Design, Synthesis And Application Of Novel Fluorescent Probes Based On Rhodamine And Coumarin Derivatives

Inbiologicalsystems,some cations,anions and biological moleculesinvolve in a varietyof physiological or pathological processes.Inorder to studytheir roles in physiology and pathology,the development ofeffective detection method s has becomearesearch hotspot. Due to its high sensitivity, fast analysis with spatial resolutionfor providing in situ and real-time information, and nondestructivesample preparation, the fluorescent probe methodseems to be an ideal candidate for both sensing and bioimagingmetal ions, anions and small molecules in various samples. In this thesis, we designed and synthesized a series of fluorescent probes based on rhodamine, coumarinand naphthalimide derivatives for detection of biological-relatedcations and molecules. Taking the above-mentioned reasonings as research objectives, the contents of this thesis are presented as follows:1. In eukaryotic cells, lysosomes(p H4.5-5.5) contain numerous enzymes and proteins exhibiting a variety of activities and functions,and abnormal variation in the lysosomal p H causes defects in lysosomal function. Thus, it is important to investigate lysosomal p H in living cells to understand its physiological and pathological functions.In Chapter 2, we design a new rhodamine-morpholine fluorescent probe RMto detect lysosomal p H changes with high sensitivity, high selectivity, high photostability and low cytotoxicity.The Probe RM shows a 140-fold increase in fluorescence intensity from p H 4.5 to 7.4 with a p Ka value of 5.23.Importantly,RMcan detect the chloroquine-inducedincreaseinlysosomal p H and monitor the dexamethasone-induced changes in lysosomal p H during apoptosis in live cells. All these features demonstrate its value of practical application in biological systems.2. Nitroxyl(HNO) is involved in a number of important physiological or pharmacological progresses, and the development of e fficient analytical methods for HNO detection is critical forunderstanding its physiological and pathological functions. Although several fluorescence probes have been reported for HNO, most of them suffer from interferences from biological reductants such as glutathione and ascorbate.In Chapter 3, we reported a novelcoumarin-based fluorescentprobe P-CM forquantitative detection of HNO based on the reaction between HNO and triphenylphosphinegroup.Also, P-CMexhibitsa high selectivityfor nitroxyl over other biologically relevant RNS, ROS, metal ions.It is particularly noteworthy that the fluorescenceintensity of P-CMwashardlyaffected by biologicalreductants, including GSH, AA, and Na2S(a hydrogen sulfide source). Moreover, the probe was applied forquantitative detection of HNO in bovine serum with satisfactory results.3. Thiophenols are a wildly used and high toxic compounds. The establishment of a highly sensitive and selective probe to discriminate thiophenols a nd biologically relevant aliphatic thiols is of great importance in the fields of chemical, biological, and environmental sciences. In Chapter 4, we reporteda two-photon fluorescence probe for thiophenols, NATP1, has been developed basedon the principle of photoinduced electron transfer(PET)byemploying 2,4-dinitrobenzenesulfonateas a recognition unit( also a fluorescence quencher) and 1,8-naphthalimidederivative as the two-photon fluorophore.Theprobe exhibited high selectivity and excellent sensitivity. Moreover, it was successfully applied for two-photon imaging of thiophenol in living Hela cells.