New Chemiluminescent And Electrochemical Methods For Detection Of Some Biomarkers

One of the most brilliant sensitive methods for the detection of important analytes in biological fluids is chemiluminescence(CL).CL is a light-emitting process that occurs as a result of a chemical interaction between luminophore and its coreactant without utilizing an outer light source.The most common advantages of CL are rapidness,cheapness,sensitivity,selectivity,wide linear ranges,and controlled emission.Since 1928,most of the developed CL systems have been utilized hydrogen peroxide(H2O2)and dissolved oxygen(DO)for the development of luminol and lucigenin CL systems.These developed CL systems suffered from poor selectivity as well as weak system stability due to H2O2 and DO can interact with several transition metal cations,besides the instability of H2O2.Thus,it is highly demanded to propose new coreactants for different types of CL luminophores with excellent selectivity as well as good stability to extend the scope of their analytical applications.In this dissertation,we mainly focused on the establishment of new CL systems having different detecting applications.We proposed new coreactants for different kinds of luminophores(luminol and lucigenin)for the construction of new CL systems.Also,we fabricated a novel,selective and simple electrochemical probe for the assay of biothiols(cysteine,glutathione and homocysteine)in human plasma.The followings are the key points:1.Luminol-silicotungstic acid(STA)CL system has been introduced for the first time as a new CL system.The proposed luminol-STA system gave notable CL improvement(65 times)over the old luminol-H2O2 CL system.This CL enhancement is attributed to tungsten trioxide(strong oxidizing agent)that was produced from STA.Interestingly,uric acid could quench the CL intensity of the developed method,thus the new CL system was employed for the sensitive and selective assay of the pure state of uric acid(LOD=0.75 nM)and in real human urine with acceptable recoveries(99.6-102.3%).Moreover,this CL system was used for the effective determination of STA(LOD=0.24μM).2.In the analytical area of developing sensitive and selective CL platforms having numerous sensing properties,we proposed lucigenin-pyrogallol(PG)CL system for the different sensing applications(environmental and biological applications).PG could enhance lucigenin CL intensity 190 times over the H2O2.Notably,cobalt ion and tyrosinase can inhibit lucigenin-PG CL intensity.Based on these phenomena,the established CL system has been used for the multiple determination of PG(LOD=0.94 μM),lucigenin(LOD=0.42μM),cobalt(LOD=68 nM),and tyrosinase(LOD=1.8 μg/mL).Furthermore,the established system has been employed for the assay of PG,Co2+,and tyrosinase in coffee,lake water,and human plasma,respectively.3.We reported a novel and simple structure electrochemical probe for the selective detection of biothiols.The developed probe is based on using 2,4-dinitrobenzenesulfonyl moiety(DNBS)as an efficient and selective recognition moiety for biothiols detection.The electrochemical probe was successfully fabricated through a facile and one-step reaction between 2,4-dinitrobenzenesulfonyl chloride(DNBS-C1)and p-aminophenol.Biothiols could selectively cleave DNBS moiety through an aromatic nucleophilic substitution(ANS)reaction within 10 minutes to release p-aminophenol which is a highly electrochemical active molecule that can be easily selectively detected by cyclic voltammetry at low potential.The probe has been applied for the assay of Cys,GSH,and Hey with LOD of 1.50,3.48,and 4.67 μM,respectively.Excellent recoveries have been achieved in the range of 95.44-98.71%by the assays of the total biothiols in the human plasma sample.