorenes containing three, five, and seven repetitive units by employing the wavelength-tunable femtosecond Z-scan technique. Our outcomes have shown that the 2PA cross-section in oligofluorenes presents an enhanced value of around 18 GM per N, in which N is the effective number of π-electrons, for the pure 2PA allowed transition (1A-like → 2A-like). Furthermore, a weak 2PA transition was observed in the same spectral region strongly allowed by one-photon absorption (1A-like → 1B-like). This last result suggests a molecular symmetry perturbation, probably induced by the molecular disorder triggered by the increase of moieties in the oligofluorene structure. We have calculated the permanent dipole moment difference related to the lowest-energy transition using the Lippert-Matagaformalism and the 2PA sum-over-states approach to confirm this assumption. Moreover, we have estimated the fundamental limits for the 2PA cross-section in oligofluorenes.
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http://dx.doi.org/10.1039/d1cp02553hDOI Listing
September 2021

3D Printing and Pyrolysis of Optical ZrO Nanostructures by Two-Photon Lithography: Reduced Shrinkage and Crystallization Mediated by Nanoparticles Seeds.

Small 2021 10 14;17(42):e2102486. Epub 2021 Sep 14.

Laboratoire de Chimie, CNRS UMR 5182, Ecole Normale Supérieure de Lyon, Université de Lyon 1, 46 allée d'Italie, Lyon, 69364, France.

Two-photon lithography is a potential route to produce high-resolution 3D ceramics. However, the large shrinkage due to the elimination of an important organic counterpart of the printed material during debinding/sintering remains a lock to further development of this technology. To limit this phenomenon, an original approach based on a composite resin incorporating 45 wt% ultrasmall (5 nm) zirconia stabilized nanoparticles into the zirconium acrylate precursor is proposed to process 3D zirconia microlattices and nanostructured optical surfaces. Interestingly, the nanoparticles are used both as seeds allowing control of the crystallographic phase formed during the calcination process and as structural stabilizing agent preventing important shrinkage of the printed ceramic. After 3D photolithography and pyrolysis, the weight and volume loss of the microstructures are drastically reduced as compared to similar systems processed with the reference resin without nanoparticles, and stable 3D microstructures of cubic zirconia are obtained with high spatial resolution. In the case of a patterned surface, the refractive index of 2.1 leads to a diffraction efficiency large enough to obtain microfocusing with linewidths of 0.1 µm, and the demonstration of a microlens array with a period as small as 0.8 µm.
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http://dx.doi.org/10.1002/smll.202102486DOI Listing
October 2021

On the origin of controlled anisotropic growth of monodisperse gold nanobipyramids.

Nanoscale 2021 Sep 23;13(36):15292-15300. Epub 2021 Sep 23.

Dipartimento di Chimica Industriale "Toso Montanari", Universitá degli Studi di Bologna, Viale del Risorgimento 4, I-40136 Bologna, Italy.

We elucidate the crucial role of the cetyl trimethylammonium bromide (CTAB) surfactant in the anisotropic growth mechanism of gold nano-bipyramids, nano-objects with remarkable optical properties and high tunability. Atomistic molecular dynamics simulations predict different surface coverages of the CTAB (positively charged) heads and their (bromide) counterions as function of the gold exposed surfaces. High concentration of CTAB surfactant promotes formation of gold nanograins in solution that work as precursors for the smooth anisotropic growth of more elongated nano-bipyramidal objects. Nanobipyramids feature higher index facets with respect to nanorods, allowing higher CTAB coverages that stabilize their formation and leading to narrower inter-micelles channels that smooth down their anisotropic growth. Absorption spectroscopy and scanning electron microscopy confirmed the formation of nanograins and demonstrated the importance of surfactant concentration on driving the growth towards nano-bipyramids rather than nanorods. The outcome explains the formation of the monodisperse bipyramidal nano-objects, the origin of their controlled shapes and sizes along with their remarkable stability.
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http://dx.doi.org/10.1039/d1nr01768cDOI Listing
September 2021

Light-induced in situ chemical activation of a fluorescent probe for monitoring intracellular G-quadruplex structures.

Nanoscale 2021 Aug 4;13(32):13795-13808. Epub 2021 Aug 4.

Department of Medical Biochemistry and Biophysics, Umeå University, 90187 Umeå, Sweden.

Light-activated functional materials capable of remote control over duplex and G-quadruplex (G4) nucleic acids formation at the cellular level are still very rare. Herein, we report on the photoinduced macrocyclisation of a helicenoid quinoline derivative of binaphthol that selectively provides easy access to an unprecedented class of extended heteroaromatic structures with remarkable photophysical and DNA/RNA binding properties. Thus, while the native bisquinoline precursor shows no DNA binding activity, the new in situ photochemically generated probe features high association constants to DNA and RNA G4s. The latter inhibits DNA synthesis by selectively stabilizing G4 structures associated with oncogenic promoters and telomere repeat units. Finally, the light sensitive compound is capable of in cellulo photoconversion, localizes primarily in the G4-rich sites of cancer cells, competes with a well-known G4 binder and shows a clear nuclear co-localization with the quadruplex specific antibody BG4. This work provides a benchmark for the future design and development of a brand-new generation of light-activated target-selective G4-binders.
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http://dx.doi.org/10.1039/d1nr02855cDOI Listing
August 2021

Exploring the Concept of Dimerization-Induced Intersystem Crossing: At the Origins of Spin-Orbit Coupling Selection Rules.

