Construction Of Fluorescence Probes For Mitochondrial Polarity And Their Bioimaging Applications

Polarity is a crucial microenvironmental parameter,which can affect various life activities in biological microenvironment,such as the permeability of cell membrane and the conduction of biological signals.Biological cell is a complex system containing a variety of organelles.As an extremely significant organelle,mitochondria not only exhibit important functions including supplying energy to cells and participating in metabolism,but also participate in important biological processes such as cell signal transduction.The structure and function of mitochondria are closely related to neurodegeneration,cardiovascular disease and cancer.Changes in mitochondrial polarity can affect many processes in cell life including membrane permeability,enzyme activity and stability,cell proliferation,metabolic regulation,and cell homeostasis.Therefore,accurately monitoring mitochondrial polarity changes is of great significance.In this paper,based on the current research status of mitochondria-targetable fluorescent probes,we successfully designed and synthesized a series of mitochondria-targetable fluorescent probes.Nile red and flavone that are sensitive to environmental polarity have been selected as the fluorescence platforms.We investigated their spectral properties and biological imaging applications.Firstly,we chose Nile red as the fluorescence platform to design and synthesize a mitochondrial targeted fluorescent probe NRTP for detecting polarity.Probe NRTP had obvious solvation effect,the fluorescence spectrum was redshifted with the increasing polarity of solvent.The compound had the advantages of high fluorescence quantum yield and longer luminous wavelength.The co-localization rate of MTDR was up to 0.89.Therefore,probe NRTP can locate the intracellular mitochondria and measure the mitochondrial polarity of the cells.Secondly,a novel fluorescent probe MT-PL for intracellular mitochondria targeted imaging was synthesized with the hydroxyflavone fluorphore and a mitochondria-targeting group triphenylphosphine.The triphenylphosphine moiety is lipophilic and positively charged,which can specifically bind to the mitochondrial inner membrane with the negative charge established by the mitochondrial membrane potential.The fluorescent spectra and thefluorescent imaging experiments indicate that the probe is suitable for targeted labeling and fluorescent imaging of intracellular mitochondria.