| Escherichia coli is the most common bacteria in human and animal intestines.It mainly lives in the large intestine of the body and can be excreted with feces.It is widely distributed in soil and water.E.coli can spread both horizontally and vertically.It mainly causes pneumonia,diarrhea and septicemia in poultry.According to statistics,E.coli causes an average of 400 million US dollars of economic losses every year,seriously endangering human health.At present,the detection methods of E.coli mainly include isolation culture,culture medium detection and immunoenzyme detection.However,these methods are not conducive to the rapid and effective detection of E.Because of the above reasons,this paper combines immunoassay with electrochemical detection.The immunosensor is made of screen printed electrode with the advantages of low cost,good reproducibility and easy mass production.The antigen antibody was fixed on the electrode surface and put into the buffer solution of potassium ferricyanide / potassium ferrocyanide redox pair.The cyclic voltammetric curve and electrochemical impedance spectrum of the electrode treatment results were measured and analyzed by the electrochemical workstation.The detection system of electrochemical method and immunosensor was established to realize the effective detection and instrument design of E.coli.The research contents are as follows:1.The gold electrode was pretreated by screen printing.The 103 CFU/m L Escherichia coli O157:H7antigen was immobilized on the surface of the working electrode by protein A.Immunobinding was carried out with monoclonal antibodies against E.coli O157: H7 at concentrations of 10-3,10-2,10-1,1,10?g/ml.The best reaction concentration of antigen antibody binding was analyzed by AC impedance method.It was determined that 10 ?g/ml of monoclonal antibody solution of E.coli O157: H7 was used to make E.coli immunosensor.2.The electrical characteristics of the antigen concentration of E.coli O157: H7 were studied.The concentrations of 103,104,105,106,107 and 108 CFU / ml of E.The experimental results were fitted with zsimpwin software.The relationship between the concentration of E.coli antigen and the electrical impedance was found.3.The effects of bacillus subtilis and antibiotics on escherichia coli O157 were studied.H7 growth inhibition effect,bacteriostatic drugs will drop on different culture medium in the solution,e.coli using electrochemical workstation for each time period of the culture medium solution test,ac impedance and the measured resistance value into conductance value,mapped the graph,in time and the conductance value changes with different medium solution conductance curve shape difference to judge e.coli O157: H7 drug sensitivity degree,the results showed that the antibiotic than bacillus subtilis antibacterial effect is good.4.Based on FPGA control system,a set of electrochemical detection device for Escherichia coli was designed.The device can judge the concentration of E.coli by detecting the weak current signal generated on the sensor.Connect the immunosensor to the detection device.The current signal of microampere level is detected.After the signal processing,the corresponding current signal waveform will be displayed.According to the change of waveform,the current value corresponding to different concentrations of E.coli solution can be read directly.To establish the functional relationship between the concentration of E.coli O157: H7 and the current value.5.The electrochemical detection device of escherichia coli was tested and analyzed,and the relationship between current value and escherichia coli concentration was modified to make the detection error less than 5%.The detection limit of the device is 1012CFU/m L and 103CFU/m L.At the same time,the detection equipment was used to detect the drug sensitivity of escherichia coli.The detection result is the same as that of electrochemical workstation.All of them showed better antibacterial effect than bacillus subtilis. |
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