Construction And Application Of Optical Sensing Platform Based On Metal Ion Mimic Enzyme

Metal ionic enzymes possess some outstanding advantages such as simple design,low cost,high stability,and high catalysis.In this thesis,three kinds of optical sensing platforms have been developed by using silver ions?Ag⁺?and copper ions(Cu²⁺)as the mimic enzymes.o-Phenylenediamine?OPD?and 3,3',5,5'-tetramethylbenzidine?TMB?were chosen as the substrate of the catalytic reactions.A fluorimetric analysis platform was thus constructed with the Ag⁺-OPD system for detecting biothiols including cysteine?Cys?,homocysteine?Hcy?,and glutathione?GSH?based on the Ag⁺-OPD system.Another fluorescent sensing platform with Cu²⁺-OPD reaction was developed for the trace detection of quinolones,including nalidixic acid,cinoxacin,ciprofloxacin,and moxifloxacin based on the Cu²⁺-OPD system.Additionally,a visual colorimetric detection platform with the Cu²⁺-TMB system was fabricated for probing ciprofloxacin?CIP?.The main contents are presented as follows:?1?A fluorescence sensing platform has been developed for the detections of biothiols based on the Ag⁺-OPD system?Chapter 2?.It is well established that OPD can be oxidized by Ag⁺to generate fluorescent 2,3-diaminophenazine?OPDox?with a maximum emission peak at560 nm,and the colorless solutions changed to light yellow.The introduction of biothiols would inhibit the oxidation of OPD by Ag⁺due to the strong coordination between biothiols and Ag⁺.The changes of fluorescence intensities obtained in the Ag⁺-OPD system exhibited good linear correlations in the ranges of 0.50-30.0?M for Cys,1.0-45.0?M for Hcy and 0.50-40.0?M for GSH.The detection limits?S/N=3?of Cys,Hcy and GSH were 110 nM,200 nM and 150 nM,respectively.Subsequently,the developed fluorimetric method was successfully applied for the detection of these biothiols in human serum.?2?A turn-off fluorescence sensing platform was developed for the detection of quinolones based on Cu²⁺-OPD sensing system?Chapter 3?.It is well established that Cu²⁺can catalyze the oxidization OPD to generate fluorescent OPDox with a strong fluorescence.The presence of quinolones could inhibit the oxidation of OPD by Cu²⁺due to the strong interaction between quinolones and Cu²⁺ions.As a result,the fluorescence intensities of Cu²⁺-OPD system would decrease obviously in the presence of quinolones.The fluorescence intensity decreases depending the quinolone concentrations could facilitate the determination of quinolones including nalidixic acid,cinoxacin,ciprofloxacin,and moxifloxacin,with the limit of detection down to 50 nM.In addition,the fluorimertic evaluation of the quinolones in human urine was conducted with high detection recoveries.?3?A simple and label-free colorimetric method for ciprofloxacin?CIP?detection has been proposed based on the inhibition of peroxidase-like activity of Cu²⁺ions?Chapter 4?.Cu²⁺ions possess the peroxidase-like catalysis that could catalyze the oxidation of TMB to the oxidized TMB?ox TMB?in the presence of H₂O₂.However,the peroxidase-like activity of Cu²⁺ions could be greatly hindered by CIP due to the formation of CIP-Cu²⁺complexes,resulting in the rational decrease of the solution absorbance together with the color fading.The devloped colorimetric analysis technology with Cu²⁺-H₂O₂-TMB system can allow for the determination of CIP in the linear range of 1.0-200.0?M.