Preparation And Characterization Of Phase-change Microcapsule Based On TiO₂ Immobilized Tyrosinase Electrochemical Biosensor

Phenolic compounds are one of the main pollutants in wastewater,and the detection of phenolic compounds is a important issue in the protection of water resources today.Traditional detection methods face the problems of long pretreatment time,cumbersome operation,inability to respond in time and low sensitivity and selectivity.As a new detection method,electrochemical enzyme biosensors have fast response,high sensitivity and good selectivity to detect the phenolic compounds with simple operation.So it has been widely used in the detection of phenolic compounds.Tyrosinase is an enzyme that has a good redox response to phenols and has been widely used by researchers for the detection of phenolic compounds.However,due to the high sensitivity of enzymes to temperature,usually people can only perform detection work within the optimum temperature range,and the enzyme activity will be reduced or even inactivated at low temperature or high temperature.In this experiment,the phase change microcapsules were used as the immobilized carrier of the enzyme to prepare the electrochemical tyrosinase biosensor,which endows the biosensor with the ability of thermal temperature regulation and broadens its operating temperature.In the experiment,n-eicosane with a phase transition temperature similar to the optimum temperature of tyrosinase was used as the core material,titanium dioxide was used as the first shell of the microcapsules to prevent the core material from leaking,and then polypyrrole was introduced as the second shell to improve redox performance of the sensor.The Fe₃O₄ nano particulars with high specific surface area and many active groups are evenly embedded in the polypyrrole shell layer as the main enzyme carrier,and forming a phase change microcapsule with a multi-layer shell structure.The results show that Tyr-Fe₃O₄/PPy@TiO₂@n-C₂₀ MEPCM has smooth micro surface,excellent phase transition properties（ΔH_m=153.1 J/g andΔH_c=149.0 J/g）and thermal cycling stability（<1%enthalpy loss after 100cycles）,the constructed tyrosinase electrochemical biosensor has good electron transport ability and redox performance.And the sensor has a good response to catechol in the range of 20～50℃,and has a higher response current under the thermal temperature regulation of the phase change material.Experiments show that the sensor has a sensitivity of 0.154μA/μM and a detection limit of 2.164μM at a suitable temperature.Through the temperature regulation of MEPCM,the sensor still has a sensitivity of 0.098μA/μM and a detection limit of 3.409μM at 50℃temperature.It shows that the sensor has the detection ability in extreme environments.In addition,the sensor lost only6.3%of its activity during 30-day storage,proving that the sensor has excellent storage stability.The electrochemical tyrosinase biosensor prepared in this experiment has the ability to detect phenolic compounds at a wider range of temperatures.It helps people to detect the phenolic compounds at harsh environment.