Synthesis Of Fluorescent Probe Based On Naphthalimide And Its Application In Detection

γ-Glutamyltranspeptidase(GGT) plays crucial roles in various important physiological processes. Elevated levels of GGT are related to diseases of the liver and biliary system, and it is important in clinical diagnosis for evaluating diseases of the liver and gallbladder. Also, GGT has been reported to be overexpressed in several human tumors, including cervical and ovarian cancers. Hence, GGT is also an important indicator in clinical diagnosis for cancers. To the best of our best knowledge, to date, only a couple of fluorescent probes for GGT imaging or assay have been reported, and they all function in the fluorescence turn-on mode. Because of the inherent limitations, enhanced fluorescence probes are vulnerable to environmental interference, leading to low detection precision. However, ratiometric fluorescence probes that employ simultaneous recording of two fluorescence signals in the presence and absence of an analyte can minimize some interfering factors, and allow for more accurate readouts.Herein, we synthesize a ratiometric fluorescent probe for detecting GGT. The probe is a derivate of 1,8-naphthalimide, in which an oligoethylene glycol(OEG) was incorporated at the N-position, while the γ-glutamyl amide group was coupled onto the 4th position. OEG was incorporated into the probe, because it can minimize the nonspecific interactions between the probe and biological molecules such as proteins; also can impart good water solubility to the probe. Upon addition of GGT, the cleavage of the γ-glutamyl amide moiety of the probe results in the change in photophysical properties. With the increasing reaction time, the fluorescence of the probe solution also changes gradually from blue to green. The fluorescence intensity ratio I537/I473 increases steadily with the increasing GGT level in the same reaction time, and there is a good linear relationship between the fluorescence intensity ratio I537/I473 and the GGT level in the range of 0-50 U/L, moreover, the detection limit is determined to be 0.76 U/L. The probe can be used for detecting GGT levels with high reliability in practical sample. MTT assay proves that the probe exhibits little toxicity in vitro and is suitable for fluorescence imaging of GGT in live cells. Fluorescence imaging demonstrates the strong potential of the probe to detect endogenous GGT in live cells.