Recent progress in two-photon small molecule fluorescent probes for enzymes

Enzymes are macromolecular biological catalysts which can accelerate chemical reactions in living organisms. Almost all the physiological metabolism activities in the cell need enzymes to sustain life via rapid catalysis. Currently, medical research has proved that abnormal enzyme activity is associated with numerous diseases, such as Parkinson's disease (PD), Alzheimer's disease (AD) and cancers. On the other hand, early diagnosis of those diseases is of great significance to improve the survival rate and cure rate. In the current diagnostic tools, two-photon fluorescent probes (TPFPs) are developing rapidly due to their unique advantages, such as higher spatial resolution, deeper imaging depth, and lower biotoxicity. Therefore, the design and synthesis of two-photon (TP) small molecule enzymatic probes have broad prospects for early diagnosis and treatment of diseases. As of now, scientists have developed many TP small molecule enzymatic probes. This review aims to summarize the TP small molecule enzymatic probes and expound the reaction mechanism.