Design,Synthesis And Application Of Novel Mitochondrial-targeted Viscosity Fluorescent Probe

Viscosity is one of the most important microenvironments in human cells.Intracellular viscosity is an important index affecting the health status of cells,and it influences vital physiological processes such as the diffusion of intracellular substances,macromolecular interactions,and signal transmission.Mitochondria,as one of the most essential sources of energy in cells,plays a significant role in the process of aerobic respiration.Some stimulations could result in alterations of mitochondrial microenvironment such as viscosity,p H,and polarity.Abnormal changes of mitochondrial viscosity have been proved to be related to some diseases.Therefore,monitoring viscosity changes in mitochondria is of great significance in the fields including biochemistry,cytology,and clinical medicine.The traditional viscosity measurement instruments are only applicable to the viscosity measurement of macroscopic liquid.These instruments mainly contain capillary viscometers,rotary viscometers,and falling ball viscometers.However,they are unable to measure the viscosity in living cells.In recent years,due to the rapid development of fluorescence confocal imaging technology,the visualization of intracellular viscosity becomes possible.In this dissertation,we designed two novel fluorescent probes based on twisted intramolecular charge transfer(TICT)mechanism to monitor the viscosity changes in mitochondrial physiological processes.The studies include the following two parts:(1)A novel water-soluble fluorescent probe called BQL with mitochondria targeting function was designed,synthesized,and applied for monitoring mitochondrial viscosity.The fluorescence emission wavelength of BQL was 560 nm.BQL demonstrated a large Stokes shift(128 nm),a good response to viscosity change,and a good anti-interference ability towards p H,polarity,and other substances.Moreover,BQL was used to monitor viscosity changes in mitochondria induced by ion carriers,and also used to detect viscosity in real time during mitophagy.Therefore,BQL could be a good tool for the analysis of viscosity change in organism.(2)A novel water-soluble near-infrared fluorescent probe called JLQL was designed and synthesized.Compared with BQL,JLQL was improved in terms of fluorescence emission wavelength and response sensitivity.The probe had a maximum fluorescence emission at 735 nm,the large Stokes shift of 135 nm,and a maximum fluorescence enhancement up to 175 times with the increase of viscosity.The probe could also resist interference from other microenvironments such as p H and polarity as well as from other analytes.Moreover,JLQL could be used for the viscosity detection of the real lactulose oral solution samples.The method could also be applied for monitoring sensitively and specifically the change in mitochondrial viscosity in different states induced by monensin or nystatin.Therefore,JLQL could be a visual tool for monitoring viscosity change in mitochondria.