Polarity is an integral microenvironment parameter in biological systems closely associated with a multitude of cellular processes. Abnormal polarity variations accompany the initiation and development of pathophysiological processes. Thus, monitoring the abnormal polarity is of scientific and practical importance. Current state-of-the-art monitoring techniques are primarily based on fluorescence imaging which relies on a single emission intensity and may cause inaccurate detection due to heterogeneous accumulation of the probes. Herein, we report carbon dots (CDs) with ultra-sensitive responses to polarity. The CDs exhibit two linear relationships: one between fluorescence intensity and polarity and the other between polarity and the maximum emission wavelength. The emission spectrum is an intrinsic property of the probes, independent of the excitation intensity or probe concentration. These features enable two-color imaging/quantitation of polarity changes in lipid droplets (LDs) and in the cytoplasm via in situ emission spectroscopy. The probes reveal the polarity heterogeneity in LDs which can be applied to make a distinction between cancer and normal cells, and reveal the polarity homogeneity in cytoplasm.

极性是与多种细胞过程密切相关的生物系统中不可或缺的微环境参数。异常的极性变化伴随着病理生理过程的开始和发展。因此，监测异常极性具有科学和现实意义。目前最先进的监测技术主要基于荧光成像，其依赖于单一的发射强度，并且可能由于探针的异质积累而导致检测不准确。在这里，我们报告了对极性具有超灵敏响应的碳点 (CD)。CD表现出两种线性关系：一种在荧光强度和极性之间，另一种在极性和最大发射波长之间。发射光谱是探针的固有特性，与激发强度或探针浓度无关。这些特征能够通过原位发射光谱对脂滴 (LD) 和细胞质中的极性变化进行双色成像/定量。该探针揭示了LD中的极性异质性，可用于区分癌细胞和正常细胞，并揭示细胞质中的极性同质性。