氧化反应调控的金纳米簇“关-开”型荧光探针检测过氧化氢和葡萄糖

基于过氧化氢（H₂O₂）氧化单巯基（—S）为双巯基（S—S），抑制金纳米簇（AuNCs）荧光猝灭，建立了一种灵敏的荧光传感方法用于过氧化氢和葡萄糖（Glu）的检测。DNA为模板合成的金纳米簇作为荧光探针，荧光强度高、稳定且合成简单快速。加入半胱氨酸（Cys），半胱氨酸上的单巯基可以与金纳米簇发生化学键合反应形成稳定的Au—S键，破坏金纳米簇的结构，导致金纳米簇荧光强度猝灭。但当体系中存在过氧化氢时，将单巯基半胱氨酸氧化成双巯基的胱氨酸。双巯基的胱氨酸不能与金纳米簇发生键合作用，金纳米簇在471 nm处发射出强烈的荧光信号。葡萄糖可以在葡萄糖氧化酶（Gox）的作用下产生过氧化氢，利用该方法进一步开展了对葡萄糖的检测。以金纳米簇荧光强度的变化值F/F₀为纵坐标，过氧化氢或葡萄糖浓度为横坐标，实现了对过氧化氢和葡萄糖的灵敏检测，线性范围分别为10~100和10~200 μmol·L-1，检测下限分别为2.8和3.1 μmol·L-1。选择4种其他糖类化合物和5种金属离子作为干扰物质，均不会抑制半胱氨酸对金纳米簇的荧光猝灭效应，表明该方法具有很好的选择性。用该方法成功检测了胎牛血清样品中的葡萄糖，加标回收率为94.5%~112.7%。此外，该方法可拓展到其他基于酶催化产生过氧化氢体系的分析物检测，如胆固醇、辣根过氧化物酶等，为过氧化氢相关反应的分析提供了一种通用、简便的方法，在临床诊断、食品科学和环境分析等领域具有潜在的应用价值。

Redox-Controlled Turn-on Fluorescence Sensor for H2O2 and Glucose Using DNA-Template Gold Nanoclusters

A novel turn-on sensitive fluorescent assay was proposed for H₂O₂ and glucose based on H₂O₂ oxidation of thiols to disulfides inhibiting the quenching of AuNCs with highly fluorescent emission. As a fluorescence probe, gold nanoclusters (AuNCs) have exhibited outstanding properties, such as superior fluorescence properties, excellent stability and facile synthesis. Cysteine with free —SH group could interact with AuNCs through Au-S bonds, leading to the fluorescence quenching of AuNCs. After adding H₂O₂, cysteine was oxidized to cystine with disulfide bonds. The thiols’ effect between cysteine and AuNCs was prevented, and obvious fluorescence emissions of AuNCs at 471 nm could be observed. Moreover, it was known that GOx could specifically catalyze glucose to generate H₂O₂ in the presence of oxygen. Therefore, fluorescent glucose detection could be achieved through the oxidase-catalyzed producing H₂O₂. Utilizing the variation of fluorescence intensity F/F₀ as abscissa, H₂O₂ or glucose concentration as ordinate, a sensitive, selective, simple and fast analysis method for H₂O₂ and glucose was constructed. A linear relationship was observed from 10 to 100 μmol·L-1 for H₂O₂, 10 to 200 μmol·L-1 for glucose, with the detection limit of 2.8 and 3.1 μmol·L-1, respectively. Four other carbohydrates and five metal ions were selected as the interferent. All of them could not inhibit the Au-S bonding reaction triggered quenching effect, which revealed the high selectivity of the sensor towards glucose. In addition, the strategy was successfully applied for the detection of glucose in FBS samples with satisfactory recoveries from 94.5%~112.7%. Moreover, the present sensing system could be easily broadened to detect multi-analytes (cholesterol, horseradish peroxidase) based on oxidase-catalyzed producing H₂O₂. Therefore, the method may offer a new clinical diagnosis and food analysis platform.