Development of low-cost colourimetric and pH sensors based on PMMA@Cyanine polymers

Cyanine derivatives 1–3 were successfully characterized and their sensorial ability studied against Zn2+, Co2+, Cd2+, Ni2+, Cu2+, Hg2+ and Ag+ metal ions. All dyes revealed a colourimetric selectivity towards Cu2+ metal ions, with the formation of mononuclear species. Cyanine 2 can detect and quantify the lowest concentrations of Cu2+ in aqueous media, 0.3 and 0.6 μM. With the aim of exploring the optical properties of these dyes, solid-supported devices were designed by the synthesis of polymethylmethacrylate (PMMA) polymers doped with dyes 1, 2, and 3 and their copper complexes. All PMMA_doped polymers were tested as temperature and low-pH sensors. PMMA_1 and PMMA_1@Cu2+ showed to be reversible fluorimetric thermoresponsive polymers, while PMMA_2, PMMA_3, PMMA_2@Cu2+ and PMMA_3@Cu2+ irreversible colourimetric and fluorimetric thermoresponsive polymers. From all acids tested, HCl, HBr, HClO4, H3PO4, HCOOH and CH3SO3H, the best results were obtained for PMMA_3 and PMMA_3@Cu2+ with HCl. After activation in 12 M HCl, both polymers were capable of sensing 8 M, 10 M, 11 M and 12 M HCl: their color changed from green to yellow and they showed an increase in their emission maxima at 805 nm in seconds. The capability to reversibly sense higher acid concentrations in seconds, after activation, for more than 10 cycles, make PMMA_3 and PMMA_3@Cu2+ good candidates for superacid sensing, allowing for a real-time follow up of contaminated affluents, or their incorporation in quality control in industrial processes

Non-cytotoxic photostable monomethine cyanine platforms: Combined paradigm of nucleic acid staining and in vivo imaging

Cyanine based chemosensing platforms have successfully been employed over the past couple of decades in various fields of biomolecular sciences. Still a substantial number of recent advances and improvements on this class of compounds are reported in the art. This paper presents our latest work on the improved synthetic approach, study on photophysical properties, and biosensing applicability of monomethine cyanine dyes. The series of mono-, di- and tricationic dyes showed up to 5-fold enhanced resistance against photobleaching compared to the commercially available Thiazole Orange (TO). The title compounds were studied as potential molecular probes for the detection of deoxyribonucleic acid, demonstrating their capacity as excellent fluorescent labeling agents. Depending on the dye chemical structure, current Cl-TO compounds exhibit up to 834-fold enhanced fluorescence emission and form stable complexes with Calf Thymus-DNA. The calculated binding constants were found to be higher than several conventional fluorogenic dyes for nucleic acid detection. All studied derivatives appeared as less cytotoxic than the Thiazole Orange. IC50 concentrations in human fibro-blasts MRCS cell line were calculated up to 50 mu M for the synthesized Cl-TO dyes, and 0.5 mu M for the parental Thiazole Orange. Two of the dyes were found very competent in post-electrophoretic visualization of DNA. As demonstrated by the agarose gel electrophoresis, the staining efficiency and detection limits of the dyes were comparable to the widely used Ethidium Bromide. The tricationic dye revealed great potential for cell cycle analysis in G1, S and G2 phases. The chlorinated TO derivatives readily stain human cells in vivo, while they can effectively be applied for eukaryotic and microbial cell staining

NOVEL CYANINE DYES AS POTENTIAL AMYLOID PROBES: A FLUORESCENCE STUDY

The applicability of the novel heptamethine cyanine dyes AK7-5 and AK7-6 to the detection and characterization of one-dimensional protein aggregates (amyloid fibrils) associated with numerous pathologies has been evaluated using the method of fluorescence spectroscopy. It was found that both the monomeric and aggregated forms of these dyes can bind to amyloidogenic protein lysozyme, but the concomitant changes in the electronic structure of H-aggregates render them capable of fluorescing. The growth of the hypsochromic bands with negligible changes of the monomeric peaks induced by the native protein and the opposite effects induced by the lysozyme fibrils suggest that the native lysozyme has more binding sites for the dye aggregates than fibrillar protein, while the fibril grooves represent specific binding site for the dyes monomers. The observed spectral behavior of the cyanine dyes, viz. significant distinctions in the fluorescence responses produced by the monomeric and fibrillar forms of lysozyme, suggest the possibility of recruiting these compounds as fluorescent amyloid markers along with the classical amyloid marker Thioflavin T

Non-cytotoxic photostable monomethine cyanine platforms:Combined paradigm of nucleic acid staining and in vivo imaging

Cyanine based chemosensing platforms have successfully been employed over the past couple of decades in various fields of biomolecular sciences. Still a substantial number of recent advances and improvements on this class of compounds are reported in the art. This paper presents our latest work on the improved synthetic approach, study on photophysical properties, and biosensing applicability of monomethine cyanine dyes. The series of mono-, di- and tricationic dyes showed up to 5-fold enhanced resistance against photobleaching compared to the commercially available Thiazole Orange (TO). The title compounds were studied as potential molecular probes for the detection of deoxyribonucleic acid, demonstrating their capacity as excellent fluorescent labeling agents. Depending on the dye chemical structure, current Cl-TO compounds exhibit up to 834-fold enhanced fluorescence emission and form stable complexes with Calf Thymus-DNA. The calculated binding constants were found to be higher than several conventional fluorogenic dyes for nucleic acid detection. All studied derivatives appeared as less cytotoxic than the Thiazole Orange. IC50 concentrations in human fibro-blasts MRCS cell line were calculated up to 50 mu M for the synthesized Cl-TO dyes, and 0.5 mu M for the parental Thiazole Orange. Two of the dyes were found very competent in post-electrophoretic visualization of DNA. As demonstrated by the agarose gel electrophoresis, the staining efficiency and detection limits of the dyes were comparable to the widely used Ethidium Bromide. The tricationic dye revealed great potential for cell cycle analysis in G1, S and G2 phases. The chlorinated TO derivatives readily stain human cells in vivo, while they can effectively be applied for eukaryotic and microbial cell staining