J Phys Chem B 2021 08 22;125(30):8572-8580. Epub 2021 Jul 22.

Univ Lyon, ENS de Lyon, CNRS UMR 5182, Université Claude Bernard Lyon 1, F-69342 Lyon, France.

Singlet-triplet interconversions (intersystem crossing, ISC) in organic molecules are at the basis of many important processes in cutting-edge photonic applications (organic light-emitting devices, photodynamic therapy, etc.). Selection rules for these transitions are mainly governed by the spin-orbit coupling (SOC) phenomenon. Although the SOC relies on complex relativistic phenomena, theoreticians have, with time, developed increasingly sophisticated and efficient approaches to gain access to a satisfactory evaluation of its magnitude. However, recent works have highlighted the remarkable and somehow unexpected efficiency of dimers of small conjugated molecules in terms of ISC quantum yields, whose origin has not been completely investigated. In this work, we bring a coupled experimental and theoretical analysis of the origin of the unusually large ISC efficiency on a series of such dimers that differ by their nature (covalent or supramolecular). We show that considering the dynamical nature of the SOC, and especially its dependence on angular orientations between the dimer subunits sometimes overlooked in the literature, it is necessary to rationalize some counterintuitive experimental observations. This combined experimental and theoretical work paves the way for new molecular engineering rules for SOC control.
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http://dx.doi.org/10.1021/acs.jpcb.1c05082DOI Listing
August 2021

Near-infrared dyes for two-photon absorption in the short-wavelength infrared: strategies towards optical power limiting.

Chem Soc Rev 2021 Jun;50(11):6613-6658

Univ. Lyon, ENS Lyon, CNRS UMR 5182, Laboratoire de Chimie, 46 allée d'Italie, 69364 Lyon, France.

This work provides an overview of the recent advances in the field of two-photon absorbing chromophores active in the short-wavelength infrared (SWIR) spectral range. Herein the common strategies and main structure-property relationships that lead to near-infrared (NIR) electronic absorption of chromophores are described. A complete review of the molecules that feature two-photon absorption (2PA) beyond 1100 nm is presented for the purpose of further use in optical power limiting applications in the SWIR band. Recent progress in the development of optical power limiting in this particular spectral region is reported with emphasis on the use of the two-photon induced excited state absorption (ESA) process as an optical power limiting enhancer.
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http://dx.doi.org/10.1039/d0cs01221aDOI Listing
June 2021

Reevaluating the Solution Photophysics of Tetraphenylethylene at the Origin of their Aggregation-Induced Emission Properties.

Chemistry 2021 May 22;27(30):8003-8007. Epub 2021 Apr 22.

UMR 5182, Laboratoire de Chimie, Univ Lyon, ENS Lyon, CNRS, Université Claude Bernard Lyon 1, 69342, Lyon, France.

Although tetraphenylethylene (TPE) and its derivatives have been the most commonly used building blocks in the construction of molecules with aggregation-induced emission (AIE) properties, no absolute consensus exists regarding the mechanisms at the origin of the phenomenon. Restriction of intramolecular rotations (RIR) of peripheral phenyls has historically been a dominant paradigm, which has served as a valuable guideline in the molecular engineering of AIEgens. Yet, an increasing number of recent works have established that photoisomerization or photocyclization may actively participate in the nonradiative dissipation of the excitation energy. In this paper, the first experimental evaluation of the quantum efficiencies of these different processes is reported, and photoisomerization is shown to be by far the dominant photophysical pathway in solution, accounting for virtually all nonradiative decay of the molecule's excited state in degassed solution.
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http://dx.doi.org/10.1002/chem.202100926DOI Listing
May 2021

Hybrid multimodal contrast agent for multiscale investigation of neuroinflammation.

Nanoscale 2021 Feb;13(6):3767-3781

Université de Lyon, Ecole Normale Supérieure de Lyon, CNRS UMR 5182, Université Lyon 1, Laboratoire de Chimie, 46 allée d'Italie, F69364 Lyon, France.

