Search

Candida albicans-caused local and systemic diseases are a serious health issue worldwide, leading to high mycosis-associated morbidity and mortality. Efficient combinations of novel compounds with commonly used antifungals could be an important tool for fighting infections. The aim of this study was to evaluate the interaction of synthesized 4-(4-cyanostyryl)-1-dodecylpyridin-1-ium (CSDP+) bromide alone or in combination with fluconazole with yeast and mammalian cells. We investigated cytotoxicity of the tested agents to mammalian HEK-293 cells and the influence of CSDP+ on the ability of C. albicans wt and a clinical isolate to adhere to HEK-293. Accumulation of lipophilic cation ethidium (Et+) was used to monitor the activity of efflux pumps in HEK-293 cells. The effect of CSDP+ on the expression of the main efflux transporter genes and transcription factors in C.albicans cells as well as HEK-293 efflux pump gene ABCB1 was determined. The study showed that CSDP+ alone and in combination with fluconazole was nontoxic to HEK-293 cells and was able to reduce C.albicans adhesion. The treatment of C.albicans cells with CSDP+ in combination with fluconazole resulted in a considerable overexpression of the MDR1 and MRR1 genes. The findings suggest that these genes could be associated with efflux-related resistance to fluconazole. Measurements of Et+ fluorescence and analysis of ABCB1 gene expression demonstrated that mammalian cells were not sensitive to concentrations of CSDP+ affecting C. albicans.

We synthesized a set of 13 new and earlier described styrylpyridinium compounds (N-alkyl styrylpyridinium salts with bromide or tosylate anions) in order to evaluate antifungal activity against C. albicans cells, to assay the possible synergism with fluconazole, and to estimate cytotoxicity to mammalian cells. All compounds were synthesized according to a well-known two-step procedure involving alkylation of γ-picoline with appropriate alkyl bromide and further condensation with substituted benzaldehyde. Compounds with long N-alkyl chains (C18 H37 -C20 H41 ) had no antifungal activity against the cells of all tested C. albicans strains. Other styrylpyridinium compounds were able to inhibit yeast growth at the concentrations of 0.06-16 μg/ml. At fungicidal concentrations, the compound with the CN- group was least toxic to mammalian cells, showed the most effective synergism with fluconazole, and only slightly inhibited the respiration of C. albicans. The compound with the 4'-diethylamino group exhibited the strongest fungicidal properties and effectively blocked the respiration of C. albicans cells. However, toxicity to mammalian cells was also high. Summarizing, the results of our study indicate that styrylpyridinium compounds are promising candidates in the development of new antifungal drugs.

International audience; Condensation of bindone and cinnamaldehydes afforded five cyclic products instead of the expected merocyanines. The structures of all products were confirmed by the X-ray data. In solution, the weakly colored cyclic isomers form deeply colored (orange to red shades) open isomers upon irradiation in the UV and visible range (up to 530 nm). The colored isomers are very stable and undergo thermal discoloration with the half-life times between 13 h and 128 h, depending on the substituent and solvent at room temperature. Heating their solutions above 130 °C gives rise to rapid discoloration. High fatigue resistance was demonstrated by repeating the irradiation/heating cycles.

We have developed an efficient two-photon photochromic molecule by coupling a chromene with a donating 2PA chromophore via resonance energy transfer. The essential parameters of ring opening and closing are determined from transient absorption measurements.

International audience; New derivatives involving the photochromic 2H-benzo[h]chromene moieties covalently linked to the 2,7-bis(carbazolyl)fluorene-derived two-photon absorbing moiety were designed to enable the possibility of resonance energy transfer from the fluorene donor to the photochromic acceptor. The longest wavelength absorption of the photochromic acceptors overlaps with the fluorescence band of the two-photon absorbing donor and the distance between the both moieties is about 5–7 Å. Rapid coloration of colorless solutions was observed upon one- and two-photon absorption.

There is much interest in enhancement of the absorbance performance of nonlinear absorber solid-state filters. In this work we present an advanced reversible nonlinear filter based on a dye-doped sol-gel matrix. The absorbance enhancement was achieved by using a combination of two absorption mechanisms in the same molecule; a photochromic absorption which is induced by 2-photon absorption (2PA). The 2PA serves as the trigger for initiating the photochromism through Forster-resonance-energy-transfer (FRET) between the fluorescent donor and the photochromic acceptor. We synthesized a new bifunctional-chromophore that incorporated a carbazole-derived 2PA fluorescent donor and a chromene-derived photochromic acceptor, covalently linked together in a single molecule by a ~6 A carboxyl group or oxygen bridge. The bifunctional-chromophore was doped in an inorganic-organic hybrid matrix prepared by the fast-sol-gel process. These materials solidify without shrinkage or formation of cracks and present promising properties as optical matrices for smart filters. The dye-doped sol-gel disc presents high transparency in the visible region ("colorless"), which under UV-irradiation (one-photon absorption in the photochromic part of the molecule), transforms into a strongly absorbing filter ("dark colored"), due to the conversion of the photochromic moiety to its "open" absorbing form. We have demonstrated that this ring-opening can also be induced by visible-light (620 nm) using the 2PA carbazole-derived moiety of the molecule. We have studied the fabrication routes and optical performance of these filters. We present studies of the 2PA mechanism of the carbazole derivative, FRET efficiency of the combined-molecule as well as in solutions of the individual moieties, and reversible dynamics of the photochromic moiety.

FRET within a donor-acceptor composite photochromic molecule was investigated in a dye-doped sol-gel matrix using both 1 and 2-Photon absorption. The energy transfer efficiency was estimated from UV-excitation photokinetic measurements by applying a 2-level model.

The synthesis and spectroscopic properties of a series of new organic electron donors derived from dibenzo[2,3:5,6]pyrrolizino-[1,7-bc]indolo[1,2,3-lm]carbazole are described. These compounds can be considered as planar hybrids of carbazole and p-phenylenediamine and possess high thermal stability. The electron donating properties and one- and two-photon spectroscopic features of methoxy derivatives are very sensitive to the number and positions of the methoxy groups. The X-ray structure of the 2,11-dimethoxy derivatives features slipped π-stacks and short interplanar distance between the molecules in the stacks similar to those found in the unsubstituted derivative.

Of a series of 4-substituted 1,8-naphthalimides, fluorescent 4-(6-piperidinyl-1,3-dioxo-1H-benzo[de]isoquinolin-2(3H)-yl)benzoic acid (4) was found to be a sensitive molecular probe for ZnO nanoparticles. We investigated in detail one- and two-photon absorption properties of this fluorophore. In nonpolar solvents, the acid 4 absorbs at about 400 nm and fluoresces at 500 nm with a fluorescence lifetime of about 7 ns, similar to the ester 6 and typical of the lifetimes of other derivatives of this type. Although the anionic form of this acid is not fluorescent, partial ionization of 4 in polar solvents, such as ethanol and acetonitrile, is not only accompanied by the expected decrease in the fluorescence quantum yield, but also gives rise to bathochromic shifts of both absorption and fluorescence and dual fluorescence with lifetimes of 0.2–0.3 ns and 6 ns ascribed to the formation of anionic complexes. The interaction with the ZnO surface brings about further considerable changes in the fluorescence patterns.

We present a bifunctional photochromic chromophore containing both fluorescent donor and photochromic acceptor moieties. Energy transfer from donor to acceptor is indicated by fluorescence measurements.