Design,Synthesis And Sensing Properties Of Fluorescent Cd²⁺ Probe For Biological Application

Cadmium ion is a kind of heavy metal ion with serious physiological toxicity.When the water is polluted by Cd2+,it can easily enters the human body through the food chain and causes serious physiological toxicity.It is of great practical significance to develop Cd2+ fluorescent probes which can be real-time,dynamic and suitable for actual water samples and biological samples.In this paper,porphyrins with excellent optical properties were selected as signal groups and 2,2’-dipicolylamine(DPA)with special recognition effect on Cd2+was used as recognition groups,has designed and synthesized three kinds of water-insoluble probes(PD/cis-PD2/trans-PD2)to realize the detection of Cd2+in CH3OH/Tris-HCl(v/v,1/1)mixed solution.Through the experiments of coordination ratio,kinetics,sensitivity and selectivity,we have explored the detection process of Cd2+ in the three probes.The results show that the the fluorescence spectra of three fluorescent probes have a quick"turn on" response to Cd2+,a detection limit of 1×10-8 M and no interference from other metal ions.In order to expand the application scope of the probe,three water-soluble probes(PDS/cis-PD2S/trans-PD2S)were obtained through adding sulfonic acid groups into the probe molecule to change its water solubility,thus achieving high sensitivity and selectivity for Cd2+ recognition in pure aqueous solution syste,The results show that the response of the three probes is different when Cd2+is added into PDS probe solution.Among them,the PDS probe shows a "turn on" growth,while the CiS-PD2S and trans-PD2S show a ratio growth.In the view of the sensitivity point,the detection limit of water-soluble probe and non-water-soluble probe is the same,which meets the minimum detection limit of Cd2+in water(c<0.1 mg/L)and benefits to detection of Cd2+in water.Compared with non-water-soluble probe,the binding speed of three fluorescent probes with Cd2+is reduced,but it can also react completely within 60 seconds.Finally,all probe molecules were applied to A549 cells for toxicity determination and imaging research.MTT showed that all six fluorescent probes had less cytotoxicity,and water-soluble probes had much less toxicity than non-water-soluble probes.Cell experiments showed that all six fluorescent probes could enter cells and achieve fluorescence imaging of Cd2+ in cells.