Design, Synthesis And Application Of Novel Rhodamine - Based Metal Ion Fluorescent Probe

Heavy metal ions as an important component of pollution in water and soil due to its non-biodegradable characteristics, especially combined with biological organic compounds in the body, it will causes a larger destruction, resulting the body function disorder, produce a series of damage effect. Therefore, in the monitoring of heavy metal content in environment plants and animals is of great significance. In this paper, we used rhodamine as the fluorescence chromophore, then synthesis of a series of selective fluorescent probe RT1-RT6 to Hg2+ and Pd2+, and we chosed RT1-RT4 applied for vitro imaging in living cells and potentially in vivo.Firstly, a new rhodamine B derivative RT1 has been rationally designed and synthesized facilely by the condensation reaction of rhodamine B hydrazide and o-phthaloyl chloride. The recognition properties of the target compound RT1 with metal ions had been investigated by the FS and UV properties. This probe exhibit several favorable features, including instantaneous and reversible recognition, high sensitivity and selectivity to mercury ions. When the concentration of Hg2+ was in the range of 4x10-89×10-8 mol/L, there was a good linearity between the fluorescence intensity and the concentration of Hg2+. The fluorescence imaging experiments of Hg2+ in HepG2 living cells demonstrated their valuable application in biological system.Secondly, Compounds RT2 to RT6 were synthesised from RhodamineB, etc as the starting materials. We studied the optical properties of the compounds through UV and FS. The results show that probes RT2-RT6 have good selectivities to Pd2+. Between the appropriate concentration of probes, the intensity of fluorescent has a good linear relationship with the concentration of probes. In the experiment, we saw that when the ions in solutions up to 20μM the absorption of UV and the intensity of fluorescent also increased gradually. The curve of titration showed a smooth and steady increased, and about 1.0 equiv of Pd2+ was required until a plateau was reached. The Job’s plot experiment indicated that RT2 to RT6 chelate Pd2+ with a 1:1 stoichiometry. We further studied the appropriate range of pH. This observation suggested that emission intensity of probes almost unaffected by pH in the range of 4-8, and these will be very important to the applications in both environment and living cells.Thirdly, To further demonstrate the practical applicability of the probe in biological samples, fluorescence imaging experiments were conducted in HepG2 living cells. The results suggested that probe RT1 to RT4 can penetrate the cell membrane efficiently and can be applied for vitro imaging in living cells and potentially in vivo.