Construction Of Fluorescent Detection Systems Based On Chemical Reaction And Their Application In Biomarks

In recent years, a great deal of time and effort has been devoted to the exploration of new technologies to detect early signs of the disease. Biomarkers cover a broad range of biochemical entities, such as nucleic acids, proteins, sugars, small metabolites, and cytogenetic and cytokinetic parameters, as well as entire tumour cells found in the body fluid.They can be used for risk assessment, diagnosis, prognosis, and for the prediction of treatment efficacy and toxicity and recurrence. Thus, to establish the accurate, sensitive, and concise method for the specific recognition of biomarkers will play an immeasurable role in cancer risk indication, early cancer detection, and disease treatment. Among various detection techniques, fluorescence technique has been widely used in biological detection and bioimaging due to its ease of use, high sensitivity, high selectivity, excellent temporal-spatial resolution and fairly simple technical implementation. To date, a lot of new novel small molecule fluorescent chemosensors based on chemical reaction have been designed and successfully applied to detecte and recognize of biomarkers. In this paper, three kinds of new novel small molecule fluorescent chemosensors have been designed and prepared for the rapid, sensitive and selective detection of MAO-A, H2 S and NO, as well as γ-GGT.First, based on intramolecular chage transfer(ICT), we built a ratiometric sensing system for MAO-A by using 1,8-naphthalimide as a reporter. Upon MAO-A-catalysed oxidation of the amino group to aldehyde(through an imine intermediate), a propionaldehyde moiety is released spontaneously by β-elimination followed to liberate the electron-rich,highly fluorescent 1,8-naphthalimide, and the fluorescence spectra of the sensing system were significantly changed due to enzymatic reaction. Moreover, this ratiometric sensing system showed several advantages including good water solubility, better selectivity, higher sensitivity and lower detection limit(0.15 μg/m L). In addition, this ratiometric sensing system can wok well over a wide pH range.Then, by utilizing intramolecular chage transfer(ICT) and fluorescence resonance energy transfer(FRET), we have developed the first fluorescent probe(Naph-RhB) capable of simultaneous and separate detection for H2 S and NO by using a logic gate approach. This probe can respond to H2 S, NO, and H2S/NO with three different sets of fluorescence signals:“1-0-0”, “0-0-1” and “0-1-1”. In addition, fluorescent imaging of L929 cells containing H2 S and/or NO has been achieved by using this probe.Finally, we have, for the first time, successfully developed the two-photon fluorogenic imaging sensor(DCM-GA) for sensitive and selective detection of GGT in biological systems. The presence of GGT cleaves γ-glutamyl amide moiety from the sensor and thereby restore the fluorescence emission of DCM moiety under two-photon excitation.The sensor can not only determine GGT activity in serum samples from both healthy people and patients, but also image GGT in living cells. More importantly, the sensor is able to detect and spatially map the endogenous GGT level elevation as a result of drug-induced liver injury.