A simple dual-read assay for uric acid (UA) was developed based on a combined ratiometric fluorescent and colorimetric strategy using nitrogen-doped carbon dots (N-CDs). The biosensor relies on the oxidation of UA by uricase to produce H₂O₂, which was then converted to ^•OH radicals by I^-, resulting in the oxidation of o-phenylenediamine (OPD) to 2,3-diaminophenazine (DAP). In the presence of UA, the colorless biosensor system changed to yellow. Furthermore, the presence of DAP quenched the fluorescence emission of the N-CDs at 427 nm based on the inner filter effect (IFE). With increasing UA concentrations, the fluorescence intensity of the biosensor at 427 nm decreased but increased at 580 nm, demonstrating the ratiometric response. A strong linearity was observed between the fluorescence intensity ratio of DAP to N-CDs (I₅₈₀/I₄₂₇) and the corresponding UA concentration over the range 0.5−150 μM, and a limit of detection (S/N ratio of 3) of 0.06 μM was calculated. The dual-read assay was successfully employed in the quantitation of UA in human serum and urine samples, revealing its potential for measuring UA in clinical samples.

Graphical abstract

中文翻译：

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一种使用氮掺杂碳点的高灵敏度双读数测定法，用于定量人血清和尿液样本中的尿酸

基于使用氮掺杂碳点 (N-CDs) 的组合比率荧光和比色策略开发了一种简单的尿酸 (UA) 双读数测定法。该生物传感器依靠尿酸酶对UA的氧化产生H ₂ O ₂，H 2 O 2 再通过I ^{-转化为•} OH自由基，导致o的氧化。-苯二胺 (OPD) 至 2,3-二氨基吩嗪 (DAP)。在 UA 存在下，无色生物传感器系统变为黄色。此外，基于内滤效应 (IFE)，DAP 的存在使 N-CD 在 427 nm 处的荧光发射猝灭。随着 UA 浓度的增加，生物传感器在 427 nm 处的荧光强度降低但在 580 nm 处增加，证明了比率响应。DAP 与 N-CDs 的荧光强度比 ( I ₅₈₀ / I ₄₂₇) 和相应的 UA 浓度在 0.5-150 μM 范围内，计算出的检测限（S/N 比为 3）为 0.06 μM。双读数测定成功地用于人血清和尿液样本中 UA 的定量，揭示了其在临床样本中测量 UA 的潜力。

图形概要