| Brain research has become one of the most hottest research fields and along with thedevelopment of natural science and multidisciplinary, it has been studied deeper and knownbetter and as a result, considerable progress has been made. The U.S. government hasproposed a brain research program in October,2013. The in vivo analysis of neurochemicalsrelated to brain function has drawn extensive attention because it plays an important role inknowing the chemical information in physiological and pathological processes and in thediagnosis and treatment of related diseases. The research of neurochemistry is in relation toanalytical chemistry, life sciences and other subjects. The development of analytical chemistryhas promoted the development of neuroscience, which also returns more opportunities andchallenges to analytical chemistry. Although in vivo microdialysis sampling-onlinevoltammetry methods are relatively mature and have been used most for the neurochemistrystudy, however, there still needs more novel analytical approaches due to the fast developmentof neuroscience. In our opinion, the bottlenecks of analytical science in neurochemistry are toestablish new analytical systems, which can be achieved by the two ways: the innovation ofanalytical method and building new chemical systems, analytical chemistry principles andnew technology based on the latest developments in other subjects, such as materials scienceand biochemistry.Aiming at the key problems mentioned above, this dissertation focuses on thedevelopment of new in vivo analytical approaches. By exploring the application of Fe-basedinfinite coordination polymer (FeCP) and PDMS-based microfluidic technique, we fabricateda colorimetric method based on the FeCP for detecting the glucose in rat brain and also a newmicrofluidic-based online detecting system for the measurements of ascorbate and Mg2+. Thework undertaken here can be summarized as follows:(1) In this work, based on the latest development in materials science, we have prepareda series of electrochemically active infinite coordination polymers (ICPs) by a reaction ofdifferent metal ions with1,1’-ferrocenedicarboxylic acid in an aqueous solution. Themorphologies and structures of the resulting ICPs were characterized and finally FeCP waschosen to be studied further. The electrochemical and chemical properties of FeCP have beeninvestigated carefully and the research finds out FeCP shows bifunctional mediation of H2O2for electrochemical oxidation of H2O2to O2and reduction to H2O. Moreover, FeCP showsdifferent mimetic properties depending on pH. In neutral solution, FeCP exhibits thecatalase-like activity and can catalyze the disproportionation reaction of H2O2, while in acidic solution FeCP has the peroxidase-like activity and can catalytically oxidize the enzymesubstrate TMB. The different mimetic properties of FeCP make it have potential applicationsin the study of in vivo analysis.(2) Based on the different mimetic properties in different pH solution, this work focuseson the catalase-like activity and related application of FeCP in neutral solution. The researchproves that FeCP do have the catalase-like activity and can catalyze the disproportionationreaction of H2O2to H2O and O2. We speculate that the couple of Fe2+/Fe3+in FeCP plays akey role in the mimetic property. Based on the catalase-like activityof FeCP, cobalt porphyrin(CoP) is embedded into multiwalled carbon nanotube/ionic liquid (IL) bucky gel to serve asthe first electrocatalyst to reduce O2to H2O2while FeCP is also embedded into the gel as thesecond catalyst to disproportionate H2O2to H2O and O2. The new born O2was reduced againand as a result, the utilization of O2was greatly improved, evoking an apparent4e-reductionof O2into H2O in neutral media.(3) Based on the different mimetic properties in different pH solution, this work focuseson the peroxidase-like activity and related application of FeCP in acidic solution. Theresearch finds out that FeCP do have the peroxidase-like activity and has excluded thepossible interference from the leaching solution (Fe2+/Fe3+). The optimal condition for theactivity of FeCP is25mM Tris-HCl and0.1M KCl (pH4.0) and the reaction temperature is40oC. Under the optimal conditions, the FeCP as peroxidase mimetic provides a colorimetricassay for H2O2based on the catalytic oxidation of peroxidase substrate ABTS and moreperfect, an analytical platform for glucose detection was fabricated using glucose oxidase andthe as-prepared FeCP. The colorimetric detection method for glucose has good selectivity andlinearity and thus realized the measurements of glucose in rat brain.(4) By integrating microfluidic chip with in vivo microdialysis, we have successfullydeveloped a facile yet effective online electrochemical detecting system for continuous andsimultaneous monitoring of ascorbate and Mg2+in rat brain. Although in vivo microdialysissampling-online voltammetry methods are relatively mature, however, the commerciallyavailable flow cell used in these methods have been limited in the detection of two or morethan two components due to its uniform and unchangeable electrode structure and alignment.This work takes advantage of the designable and flexible cell structures of the microfluidicchip instead of the commercially available flow cell to establish a new system which enablesthe simultaneous measurements of ascorbate and Mg2+to be successfully achieved withoutcrosstalk. The microfluidic chip-based online electrochemical system is very responsive,highly selective, stable, and reproducible and is thus reliable and durable for the continuous and simultaneous measurements of ascorbate and Mg2+in cerebral systems. This study pavesa new avenue to in vivo multiple-neurochemical monitoring in a technically simple andexperimentally designable fashion, which is envisaged to find interesting applications inphysiological and pathological applications. |
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