Synthesis Of A Probe For Enzyme Detection And Preparationof A Supramolecular Hydrogel Via Reduction Reaction

Based on the development of sensor technique and self-assembly research, fluorescent molecular probes that can specifically recognize enzymes, protein and small molecule compounds in different organismshaveexhibited great potentials for the application in the field of biomedical imaging and diseasediagnosis. Due to a large number of enzymes and bioactive molecules in organisms which can stimulate and induce cascade reaction, such process can notonly be applied to generate fluorescent molecular probes for targeting biomolecule detection, but also be used to trigger supramolecular self-assembly around physiological conditions. In this thesis, we reported the generation of a novel probe for alkaline phosphatase(ALP) detection via phosphatase-mediated cascade reaction and a novel supramolecular hydrogel triggered by GSH via disulphide bond reduction reaction.In the first part of this work, based on photoinduced electron transfer(PET), we designed and synthesized a novel probe for ALP assay by incorporating a self-immolative linker between a phosphate moiety and resorufin. The incorporation of a self-immolative linker between the phosphate moiety and resorufin can greatly reduce steric hindrance and enhance the accessibility of probe towards ALP for dephosphorylation reaction. And this probe exhibited the capabilities for rapid and sensitive ALP detection in solution through both naked-eye observation and fluorescence detection, and the detection limit can be as low as 1.09 U/L. Furthermore, because of its good biocompatibility and rapid cell internalization, this probe also exhibited great potential for real-time monitoring the endogenous phosphatase activity in living cells.In the second part of this work, we simply combined cystamine with D-phenylalanine to generate a new supramolecular hydrogelator which can be reducted by GSH and proceed self-assembly at physiological conditions(pH=7.4). Due to the application of D-amino acids, the formed hydrogel can also resist to protease degradation. In addition, the storage moduli(G’) of the hydrogel was 10 times higher than its loss moduli(G”), signifying the viscoelastic behavior of this hydrogel. Besides, to fully understand the molecular packing mode of gelator and the morphologies of self-assembled nanostructures, we used circular dichroism and electron microscopy to study in detail of the self-assemblies, andfound that these molecules mainly relied on an inverted β-sheet structure for supramolecular self-assembly and formed nanofibrous structures with awidth of around 20 nm. Furthermore, because of its good biocompatibility, this hydrogel also can as a biomimetic scaffold for cell culture.