Micro-Dispensing Biosensor

Food is essential for human's survival and development.Food safety is related to the people's health and the national interest and the people's livelihood.One urgent and important work in this field is to develop a rapid detection technique with the features of convenience, inexpensiveness and precision because the traditional detection techniques need expensive equipment and are time-consuming and operated difficultly.At present the most widely used rapid detection techniques in food safety include fluorophotometer,rapid detection kit,rapid detection paper,biosensor,and so on.The biosensor is attracting more and more concern as a rapid detection technique for its excellent advantages such as small bulk,low cost,high sensitivity,good selectivity,and rapid responding ability.The research work carried out in this paper would be described as follows:1 Optimizing of micro-dispensing parametersIn this work we fabricated sensors with the help of micro-dispenser. The blockage of the needle in fabricating process and the breakage of the silver conducting circuit could affect the sensors' performance.Under this research on micro-dispensing condition,the optimal parameters were determined as follows:silver paste viscosity 8000～9000CPS,the inner diameter of the needle 0.15mm,dwell time 50～300ms,dispensing pressure 20KPa,the distance between needle and baseplate 0.1mm,and Z axes return distance 0.2～0.5mm.2 The fabrication and characterization of micro-dispensing sensorOn the basis of a three-electrode structure designed on computer with the help of software AutoCAD and Photoshop,we fabricated a biosensor using micro-dispenser after writing a programme into the micro-dispenser system.This sensor,using silver conducting circuit, comprised a Ag/AgCl reference electrode,a working electrode and a counter electrode.The working and counter electrodes were modified with the conducting polymer blend poly (3,4-ethylenedioxythiophene/polystyrene sulfonic acid)(PEDOT/PSS). The sensor was characterized by stereomicroscope,AFM and chemical method based on cyclic voltammetry in 1mmol/L thionine solution by recording the potential of anodic peak,current of anodic peak,and half-wave potential.The reproducibility of the sensor was assessed by these three chemical indicators as well as electron transfer coefficient. Experimental results indicated that the sensors demonstrated good electrochemical performance and reproducibility.3 Micro-dispensing GOD biosensorThe prototype of micro-dispensing GOD biosensor was realized by dispenser on the base of electrode modified with the conducting polymer (PEDOT/PSS),using carboxymethyl cellulose(CMC)solution which contained glucose oxidase(GOD)and potassium ferricyanide. Experimental results showed that the micro-dispensing GOD biosensor had a good response to glucose with an acceptable linear correlation coefficient of 0.9894 in the range of 0.5～5.0 mg/L.The sensor had acceptable reproducibility,stability and accuracy.4 Micro-dispensing HRP biosensorWe fabricated the micro-dispensing HRP sensor to test the performance of the sensor.In this experiment,the prototype of micro-dispensing HRP biosensor was realized by dispensing the horseradish peroxidase(HRP)on the bare sensor coated with the PEDOT/PSS film.As the final sensor construction step,in order to prevent dissolution of the enzyme and the PEDOT/PSS film in the aqueous environment,the device was encapsulated with a water-resistant semi-permeable membrane of cellulose acetate.The membrane was made up by dip-coating the active area in a solution of cellulose acetate in acetone:THF 60:40.Under the electrochemical detection,the experimental results indicated that the micro-dispensing HRP biosensor had a good response to H₂O₂ and an acceptable linear correlation coefficient of 0.9851 in the range of 0.5～5.0 mmol/L.The sensor had good reproducibility,stability and accuracy.