Development Of Novel Fluorescent Sensors With Aggregation-induce Emission Properties Based On Salicylaldehyde Hydrazone Derivatives

Aggregation-induced emission(AIE) is an unusual fluorescence phenomenon, the fluorescent dyes are nonemissive in the dissolved state but become highly emissive when aggregated. Aggregation-induced emission active fluorescent dyes effectively avoid the aggregation-caused quenching(ACQ) effect. Salicylaldehyde hydrazone derivatives are a type of fluorescent dyes with both AIE and excited state intramolecular proton transfer(ESIPT) properties showing large Stokes? shift. Using such dyes, self-absorption and inner filter effect can be effectively avoided. Therefore, salicylaldehyde hydrazone derivatives have great potential in developing novel fluorescent probes.Considering the unique emission behavior of salicylaldehyde hydrazone derivatives, the dissertation developed three new fluorescence detection methods through modifying the functional groups on salicylaldehyde hydrazone derivatives. Firstly, ammonium group functionalized salicylaldehyde hydrazone for heparin detection was established. The probe was positively charged and could aggregate on the negatively charged heparin template through electrostatic interactions and then displayed aggregation induced emission. This fluorescence detection method for heparin is sensitive, selective, quick and suitable for the analysis of heparin in the serum samples. Secondly, a method for adenosine detection with the ammonium group functionalized salicylaldehyde hydrazone derivative as a label-free fluorescent probe was described. In the presence of adenosine, the oligonucleotide aptamer folded into a hairpin-like structure containing double-stranded DNA(dsDNA) region, the salicylaldehyde hydrazone derivative could then aggregate on the negatively charged dsDNA template through electrostatic interactions and display intense fluorescence. To reduce the background fluorescence from salicylaldehyde hydrazone derivative aggregated on oligonucleotide aptamer, exonuclease I was utilized to hydrolyse the oligonucleotide aptamer that had not combined with adenosine. This detection method for adenosine is selective, sensitive and suitable for the analysis of adenosine in cell lysis samples. Thirdly, acryloyl group functionalized salicylaldehyde hydrazone derivative for cysteine(Cys) detection was developed. In the presence of Cys, the specific reaction of Cys with the fluorescent probe induced hydrolysis of acrylate, resulting in the product of salicylaldehyde hydrazone derivative which owing intramolecular hydrogen bond and the free rotation of the N-N bond being prohibited in aqueous in solution, thereby enabling the ESIPT process and turning on the AIE. This fluorescence detection method for Cys is sensitive, selective and suitable for the analysis of heparin in the serum samples. Heparin, adenosine and Cys are important biological molecules, based on their molecular characteristics of the three compounds, the dissertation established three new fluorescence detection methods through modifying the functional groups on salicylaldehyde hydrazone derivatives. The relationships between the luminescence properties of salicylaldehyde hydrazone derivatives with molecular structure and the surrounding environment was also studied.