A facile pH near-infrared fluorescence probe for the diagnosis of cancer in vivo

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.