Neuroinflammation is a process common to several brain pathologies. Despites its medical relevance, it still remains poorly understood; there is therefore a need to develop new in vivo preclinical imaging strategies to monitor inflammatory processes longitudinally. We here present the development of a hybrid imaging nanoprobe named NP3, that was specifically designed to get internalized by phagocytic cells and imaged in vivo with MRI and bi-photon microscopy. NP3 is composed of a 16 nm core of gadolinium fluoride (GdF3), coated with bisphosphonate polyethylene glycol (PEG) and functionalized with a Lemke-type fluorophore. It has a hydrodynamic diameter of 28 ± 8 nm and a zeta potential of -42 ± 6 mV. The MR relaxivity ratio at 7 T is r1/r2 = 20; therefore, NP3 is well suited as a T2/T2* contrast agent. In vitro cytotoxicity assessments performed on four human cell lines revealed no toxic effects of NP3. In addition, NP3 is internalized by macrophages in vitro without inducing inflammation or cytotoxicity. In vivo, uptake of NP3 has been observed in the spleen and the liver. NP3 has a prolonged vascular remanence, which is an advantage for macrophage uptake in vivo. The proof-of-concept that NP3 may be used as a contrast agent targeting phagocytic cells is provided in an animal model of ischemic stroke in transgenic CX3CR1-GFP/+ mice using three complementary imaging modalities: MRI, intravital two-photon microscopy and phase contrast imaging with synchrotron X-rays. In summary, NP3 is a promising preclinical tool for the multiscale and multimodal investigation of neuroinflammation.
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http://dx.doi.org/10.1039/d0nr07026bDOI Listing
February 2021

Benzothiadiazole-Substituted Aza-BODIPY Dyes: Two-Photon Absorption Enhancement for Improved Optical Limiting Performances in the Short-Wave IR Range.

Chemistry 2021 Feb 25;27(10):3517-3525. Epub 2021 Jan 25.

Laboratoire de Chimie, UMR 5182, ENS Lyon, CNRS, Université Lyon 1, 46 Allée d'Italie, 69364, Lyon, France.

Aza-boron dipyrromethenes (aza-BODIPYs) presenting a benzothiadiazole substitution on upper positions are described. The strong electron-withdrawing effect of the benzothiadiazole moiety permits enhancement of the accepting strength and improves the delocalization of the aza-BODIPY core to attain a significant degree of electronic communication between the lower donating groups and the upper accepting groups. The nature of the intramolecular charge transfer is studied both experimentally and theoretically. Linear spectroscopy highlighted the strongly redshifted absorption and emission of the synthesized molecules with recorded fluorescence spectra over 1000 nm. Nonlinear optical properties were also investigated. Strong enhancement of the two-photon absorption of the substituted dyes compared with the unsubstituted one (up to 4520 GM at 1300 nm) results in an approximately 15-20 % improvement of the optical power limiting performances. These dyes are therefore a good starting point for further improvement of optical power limiting in the short-wave IR range.
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http://dx.doi.org/10.1002/chem.202004899DOI Listing
February 2021

Two-Photon Absorbing AIEgens: Influence of Stereoconfiguration on Their Crystallinity and Spectroscopic Properties and Applications in Bioimaging.

ACS Appl Mater Interfaces 2020 Dec 20;12(49):55157-55168. Epub 2020 Nov 20.

Univ. Lyon, ENS Lyon, CNRS, Université Lyon 1, Laboratoire de Chimie, UMR 5182, 46 Allée d'Italie, 69364 Lyon, France.

This paper aims at designing chromophores with efficient aggregation-induced emission (AIE) properties for two-photon fluorescence microscopy (2PFM), which is one of the best-suited types of microscopy for the imaging of living organisms or thick biological tissues. Tetraphenylethylene (TPE) derivatives are common building blocks in the design of chromophores with efficient AIE properties. Therefore, in this study, extended TPE AIEgens specifically optimized for two-photon absorption (2PA) are synthesized and the resulting (/) isomers are separated using chromatography on chiral supports. Comparative characterization of the AIE properties is performed on the pure () and () isomers and the mixture, allowing us, in combination with powder X-ray diffraction and solid-state NMR, to document a profound impact of crystallinity on solid-state fluorescence properties. In particular, we show that stereopure AIEgens form aggregates of superior crystallinity, which in turn exhibit a higher fluorescence quantum yield compared to diastereoisomers mixtures. Preparation of stereopure organic nanoparticles affords very bright fluorescent contrast agents, which are then used for cellular and intravital two-photon microscopy on human breast cancer cells and on zebrafish embryos.
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http://dx.doi.org/10.1021/acsami.0c15810DOI Listing
December 2020

Impact of Ion-Pairing Effects on Linear and Nonlinear Photophysical Properties of Polymethine Dyes*.

Chemphyschem 2020 12 19;21(23):2536-2542. Epub 2020 Nov 19.

Laboratoire de Chimie, Univ. Lyon, ENS Lyon, CNRS, Université Lyon 1, 46 Allée d'Italie, 69364, Lyon, France.

