N6-甲基腺苷（m6A）去甲基酶可以催化去除m6A上的甲基修饰，并与恶性肿瘤的发生、增殖、分化和转移密切相关。m6A去甲基酶（例如：脂肪质量和肥胖相关蛋白(FTO)）可能作为癌症生物标志物，并对抗癌药物筛选和早期临床诊断至关重要。本文展示了通过直接编码链霉亲合素结合RNA适配子（SA适配子）用于检测m6A去甲基酶的量子点基贝尔斯特共振能量转移（FRET）纳米传感器的构建。该纳米传感器利用多个标记有Cy5分子的SA适配子作为构建材料，构建605QD-RNA-Cy5纳米组装体，并利用m6A对延伸和连接反应的阻碍效应区分带有m6A的RNA探针与去甲基化的RNA探针。当存在m6A去甲基酶时，m6A含有的RNA探针被去甲基化生成去甲基化的RNA探针，启动链延伸和连接反应，生成完整的SA适配子转录模板。随后，触发T7辅助级联转录扩增反应，转录出具有多个Cy5荧光团的丰富SA适配子。这些带有Cy5的SA适配子可以自组装到覆盖了链霉亲合素的605QD表面，形成605QD-SA适配子-Cy5纳米组装体，从而产生明显的FRET信号。该纳米传感器具有超高灵敏度和优异的特异性，可在单细胞级别检测内源性FTO。此外，该纳米传感器可以精确测量酶动力学参数，筛选m6A去甲基酶抑制剂，并区分乳腺癌患者和健康人组织中FTO的表达差异，为临床诊断和药物发现提供了多功能平台。

N6-Methyladenosine (m6A) demethylases can catalyze the removal of the methyl modification on m6A, and it is closely associated with the occurrence, proliferation, differentiation, and metastasis of malignancies. The m6A demethylases (e.g., fat mass and obesity-associated protein (FTO)) may act as a cancer biomarker and are crucial for anticancer drug screening and early clinical diagnosis. Herein, we demonstrate the construction of a quantum-dot-based Förster resonance energy-transfer (FRET) nanosensor through direct encoding of streptavidin-binding RNA aptamers (SA aptamers) for m6A demethylase detection. This nanosensor employs multiple Cy5-molecule-labeled SA aptamers as the building materials to construct the 605QD-RNA-Cy5 nanoassembly, and it exploits the hinder effect of m6A upon elongation and ligation reactions to distinguish m6A-containing RNA probes from demethylated RNA probes. When m6A demethylase is present, the m6A-containing RNA probes are demethylated to generate the demethylated RNA probes, initiating strand extension and ligation reactions to yield a complete transcription template for SA aptamers. Subsequently, a T7-assisted cascade transcription amplification reaction is activated to transcribe abundant SA aptamers with the incorporation of multiple Cy5 fluorophores. The Cy5-incorporated SA aptamers can self-assembly onto the streptavidin-coated 605QD surface to obtain the 605QD-SA aptamer-Cy5 nanoassemblies, resulting in the generation of distinct FRET signals. This nanosensor exhibits ultrahigh sensitivity and excellent specificity, and it can detect endogenous FTO at the single-cell level. Furthermore, this nanosensor can precisely measure enzyme kinetic parameters, screen m6A demethylase inhibitors, and differentiate the FTO expression between breast cancer patients and healthy individual tissues, offering a versatile platform for clinical diagnostic and drug discovery.