Molecular Design Of Chitosan - Based AIE Fluorescence Probe And Its Application In Cell Imaging

Chitosan is widely used as medical material because of its excellent biocompatibility, biodegradable and low toxicity. However, the poor water-solubility of chitosan limits the application in the field of drug release and biological monitoring. An effective way to solve this problem is the water-soluble modification of chitosan. Polyethylene modified chitosan is supposed to be an effective way. There are two main ways to get polyethylene modified chitosan:one is to graft the polyethylene onto chitosan through the amino group on C(2) position; while the other is to graft the polyethylene onto chitosan through the hydroxyl group on C(6) position. In these two methods, the second method which has kept the active amino group, making it possible for further modification, and therefore is regarded as the better one.Fluorescence(FL) detection technology, on the other hand, is widely used in the field of bioinstrumentation with many advantages such as high sensitivity and low noise. However, the conventional FL probes are sometimes incapable used for certain occasions because of the notorious aggregation-caused quenching(ACQ) effect. In contrast, FL probes which has the property of Aggregation-induced emission (AIE) would not quench even in a high concentration, they are also highly sensitive and show no FL shift when aggregating.In this thesis, combining the above two kinds of idea, we use chitosan as the main material to prepare FL probe which has the property of Aggregation-induced emission(AIE), and enhance the solubility in water in order to improve the long cycle time.We successfully synthetize the PEG grafted chitosan product through the click reaction, and thus further tetraphenyl ethane(TPE) modified PEG-chitosan FL probe ws synthetized. The excitation wavelength and the emission wavelength of this FL probe is 320 nm and 474 nm, respectively. The MTT experiment results show that this material has no cytotoxicity to the cell of HepG2 and the fluorescence microscope photographs show that the FL probe successfully get into cells and has a good imaging effect.