Silver nanoparticles in the presence of Ca2+ as a selective and sensitive probe for the colorimetric detection of cysteine

Abstract

A sensitive and selective cysteine colorimeric sensor based on the interaction between cysteine, silver nanoparticles (AgNPs) and calcium ions has been developed. In the presence of Ca 2+ and NaCl, cysteine could rapidly induce the aggregation of AgNPs, thereby resulting in a yellow-to-red color change. The presence of 10 mM NaCl in the samples decreases the electrostatic repulsion and accelerates the aggregation of AgNPs. Results demonstrated that other amino acids cannot change the color of AgNPs solution in the same conditions, probably due to the absence of the thiol groups, suggesting the selectivity of the proposed method toward cysteine. The color change was monitored by naked eye and UV-Vis spectrophotometry. The ratio of absorption at 524 to 396 nm (A 524 /A 396 ) is linearly dependent on the cysteine concentration in the range of 0.25-10 mM.

A simple green route to prepare stable silver nanoparticles with pear juice and a new selective colorimetric method for detection of cysteine

“…3, NaCl exerts strong effects on the citrate-coated AgNPs, and the strong LSPR band at 414 nm greatly decreased in the medium of 0.2 M NaCl with a yellow-to-grey color change (Fig. 3a), indicating the aggregation of AgNPs, 30,31 and suggesting the poor stability of citrate-coated AgNPs in a salty medium.…”

“…5a shows that the LSPR band of AgNPs at 406 nm decreased and a new band at 530 nm emerged with the addition of cysteine, owing to the aggregations of the as-prepared AgNPs through the electric dipole-dipole interaction and coupling between the neighbouring particles. 30,31 To conrm the formation of aggregates, DLS was employed to examine the size SEM and dark-eld light scattering images were captured to identify the cysteine-induced aggregation. In Fig.…”

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“…Another demonstration stated that cysteine was selectively detected in the presence of Ca 2+ and NaCl. The result showed other amino acids had no effect on the color change due to the absence of thiol groups [ 34 ]. Chromium ion had a similar interaction.…”

4-Amino-6-hydroxy-2-mercaptopyrimidine capped gold nanoparticles as fluorophore for the ultrasensitive and selective determination of l-cysteine

“…It is also an active site in the catalytic functions of certain enzymes called cysteine proteases and in many other peptides and proteins [1,2]. Cys present in hair and nails and speed up the proliferation of keratin rich cells and this has a positive role in a variety of important cellular functions such as metabolism, protein synthesis, detoxification, redox functions and disease [3,4].…”

“…HAuCl4 and NaBH 4 constant and varying the concentration of AHMP. Then, we have also varied the concentration of HAuCl 4 and keeping the concentrations of AHMP and NaBH 4 constant.…”