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Amino acids play a crucial role in a variety of significant metabolic processes and their homeostasis is essential for cell growth and survival. Cysteine (Cys) furnishes imperative information about peculiar physiological functions and disease diagnosis. Cys detection in a biological solution has certain challenges. In this study, we present an appropriate and cost-effective colorimetric technique for the quantitative detection of Cys using label-free silver nanoparticles (Ag-NPs) as color indicators and Be2+ ions as cross-linking agents. The determination process needed to be based on the interaction of Ag-NPs with Cys molecules in the presence of beryllium ions, which induced a rapid pale yellow to red color conversion. The results indicate that this is a rapid and simple technique for quantitative analysis of Cys. In the linear range of 0.1–1000 μM, a detection limit of 50 nM was obtained. In addition, the technique was profitably applied to the detection of cysteine in human serum samples spiked with 250–5 μM and recoveries were in an acceptable range of 95.0–120.0%. This study might promote the implementation of label-free biomolecule detection in medical diagnostics and biochemistry. [ABSTRACT FROM AUTHOR]

In this study described a green approach for synthesizing silver nanoparticles (AgNPs) with corncob acting as a reducing and stabilizing agent to rapidly detect of L -Cysteine (Cys). To obtain an appropriate condition of synthesizing AgNPs variations in the reactant condition such as concentration, pH, and processing speed were altered. The synthesized AgNPs, that have sizes of 50–100 nm were capped by corncob extract (CCB), became virtually hexagonal and re-dispersed well in aqueous solution. AgNPs were explored for their possible structural characterization. Significantly, the CCB/AgNPs combination demonstrated very high sensitivity for Cys detection with a 30 nM limit of detection (LOD) and selective detection of Cys among 12 amino acids. Furthermore, the CCB/AgNPs combination was applied to detect Cys in human serum with an error rate of less than 5%. As a result of this work, a rapid approach for Cys detection employing green-synthesized AgNPs was developed. • For the synthesis of AgNPs, corn cob aqueous extract (CCB) was used as a reducing and stabilizing agent. • AgNPs with sizes of 50–100 nm had a polygonal form and dispersed well in aqueous solution. • AgNPs potential structural characterization was examined. • With a LOD of 30 nM, CCB/AgNPs demonstrated sensitive and selective cysteine detection. • CCB/AgNPs can detect cystine in human serum with excellent recovery in rats. [ABSTRACT FROM AUTHOR]