A novel label-free surface plasmon resonance (SPR) aptasensor has been constructed for the detection of N-gene of SARS-CoV-2 by using thiol-modified niobium carbide MXene quantum dots (Nb₂C-SH QDs) as the bioplatform for anchoring N-gene-targeted aptamer. In the presence of SARS-CoV-2 N-gene, the immobilized aptamer strands changed their conformation to specifically bind with N-gene. It thus increased the contact area or enlarged the distance between aptamer and the SPR chip, resulting in a change of the SPR signal irradiated by the laser (He-Ne) with the wavelength (λ) of 633 nm. Nb₂C QDs were derived from Nb₂C MXene nanosheets via a solvothermal method, followed by functionalization with octadecanethiol through a self-assembling method. Subsequently, the gold chip for SPR measurements was modified with Nb₂C-SH QDs via covalent binding of the Au-S bond also by self-assembling interaction. Nb₂C-SH QDs not only resulted in high bioaffinity toward aptamer but also enhanced the SPR response. Thus, the Nb₂C-SH QD-based SPR aptasensor had low limit of detection (LOD) of 4.9 pg mL⁻¹ toward N-gene within the concentration range 0.05 to 100 ng mL⁻¹. The sensor also showed excellent selectivity in the presence of various respiratory viruses and proteins in human serum and high stability. Moreover, the Nb₂C-SH QD-based SPR aptasensor displayed a vast practical application for the qualitative analysis of N-gene from different samples, including seawater, seafood, and human serum. Thus, this work can provide a deep insight into the construction of the aptasensor for detecting SARS-CoV-2 in complex environments.

Graphical abstract

中文翻译：

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基于碳化铌MXene量子点的表面等离子体共振适体传感器用于检测SARS-CoV-2的核衣壳

通过使用硫醇修饰的碳化铌MXene量子点（Nb ₂ C-SH QDs）作为生物平台，构建了一种新型的无标记表面等离子体共振（SPR）适体传感器，用于检测SARS-CoV-2的N基因。锚定 N 基因靶向适体。在存在 SARS-CoV-2 N 基因的情况下，固定的适体链会改变其构象以与 N 基因特异性结合。从而增加了接触面积或扩大了适配体与SPR芯片之间的距离，导致波长( λ )为633nm的激光(He-Ne)照射的SPR信号发生变化。Nb ₂ C QD 源自 Nb ₂通过溶剂热法制备 C MXene 纳米片，然后通过自组装方法用十八烷硫醇进行功能化。随后，用于 SPR 测量的金芯片通过 Au-S 键的共价结合也通过自组装相互作用用 Nb ₂ C-SH QD 修饰。Nb ₂ C-SH QDs 不仅导致对适体的高生物亲和力，而且还增强了 SPR 响应。因此，基于Nb ₂ C-SH QD 的SPR 适体传感器在0.05 至100 ng mL ^-1的浓度范围内对N-基因具有4.9 pg mL ^{-1 的}低检测限(LOD) 。该传感器在人血清中存在各种呼吸道病毒和蛋白质的情况下也表现出优异的选择性和高稳定性。此外，Nb ₂基于 C-SH QD 的 SPR 适体传感器在定性分析来自不同样品（包括海水、海鲜和人血清）的 N 基因方面具有广泛的实际应用。因此，这项工作可以深入了解用于在复杂环境中检测 SARS-CoV-2 的适体传感器的构建。

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