Synthesis And Spectral Properties Of Novel NIR Fluorescent Probe For Detection Fluoride Ions And Its Application In Bioimaging

Fluoride ion is one of essential trace elements in the human body which closely related to the human health.In a variety of fluoride ion detection methods,fluorescence sensing is considered to be the ideal technology which has a simple operation,good specificity and high sensitivity.In this paper,a series of OFF-ON type fluorescence probes CyR-Si(3a,3b and 3c)with NIR excitation and emission wavelengths were designed and synthesized,by using hemicyanine skeleton 1,which possesses NIR spectroscopic features,good photostability,and excellent water solubility,as fluorescent chromophores and Si-O bond as the reaction site.The main content is illustrated as follows:1.The hemicyanine skeleton 1 was synthesized from cyclohexanone.Then,a kind of fluorescent substance with hydroxyl was obtained,the whole processes of which undergo the reaction of elimination,retro-Knoevenagel,cyclization and dehydration with resorcinol.Subsequently,by constructing H,Cl and F substituents at the ortho position of the hydroxyl groups,probes 3a,3b and 3c were obtained.The structures were verified by HRMS,1H NMR and 13C NMR.In addition,the calculation methods of the photophysical datas of the probes and other operation steps are briefly described,such as fluorescence quantum yield,pKa and detection limit etc.2.The responses of the probes 3a,3b and 3c to fluoride ions in the solution of DMSO/PBS= 7:3(v/v,0.01 M,pH = 7.4)were investigated.Fluorescence selective and competitive experiments showed that the probes 3a-c have specific selectivity and good tolerance for fluoride ions over other analytes.Fluorescence titration experiments showed that the fluorescence intensity has an excellent linear correlation with the concentration of NaF in the range of 0 to 100 mM(probe 3a),0 to 70 mM(probe 3b),and 0 to 70 mM(probe 3c).The detection limits of the probe 3a-c for F-were calculated to be 0.116,0.061 and 0.152 μM(S/N = 3),indicating that the probes for the fluoride ion detection have a high sensitivity.The response mechanism of the probe to fluoride ion was verified by high performance liquid chromatography(HPLC)and HRMS.The MTT assays show that the probes 3a-c have good biocompatibility at 20 μM,and the imaging effect of fluoride ion in HepG2 cells was remarkble.In addition,the spectral data indicate that the probe 3c has a faster response rate and a stronger fluorescence signal,therefore it was used for the detection of fluoride ions in mice and the minimum fluoride ion detected in vivo was 1 mgF/Kg.