Fluorescence ratiometric biosensors are valuable tools for the accurate and sensitive prediction and diagnosis of diseases. However, seldom have fluorescence ratiometric biosensors for protein and DNA been reported because of the shortage of suitable nanoscale scaffolds. Herein, a tripyridinyl Ru^II complex–encapsulated SiO₂@polydopamine (Ru–SiO₂@PDA) nanocomposite was designed as a universal platform for fluorescence ratiometric detection of DNA and protein in serum samples. The Ru–SiO₂@PDA nanocomposites have a narrow size distribution, exhibit good biosafety, and are convenient for the postmodification of biorecognition elements. Under irradiation, they can emit a stable and strong luminescence at 650 nm and simultaneously quench the fluorescence emitted from the fluorophores getting close to them. Once the capture probes such as single-stranded DNA and aptamer are assembled, the fluorophores labeled on them are then brought close to their PDA shell and quenched. However, the biorecognition behaviors change the probe’s configuration and take the fluorophore far away from the PDA shell. Correspondingly, the fluorescence recovers and its ratio to the constant fluorescence reference is linear to the targets’ concentration. Using a D-catalyst and thrombin as model analytes, the Ru–SiO₂@PDA-based nanoplatform shows high sensitivity and good accuracy in the serum sample analysis. Regarding these attractive properties, the Ru–SiO₂@PDA nanoplatform provides a new avenue for the accurate and sensitive fluorescence assay of a wide range of targets in complex systems.

中文翻译：

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通用三吡啶基Ru ^II配合物包裹的SiO ₂ @聚多巴胺荧光纳米平台按比例检测血清中的DNA和蛋白质

荧光比例生物传感器是准确，灵敏地预测和诊断疾病的宝贵工具。然而，由于缺乏合适的纳米级支架，很少有关于蛋白质和DNA的荧光比例生物传感器的报道。在此，将三吡啶基Ru ^II复合物包裹的SiO ₂ @聚多巴胺（Ru-SiO ₂ @PDA）纳米复合材料设计为用于荧光定量检测血清样品中DNA和蛋白质的通用平台。Ru–SiO ₂PDA纳米复合材料的尺寸分布窄，具有良好的生物安全性，并且便于生物识别元素的后修饰。在辐射下，它们可以在650 nm处发出稳定而强烈的发光，同时淬灭从靠近它们的荧光团发出的荧光。组装好捕获探针（如单链DNA和适体）后，将标记在其上的荧光团靠近其PDA外壳并淬灭。但是，生物识别行为会改变探针的配置，并使荧光团远离PDA外壳。相应地，荧光恢复，并且其与恒定荧光参比的比率与靶标浓度成线性关系。使用D催化剂和凝血酶作为模型分析物，Ru–SiO ₂基于PDA的纳米平台在血清样品分析中显示出高灵敏度和良好的准确性。关于这些吸引人的特性，Ru-SiO ₂ @PDA纳米平台为复杂系统中多种靶标的准确而灵敏的荧光测定提供了新途径。