Design, Synthesis, And Biological Applications Of Fast-responsive Fluorescent Probes For Detecting Active Small Molecules

Reactive small molecule is closely associated with organism physiology, pathology and aging. Abundant evidence suggests that excessively produced reactive small molecule have been implicated in a wide variety of diseases. Therefore, reactive small molecule plays an important role in biology, it is pressing to develop powerful tools for real-time monitor in cellular level.At present, various fluorescence probes has been developed and applied for the reactive small molecule analysis. However, when the probe reacted with the reactive molecule, the recognition reaction is completed after a long times, it has become an important yet complex issue for monitoring reactive molecule concentration level in living cells. If you want to study true concentration of reactive molecule in living cells at specific areas, the slow response probe can not meet the demand. Therefore, development of a rapid and highly selective method for reactive small molecule analysis in living cells is of great significances.Therefore we develop three rapid-response fluorescence probes to detect hypochlorous acid(HOCl), Superoxide anion(O2?-) and hydrogen peroxide(H2O2).The main results of the dissertation were shown as follows:1. We design a novel turn-on probe(FO-PSe) for HOCl was designed based on the 9-fluorenone covalently conjugating with two selenium-containing compounds. The reversible recognition ability of the probe can be achieved through the oxidation–reduction cycles of the selenium center. The 9-fluorenone was selected as a two-photon(TP) fluorophore because of its excellent TP fluorescent performance. In the presence of HOCl, the selenium of the probe was oxidized specifically and the ?-electron of the conjugated system redistributed accordingly. Results showed that one-photon and two-photon fluorescence of FO-PSe enhanced markedly in the presence of HOCl. Importantly, the probe FO-PSe was successfully applied to cells, zebrafish and mice to dynamically visualize the changes of the HOCl levels under various stimulations. Compare with previous fluorescent probe for HOCl, the probe combined the merits of deep penetration, less photodamage, reversibility and instantaneity.2. We present a simple but effective carbon dots(CDs)-based sensor for reversible fluorescence imaging of O2?- in live cells and in vivo. The CDs-based sensor is fabricated by one-step strategy, using FO-PSe as the sole precursor. The as-prepared CDs-based sensor is directly functionalized by selenium center in the process of the synthesis, which directly introducing active sites and no any additional surface modification was needed. Moreover, the sensor was successfully applied to imaging of the O2?- levels in mice via two-photon imaging according to depths of various vivo. Due to simplicity and effectivity, the sensor was demonstrated as a useful fluorescent tool for tracking O2?- levels in cells and in vivo. To our knowledge, it is the most simplicity and effectivity CDs-based fluorescent sensor for O2?-. Therefore, it can be employed as a useful fluorescent tool for tracking superoxide anion levels in cells and in vivo.3. Aiming at widespread reaction speed problem of hydrogen peroxide probe, we have designed and synthesized a novel aggregation induced emission(AIE) fluorescence probe TPE-BO with activity based on increased polarity of C-B bonds, which can rapid-response and highly selective monitoring of H2O2 in living cells. The present study provides a fluorescent tool for rapid monitoring of hydrogen peroxide in living cells and we believe that the strategy for improve the electrophilic reaction activity to achieve the rapid fluorescence response will be broadly applicable to the quantitative monitoring active small molecules in biological systems.