Applications Of Water-soluble Chitosan-based Fluorescence Probe With Aggregation-induced Emission Characteristic In Biological Detection

Fluorescent(FL)probe is a kind of molecular system to detect target molecules qualitatively or quantitatively through changes of ultraviolet absorption,fluorescence emission spectrum or redox potential,which has been widely used in life science and environmental science fields with its high sensitivity,ultrafast speed and simple operation.However,for conventional FL probes,due to the aggregation-caused quenching(ACQ)and toxicity,they are not suitable for certain occasions.Fluorescent molecular with aggregation-induced emission(AIE)characteristic overcomes the drawbacks and has been deeply accepted with its highly sensitive,stability and the special mechanism.Nowadays,numbers of AIE-based probes have been successfully explored,and kinds of applications have been dramatically extended,especially in biological field.Among these,water-soluble FL probes are in urgent demand.Chitosan(CS),a polysaccharide with rich amino groups obtained by the deacetylation of chitin,is the second-largest renewable resource in nature and has received considerable attention for its intrinsic properties,especially the excellent biocompatibility,nontoxic,easily biodegradation and complexing with heavy metals,which has been widely used in cosmetical,pharmaceutical,biomedical fields.In this thesis,we synthesized a novel chitosan-based fluorescent bioconjugate with AIE characterstic by labeling tetraphenylethene(TPE)fluorogen to chitosan or its derivatives(N-succinyl chitosan,NSCS;N-trimethyl chitosan chloride,TMC)and farther explored its applications in biological fields and environmental monitoring.Firstly,a novel water-soluble fluorescent bioconjugate(TPE-NSCS)with negative charge was synthesized and used as a fluorescent probe for long-term cell tracing.FL spectroscopy and UV-vis spectroscopy indicate that TPE-NSCS has excellent AIE property,stability and water-solubility in wide pH ranges.FL microscope and confocal laser scan microscopy(CLSM)show the outstanding capacity for cell tracing to 30 passages.Secondly,a novel water-soluble fluorescent bioconjugate(TPE-TMC)with positive charge was synthesized and used as a fluorescent probe for long-term cell tracing.FL spectroscopy and UV-vis spectroscopy indicate that TPE-TMC has excellent AIE property,stability and water-solubility.FL microscope and CLSM show the superb capacity for cell tracing to 25 passages,which is superior to TPE-NSCS due to the surface charge.Finally,the water-soluble AIE bioconjugate TPE-CS was used for quantitative detection of Cu(?).The FL intensity of TPE-CS is obviously decreased for the Photoinduced Electron Transfer(PET)effect.FL spectroscopy shows the quenched FL intensity of TPE-CS was proportional to the concentration of Cu(?)in the range of 5 to 100 ?mol/L,which could be used to quantitatively detect Cu(?).