Anilinopyridine metal complexes for the selective chromogenic sensing of cyanide anion

[EN] Probe 1, which contains an anilinopyridine chromophore and an aza-oxa macrocyclic subunit, presented an absorption band centered at 340 nm in acetonitrile. Addition of Fe(III), Cr(III) and Hg(II) induced the growth of a new absorption band at 430 nm (with color change from colorless to yellow), whereas in the presence of Cu(II), Zn(II) and Pb(II), less marked changes were observed. The color changes observed upon addition of Fe(III), Cr(III) and Hg(II) were ascribed to the formation of 1:1 stoichiometry complexes with probe 1. Coordination of Fe(III), Cr(III) and Hg(II) with the pyridine fragment of 1 induced an enhancement of the charge transfer character accompanied with a marked bathochromic shift that was reflected in a color change from colorless to yellow. The strength of the interaction between probe 1 and Fe(III) cation was modulated upon interaction with anions. Of all the anions tested, only cyanide was able to induce the bleaching of the yellow 1Fe(III) complex solution. This bleaching was ascribed to the formation of 1Fe(III)-CN complex that restored, to some extent, the optical features of the free probe allowing the chromogenic sensing of cyanide. Besides, 1Fe(III) complex was used to detect cyanide in acetonitrile-water 90:10 v/v mixtures with good recoveries.This work was supported by the Generalitat Valenciana [grant number PROMETEOII/2014/047]; Ministerio de Economia y Competitividad [grant number MAT2015-64139-C4-1-R], [grant number AGL2015-70235-C2-2-R (MINECO/FEDER)].Lozano-Torres, B.; Marcos Martínez, MD.; Pardo Vicente, MT.; Sancenón Galarza, F.; Martínez-Máñez, R.; Rurack, K. (2018). Anilinopyridine metal complexes for the selective chromogenic sensing of cyanide anion. Journal of Coordination Chemistry. 71(6):786-796. https://doi.org/10.1080/00958972.2018.1434719S786796716Boening, D. W., & Chew, C. M. (1999). Water, Air, and Soil Pollution, 109(1/4), 67-79. doi:10.1023/a:1005005117439Tylleskar, T., Howlett, W. P., Rwiza, H. T., Aquilonius, S. M., Stalberg, E., Linden, B., … Rosling, H. (1993). Konzo: a distinct disease entity with selective upper motor neuron damage. Journal of Neurology, Neurosurgery & Psychiatry, 56(6), 638-643. doi:10.1136/jnnp.56.6.638(a) WHO. Guidelines for Drinking-Water Quality, p. 342, World Health Organisation, Geneva, Switzerland (2011)Safavi, A., Maleki, N., & Shahbaazi, H. . (2004). Indirect determination of cyanide ion and hydrogen cyanide by adsorptive stripping voltammetry at a mercury electrode. Analytica Chimica Acta, 503(2), 213-221. doi:10.1016/j.aca.2003.10.032Batista, R. M. F., Oliveira, E., Costa, S. P. G., Lodeiro, C., & Raposo, M. M. M. (2013). Cyanide and fluoride colorimetric sensing by novel imidazo-anthraquinones functionalised with indole and carbazole. Supramolecular Chemistry, 26(2), 71-80. doi:10.1080/10610278.2013.824082Santos-Figueroa, L. E., Moragues, M. E., Climent, E., Agostini, A., Martínez-Máñez, R., & Sancenón, F. (2013). Chromogenic and fluorogenic chemosensors and reagents for anions. A comprehensive review of the years 2010–2011. Chemical Society Reviews, 42(8), 3489. doi:10.1039/c3cs35429fWiskur, S. L., Ait-Haddou, H., Lavigne, J. J., & Anslyn, E. V. (2001). Teaching Old Indicators New Tricks. Accounts of Chemical Research, 34(12), 963-972. doi:10.1021/ar9600796Kaur, K., Saini, R., Kumar, A., Luxami, V., Kaur, N., Singh, P., & Kumar, S. (2012). Chemodosimeters: An approach for detection and estimation of biologically and medically relevant metal ions, anions and thiols. Coordination Chemistry Reviews, 256(17-18), 1992-2028. doi:10.1016/j.ccr.2012.04.013García-Acosta, B., Albiach-Martí, X., García, E., Gil, L., Martínez-Máñez, R., Rurack, K., … Soto, J. (2004). Coordinative and electrostatic forces in action: from the design of differential chromogenic anion sensors to selective carboxylate recognition. Chem. Commun., (7), 774-775. doi:10.1039/b314997hGarcía-Acosta, B., Martínez-Máñez, R., Sancenón, F., Soto, J., Rurack, K., Spieles, M., … Gil, L. (2007). Ditopic N-Crowned 4-(p-Aminophenyl)-2,6-diphenylpyridines:  Implications of Macrocycle Topology on the Spectroscopic Properties, Cation Complexation, and Differential Anion Responses. Inorganic Chemistry, 46(8), 3123-3135. doi:10.1021/ic062069zVerhoeven, J. W. (s. f.). Sigma-coupled Charge-transfer Probes of the Fluoroprobe and Fluorotrope Type. Topics in Fluorescence Spectroscopy, 249-284. doi:10.1007/0-387-23335-0_7Kurihara, M., Kawashima, T., & Ozutsumi, K. (2000). Complexation of Cobalt(II), Nickel(II), and Copper(II) Ions with Pyridine, 2-Methylpyridine, 3-Methylpyridine, and 4-Methylpyridine in Acetonitrile. Zeitschrift für Naturforschung B, 55(3-4), 277-284. doi:10.1515/znb-2000-3-409Xu, Z., Chen, X., Kim, H. N., & Yoon, J. (2010). Sensors for the optical detection ofcyanide ion. Chem. Soc. Rev., 39(1), 127-137. doi:10.1039/b907368

