Construction And Application Of Whole Cell Bioelectrochemical Sensor For Detecting Trimethylamine Oxide

Biosensors are mainly composed of recognition elements,conversion elements,and signal amplification conversion elements.Bioelectrochemical sensors that use electrical signals as input signals for signal amplification conversion elements are one of the important applications of microbial electrochemical systems.It has strong characteristics,convenient operation,simple composition,low cost,wide application range,and no biological toxicity.It has shown its potential in the fields of environmental monitoring,biomedicine,food analysis,and defense and military,and has attracted researcher's attention at home and abroad.How to improve the analytical performance such as the detection range and sensitivity of biosensor detection is a key problem in biosensor related research.Improving the electronic transfer efficiency of the system is considered to effectively improve the sensing performance of the biosensor.Therefore,in this thesis,we chose the disease-related compound trimethylamine oxide,which can be reduced by Shewanella Onedensis MR-1,as the determinand.The feasibility of whole cell bioelectrochemical sensors for the analysis and detection of trimethylamine oxide was studied,and the effect of nanomaterial modified electrodes on the electron transfer efficiency between electrodes and microbial cells was further explored.New electrode materials are being explored in the application of whole cell bioelectrochemical sensors to detect trimethylamine oxide.Firstly,a whole-cell bioelectrochemical sensor with Shewanella Onedensis MR-1as a recognition element was constructed for the study of detecting trimethylamine oxide.According to the characteristics of the electrogens Shewanella Onedensis MR-1,it can pass through electrons from redox reactions with some substrates by its own electron transfer chain and then the electrons can be displayed in the form of electrical signals.A three-electrode system is used to construct a whole-cell bioelectrochemical sensor,which is used to detect trimethylamine oxide.The effects of bacterial state and bacterial solution concentration on it's output signals wereexplored.To obtain the best detection effect,the culture time of Shewanella Onedensis MR-1 reached 18 h,the sensor system bacterial liquid OD600 = 6.0,and the three-electrode system was allowed to stand for 48 h before detection.Under the optimal operating conditions,the linear range,stability,and repeatability of the sensor were examined.The minimum detection limit for detecting trimethylamine oxide was10 ?M.When the detection range was between 10 ?M and 2 mM,the linearity of the correlation equation is y = 6.141 x + 91.511,and the correlation coefficient reaches0.9985.Taking the first sample as the standard,the peak area of the current response peaks within 91.42% ~ 105.77% within 35 consecutive samples.Within 8 days after the start of the test,the peak area fluctuates between 92.92% ~ 111.11%.Dimethylamine,trimethylamine,glucose and citric acid cannot cause significant interference to the current response curve.It shows that the constructed sensor can detect trimethylamine oxide with repeatability,stability and specificity.A new graphene-polyaniline composite modified carbon cloth electrode was prepared by electroplated graphene and in-situ polymerization deposition of polyaniline,and characterized by XRD,Raman spectroscopy,and Scanning Electron Microscope.The method was used to characterize and analyze the electrochemical performance of composite nanomaterial modified electrodes,and further applied it in microbial fuel cells to explore its effect on the efficiency of electron transfer between microorganisms and electrodes.The results show that the graphene-polyaniline composite modified electrode can significantly increase the specific capacitance compared with the carbon cloth control,and the internal resistance of polarization is reduced by 33.33%.The maximum output efficiency of the MFC on the composite modified electrode is 10.59 times that of the control group.The results show that modified electrodes can effectively improve the efficiency of electron transfer between microorganisms and electrodes.A graphene polyaniline modified electrode was used to construct a whole-cell bioelectrochemical sensor.The current signal intensity,current response curve peakarea,and peak width of the blank carbon cloth group were increased by 27.21%,51.01%,and 22.02% respectively;the sensor of the new composite electrode The corresponding current response curve noise peak intensity and noise peak area corresponding to the blank carbon cloth group increased by 35.9% and 75%.Such exploration shows that the new graphene polyaniline electrode can effectively improve the intensity of the current response signal and the peak width and peak area of the current peak of the whole cell bioelectrochemical sensor,but at the same time,the intensity of the noise peak and the area of the noise peak also increase significantly.This provides guidance for the use of nanomaterials to modify sensor electrodes.Increasing the efficiency of electron transfer while reducing the intensity of noise will more effectively improve the detection capability of biosensors.In summary,the paper successfully constructed a whole-cell bioelectrochemical sensor that can be used for the analysis and quantification of trimethylamine oxide,and prepared a new type of graphene polyaniline modified carbon cloth electrode that can effectively improve electron transfer.The electrochemical sensor can effectively improve the signal intensity of the current response curve.The conclusions obtained in this paper have guiding significance for the new quantitative detection method of trimethylamine oxide and the improvement of the detection ability of biosensors for quantitative detection of substances.It can be further applied to the quantitative detection of trimethylamine oxide in practice.It is of great significance for trimethylamine oxide-related disease detection.