Marie-Laure Viriot

Nanoparticles as vehicles for delivery of photodynamic therapy agents

Photodynamic therapy (PDT) in cancer treatment involves the uptake of a photosensitizer by cancer tissue followed by photoirradiation. The use of nanoparticles as carriers of photosensitizers is a very promising approach because these nanomaterials can satisfy all the requirements for an ideal PDT agent. This review describes and compares the different individual types of nanoparticles that are currently in use for PDT applications. Recent advances in the use of nanoparticles, including inorganic oxide-, metallic-, ceramic-, and biodegradable polymer-based nanomaterials as carriers of photosensitizing agents, are highlighted. We describe the nanoparticles in terms of stability, photocytotoxic efficiency, biodistribution and therapeutic efficiency. Finally, we summarize exciting new results concerning the improvement of the photophysical properties of nanoparticles by means of biphotonic absorption and upconversion.

Detection of hydrophobic microdomains in aqueous solutions of amphiphilic polymers using fluorescent molecular rotors

Homopolymers and random copolymers derived from 3-vinylpyridium salts form compact coils in aqueous solutions. The resulting hydrophobic microdomains were characterized by both the hypsochromic shift of the wavelength emission band and the fluorescence quantum yield increase of a molecular rotor used as a fluorescence probe.

Synthesis and behaviour study of amphiphilic polyvinylimidazolium salts in aqueous media: Effects of the microdomains on a bimolecular reaction involving hydrophobic reactants

Abstract Homopolymers of 3-alkyl-1-vinylimidazolium bromides series have been prepared by free radical polymerization in aqueous solution or in benzene. The tendency of aggregation of these water soluble polymers was studied by viscosity measurements and fluorescence probes which have revealed the formation of hydrophobic microdomains. These polymers were tested in water media as a macromolecular matrix for the introduction of a microenvironment able to induce an acceleration effect for a bimolecular reaction involving two hydrophobic reactants. The reaction rates of 5(6)-decylbenzimidazole on the hydrolysis of 4′-nitrophenyl-5-alkoxypicolinates in the presence of the poly(3-hexadecyl-l-vinylimidazolium bromide) or its low molecular weight analogue at pH = 7.09, T = 30° C were estimated and compared.

Lateral diffusion in synthetic membranes: models and experiments on protein influence

Diffusion-influenced theories of the Smoluchowsky type are applied to the case of synthetic membranes in which a fluorescent probe (pyrene) is included. These models make the assumption of a pseudo-two-dimensional medium with some refinements such as the curvature of space or the thickness of the membrane. After having shown that it is possible to measure a diffusion coefficient inside the membranes with photophysical methods and to characterize the effects of the temperature and of the length of the carbon chains on the lateral diffusion, some proteins are added to the membranes in order to observe their influence on the lateral molecular transport.

Poly(N-alkylacrylamide-co-vinylpyridinium): synthesis and aqueous solution properties

Copolymers of 4-vinylpyridine and N-alkylacrylamides (alkyl chain bearing 6, 10 and 12 carbon atoms) were prepared by bulk free radical copolymerization using 2,2′-azobisisobutyronitrile and 2,2′-azobis(2,4-dimethylvaleronitrile) as initiators. Poly(N-alkylacrylamide-co-4-vinylpyridine)s were then converted into cationic copolymers by quaternization of the pyridine rings with methylbromide. Their amphiphilic properties in dilute aqueous media were studied by viscosimetry, fluorescence and tensiometry. In selected solvents (water + methanol), the association phenomenon was investigated as a function of the solvent composition and the chemical structure of the copolymers.

Specific fluorescent tracers. Imaging and applications for photodynamic therapy

Our main objective is to enlarge the fluorescence use in biosciences, with especially the photodynamic therapy (PDT) used for cancer treatment as one of the target applications. Meta-tetra(hydroxyphenyl)chlorin (m-THPC) is a second-generation photosensitiser, applied in photodynamic therapy. The localisation of this sensitiser as well as its induced cell death mechanisms in human breast cancer cells (MCF-7 and its resistant subline MCF-7DXR, DXR: doxorubicin) were evaluated using fluorescence microscopy. In addition, we will present two additional routes, whose aims are to create new features to respond to the PDT questioning: firstly, the synthesis of fluorescent tracers, with a particular attention to the presence of hydrophilic groups (glucosamine ring) on the basic fluorophore structure to orientate the localisation of the probe and, secondly, the use of scanning near-field optical microscopy to reach a better resolution for the fluorescence microscopy analysis.

Fluorescence as a Characterization Tool to Study Amphiphilic Polymer Aggregation in Aqueous Media

Abstract Fluorescence spectroscopy based on pyrene and DMAC (i.e., 1,1-dicyano-4-(4′-(N,N-dimethylamino)phenyl)-1,3-butadiene) probes was used to investigate the aggregation of amphiphilic polymers in aqueous solution. The fluorescence data related to the cohesion of the microdomains formed were correlated to the polymer microstructure, either by taking into account the sequence distribution for poly(NVP-co-C16VIB) (i.e., poly(N-vinyl-2-pyrrolidinone)-co-(3-hexadecyl-1-vinylimidazolium bromide)) or the cryo-TEM images for poly(C1VPB-co-C16VPB) (i.e., poly(1-methyl-3-vinylpyridinium bromide)-co-(1-hexadecyl-3-vinylpyridinium bromide)).

Cryo-TEM and molecular rotor fluorescence as complementary techniques for the characterization of cationic amphiphilic copolymer microdomains in aqueous medium

The behaviour in aqueous medium of cationic amphiphilic copolymers derived from 3-vinylpyridine has been studied. The ability of these polymers to form hydrophobic microdomains was shown by fluorescence spectroscopy using a molecular rotor as a fluorescent probe, and the resulting structure was visualized by cryo-transmission electron microscopy (cryo-TEM). The parameters (shape and size) obtained from cryo-TEM are discussed in relation to the copolymer composition and the local viscosity defined by the rotor fluorescence quantum yield.