Biomolecular-based Sensors And Their Applications In Heavy Metal Detection And Urinary Citric Acid Analysis

With the development of society and the awakening of health consciousness,issues related to the quality of life,such as environmental pollution,health assessment and so on,have attracted significant attentions all over the world.Simultaneously,the scientific problems derived from these areas have put out higher and higher requirementsof sensing technology in parameters including sensitivity,response time,etc..As a direct and effective sensing method,biomolecular-based sensor,which shows its advantages of fast response,high sensitivity and good specificity,has been widely investigated in the field of environment and health.This dissertation mainly discusses three effective biomolecule-based sensors with highly sensitive and selective biomolecules(DNA and bio-enzymes)as the receptors for ions detection in liquid environment.Firstly,two electrochemical biosensors based on traditional electrochemical electrode and graphene field-effect transistor(FET)array respectively,were constructed by immobilizing single-stranded DNA(ssDNA)onto the sensor surface.On the basis of research of sensing mechanism,the DNA biosensor was applied to the highly sensitive detection of mercury ion in water environment.On the other hand,a flow injection analysis(FIA)system with bio-enzymatic detection and microfluidic chip was proposed for determination of citrate in urine.The design and implementation of the sensing system were described in detail.Moreover,a partial least squares regression(PLSR)model was constructed to improve the detection accuracy of sensing system.The research work in this study was supported by the National Key Basic Research Program(973 Program)and the International Cooperation Foundations Between NSFC-RFBR.The major innovations of this study are listed below:1,A portable electrochemical analysis method based on multi-sensors and intelligent terminal was proposed to realize the rapid on-site detection of various heavy metals in water environmentIn this paper,a portable electrochemical analyzer was designed based on multi-electrodes and intelligent terminal.The portable electrochemical analyzer realized the function of time-sharing detection for multiple working electrodes by sharing the reference electrode and counter electrode,thereby,achieving determination of several heavy metal ions by using different working electrodes and different detection methods.In this system,differential pulse voltammetry,cyclic voltammetry and other electrochemical methods were implemented,and the detection circuit design and corresponding software were also completed.Also,the performance of this sensing system was validated and an on-site test was performed nearby West Lake.These results validated thefeasibility of the smart-terminal-based sensing system for various heavy metal ions on-site detection.2,A novel ssDNA electrochemical sensor was developed for highly sensitive detection of mercury ion in water environment.In this paper,the sensitive sensing mechanism of ssDNA electrochemical sensor was studied,and the "hairpin-like" ssDNA electrochemical sensor was designed and constructed to detect mercury in water environment.The conditions of ssDNA co-immobilization were optimized to improve the efficiency of immobilization.Combined with electrochemical impedance analysis technology,electrochemical response changes of this biomolecule-based sensor,which caused by DNA structural change,could be detected for quantitative detection of divalent mercury ion.With good reproducibility,the ssDNA electrochemical sensor had a detection limit of 0.4 nM and a linear range of 2-10 nM.3,A novel integrated common-source graphene FET array sensor was designed and applied for ultra-sensitive detection of heavy metal in liquid environmentThis paper had conducted a thorough research on the design of a graphene field effect transistor sensor,and then a novel integrated common-source graphene FET array sensor was implemented.Also,the performance of the graphene FET array sensor was discussed according to the related models of FET sensor.Meanwhile,the common-source graphene FET array sensor and a specific ssDNA were used to construct a novel biomolecular-based sensor and the application of the biomolecule-based sensor in the ultra-sensitive detection of mercury ion in water environment was implemented.The results showed that the sensor was highly selective for mercury ions with a detection range from 100 pM to 10 μM and a detection limit of 71 pM.4,An analysis method based on bio-enzyme sensor and flow injection analysis system was proposed to improve the accuracy of urinary organic acid analysis,and the quantitative analysis of urine for disease diagnosis was preliminarily realized.In this paper,an optical flow injection analysis system combining bio-enzyme method and microfluidic chip was used to selectively detect citrate ion in urine samples.The mechanism of the bio-enzyme method for the selective detection of citrate was discussed in detail,and the design and detection method of biomolecule-based sensing system was also described in detail.Also,the biosensing system was used for the selective detection of citrate in urine.Meanwhile,the PLSR model was introduced to improve the accuracy of detection.The concentration of citrate in the biomolecule sensing system ranged from 0.1 mM to 6 mM,and the root mean square error of prediction was 0.40 mM,which satisfied the requirement of medical clinical detection.