The two-photon absorption (2PA) and photophysics of heptamethine dyes featuring cyanine or dipolar electronic structures have been compared for the first time. The perfectly delocalized cyanine system is classically characterized by a two-photon transition matching the vibronic component of its lower energy absorption band. The dipolar species is generated by ion-pairing with a hard counterion in a non-dissociating solvent and displays significant modifications oft he optical properties, including a significant hypochromic shift of absorption, weaker emission and 2PA matching the lower energy transition, thus revealing symmetry breaking within the polymethine electronic structure.
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http://dx.doi.org/10.1002/cphc.202000731DOI Listing
December 2020

σ-Conjugation and H-Bond-Directed Supramolecular Self-Assembly: Key Features for Efficient Long-Lived Room Temperature Phosphorescent Organic Molecular Crystals.

Angew Chem Int Ed Engl 2021 Feb 1;60(5):2446-2454. Epub 2020 Dec 1.

Building Blocks for FUture Electronics Laboratory, UMI 2002, CNRS-Sorbonne Université-Yonsei University, Yonsei University, 50 Yonsei-ro, Seodaemun-gu, Seoul, 03722, South Korea.

Long-lived room temperature phosphorescence from organic molecular crystals attracts great attention. Persistent luminescence depends on the electronic properties of the molecular components, mainly π-conjugated donor-acceptor (D-A) chromophores, and their molecular packing. Here, a strategy is developed by designing two isomeric molecular phosphors incorporating and combining a bridge for σ-conjugation between the D and A units and a structure-directing unit for H-bond-directed supramolecular self-assembly. Calculations highlight the critical role played by the two degrees of freedom of the σ-conjugated bridge on the chromophore optical properties. The molecular crystals exhibit RTP quantum yields up to 20 % and lifetimes up to 520 ms. The crystal structures of the efficient phosphorescent materials establish the existence of an unprecedented well-organization of the emitters into 2D rectangular columnar-like supramolecular structure stabilized by intermolecular H-bonding.
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http://dx.doi.org/10.1002/anie.202011770DOI Listing
February 2021

Simulating Plasmon Resonances of Gold Nanoparticles with Bipyramidal Shapes by Boundary Element Methods.

J Chem Theory Comput 2020 Jun 21;16(6):3807-3815. Epub 2020 May 21.

Laboratoire de Chimie UMR 5182, CNRS, Université Lyon 1, Univ Lyon, Ens de Lyon, F-69342 Lyon, France.

Computational modeling and accurate simulations of localized surface plasmon resonance (LSPR) absorption properties are reported for gold nanobipyramids (GNBs), a class of metal nanoparticle that features highly tunable, geometry-dependent optical properties. GNB bicone models with spherical tips performed best in reproducing experimental LSPR spectra while the comparison with other geometrical models provided a fundamental understanding of base shapes and tip effects on the optical properties of GNBs. Our results demonstrated the importance of averaging all geometrical parameters determined from transmission electron microscopy images to build representative models of GNBs. By assessing the performances of LSPR absorption spectra simulations based on a quasi-static approximation, we provided an applicability range of this approach as a function of the nanoparticle size, paving the way to the theoretical study of the coupling between molecular electron densities and metal nanoparticles in GNB-based nanohybrid systems, with potential applications in the design of nanomaterials for bioimaging, optics and photocatalysis.
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http://dx.doi.org/10.1021/acs.jctc.0c00269DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7584360PMC
June 2020

Pyclen-Based Ln(III) Complexes as Highly Luminescent Bioprobes for and One- and Two-Photon Bioimaging Applications.

J Am Chem Soc 2020 06 21;142(22):10184-10197. Epub 2020 May 21.

Univ Brest, UMR CNRS 6521 CEMCA, 6 Avenue Victor le Gorgeu, 29200 Brest, France.

In addition to the already described ligand , two pyclen-based lanthanide chelators, and , bearing two specific picolinate two-photon antennas (tailor-made for each targeted metal) and one acetate arm arranged in a dissymmetrical manner, have been synthesized, to form a complete family of lanthanide luminescent bioprobes: [Eu], [Sm], [Yb], [Tb], and [Dy]. Additionally, the symmetrically arranged regioisomer was also synthesized as well as its [Eu] complex to highlight the astonishing positive impact of the dissymmetrical -distribution of the functional chelating arms. The investigation clearly shows the high performance of each bioprobe, which, depending on the complexed lanthanide, could be used in various applications. Each presents high brightness, quantum yields, and lifetimes. Staining of the complexes into living human breast cancer cells was observed. In addition, two-photon microscopy was performed for the first time on a living zebrafish model with [Eu]. No apparent toxicity was detected on the growth of the zebrafish, and images of high quality were obtained.
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http://dx.doi.org/10.1021/jacs.0c03496DOI Listing
June 2020

Cationic Biphotonic Lanthanide Luminescent Bioprobes Based on Functionalized Cross-Bridged Cyclam Macrocycles.

Chemphyschem 2020 05 7;21(10):1036-1043. Epub 2020 Apr 7.

