| Food safety is one of the livelihood issues,and is closely related to people’s lives.Escherichia coli O157:H7 is a typical pathogenic bacterium.However,most E.coli testing laboratories cooperate with professional technicians.How to carry out large-scale,fast and easy to operate E.coli detection is an urgent problem to be solved.In this paper,cyclic voltammetry is used to detect the relationship between the concentration and current of E.coli,design and construct an electrochemical integrated immunoassay platform,and propose a rapid detection method based on electrochemistry and embedded microcontroller STM32.The main work is as follows:according to the functional requirements of the system,established the overall design scheme.The binding degree of Escherichia coli O157:H7 to antimicrobial peptides and antibodies at different concentrations and temperatures was studied.Through the experiment,it is found that temperature and concentration will have a great impact on the experimental results.The influence of these parameters on the experiment is studied,and the optimal conditions for the reaction are summarized.Cyclic voltammetry was used to explore the quantitative relationship between E.coli concentration and current,which laid a foundation for the subsequent work.The electrochemical biosensor was designed and the electrochemical horizontal immunoassay platform was prepared.An embedded detection system based on STM32F407 chip is designed.A set of APP software with perfect functions is developed,which can realize the functions of underlying communication,automatic data storage,result discrimination and so on.The detection system mainly consists of three parts:electrochemical integrated lateral flow immunoassay platform,embedded detection system and mobile APP function module.The electrochemical horizontal immunoassay platform consists of sample pad,binding pad,test strip,absorption pad and screen-printed electrode.The sample pad can absorb the drip added E.coli O157:H7 solution.The combination of the pad and test strip provides an electrochemical reaction environment for the platform,and the screen-printed electrode provides a current loop.Embedded detection system integrates detection,analysis and communication functions,which can realize data detection,processing and sending,including I/V conversion circuit,filter circuit,A/D conversion circuit,system power circuit,main control module and so on.The I/V conversion circuit can amplify the current signal output by the electrochemical integrated lateral flow immunoassay platform into a detectable voltage signal.The filter circuit can improve the signal-to-noise ratio and reduce the experimental interference.A/D conversion circuit can convert the analog signal to the digital signal recognized by the main control chip.The main control module uses STM32microcontroller as the bottom control center,which controls the operation of embedded system and transmits real-time information with mobile APP.The mobile APP function module is based on Android studio to develop human-computer interaction interface,including one main functional interface and five sub-menus functional interface.The software is embedded with data processing and result discrimination model,which enhances the automatic analysis ability of the system.After testing,the linear detection range of the system is 10~2-10~9 CFU/m L,the lowest detection concentration is 10~2 CFU/m L,the detection error is less than 4.5%,and the system repetition error is less than 4%.In the optimization of system performance,the wavelet algorithm software processing is carried out to reduce the influence of basic noise of the system.The system uses baseline drift,curve crest calibration and reconstruction algorithms to reduce the specific errors of the system,and uses MATLAB data fitting to establish a discrimination model.All of the results show that the system can be effectively used for the detection of Escherichia coli. |
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