The Design,Synthesis And Application Of A Series Of Small Molecular Fluorescent Probe For Detection Of Cellular Viscosity

The cells have complex inhomogeneous microenvironment.There are various intracellular organelles and numeric macromolecules such as proteins,lipids,nucleic acids,and sugars in cytoplasm,which made the intracellular microenvironment crowding.The consequences of this crowding in cells may hinder the solute diffusion to influence the key cellular functions,including protein folding,enzyme catalysis,intracellular signalling,intracellular transport,and localization of molecules and organelles,and also caused the microviscosity in the cell varying from one region to another.Therefore,it is helpful to understand physiological activitives and functions in various cellular processes with the fluorescent probes which could monitor microviscosity changes.Mitochondria and lipid droplets(LDs)are two organelles which play important functions in the cells.Mitochondria are semi-autonomous are cytosolic organelles which are crucial for energy production in the form of adenosine triphosphate.They also involve in a plethora of cellular activities including like signalling,cellular differentiation,cell senescence and the controlling of cell cycle and cell growth.The matrix of mitochondria contains high density of enzymes and other proteins,the diffusion of which are severely restricted by the cristae,making it the most crowded aqueous cellular compartment.The dysfuction of mitochondria may cause the composition of mitochondrial matrix,which may change the viscosity of mitochondria.LDs are the lipid storage organelles of all organisms,which consist of a core of neutral lipids surrounded by a layer of amphipathic lipids,such as phospholipids and cholesterol,and proteins.In the aqueous cellular cytosol,LDs are the dispersed phase of an oil-in-water emulsion,which store triglycerides,steryl esters,and andretinyl esters.Therefore,the viscosity inLDs is different from the viscosity in cytosol.The viscosity changes in mitochondria or LDs may have influences on the cellular fuctions in various biological activities.Therefore,monitoring viscosity changes in mitochondrion or LDs could offer more information about intracellular dynamic changes,which may be important for investigating cellular biology.Therefore,we designed and synthesized three fluorescent probes for detection of viscosity changes in mitochondria or LDs.RV-1 was a rhodamine analogue.Compared with classical rhodamine dyes,RV-1 had longer absorption,longer emission wavelength and larger Stokes shift.Its emission wavelength was 655 nm,and its Stokes shift was 82 nm.RV-1 has been successfully applied for dectection of viscosity changes in mitochondria in living cells,zebra fishes and living mice.NV-1 was a merocyanine dye which had longer absorption(644 nm in methanol and 680 nm in glycerol)and near-infrared emission(706 nm in methanol and 719 nm in glycerol),NV-1 could be specifically localized in lipid droplets in the cells.Therefore,it was able to monitor viscosity changes in lipid droplets,and it was also successfully utilized for monitoring the viscosity changes in zebra fishes and living mice.NV-2 was a hemicynanine dye,which had large Stokes shift(172 nm in methanol and 141 nm in glycerol)and near-infrared emission(763 nm in methanol and 744 nm in glycerol).NV-2 could be localized in mitochondria.It was also able to detection of viscosity changes in living cells,zebra fishes and living mice.