Univ Lyon, ENS de Lyon, CNRS UMR 5182, Université Claude Bernard Lyon 1, F-69342, Lyon, France.

Cationic lanthanide complexes are generally able to spontaneously internalize into living cells. Following our previous works based on a diMe-cyclen framework, a second generation of cationic water-soluble lanthanide complexes based on a constrained cross-bridged cyclam macrocycle functionalized with donor-π-conjugated picolinate antennas was prepared with europium(III) and ytterbium(III). Their spectroscopic properties were thoroughly investigated in various solvents and rationalized with the help of DFT calculations. A significant improvement was observed in the case of the Eu complex, while the Yb analogue conserved photophysical properties in aqueous solvent. Two-photon (2P) microscopy imaging experiments on living T24 human cancer cells confirmed the spontaneous internalization of the probes and images with good signal-to-noise ratio were obtained in the classic NIR-to-visible configuration with the Eu luminescent bioprobe and in the NIR-to-NIR with the Yb one.
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http://dx.doi.org/10.1002/cphc.202000085DOI Listing
May 2020

Influence of Polymer Charge on the Localization and Dark- and Photo-Induced Toxicity of a Potential Type I Photosensitizer in Cancer Cell Models.

Molecules 2020 Mar 3;25(5). Epub 2020 Mar 3.

Laboratoire de Chimie, CNRS UMR 5182, ENS de Lyon, Université Lyon 1, F-69342 Lyon, France.

A current trend within photo-dynamic therapy (PDT) is the development of molecular systems targeting hypoxic tumors. Thus, type I PDT sensitizers could here overcome traditional type II molecular systems that rely on the photo-initiated production of toxic singlet oxygen. Here, we investigate the cell localization properties and toxicity of two polymeric anthracene-based fluorescent probes (neutral Ant-PHEA and cationic Ant-PIm). The cell death and DNA damage of Chinese hamster ovary cancer cells (CHO-K1) were characterized as combining PDT, cell survival studies (MTT-assay), and comet assay. Confocal microscopy was utilized on samples incubated together with either DRAQ5, Lyso Tracker Red, or Mito Tracker Deep Red in order to map the localization of the sensitizer into the nucleus and other cell compartments. While Ant-PHEA did not cause significant damage to the cell, Ant-PIm showed increased cell death upon illumination, at the cost of a significant dark toxicity. Both anthracene chromophores localized in cell compartments of the cytosol. Ant-PIm showed a markedly improved selectivity toward lysosomes and mitochondria, two important biological compartments for the cell's survival. None of the two anthracene chromophores showed singlet oxygen formation upon excitation in solvents such as deuterium oxide or methanol. Conclusively, the significant photo-induced cell death that could be observed with Ant-PIm suggests a possible type I PDT mechanism rather than the usual type II mechanism.
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http://dx.doi.org/10.3390/molecules25051127DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7179247PMC
March 2020

4,5,5-Trimethyl-2,5-dihydrofuran-Based Electron-Withdrawing Groups for NIR-Emitting Push-Pull Dipolar Fluorophores.

J Org Chem 2019 Aug 1;84(16):9965-9974. Epub 2019 Aug 1.

Univ Lyon, ENS de Lyon, CNRS UMR 5182, Université Lyon I, Laboratoire de Chimie , F-69342 Lyon , France.

In the context of molecular engineering of push-pull dipolar dyes, we introduce a structural modification of the well-known electron-accepting group 2-dicyanomethylidene-3-cyano-4,5,5-trimethyl-2,5-dihydrofuran (). Introduction of a (benzo[]thiazol-2-yl) moiety failed, and unexpected structures were obtained. On the other hand, phenylthio and phenylsulfonyl entities were successfully introduced at position 3 of the 2-(dicyanomethylidene)-2,5-dihydrofuran ring, giving access to new electron-acceptor groups and dipolar fluorophores displaying near-infrared emission in solution or in the solid state, brighter than their analogues.
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http://dx.doi.org/10.1021/acs.joc.9b01120DOI Listing
August 2019

Synthesis of the New Cyanine-Labeled Bacterial Lipooligosaccharides for Intracellular Imaging and in Vitro Microscopy Studies.

Bioconjug Chem 2019 06 11;30(6):1649-1657. Epub 2019 Jun 11.

Department of Biotechnology and Biosciences , University of Milano-Bicocca . Piazza della Scienza, 2 , 20126 Milano , Italy.

