The Construction Of Naphthalimide-based Fluorescent Probes And Their Application In Enzymes And Reactive Nitrogen Detection

In recent years,small-molecule fluorescent sensors have been widely applied in chemistry,environment,and biology,as well as their cross-subjects.This is because small-molecule fluorescence sensors are generally easy to synthesis,low-cost,and versatile to use.In addition,the organic fluorescence sensor is easy to operate during the testing procedure.There is no need of complicated pretreatment processes and real-time monitoring can beachieved with good cell permeability for live-cell or tissue imaging.Therefore they have good prospects for biological applications.In this paper,two kinds of naphthalimide fluorescent probes based on intramolecular charge transfer mechanism(ICT)were designed and synthesized to realize the quantitative detection of enzyme and reactive nitrogen.(1)Firstly,we synthesized a fluorescent probe NI-1 for detecting chymotrypsin(CHT)via ICT.NI-1 was synthesized by coupling a 4-bromobutyryl group onto naphthalimide-based fluorophore.For this probe,the 4-bromobutyryl group serves both as the blocking agent for ICT and the responsive moiety toward CHT.When 4-bromobutyryl is introduced,the hydroxyl group in the probe is protected and the ICT effect is weakened.And the fluorescence emission occurs at 450 nm.CHT cleaves the ester bond of the probe and generates hydroxyl group,thereby enabling the ICT and generating strong ICT-based emission with a large Stokes shift.The fluorescence emission redshifts to 550 nm.NI-1 exhibits high selectivity for CHT detection with a very low detection limit of 8.4 ng/mL.The results also demonstrate that the designing strategy in the text provides a more promising application prospect for screening others CHT inhibitors.At present,there are no reports on the detection of CHT using ratio fluorescent probes.We provide a new approach for the detection of CHT.(2)We synthesized a new fluorescent probe NI-2 for detecting ONOO-with the"Turn-On" fluorescent sensing modes.After the probe was introduced into?-ketoamide,the ICT effect was inhibited,and the fluorescence intensity was very weak.After reacting with ONOO-,NI-2 released amino group in naphthalimide,which changed the photophysical properties of the probe with a large Stokes shift.NI-2 is characterized of good selectivity,fast response,and high sensitivity,making it an ideal probe for sensing ONOO" in a physiological environment.