Fluorescent Molecularly Imprinted Polymer Layers against Sialic Acid on Silica-Coated Polystyrene Cores-Assessment of the Binding Behavior to Cancer Cells

Simple Summary Cancer cells often have aberrant sialic acid expression. We used molecularly imprinted polymers in this study as novel tools for analyzing sialic acid expression as a biomarker on cancer cells. The sialic acid imprinted polymer shell was synthesized on a polystyrene core, providing low-density support for improving the suspension stability and scattering properties of the molecularly imprinted particles compared to previous core-shell formats. Our results show that these particles have an increased ability to bind to cancer cells. The binding of these particles may be inhibited by two different pentavalent sialic acid conjugates, pointing to the specificity of the sialic acid imprinted particles. Sialic acid (SA) is a monosaccharide usually linked to the terminus of glycan chains on the cell surface. It plays a crucial role in many biological processes, and hypersialylation is a common feature in cancer. Lectins are widely used to analyze the cell surface expression of SA. However, these protein molecules are usually expensive and easily denatured, which calls for the development of alternative glycan-specific receptors and cell imaging technologies. In this study, SA-imprinted fluorescent core-shell molecularly imprinted polymer particles (SA-MIPs) were employed to recognize SA on the cell surface of cancer cell lines. The SA-MIPs improved suspensibility and scattering properties compared with previously used core-shell SA-MIPs. Although SA-imprinting was performed using SA without preference for the alpha 2,3- and alpha 2,6-SA forms, we screened the cancer cell lines analyzed using the lectins Maackia Amurensis Lectin I (MAL I, alpha 2,3-SA) and Sambucus Nigra Lectin (SNA, alpha 2,6-SA). Our results show that the selected cancer cell lines in this study presented a varied binding behavior with the SA-MIPs. The binding pattern of the lectins was also demonstrated. Moreover, two different pentavalent SA conjugates were used to inhibit the binding of the SA-MIPs to breast, skin, and lung cancer cell lines, demonstrating the specificity of the SA-MIPs in both flow cytometry and confocal fluorescence microscopy. We concluded that the synthesized SA-MIPs might be a powerful future tool in the diagnostic analysis of various cancer cells.</p

A New bis(rhodamine)-Based Fluorescent Chemosensor for Fe3+

A new bis(rhodamine)-based fluorescent probe 4 was synthesized, and it exhibited high selectivity for Fe3+ over other commonly coexistent metal ions in both 50% ethanol and Tris–HCl buffer. Upon the addition of Fe3+, the spirocyclic ring of 4 was opened and a significant enhancement of visible color and fluorescence in the range of 500–600 nm was observed

Multicolour Single Molecule Imaging in Cells with Near Infra-Red Dyes

Background: The autofluorescence background of biological samples impedes the detection of single molecules when imaging. The most common method of reducing the background is to use evanescent field excitation, which is incompatible with imaging beyond the surface of biological samples. An alternative would be to use probes that can be excited in the near infra-red region of the spectrum, where autofluorescence is low. Such probes could also increase the number of labels that can be imaged in multicolour single molecule microscopes. Despite being widely used in ensemble imaging, there is a currently a shortage of information available for selecting appropriate commercial near infra-red dyes for single molecule work. It is therefore important to characterise available near infra-red dyes relevant to multicolour single molecule imaging. Methodology/Principal Findings: A range of commercially available near infra-red dyes compatible with multi-colour imaging was screened to find the brightest and most photostable candidates. Image series of immobilised samples of the brightest dyes (Alexa 700, IRDye 700DX, Alexa 790 and IRDye 800CW) were analysed to obtain the mean intensity of single dye molecules, their photobleaching rates and long period blinking kinetics. Using the optimum dye pair, we have demonstrated for the first time widefield, multi-colour, near infra-red single molecule imaging using a supercontinuum light source in MCF-7 cells

