Preparation Of Organelle-Targeted Fluorescent Carbon Dots And Their Applications In Biological Imaging

Carbon dots(CDs),as emerging fluorescent nanomaterials,have received increasing attention since first appeared in 2004.Due to the advantages of good photophysical properties,excellent water solubility,light stability,negligible cytotoxicity,easy surface modification,and wide source,CDs have been widely used in biological imaging,medicine,pharmacy,batteries,fluorescence sensing,nanomaterials,environmental detection,and so on.Organelles play a specific and indispensable role in cells.Selective imaging of organelles can reflect the structural and functional characteristics of cells,which is essential for revealing the biological basis,designing targeted delivery systems,and screening therapeutic drugs.This thesis focuses on the application of biological imaging,and constructs fluorescent carbon dots with different organelle-targeted capabilities,which is mainly divided into the following three chapters:Preparation of mitochondrial membrane potential response carbon dots and evaluation of cell viability.Based on the self-polymerization properties of 2,4-dihydroxybenzaldehyde and the mitochondria targeting properties of 1,2,3,3-tetramethyl-3H-indole iodide,the above two substances as the carbon source to prepare functionalized CDs with mitochondria-targeted through the microwave.The CDs can sensitively respond to the change of mitochondrial membrane potential and reflect the cell viability.In healthy living cells with high mitochondrial membrane potential,CDs can selectively target mitochondria;in apoptotic cells with decreased mitochondrial membrane potential,CDs target lysosomes;in dead cells with vanished mitochondrial membrane potential,CDs target nucleus.Three different spatiotemporally organelle distributions(mitochondria/lysosome/nucleus)of the CDs were successfully used for the evaluation of cell viability which caused by carbonyl cyanide chlorophenylhydrazone(CCCP),hydrogen peroxide and autophagy.This study designed the first CDs that can distinguish different cell states.The obtained results provide an important reference and basis for the design and construction of functional CDs and the monitoring of cell states.Preparation of lysosome polar viscosity double response carbon dots and recognition of cancer cell.Based on retrosynthesis analysis,amino group and electronwithdrawing group of 2-hydroxymethyl-5-aminophenylboronic acid,the carboxyl group and electron-donating group of tartaric acid,and the Friedel-Crafts reaction between 2-hydroxymethyl-5-aminophenylboronic acid and tartaric acid,functionalized CDs with lysosome-targeted were synthesized by one-step hydrothermal method.Due to the intramolecular charge transfer(ICT)effect on the surface of CDs,they are sensitive to polarity viscosity and identify cancer cells by the difference of fluorescence intensity and achieve the purpose of distinguishing cancer cells from normal cells.The retrosynthesis strategy of CDs provides a platform for the construction of functional CDs,and its cytology application provides a basis for cancer diagnosis.Preparation of nucleoli-targeted carbon dots and analysis of RNA response.Based on the self-polymerization properties of 2,4-dihydroxybenzaldehyde and the nucleoli targeting properties of 2,3-dimethylbenzothiazolium iodide,functionalized CDs with nucleoli-targeted were prepared through the microwave.Due to the presence of cationic benzothiazolium groups in the CDs,“turn-on” fluorescence signal was achieved between CDs and RNA.The CDs exhibit excellent RNA selectivity and a good linear relationship.The small particle size,polarity sensitivity and RNA response behavior of CDs realized fast and wash-free nucleoli imaging effectively.The CDs provide a powerful tool for elucidating RNA dynamics and basic biological processes,and have valuable value in the visual screening of RNA anticancer drugs and pharmacodynamic evaluation.