Early diagnosis of cancer is important to improve the chance of curing cancer. Intracellular pH plays a key role in many cellular events and is considered to be an important cancer marker. Unfortunately, near-infrared (NIR) fluorescence probe for detecting pH is rare. Herein, we designed and synthesized a pH NIR fluorescence probe termed CyO for cancer diagnosis. The acidic environment induces the protonation of CyO to form CyOH, resulting in fluorescence enhancement in NIR region. When pH varies from 7.4 to 5.0, the near-infrared fluorescence is increased by 20-fold. And there is a good linear relationship between fluorescence intensity and pH. In particular, the NIR fluorescence probe is applied for discriminating between normal and cancer environment by the detection of pH in various biological samples such as cell, tissue and living animal. This provides basic information that is helpful in early diagnosis of cancer.

癌症的早期诊断对于提高治愈癌症的机会很重要。细胞内pH在许多细胞事件中起着关键作用，被认为是重要的癌症标志物。不幸的是，用于检测pH值的近红外（NIR）荧光探针很少。在本文中，我们设计并合成了用于癌症诊断的pH近红外荧光探针CyO。酸性环境诱导CyO质子化以形成CyOH，从而导致NIR区域的荧光增强。当pH从7.4变为5.0时，近红外荧光增加20倍。并且荧光强度和pH之间存在良好的线性关系。特别是，NIR荧光探针通过检测各种生物样品（例如细胞，组织和活体动物）中的pH值，用于区分正常环境和癌症环境。