Preparation And Properties Of Enzyme Membrane For Uric Acid Electrochemical Biosensor

The rapid and accurate detection of uric acid is of great significance in the field of clinical medicine.In this paper,nitrocellulose membrane(NCM)with good biocompatibility,high mechanical strength and three-dimensional pore structure was selected as the basement membrane and uric acid oxidase(UOx)as a biometric element to construct a membrane-based uric acid electrochemical biosensor.The enzyme membrane has the characteristics of removable,repeatable use and so on.In order to further improve the response time and detection sensitivity of the enzyme membrane,the uricase nitrocellulose membrane was modified by 1-butyl-3-methylimidazolium tetrafluoroborate and multi-walled carbon nanotubes.The main research is divided into the following three parts:1.In this thesis,NCM was used as the basement membrane,and UOx mixed with glutaraldehyde on NCM to prepare an enzyme-type electrochemical uric acid biosensor for UA highly sensitive,rapid and accurate detection.In order to maximize the activity of UOx,the UOx and glutaraldehyde concentrations of the membrane were optimized by using a single variable method,after that the optimum test conditions were obtained,mainly include the pH and test voltage were optimized.Based on the above optimization,the electrochemical performance of the uricase nitrocellulose membrane was tested,the linear range of the uricase nitrocellulose membrane was 0.05-8.32 mmol/L,the response time was 100 s,the sensitivity was 1.85 ?A/(mmol/L),Kmapp = 3.02 mmol/L,the uricase nitrocellulose membrane could be stored for a long-term stability of 7 weeks(maintain 70%and above of initial response).2.In order to further improve the performance of the uricase nitrocellulose membrane,[BMIM]BF4 was added and used for the modification of uricase nitrocellulose membrane's performance.[BMIM]BF4 has good conductivity and is miscible with UOx when existing as liquid at room temperature,and it could be loaded on the NCM uniformly.We researched the optimum preparation and optimum test conditions of[BMIM]BF4 modified uricase nitrocellulose membrane and tested the electrochemical performance and stability of the modified uricase nitrocellulose membrane.Additionnaly,the action mechanism of[BMIM]BF4 was explored.The results exhibitied that the addition of[BMIM]BF4 improved the conductivity,sensitivity and stability of the enzyme membrane and shortend the reaction time.The electrochemical performance of[BMIM]BF4 modified uricase nitrocellulose membrane was as follows:linear range:0.005?7.053 mmol/L,response time:30 s,sensitivity:3.645 ?A/(mmol/L),Kmapp = 1.16 mmol/L,the enzyme membrane long-term storage time of 14 weeks(maintain 70%and above of initial response).3.In order to improve the conductivity of the enzyme membrane,we used MWCNTs to modify it.As a kind of carbon nanomaterials,MWCNTs could be used as electron transport channels which can speed up the electron transfer rate.We studied the optimum preparation conditions and optimum test conditions of MWCNTs modified uricase nitrocellulose membrane and tested the electrochemical performance,selectivity and stability of the modified enzyme membrane respectively.The results show that the addition of MWCNTs improves the conductivity,sensitivity and response time of the modified enzyme membrane.The electrochemical performance of MWCNTs modified uricase nitrocellulose membrane was as follows:linear range:0.005?7.615 mmol/L,response time:30 s,sensitivity:3.919 ?A/(mmol/L),Kmapp =1.08 mmol/L.In this thesis,we researched the detailed preparation process of electrochemical uricase nitrocellulose membrane biosensor.The preparation process is a guide for the industrialization of enzyme membrane biosensor.