Nanocolloidal albumin-IRDye 800CW: a near-infrared fluorescent tracer with optimal retention in the sentinel lymph node

Purpose: At present, the only approved fluorescent tracer for clinical near-infrared fluorescence-guided sentinel node (SN) detection is indocyanine green (ICG), but the use of this tracer is limited due to its poor retention in the SN resulting in the detection of higher tier nodes. We describe the development and characterization of a next-generation fluorescent tracer, nanocolloidal albumin-IRDye 800CW that has optimal properties for clinical SN detection Methods: The fluorescent dye IRDye 800CW was covalently coupled to colloidal human serum albumin (HSA) particles present in the labelling kit Nanocoll in a manner compliant with current Good Manufacturing Practice. Characterization of nanocolloidal albumin-IRDye 800CW included determination of conjugation efficiency, purity, stability and particle size. Quantum yield was determined in serum and compared to that of ICG. For in vivo evaluation a lymphogenic metastatic tumour model in rabbits was used. Fluorescence imaging was performed directly after peritumoral injection of nanocolloidal albumin-IRDye 800CW or the reference ICG/HSA (i.e. ICG mixed with HSA), and was repeated after 24 h, after which fluorescent lymph nodes were excised. Results: Conjugation of IRDye 800CW to nanocolloidal albumin was always about 50% efficient and resulted in a stable and pure product without affecting the particle size of the nanocolloidal albumin. The quantum yield of nanocolloidal albumin-IRDye 800CW was similar to that of ICG. In vivo evaluation revealed noninvasive detection of the SN within 5 min of injection of either nanocolloidal albumin-IRDye 800CW or ICG/HSA. No decrease in the fluorescence signal from SN was observed 24 h after injection of the nanocolloidal albumin-IRDye 800CW, while a strong decrease or complete disappearance of the fluorescence signal was seen 24 h after injection of ICG/HSA. Fluorescence-guided SN biopsy was very easy. Conclusion: Nanocolloidal albumin-IRDye 800CW is a promising fluorescent tracer with optimal kinetic features for SN detection. © The Author(s) 2012

The mechanisms of boronate ester formation and fluorescent turn-on in ortho-aminomethylphenylboronic acids

ortho-Aminomethylphenylboronic acids are used in receptors for carbohydrates and various other compounds containing vicinal diols. The presence of the o-aminomethyl group enhances the affinity towards diols at neutral pH, and the manner in which this group plays this role has been a topic of debate. Further, the aminomethyl group is believed to be involved in the turn-on of the emission properties of appended fluorophores upon diol binding. In this treatise, a uniform picture emerges for the role of this group: it primarily acts as an electron-withdrawing group that lowers the pK(a) of the neighbouring boronic acid thereby facilitating diol binding at neutral pH. The amine appears to play no role in the modulation of the fluorescence of appended fluorophores in the protic-solvent-inserted form of the boronic acid/boronate ester. Instead, fluorescence turn-on can be consistently tied to vibrational-coupled excited-state relaxation (a loose-bolt effect). Overall, this Review unifies and discusses the existing data as of 2019 whilst also highlighting why o-aminomethyl groups are so widely used, and the role they play in carbohydrate sensing using phenylboronic acids

Synthesis and prospective study of the use of thiophene thiosemicarbazones as signalling scaffolding for the recognition of anions

A family of phenyl-thiosemicarbazone dyes have been prepared and their interactions with anions monitorized via UV-Vis, fluorescence and 1H NMR titrations. Additionally quantum chemical calculations and electrochemical studies completed the studies carried out. The phenyl-thiosemicarbazone dyes show a modulation of their hydrogen-bonding and electron-donating capabilities as a function of the chemical groups attached and display two different chromo-fluorogenic responses towards anions in acetonitrile solutions. The more basic anions fluoride and cyanide are able to induce the dual coordination-deprotonation processes for all the receptors studied, whereas acetate only interacts with receptors 2, 3, 6, 7, 8, 9 and dihydrogen phosphate displays sensing features only with the more acidic receptors 6. Coordinative hydrogen bonding interactions is indicated by a small bathochromic shift, whilst deprotonation results in the appearance of a new band at ca. 400-450 nm corresponding to a colour change from colourless-yellow to yellow-red depending on the receptor. In the emission fluorescence, hydrogen bonding interaction is visible through the enhancement of the emission band, whereas deprotonation induced the growth of a new red-shifted emission. The chromo-fluorogenic behaviour could be explained on the basis of the deprotonation tendency of the binding sites and the proton affinity of the anions. PM3 and 1H NMR calculations are in agreement with the existence of the dual complexation-deprotonation process, whereas both studies are in discrepancy in relation to which is the proton involved in the deprotonation. Electrochemical studies carried with receptor 3 showed a quite complex redox behaviour and anodic shifts of the reduction peaks in the presence of the basic anions fluoride, cyanide and acetate.Fundação para a Ciência e a Tecnologia (FCT