Construction Of PH Fluorescent Probes

Intracellular pH plays an important role in our lives. There are intimate connections between intracellular pH and normal cell functions. Abnormal pH values are easy to induce inappropriate cell function, growth and division, and may lead to diseases such as cancer and Alzheimer's. Abnormal pH values, especially at acidic conditions, the human bodies are much more likely to suffer from cancer, high cholesterol, gout, diabetes and other diseases. Detection of intracellular pH can provide critical information for studying physiological and pathological processes of cells. Determination of pH by fluorescent methods is attracting more and more attention due to its unique advantages such as high sensitivity and specificity with pH and non-invasiveness to cells.First, this paper introduced the importance of intracellular pH in the human body, and briefly reviewed the development of pH fluorescent probes in the past decades, the fluorophores usually used to develop new pH probes and the strategies of construction of pH fluorescent probes.In the second part, we improved the structure of fluorescent probe BTP1 developed by our group based on ICT effect to build a new pH fluorescent probe BTP2 that can detect pH changes in the acidic environment with large Stokes shift. Property experiments showed that the change of structure improved the properties of BTP1 such as increasing the Stokes shift and increasing the pKa value which makes it more consistent to detect pH values in acidic organelles like lysosome. This strategy provides us a new idea to design probes more rationally.Third, we constructed a new pH fluorescent probe DBD-MPSA based on benzo-oxadiazole derivatives with a D-Ï€-A structure type, hopes to get a ratiometric pH probe by changing ICT effect through protonation. Spectroscopy experiments revealed that the probe accomplished the ratiometric target due to the maximum excitation peak had a blue shift when the pH decreased. This result provides us a strategy to construct ratiometric fluorescent probes with ICT effect.