DNA甲基化是一种表观遗传学改变，通过在胞嘧啶(C)残基的第五碳上加入一个甲基基团而形成5-甲基胞嘧啶(5-mC)。尿液中的甲基化水平，即5-mC与C的比值，可能与全身表观遗传状态和常见癌症的发生有关。迄今为止，从未有过任何纳米材料可用于同时检测尿液样品中的C和5-mC。在这里，我们开发了一种用于尿液中C和5-mC检测的双响应荧光传感器。该检测依赖于由微波辅助热解制备的氮掺杂碳量子点(CQDs)的光学特性的变化。在存在C的情况下，CQDs的蓝移荧光强度增加。然而，添加5-mC后观察到荧光淬灭。这主要是由于光诱导电子转移，在密度泛函理论计算中得到了证实。在尿液样品中，我们的敏感荧光传感器对C和5-mC的检测限度分别为43.4和74.4 μM，并实现了从103.5到115.8%的令人满意的回收率。同时检测C和5-mC可实现有效的甲基化水平检测，回收率范围为104.6-109.5%。此外，还开发了一款机器学习智能手机，可有效用于甲基化水平的测定(0-100%)。这些结果展示了一种简单但非常有效的尿液甲基化水平检测方法，对于预测临床预后可能具有重要意义。

DNA methylation is an epigenetic alteration that results in 5-methylcytosine (5-mC) through the addition of a methyl group to the fifth carbon of a cytosine (C) residue. The methylation level, the ratio of 5-mC to C, in urine might be related to the whole-body epigenetic status and the occurrence of common cancers. To date, never before have any nanomaterials been developed to simultaneously determine C and 5-mC in urine samples. Herein, a dual-responsive fluorescent sensor for the urinary detection of C and 5-mC has been developed. This assay relied on changes in the optical properties of nitrogen-doped carbon quantum dots (CQDs) prepared by microwave-assisted pyrolysis. In the presence of C, the blue-shifted fluorescence intensity of the CQDs increased. However, fluorescence quenching was observed upon the addition of 5-mC. This was primarily due to photoinduced electron transfer as confirmed by the density functional theory calculation. In urine samples, our sensitive fluorescent sensor had detection limits for C and 5-mC of 43.4 and 74.4 μM, respectively, and achieved satisfactory recoveries ranging from 103.5 to 115.8%. The simultaneous detection of C and 5-mC leads to effective methylation level detection, achieving recoveries in the range of 104.6-109.5%. Besides, a machine learning-enabled smartphone was also developed, which can be effectively applied to the determination of methylation levels (0-100%). These results demonstrate a simple but very effective approach for detecting the methylation level in urine, which could have significant implications for predicting the clinical prognosis.