Publications by authors named "Guillaume Micouin"

6 Publications

  • Page 1 of 1

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

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

Fluorescent push-pull pH-responsive probes for ratiometric detection of intracellular pH.

Org Biomol Chem 2014 Jun 23;12(22):3641-8. Epub 2014 Apr 23.

Laboratoire de Chimie de l'ENS de Lyon, CNRS UMR 5182, Ecole Normale Supérieure de Lyon, Université Lyon I, 46 allée d'Italie, 69364 Lyon cedex 07, France.

A family of fluorescent push-pull pH-responsive probes based on 2-dicyanomethylidene-3-cyano-4,5,5-trimethyl-2,5-dihydrofuran as a strong electron acceptor group is described. Small structural variations allow obtaining pK(a) ranging from 4.8 to 8.6, underlining the role of the substituent in modulating the acidic properties. Remarkable changes in the optical properties (in particular the fluorescence intensity ratios) were observed as a function of pH. The most interesting probes with pK(a) close to neutrality were used for ratiometric imaging of intracellular pH.
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http://dx.doi.org/10.1039/c4ob00147hDOI Listing
June 2014

Nanocarriers with ultrahigh chromophore loading for fluorescence bio-imaging and photodynamic therapy.

Biomaterials 2013 Nov 31;34(33):8344-51. Epub 2013 Jul 31.

Laboratoire de Chimie UMR 5182, Ecole Normale Supérieure de Lyon, CNRS, université Lyon 1, 46, allée d'Italie, Lyon cedex 07 F-69364, France.

We describe the design of original nanocarriers that allows for ultrahigh chromophore loading while maintaining the photo-activity of each individual molecule. They consist in shells of charged biocompatible polymers grafted on gold nanospheres. The self-organization of extended polymer chains results from repulsive charges and steric interactions that are optimized by tuning the surface curvature of nanoparticles. This type of nano-scaffolds can be used as light-activated theranostic agents for fluorescence imaging and photodynamic therapy. We demonstrate that, labeled with a fluorescent photosensitizer, it can localize therapeutic molecules before triggering the cell death of B16-F10 melanoma with an efficiency that is similar to the efficiency of the polymer conjugate alone, and with the advantage of extremely high local loading of photosensitizers (object concentration in the picomolar range).
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http://dx.doi.org/10.1016/j.biomaterials.2013.07.032DOI Listing
November 2013

Tuning dye-to-particle interactions toward luminescent gold nanostars.

Langmuir 2013 Aug 12;29(34):10915-21. Epub 2013 Aug 12.

Ecole Normale Supérieure de Lyon, CNRS, Université Lyon 1, Laboratoire de Chimie UMR 5182, 46, allée d'Italie, F-69364, Lyon cedex 07, France.

Light-matter interactions are of great interest for potential biological applications (bioimaging, biosensing, phototherapy). For such applications, sharp nanostructures exhibit interesting features since their extinction bands (surface plasmon resonance) cover a large bandwidth in the whole visible wavelength region due to the existence of "hot spots" located at the end of the tips. In this context, gold nanostars appear to be interesting objects. However, their study remains difficult, mainly due to complicated synthetic methods and further functionalization. This paper reports the synthesis, functionalization, and photophysics of luminescent hybrid gold nanostars prepared using a layer-by-layer (LbL) deposition method for the tuning of chromophore-to-particle distances together with the impact of the spectral overlap between the plasmon and the emission/absorption of the dyes. Several luminescent dyes with different optical signatures were selectively adsorbed at the nanoparticle surface. The optimized systems, exhibiting the highest luminescence recovery, clearly showed that overlap must be as low as possible. Also, the fluorescence intensities were quenched in close vicinity of the metal surface and revealed a distance-dependence with almost full recovery of the dyes emission for 11 LbL layers, which corresponded to 15 nm distances evaluated on dried samples. The photophysics of the luminescent core-shell particles were carried out in suspension and correlated with the response of isolated single objects.
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http://dx.doi.org/10.1021/la402222cDOI Listing
August 2013

Synthesis of PEGylated gold nanostars and bipyramids for intracellular uptake.

Nanotechnology 2012 Nov 24;23(46):465602. Epub 2012 Oct 24.

Université de Lyon, ENS Lyon, CNRS, Université Lyon 1, Laboratoire de Chimie UMR 5182, 46, allée d'Italie, F-69364, Lyon cedex 07, France.

A great number of works have focused their research on the synthesis, design and optical properties of gold nanoparticles for potential biological applications (bioimaging, biosensing). For this kind of application, sharp gold nanostructures appear to exhibit the more interesting features since their surface plasmon bands are very sensitive to the surrounding medium. In this paper, a complete study of PEGylated gold nanostars and PEGylated bipyramidal-like nanostructures is presented. The nanoparticles are prepared in high yield and their surfaces are covered with a biocompatible polymer. The photophysical properties of gold bipyramids and nanostars, in suspension, are correlated with the optical response of single and isolated objects. The resulting spectra of isolated gold nanoparticles are subsequently correlated to their geometrical structure by transmission electron microscopy. Finally, the PEGylated gold nanoparticles were incubated with melanoma B16-F10 cells. Dark-field microscopy showed that the biocompatible gold nanoparticles were easily internalized and most of them localized within the cells.
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http://dx.doi.org/10.1088/0957-4484/23/46/465602DOI Listing
November 2012
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