Atanas Kurutos

Symmetric Meso-Chloro-Substituted Pentamethine Cyanine Dyes Containing Benzothiazolyl/Benzoselenazolyl Chromophores Novel Synthetic Approach and Studies on Photophysical Properties upon Interaction with bio-Objects

A series of symmetric pentamethine cyanine dyes derived from various N-substituted benzothiazolium/benzoselenazolium salts, and a conjugated bis-aniline derivative containing a chlorine atom at meso-position with respect to the polymethine chain, were synthesized using a novel improved synthetic approach under mild conditions at room temperature. The reaction procedure was held by grinding the starting compounds for relative short times. The novel method is reliable and highly reproducible. Some photophysical characteristics were recorded in various solvents, including absorption, and fluorescence quantum yields using Cy-5 as a reference. Additional studies on interactions with several bio-objects such as liposomes, DNA, and proteins have been investigated in the present work.

2,3-Dimethylbenzoxazolium Methosulfate

An economically benign solvent-free approach to synthesise 2,3-dimethylbenzoxazolium methosulfate is reported in the present work. The title compound is derived from 2-methylbenzoxazole reacting with a slight excess of dimethylsulfate, at room temperature. The reaction proceeds via an intrinsic exothermic reaction, and the benzoxazolium salt crystallized after a short time into a white crystalline form. The product was filtered off and washed with acetone and diethyl ether to provide the desired product in 89% yield. The target compound was evaluated by ESI/MS analysis.

1-(3-Iodopropyl)-4-methylquinolin-1-ium Iodide

A solvent-free “one-pot” synthetic approach to 1-(3-iodopropyl)-4-methylquinolin-1-ium iodide is reported in the present work. The title compound is derived from N-alkylation of 4-methylquinoline with 1,3-diiodopropane proceeded at room temperature. The target quinolinium salt is obtained in a highly pure form. It’s structure was evaluated by 1H-NMR, 13C-NMR, and DEPT135 spectra.

Aggregation of cyanine dyes in lipid environment

Cyanine dyes, a wide class of fluorescent probes with unique photophysical properties, have found numerous application in different areas as optical imaging agents, active ingredients in semiconducting materials, laser dyes, photographic sensitizers, photopolymerization initiators, stains and fluorescent labels, to name only a few. These compounds are of particular interest for biomedical research and diagnostics due to their favorable spectral characteristics, namely, longwave absorption and emission, large extinction coefficient, high fluorescence quantum yield, etc. Cyanine dyes are photosensitive compounds possessing two quaternized, nitrogen-containing, heterocyclic structures, which are linked through a polymethine bridge [1]. Due to dual hydrophobic and cationic nature of these dyes, which leads to strong interaction with polyanionic DNA duplex, cyanines are mainly used as bright labels for nucleic acids in microarray-based expression analysis, DNA sequencing and DNA intercalation bioanalytical assays [2–14]. It has been demonstrated that mono-, tri- and pentamethine cyanine dyes are suitable for quantitative detection of amyloid formation and protein labeling [5]. Fluorescence intensity of cyanine dyes is greatly increased upon their binding to nucleic acids or proteins as a result of the rigidization of the fluorophores [2–5]. Furthermore, the utility of near infrared cyanine dyes demonstrates unique hydrophobic characteristics in aqueous medium that were exploited for target-specific pH probing [6]. Moreover, it is known that the central polymethine chain of cyanine dyes can be cleaved by reactive oxygen and nitrogen species, which gives the impetus for cyanine use for in vivo sensing of oxidative stress and monitoring the dynamics of redox cycles in living cells [7]. In addition, cyanine dyes showed unique properties as optical imaging probes for cancer labeling [8].