Alula Melisew Tadele
Department of Chemical and Forensic Sciences, Faculty of Science, Botswana International University of Science and Technology Plot 10071, Private Bag 16 Palapye Botswana
RSC Adv. 2023 May 31;13(24):16396-16404. doi: 10.1039/d3ra01587d. eCollection 2023 May 30.
Cysteine is one of the important amino acids that is involved in various physiological processes, food industries, pharmaceuticals, and personal care. It also serves as a biomarker for some diseases. The large use of cysteine necessitates rapid, cheap, and accurate determination of cysteine in a range of samples. Although many techniques have been employed for the detection of cysteine, they suffer from limitations that make them unsuitable for routine analysis. Here we report on a cheap colorimetric method using biosynthesized silver nanoparticles (AgNPs) as nanozymes. The AgNPs were characterized by UV/visible spectrophotometry, scanning electron microscopy (SEM), and surface-enhanced Raman spectroscopy (SERS). The AgNPs exhibit peroxidase-like activity using -phenylenediamine (OPD) as a chromogenic reagent. The low values observed for OPD and HO (0.9133 and 61.56 mM respectively) show strong affinity of the substrates to AgNPs. The peroxidase-like activity of AgNPs, however, was inhibited on the addition of cysteine. The results show that the absorption intensity of the oxidized OPD decreased linearly with the concentration of cysteine in the range of 0.5-20 μM. The limit of detection (LOD) in this linear range was found to be as low as 90.4 nM. The recovery from urine sample (spiked with cysteine) analyses demonstrated the feasibility of the method in real sample application. From our findings, we anticipate that our method can be applied for the analysis of cysteine in various samples.
半胱氨酸是参与各种生理过程、食品工业、制药和个人护理的重要氨基酸之一。它还可作为某些疾病的生物标志物。大量使用半胱氨酸使得快速、廉价且准确地测定一系列样品中的半胱氨酸成为必要。尽管已采用多种技术检测半胱氨酸，但它们存在局限性，不适用于常规分析。在此，我们报道一种使用生物合成银纳米颗粒（AgNPs）作为纳米酶的廉价比色法。通过紫外/可见分光光度法、扫描电子显微镜（SEM）和表面增强拉曼光谱（SERS）对AgNPs进行了表征。以邻苯二胺（OPD）作为显色剂时，AgNPs表现出类过氧化物酶活性。观察到的OPD和H₂O₂的低Kₘ值（分别为0.9133和61.56 mM）表明底物对AgNPs具有很强的亲和力。然而，加入半胱氨酸后，AgNPs的类过氧化物酶活性受到抑制。结果表明，在0.5 - 20 μM范围内，氧化型OPD的吸收强度随半胱氨酸浓度呈线性下降。在此线性范围内，检测限（LOD）低至90.4 nM。尿样（添加半胱氨酸）分析的回收率证明了该方法在实际样品应用中的可行性。根据我们的研究结果，我们预计我们的方法可用于分析各种样品中的半胱氨酸。
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