Design,Synthesis And Application Of Novel Environmental Sensitive And Small Molecule Fluorescent Probes

Fluorescent sensors have been widely used in daily life,environmental monitoring and medical research because of their high sensitivity,specific selectivity and low cost.In this paper,Based on the special molecular rotors,the environmentally sensitive probe was designed to detect the viscosity of living cells and a formaldehyde probe was designed to detect the low concentration of formaldehyde in real time in living cells.Finally,we successfully screened out formaldehyde fluorescence probes with high selectivity to formaldehyde through the combination of ICT and ESIPT.The main contents are as follows:Firstly,Subcellular viscosity is essential for cell functions and may indicate its physiological status.In this work,we screen two fluorescent probes by engineering tetraphenylethene(TPE)for measuring viscosity in mitochondria and lysosomes,respectively.These two probes are only weakly emissive in nonviscous medium and the emission signals are greatly enhanced in viscous medium due to the restriction of intramolecular motion.The presence of pyridium has endowed one probe with mitochondrial specificity,while the presence of indole ring has granted the other probe with lysosome-targeting ability.Their optical properties are characterized in vitro and their applications in imaging viscosity variations in mitochondria and lysosomes are also demonstrated in living cells under different stimulated processes.In addition,an increase in both mitochondrial and lysosomal viscosity during mitophagy was revealed for the first time with our probes.To our knowledge,this is the first time that TPE is engineered to be fluorescent molecular viscosimeters that possess desirable aqueous solubility,red-shifted emission and organelle specificity.Secondly,In this work,a series of fluorescent molecular probes on a rotor mechanism have been designed and synthesized,and their optical properties are characterized in vitro.After screening,Lyso-VR and Mito-VR2 are selected as two-color viscosity probes for simultanious lysosomal and mitochondrial imaging in live cells,since they are hardly emissive in non-viscous medium but highly fluorescent in viscous environment due to the restriction of intra-molecular motion.For both probes their fluorescence intensity is solely related to the environmental viscosity affording a linear relationship between the logarithm values.And their coincident absorptions but well-separated fluorescent emissions make these probes ideal for two-color labeling.Other advantages of the probes include good selectivity and stability,membrane permeability,no color crosstalk effect,and low toxicity as observed by MTT assay.All these merits render this protocol a valuable extension on mitochondrial and lysosomal related investigations,and by using probes Lyso-VR and Mito-VR2 the biologically important process of mitophagy can be conveniently monitored,in which an elevating viscosity is observed during the formation of autophagosomes and autolysosomes.This is the first protocol ever reported to monitor mitophagy by using two-color viscosity probes with desirable aqueous solubility,far separated emission and organelle specificity.Thirdly,In this work,we develop a new activatable fluorescence probe for highly selective visualization of FA in living cells.Our probe(Naph-1)is designed using a naphthalene derivative as the fluorophore and hydrazone as a recognition site for FA.Naph-1 is essentially nonemissive.After reacting with FA,the amine moiety is converted to a Schiff base with electron-withdrawing ability and the fluorescence is simultaneously turned on due to synergetic intramolecular charge transfer and favoured excited state intramolecular proton transfer effects.Naph-1 displays a large Stokes shift upon reaction with FA.Furthermore,it possesses high selectivity and superior sensitivity toward FA with an estimated limit of detection of 0.35 ?M.Moreover,Naph-1 is also successfully applied to image both endogenous and exogenous formaldehyde in living cells.These features demonstrate that Naph-1 hold a great potential in detection and imaging of formaldehyde in biological systems.Fourthly,Formaldehyde(FA),as a reactive carbonyl species and signaling molecule,plays an important role in living systems.Here a FA-responsive probe with fast response and great selectivity is designed based on aggregation induced emission(AIE).The probe is prepared by functionalizing tetraphenylethene(TPE)with two amine groups.FA is detected based on the solubility differences between the amine functionalized TPE and the corresponding Schiff bases after reaction with FA.The probe exhibits a limit of detection of 40 n M and a response time of ~90 s.Furthermore,its ability to detect both endogenous and exogenous FA is demonstrated in living cells with high specificity.Moreover,the probe is also introduced to image endogenous FA in real time with fast response.These results suggest that our probe holds great potential for tracking FA in living systems under various physiological conditions as well as related biomedical applications.