Design And Synthesis Of Novel Fluorogenic Probes From Tetraphenylethylene Derivatives For Biological Entity Detection Via Aggregation-induced Emission

The Organic molecules which are practically non-luminescent in solution state but become strongly emissive when in aggregated state have received increasing interest in recent years. This unusual fluorescence phenomenon was referred as to “aggregation-induced emission”(AIE). By taking advantage of “turn on” or ‘‘light up’’ mechanism, a lot of nanoaggregate-based bio/chemosensors has been developed. Among these AIE molecules, tetraphenylethylene(TPE) and its derivatives have numerous advantages, such as facile synthesis, high efficient emission, and high thermal stability. In this work, two kinds of fluorogenic probe based on tetraphenylethylene derivatives have been synthesized. The main contents of the thesis are as follows:1. Using 4,4’-dihydroxybenzophenone as the starting material to synthesize a novel fluorescent “light-up” probe for carboxylesterase assay based on a tetraphenylethylene derivative which contains carboxylic ester groups. The specific cleavage of the carboxylic ester bonds by carboxylesterase resulted in the generation of a relatively hydrophobic moiety for supramolecular microfibers formation and “turned on” fluorescent signals. Under these conditions, high sensitivity towards carboxylesterase was achieved with a detection limit as low as 29 pM, which was much lower than the corresponding assays based on other fluorescent approaches. Moreover, it also exhibited the potential for carboxylesterase inhibitor screenings.2. Using 4-hydroxybenzophenone and benzophenone to synthesize a novel initiator for free radical polymerization reaction, which contains tetraphenylethylene moity at the end of the molecule. Then we used visible-light-induced polymerization to get poly(Nvinylpyrrolidone-dopamine methacrylamide) for the detection of ferric iron(Fe3+). This is achieved by the site-specific incorporation of Fe3+-binding catechol units onto the polymer chain side, inspired by the mechanism by which bacterial siderophores sequester iron from mammalian hosts. The coordination would induce the formation of extended coordination complexes, and result in the aggregation of TPE untis to emit strong fluorescence. Moreover, other metal ions exert no interference on this probe for Fe3+ detection.