Background: Gold nanoparticles have been studied extensively for their potential application in the detection of important analytes. Their relative ease of synthesis through numerous procedures makes possible their implementation in a variety of assays. Cysteine (cys), a thiol-containing amino acid implicated in numerous pathologies such as obstructive sleep apnea (OSA), has been routinely detected through expensive fluorometric assay kits. Objectives: As such, this study aimed to develop a carbohydrate-based gold nanoparticle colorimetric assay for the convenient and straightforward detection of cys. Methodology: Carbohydrate-based gold nanoparticles (c-AuNPs) were synthesized following a microwaveassisted procedure. The as-prepared c-AuNPs were used to detect cys by plotting the ratio of the absorbances of the aggregated and dispersed gold nanoparticles against the concentration of cys. Results: The c-AuNP solutions were able to detect cys in the micromolar range, with the glucose-based AuNPs (glc-AuNPs) showing the widest linear range (16.7 μm to 167 μm), and the fructose-based gold nanoparticles (frc-AuNPs) exhibiting the lowest detection limit (9.0 μm) for cys. Aside from being able to detect cys, the c-AuNPs were also responsive to tyr and lys. Conclusion This study demonstrates that carbohydrate-based gold nanoparticles prepared following a microwave-assisted procedure using sugars as reducing agents and capping agents can be used successfully in the detection of cysteine.
Cysteine ; Carbohydrates ; Starch