Research And Design Of Fluorescence Biosensor System

Green food and food safety problem are important problems that affect the quality ofpeople’s life. Food is contaminated by varieties of pathogenic bacteria, such as staphylococcusaureus, Fu’s Shigella, etc., and they would cause serious diseases to human body. It is verymeaningful for food safety and human health to design a simple, rapid and accurate detectionmethod of pathogens in food.On the basis of the development and application of immune nano magnetic beads andquantum dot, a fluorescence biosensor detecting system, which is based on the principle offluorescence spectrophotometer, is designed. It is feasible to detect the pathogenic bacteriacontents indirectly by testing the emission fluorescence intensity values of quantum dot. Thesystem is designed with MCU(Micro Controller Unit) STC89C52as core, combining withoptical, electronic and computer science. The fluorescence signal is conversed to voltagesignal by Si-photodiode, and then amplified and filleted before to the A/D converter. ThroughA/D converting, MCU calculating and displaying on LCD, it realizes the function of real-timedetection and displaying. It also can alarm when transfinite. The main research contents andthe results are as follows:(1) Optical system module was designed with led as light source, G0606M-I photodiodeand I/V circuit converses the light signal to voltage signal.(2) The hardware circuit of the system was designed. System included STC89C52,photoelectric conversion circuit, electrical signal processing circuit, A/D conversion module,LCD display module, keyboard scan module and alarming circuit.(3) The software language was programmed using C51language. The programsconsisted of main program, A/D conversion subroutine, keyboard scanning subroutine, LCDdisplay subroutine, alarming subroutine and data processing subroutine, etc.(4) The system was joint debugged and optimized both software and hardware.C51program is compiled using Keil uVision2microcontroller program debugging software.The system hardware and software was simulated and debugged in the MCU simulationsoftware Proteus, combining with the generated hex procedure. And at last, the most optimal scheme was designed.(5) The mathematical determination model was established. Fluorescence detection wasdone using quantum dots instead of gems. It was concluded that the voltage values werelinearing with the logarithmic of colony, and the mathematical model was solved andverificated. The mathematical model is feasible.Through debugging of the hardware and software and system testing, the fluorescencebiosensor system designed could realize the functions of pathogen detection, calculation andcomparison, display and transfinite alarm etc., and reach the expected goals.