Novel Fluorometric Assay for Detection of Cysteine as a Reducing Agent and Template in Formation of Copper Nanoclusters

Abstract

This study was designed to develop a highly selective and sensitive method towards fluorimetric sensing of cysteine (Cys) in water and human serum by using copper nanocluster. The Cys-CuNCs were characterized by scanning electron microscopy (SEM), FTIR, fluorescence and UV-Vis analysis. Spectroscopic evidences showed different intensities that were attributed to the different size of Cys-CuNCs. Enhancement in fluorescence intensity of copper nanoclusters with an increase in concentration of cysteine may enable them to be good candidates in detection systems. Selective recognition of cysteine in aqueous and serum samples was achieved during the formation of various copper nanoclusters (Cys-CuNCs) with different size. Under the optimized conditions, two linear range of the nanobiosensor for cysteine were between the 5 μM to 50 μM with detection limit of 2.4 μM and between 60 μM to 500 μM with detection limit of 55 μM. Fluorescence intensity increased with addition of cysteine concentration from 5 to 50 μM. The proposed low-cost nanobiosensor exhibited high reproducibility and good selectivity. It has been used also for the determination of cysteine in human serum samples with recoveries of 97-103 % and RSDs of 1.8-3.6.

The synthesis of switch-off fluorescent water-stable copper nanocluster Hg2+ sensors via a simple one-pot approach by an in situ metal reduction strategy in the presence of a thiolated polymer ligand template

“…We obtained, in all cases, hybrid CuNCs with intense yellow-green emission (around 535 nm) and high fluorescence QYs, in the region of those obtained by other authors. [42][43][44][45][46][47] As shown in Table 2, no significant changes are observed in the emission band maxima of the nanohybrids with variations in the percentage of thiol present in the polymer or the molecular weight, although these parameters are critical for the obtained QY. The highest fluorescence QY values were obtained for polymers with intermediate thiol content values (6 or 8 mol%) and molecular weights of around 20 kg mol −1 ( Table 2 and Fig.…”

“…40,41 Different biomolecules have been tested as stabilizing ligands for red-emitting CuNCs on the basis of complexation and redox reactions between copper(II) and different biomolecules, such as D-penillamine, 14,20,42 glutathione, 2,35 albumin, 18,43 and cysteine. 44,45 In addition to small ligands, macromolecules have been assayed, giving rise to green-emitting CuNCs with polyvinylpyrrolidone, 46 red-emitting CuNCs with β-galactosidase, 21 blue-emitting CuNCs with lysozyme, 47 and blue and yellow-emitting CuNCs stabilized with trypsin. 24 These results show how the photophysical properties of CuNCs may derive from both the metal core (quantum size effects) and from metal surface effects (interactions between the metal core and the surface ligands).…”

Luminescent Metal Nanoclusters for Potential Chemosensor Applications

“…Lys-Cu NCs displayed the two linear response ranges with glucose between 0.03-10 μM and 0.5-10 mM with an LOD of 1.9 nM. In this course, fluorimetric sensing of Cys through the formation of various copper nanoclusters (Cys-Cu NCs) with different sizes were described [148]. As shown in Figure 13, in contrast to other amino acids, addition of Cu 2+ to Cys solution leads to production of Cys-Cu NCs, and the fluorescence intensity increased with the accumulation of cysteine from 5 μM to 50 μM.…”

Copper nanoclusters: an efficient fluorescence sensing platform for quinoline yellow

“…Commonly used nanoclusters are based on noble metals such as gold and silver, which are expensive . Although, copper nanoclusters (CuNCs) are comparatively cheap, their use in the field of sensing has not been much explored . The sensitive and selective sensing potential of CuNCs results from their unique properties such as excellent water solubility, ultrasmall size, bright fluorescence and photostability .…”