Preparation Of Electrochemical Sensor Based On Magnetic Ferrous Material Immobilized E.coli In Detection

ObjectiveUnder the background of the development of science and technology,more new detection technologies are invented by people.However,instruments with high sensitivity and precision often need expensive prices,most laboratories can not meet the requirements of detection.Therefore,it is of great significance to develop a cheap and convenient detection technology.Microbial sensors are biosensors that take microorganisms as identification elements and convert respiration or metabolic changes of microorganisms into electrical signals.They have the advantages of high sensitivity and simple operation.This paper attempts to develop a low-cost and easy-to-use detection technology by combining magnetic nano-materials with microbial sensors with excellent biocompatibility.Fe₃O₄/PVA composite materials are prepared by mixing magnetic iron materials(Fe₃O₄)with polyvinyl alcohol(PVA)and E.coli is immobilized in the composite materials by embedding method and crosslinked with supersaturated boric acid to prepare granluar Fe₃O₄/PVA/E.coli biocomposite material.Combined with electrochemical technology,the preliminary exploration of biological detection in different domain is realized.MethodIn this study,Fe₃O₄was synthesized by coprecipitation method and characterized by Fourier transform infrared spectrometer,X-ray diffractometer and scanning field electron microscope.The Fe₃O₄/PVA/E.coli composite particles were prepared by ultrasonically mixing Fe₃O₄and PVA,using E.coli as the biological component,fixing it by embedding method,and crosslinking with saturated boric acid.Combined with electrochemical detection technology,potassium ferricyanide is used as a mediator to transport electrons generated by respiration of microorganisms,and the activity change of microorganisms is determined by detecting the current change generated by oxidation of reduced potassium ferricyanide on the electrode surface again.The optimal preparation conditions of Fe₃O₄/PVA/E.coli composite biomaterial were selected by single factor test and orthogonal factor test.The factors investigated included:crosslinking time of composite particles,p H of saturated boric acid,correlation between crosslinking time,mechanical stability of the material and influence of storage conditions.The optimized Fe₃O₄/PVA/E.coli has been widely used in biological detection of toxicants,Surface water,pesticide residues and antibiotics.Results(1)Fe₃O₄nanoparticles prepared by coprecipitation method are bright black spheroids with a little agglomeration phenomenon.The purity of Fe₃O₄nanoparticles is high and meets the requirements of experimental conditions.(2)Fe₃O₄/PVA/E.coli biocomposites have the highest activity when Fe₃O₄uses 2 g/L saturated suspension,PVA concentration is 6%and the optical density value(OD₆₀₀)of immobilized E.coli at 600 nm is 14.Through the comprehensive investigation of orthogonal test and single factor test,the optimal conditions for preparing Fe₃O₄/PVA/E.coli are obtained as follows:the optimal p H is saturated boric acid solution(3.48);The best crosslinking time is1 h.The Fe₃O₄/PVA/E.coli prepared at this time not only has good mechanical strength(ball breaking rate is 0),but also has a biological activity of 77.7%after being stored at 4?for 30 days.(3)The spherical Fe₃O₄/PVA/E.coli composite materials prepared under optimal conditions are selected for multi-field biological detection.The concentration of conventional poison(DCP)at 50%inhibition(IC₅₀)was 30.32mg/L;When the mother liquid dilution multiple was 3659 times and 272 times,the biosuppressing rate was 50%,the corresponding active ingredient content was 0.012‰?0.092‰and the inhibition rate was negative when the effectiveness test of gentamicin and amkacin was negative.ConclusionsIn this experiment,spherical-like Fe₃O₄nanomaterials were successfully synthesized by coprecipitation method and used in the preparation of Fe₃O₄/PVA/E.coli biocomposites.The results show that the material is suitable for monitoring and detecting the toxicity of conventional poisons and water quality,but further exploration is needed in the field of drug sensitivity.Combining the advantages of Fe₃O₄/PVA/E.coli,such as simple preparation,low price of raw materials,long storage period and the unique advantages of electrochemical detection method,such as fast,simple and portable,the electrochemical sensor based on Fe₃O₄/PVA/E.coli developed by this research has certain application potential in the fields of chemical toxicity assessment,water environment on-site detection and pollution early warning.