Research On Automatic Detection System Of Escherichia Coli In Aquaponics Water

The Escherichia coli O157:H7 is a common waterborne pathogen that can not only cause disease through contaminated aquatic environment to fish,but also cause food safety problems through internalization of contaminated irrigation water to the edible parts of hydroponic vegetables.Therefore,the detection of Escherichia coli O157:H7 in a green and efficient aquaponics production model is the key to control aquatic diseases and ensure the food safety of agricultural products.The existing Escherichia coli O157:H7 detection methods have some problems such as complicated operation steps,long detection time and low automation.Accordingly,this paper combines analytical chemistry,microfluidic technology,immunomagnetic separation technology and electronic information technology to innovate a microfluidic colorimetric biosensor for the rapid,sensitive and specific automated detection of Escherichia coli O157:H7 in aquaponics water,which ensures the disease prevention of aquatic products and the food safety of agricultural products under the green and efficient production mode of aquaponics.The main research contents and results are as follows:（1）A colorimetric biosensing method was constructed for the detection of Escherichia coli O157:H7.Synthetic immunomagnetic beads and immune platinum nanoenzymes were reacted with the target bacteria to form"immunomagnetic beads-target bacteria-immune platinum nanoenzymes"double antibody sandwich complexes,and the specific separation of the target bacteria from the sample background was achieved under the action of magnetic field.The platinum nanoenzymes bound to the bacteria mediates the color display of the catalytic TMB-H₂O₂ reaction,and the normalized spectral value of the AS7265x spectral sensor at the 645 nm band is applied to reflect the light absorption capacity of the colored solution,which leads to the concentration of the target bacteria.In addition,the use of plastic optical fibers to conduct incident and reflected light reduces the loss of light in the transmission process.（2）A microfluidic chip for Escherichia coli O157:H7 detection was developed.A"pearl chain"microfluidic chip integrating injection,mixing,incubation,separation and detection was designed and fabricated to address the problem of complex pre-treatment in the bacterial detection process.The Comsol fluid simulation and actual test results show that the microfluidic chip has high mixing efficiency,good magnetic separation performance and strong bonding quality,and can complete the whole process of target bacteria detection on a chip.（3）An automated device for the detection of Escherichia coli O157:H7 was integrated.The STM32F103ZET6 microcontroller-based portable optical detection device uses a precision peristaltic pump to control the microfluidic chip fluid and automate the sample feeding,mixing,incubation,cleaning,catalysis and detection operations to achieve an automated"sample in-result out"detection process.The biosensor was able to quantify Escherichia coli O157:H7 in the concentration range of 5×10¹～5×10⁶ CFU/mL within 50 min with a minimum detection limit of 17 CFU/mL by optimizing the parameters,and has good specificity and practicality.