Endotoxin (lipooligosaccharide, LOS, and lipopolysaccharide, LPS) is the major molecular component of Gram-negative bacteria outer membrane, and very potent pro-inflammatory substance. Visualizing and tracking the distribution of the circulating endotoxin is one of the fundamental approaches to understand the molecular aspects of infection with subsequent inflammatory and immune responses, LPS also being a key player in the molecular dialogue between microbiota and host. While fluorescently labeled LPS has previously been used to track its subcellular localization and colocalization with TLR4 receptor and downstream effectors, our knowledge on lipopolysaccharide (LOS) localization and cellular activity remains almost unexplored. In this study, LOS was labeled with a novel fluorophore, Cy7N, featuring a large Stokes-shifted emission in the deep-red spectrum resulting in lower light scattering and better imaging contrast. The LOS-Cy7N chemical identity was determined by mass spectrometry, and immunoreactivity of the conjugate was evaluated. Interestingly, its application to microscopic imaging showed a faster cell internalization compared to LPS-Alexa488, despite that it is also CD14-dependent and undergoes the same endocytic pathway as LPS toward lysosomal detoxification. Our results suggest the use of the new infrared fluorophore Cy7N for cell imaging of labeled LOS by confocal fluorescence microscopy, and propose that LOS is imported in the cells by mechanisms different from those responsible for LPS uptake.
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http://dx.doi.org/10.1021/acs.bioconjchem.9b00044DOI Listing
June 2019

A "Multi-Heavy-Atom" Approach toward Biphotonic Photosensitizers with Improved Singlet-Oxygen Generation Properties.

Chemistry 2019 Jul 30;25(38):9026-9034. Epub 2019 May 30.

Laboratoire de Chimie de l'ENS de Lyon, Univ Lyon, ENS de Lyon, CNRS UMR 5182, Université Claude Bernard Lyon 1, 69342, Lyon, France.

Two trispicolinate 1,4,7-triazacyclonane (TACN)-based ligands bearing three picolinate biphotonic antennae were synthetized and their Yb and Gd complexes isolated. One series differs from the other by the absence (L )/presence (L ) of bromine atoms on the antenna backbone, offering respectively improved optical and singlet-oxygen generation properties. Photophysical properties of the ligands, complexes and micellar Pluronic suspensions were investigated. Complexes exhibit high two-photon absorption cross-section combined either with NIR emission (Yb) or excellent O generation (Gd). The very large intersystem crossing efficiency induced by the combination of bromine atom and heavy rare-earth element was corroborated with theoretical calculations. The O generation properties of L Gd micellar suspension under two-photon activation leads to tumour cell death, suggesting the potential of such structures for theranostic applications.
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http://dx.doi.org/10.1002/chem.201901047DOI Listing
July 2019

Intramolecular Cooperative and Anti-Cooperative Effect on the Two-Photon Absorption Cross Section in Triphenylamine Derivatives.

J Phys Chem Lett 2019 May 22;10(9):2214-2219. Epub 2019 Apr 22.

Instituto de Física de São Carlos , Universidade de São Paulo , 13560-970 São Carlos , SP , Brazil.

The intramolecular cooperative effect in branched molecules is a consequence of the interaction and extent of electronic coupling among the different axes of charge transfer. Such an effect is the key to obtain remarkable nonlinear optical response in molecular systems. Here we show that triphenylamine derivative molecules containing only two branches present the strongest electronic interaction between them at the excited state, generating exponential enhancement of the 2PA cross section. The primary factor for such behavior was ascribed to the substantial extent and interaction of the π-electron delocalization promoted by the strong electron-donating and acceptor antisymmetrical groups present in each branch. However, for the three-branch molecules we observed an anticooperative effect, i.e., the 2PA cross section decreases as compared to the one-branch structure as we normalized the signal by the effective π-electron number in each molecule.
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http://dx.doi.org/10.1021/acs.jpclett.9b00518DOI Listing
May 2019

Polyanionic Polydentate Europium Complexes as Ultrabright One- or Two-photon Bioprobes.

Chemphyschem 2018 Sep 10. Epub 2018 Sep 10.

Univ Lyon, ENS de Lyon, CNRS UMR 5182, Université Claude Bernard Lyon 1, Laboratoire de Chimie, F69342, Lyon, France.

A family of europium (III) complexes based on a polydentate ligand functionalized by charge-transfer antennae presents remarkable one- and two-photon photophysical proper-ties in water or buffer. A detailed analysis of their emission properties suggests that the wrapping of the ligand around the central rare-earth ion results in an overall Cs symmetry in agreement with the theoretical simulation and that about 65-70 % of the emission intensity is concentrated in the hypersensitive D → F transition at 615 nm. Their brightness is excellent, in the range of the best lanthanide bioprobes making them very attractive for bio-imaging experiments.
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http://dx.doi.org/10.1002/cphc.201800557DOI Listing
September 2018

Two-Photon Macromolecular Probe Based on a Quadrupolar Anthracenyl Scaffold for Sensitive Recognition of Serum Proteins under Simulated Physiological Conditions.

ACS Omega 2017 Sep 12;2(9):5715-5725. Epub 2017 Sep 12.

Advanced Materials Engineering and Modelling Group, Faculty of Chemistry, Wroclaw University of Science and Technology, Wyb. Wyspianskiego 27, 50-370 Wroclaw, Poland.

