As an important biomarker for the early stage of apoptosis, cytochrome c (Cyt c) has been recognized as a key component of the intrinsic apoptotic pathway. Fluorescence imaging tools enabling detection of Cyt c in apoptotic signaling have been rarely explored, though they are critical for cell biology and clinical theranostics. Here, we designed a novel label-free N-doped carbon dot (N-doped CD)-based nanosensor that enables fluorescence activation imaging of Cyt c release in cell apoptosis. The inner filter effect of Cyt c towards N-doped CDs enabled quantitative Cyt c measurement. The nanosensor exhibited high sensitivity and selectivity, rapid response, good cell-membrane permeability and low cytotoxicity. All these features are favorable for in situ visualization of Cyt c for apoptosis research. Notably, the developed nanosensor was successfully applied to monitor intracellular release of Cyt c, and to visualize Cyt c in living zebrafish for the first time. Moreover, it also provided a viable platform for cell-based screening of apoptosis-inducing compounds. In virtue of these advantages and potential, the developed assay not only holds great significance for the better understanding of certain diseases at the cellular level, but also provides an invaluable platform for apoptotic studies and screening of anti-cancer drugs toward drug development.

中文翻译：

---

活体系统 中细胞色素c的无标记荧光成像和氮掺杂碳量子点进行的抗癌药物筛选†

作为细胞凋亡早期的重要生物标志物，细胞色素c（Cyt c）被认为是内在凋亡途径的关键组成部分。荧光成像工具能够检测凋亡信号中的Cyt c，尽管对于细胞生物学和临床治疗学至关重要，但很少进行探索。在这里，我们设计了一种新型的无标签的基于N掺杂的碳点（N掺杂的CD）的纳米传感器，该传感器能够对细胞凋亡中Cyt c释放的荧光进行激活成像。Cyt c对N掺杂CD的内部过滤作用使定量Cyt c得以实现测量。该纳米传感器显示出高灵敏度和选择性，快速响应，良好的细胞膜通透性和低细胞毒性。所有这些特征对于细胞凋亡研究的Cyt c的原位可视化是有利的。值得注意的是，开发的纳米传感器已成功应用于监测Cyt c的细胞内释放并可视化Cyt c。第一次生活在斑马鱼中。此外，它还为基于细胞的凋亡诱导化合物筛选提供了一个可行的平台。凭借这些优势和潜力，开发的测定方法不仅对于在细胞水平上更好地了解某些疾病具有重要意义，而且为凋亡研究和针对药物开发的抗癌药物筛选提供了宝贵的平台。