Synthesis And Application PH And Palladium Ion Fluorescent Probe Of Xanthene Derivatives

As an important analytical method,the detection target of fluorescent probe?fluorescent sensor?not only includes small molecules with physiological activity?ROS,NO and RNS,etc.?,biological functional macromolecules?enzymes,proteins and nucleic acids,etc.?and various kinds of anions,but also includes physiological conditions such as pH,temperature,humidity and viscosity.Xanthene dyes,which is a commonly used fluorescent probe precursor molecule,has many advantages such as good light stability,high molar extinction coefficient and high quantum yield.Thus,fluorescent probe based on xanthene dyes has been widely used in food safety,medical diagnosis,environmental pollution testing and other fields.Xanthene dyes generally can be divided into three categories:rhodamine-type fluorescent dyes,fluorescein fluorescent dyes and Rhodafluor fluorescent dyes.In view of the advantages of xanthene fluorescent probe,combined with the important physiological or environmental significance of pH and palladium ion detection,two fluorescent probes with high sensitivity and specificity were synthesized based on rhodamine B and naphthalene fluorescein for pH and palladium ion detection respectively.pH fluorescence probe RBN.Based on the principle of protonated fluorescence quenching and fluorescence resonance energy transfer?FRET?,naphthalimide was connected with rhodamine B through a linker.A fluorescent probe RBN with wide range of linear detection was designed and synthesized.In the range of pH 5.25-8.00,an oxygen atom of naphthalimide,a nitrogen atom of an imino group in the linker and an oxygen atom of rhodamine B ester ring may form a hydrogen bond,resulting in the fluorescence quenching of naphthalimide,thus pH detection with single wavelength(I₅₄₀)was realized.While,in the range of pH of 4.02-4.60,rhodamine B changed into open-cycle forms,FRET between naphthalimide and rhodamine B happened,thus pH detection with the ratio(I₅₇₇/I₅₄₀)was realized.Competitive experiments showed that the detection of pH is not affected by the common cations and cations in the system.Moreover,RBN showed low cytotoxicity and can be used to distinguish normal cells and cancer cells.Compared with the reported pH fluorescent probe,RBN has good water solubility,high selectivity and high sensitivity,overcoming the drawbacks of single fluorophore for pH detection,which provides a reference for the development and application of this kind of probe.Palladium ion probe M-PD.A near-infrared palladium ion fluorescent probe M-PD was designed and synthesized with naphthalene fluorescein as the parent and propynyl groups as the reactive groups.Palladium ion catalyzed the deacetylenil reaction of M-PD to enhance its fluorescence at 668 nm thus achieving near-infrared fluorescence detection of palladium ions.The probe has good water solubility,specificity?independent of other ions in the system?,wide detection linear range?1-70?M?,low detection limit?10.8 nM?and low cytotoxicity,and can be used for intracellular fluorescence imaging of palladium ions,providing an important method for the study of environmental toxicology of palladium ions.