The binding interaction of a biocompatible water-soluble polycationic two-photon fluorophore () toward human serum albumin (HSA) was thoroughly investigated under simulated physiological conditions using a combination of steady-state, time-resolved, and two-photon excited fluorescence techniques. The emission properties of both and the fluorescent amino acid residues in HSA undergo remarkable changes upon complexation allowing the thermodynamic profile associated with -HSA complexation to be accurately established. The marked increase in fluorescence intensity and quantum yield in the proteinous environment seems to be the outcome of the attenuation of radiationless decay pathways resulting from motional restriction imposed on the fluorophore. Fluorescence resonance energy transfer and site-marker competitive experiments provide conclusive evidence that the binding of preferentially occurs within the subdomain IIA. The pronounced hypsochromic effect and increased fluorescence enhancement upon association with HSA, compared to that of bovine serum albumin (BSA) and other biological interferents, makes the polymeric probe a valuable sensing agent in rather complex biological environments, allowing facile discrimination between the closely related HSA and BSA. Furthermore, the strong two-photon absorption (TPA) with a maximum located at 820 nm along with a TPA cross section σ > 800 GM, and the marked changes in the position and intensity of the band upon complexation definitely make a promising probe for two-photon excited fluorescence-based discrimination of HSA from BSA.
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http://dx.doi.org/10.1021/acsomega.7b00665DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6045344PMC
September 2017

General and Scalable Approach to Bright, Stable, and Functional AIE Fluorogen Colloidal Nanocrystals for in Vivo Imaging.

ACS Appl Mater Interfaces 2018 Aug 23;10(30):25154-25165. Epub 2018 Jul 23.

Université de Lyon , F-69003 Lyon , France.

Fluorescent nanoparticles built from aggregation-induced emission-active organic molecules (AIE-FONs) have emerged as powerful tools in life science research for in vivo bioimaging of organs, biosensing, and therapy. However, the practical use of such biotracers has been hindered owing to the difficulty of designing bright nanoparticles with controlled dimensions (typically below 200 nm), narrow size dispersity and long shelf stability. In this article, we present a very simple yet effective approach to produce monodisperse sub-200 nm AIE fluorescent organic solid dispersions with excellent redispersibility and colloidal stability in aqueous medium by combination of nanoprecipitation and freeze-drying procedures. By selecting polymer additives that simultaneously act as stabilizers, promoters of amorphous-crystalline transition, and functionalization/cross-linking platforms, we demonstrate a straightforward access to stable nanocrystalline FONs that exhibit significantly higher brightness than their amorphous precursors and constitute efficient probes for in vivo imaging of the normal and tumor vasculature. FONs design principles reported here are universal, applicable to a range of fluorophores with different chemical structures and crystallization abilities, and are suitable for high-throughput production and manufacturing of functional imaging probes.
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http://dx.doi.org/10.1021/acsami.8b07859DOI Listing
August 2018

Combining a pyclen framework with conjugated antenna for the design of europium and samarium luminescent bioprobes.

Chem Commun (Camb) 2018 Jun;54(48):6173-6176

Université de Brest, UMR-CNRS 6521, UFR des Sciences et Techniques 6 avenue Victor le Gorgeu, C.S. 93837, 29238, Brest, Cedex 3, France.

The first pyclen based ligand bearing two picolinate intra-ligand charge transfer transition antennae and one acetate arm organized in a dissymmetric manner was synthesized for Eu(iii) and Sm(iii) complexation. The europium complex presents an excellent brightness and biphotonic imaging of T24-cells has been performed using Eu(iii) and the less common Sm(iii) bioprobes.
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http://dx.doi.org/10.1039/c8cc02035cDOI Listing
June 2018

Twisted Charge-Transfer Antennae for Ultra-Bright Terbium(III) and Dysprosium(III) Bioprobes.

Chemistry 2018 Mar 5;24(14):3408-3412. Epub 2018 Feb 5.

Univ Lyon, ENS de Lyon, CNRS UMR 5182, Université Claude Bernard Lyon 1, Laboratoire de Chimie, 69342, Lyon, France.

The design of original twisted charge transfer antennae in which a non-planar geometry is enforced thanks to one or two bulky ortho-Me substituents allows us to prepare the corresponding ultra-bright Tb and Dy bioprobes. The brightness of the Tb derivative compares well with that of the benchmark Tb-Lumi4 complex. The first bio-imaging experiments with a Dy luminescent bioprobe are also reported.
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http://dx.doi.org/10.1002/chem.201705933DOI Listing
March 2018

Specific Recognition of G-Quadruplexes Over Duplex-DNA by a Macromolecular NIR Two-Photon Fluorescent Probe.

J Phys Chem Lett 2017 Dec 22;8(23):5915-5920. Epub 2017 Nov 22.

Advanced Materials Engineering and Modelling Group, Faculty of Chemistry, Wroclaw University of Science and Technology , Wybrzeze Wyspianskiego 27, 50-370 Wroclaw, Poland.

The implication of guanine-rich DNA sequences in biologically important roles such as telomerase dysfunction and the regulation of gene expression has prompted the search for structure-specific G-quadruplex agents for targeted diagnostic and therapeutic applications. Herein, we report on a near-infrared (NIR) two-photon poly(cationic) anthracene-based macromolecule able to selectively target G-quadruplexes (G4s) over genomic double-stranded DNA. In particular, the striking changes in its linear and third-order nonlinear optical properties, combined with the emergence of a strong induced electronic circular dichroism (ECD) signal upon binding to canonical and noncanonical DNA secondary structures allowed for a highly specific detection of several different G4s. Furthermore, through a detailed computational analysis we bring compelling evidence that our probe intercalation within G4s is a thermodynamically favored event, and we fully rationalize the spectroscopic evolution resulting from this complexation event by providing a reasonable explanation regarding the origin of the peculiar ECD effect that accompanies it.
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http://dx.doi.org/10.1021/acs.jpclett.7b02547DOI Listing
December 2017

Two-Photon Photosensitizer-Polymer Conjugates for Combined Cancer Cell Death Induction and Two-Photon Fluorescence Imaging: Structure/Photodynamic Therapy Efficiency Relationship.

Biomacromolecules 2017 Dec 10;18(12):4022-4033. Epub 2017 Nov 10.

Univ Lyon, INSERM, ENS de Lyon, CNRS, Université Claude Bernard, Centre International de Recherche en Infectiologie (CIRI) , U1111, F-69007 Lyon, France.

One of the challenges of photodynamic therapy is to increase the penetration depth of light irradiation in the tumor tissues. Although two-photon excitation strategies have been developed, the two-photon absorption cross sections of clinically used photosensitizers are generally low (below 300 GM). Besides, photosensitizers with high cross section values are often non-water-soluble. In this research work, a whole family of photosensitizer-polymer conjugates was synthesized via the covalent binding of a photosensitizer with a relatively high cross section along a biocompatible copolymer chain. The resulting photosensitizer-polymer conjugates were water-soluble and could be imaged in cellulo by two-photon microscopy thanks to their high two-photon absorption cross sections (up to 2600 GM in water, in the NIR range). In order to explore the structure/photodynamic activity relationship of such macromolecular photosensitizers, the influence of the polymer size, photosensitizer density, and presence of charges along the polymer backbone was investigated (neutral, anionic, cationic, and zwitterionic conjugates were compared). The macromolecular photosensitizers were not cytotoxic in the absence of light irradiation. Their kinetics of cellular uptake in the B16-F10 melanoma cell line were followed by flow cytometry over 24 h. The efficiency of cell death upon photoactivation was found to be highly correlated to the cellular uptake in turn correlated to the global charge of the macromolecular photosensitizer which appeared as the determining structural parameter.
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http://dx.doi.org/10.1021/acs.biomac.7b01090DOI Listing
December 2017

Light-induced self-written waveguide fabrication using 1550  nm laser light.

Opt Lett 2017 Jun;42(11):2236-2238

Light-induced self-written (LISW) optical waveguides were fabricated for the first time, to the best of our knowledge, using a photopolymerizable resin system formed by 1550 nm pulse laser light. A two-photon absorption (TPA) chromophore with a TPA cross section of several hundred Goeppert-Mayer (GM) at 1550 nm was used. Furthermore, the optical interconnection between a single-mode fiber and a fiber Bragg grating was demonstrated by the present technique, using one-way irradiation of 1550 nm laser light through the single-mode fiber. The LISW waveguide formation using 1550 nm laser light offers a new and promising alternative route for optical interconnection in silicon photonics technology.
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http://dx.doi.org/10.1364/OL.42.002236DOI Listing
June 2017

Terbium(III) Luminescent Complexes as Millisecond-Scale Viscosity Probes for Lifetime Imaging.

J Am Chem Soc 2017 06 31;139(23):7693-7696. Epub 2017 May 31.

Laboratoire de Chimie, École Normale Supérieure de Lyon, CNRS UMR 5182, Université Claude Bernard Lyon 1 , 46 allée d'Italie, 69364 Lyon Cedex 07, France.

Fluorescent probes that are able to directly measure viscosity are attractive candidates for the study of intracellular environments. We report a new class of luminescent rotors, based on the sensitized emission of a terbium(III) complex. A 4-fold increase in both quantum yield and luminescence lifetime was observed in viscous media for the studied complexes, with a lifetime ranging from 0.23 to 0.89 ms over a broad range of viscosities (0.6-1200 cP). The presented approach, relying on the millisecond-scale luminescence lifetime of the lanthanide ions, was applied to fixed T24 cancer cells using temporal sampling lifetime imaging microscopy.
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http://dx.doi.org/10.1021/jacs.7b02951DOI Listing
June 2017
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