Research On A STM32-based Nucleic Acid Detection System

Presently, disease prevention and treatment is often based on the measurement ofchemical parameters in biological samples such as blood and urine. In most cases, thesamples need to be sent to a central laboratory for analysis by a skilled technician, and theresults of routine tests become available after several hours, sometimes days. Therefore,small, fast and easy-to-operate devices are needed to reduce the costs and to improveefficiencies. POCT (point-of-care testing), compact and flexible clinical chemistry testingdevices move diagnostic testing out of central laboratories into sites closer to the patient toprovide results rapidly. Nucleic Acid Testing (NAT) promises rapid, sensitive and specificdiagnosis of infectious, inherited and genetic disease. PCR provides a simple and elegantmethod for nucleic acid amplification using thermostable polymerase enzymes and acyclic heating and cooling to obtain strand separation and annealing, respectively.Unfortunately, the repeated heating cycles required for PCR necessitate a complex, powerconsuming and bulky design, making micro-scale PCR an imperfect solution forincorporation into POCT platforms. In order to circumvent the limitations of traditionalPCR in the amplification stages, recent research has turned towards the isothermalmethods for nucleic acid amplification. The isothermal nucleic acid methods offer thePOCT diagnostic platforms a powerful tool to amplify nucleic acids without the need forthe additional complexity of thermal cycling steps and the associated control mechanisms.This work combined the loop-mediated isothermal amplification (LAMP) andmicrofluidic technology, and focused on the development of a point of care deviceintegrating PCR amplification, optical detection and thermal control.This work finished the design of nucleic acid detection system based on STM32andmainly contained microfluidic chip, temperature control module and optical module. Thesystem completed loop-mediated isothermal amplification on SlipChip. Microfluidic chipthat adopted SlipChip technology and implemented the flexible operation of micro sampleprovided a platform for nucleic acid amplification. The result was obtained by rotating andreacting, so that it had the advantages of easy to use, fast analytical speed and efficiency.The role of temperature control module was to control the temperature of nucleic acidreaction. In order to simplify and facilitate the commercialization process, contact heatingmethod based on thermoelectric cooler was used, by changing the direction of currentflow of TEC to change the working condition of cooling and heating. The optical module excited the fluorescent dye in the sample and detected the emitted light to determinewhether the target existed.The hardware design of system used STM32F103ZET6which based on the kernel ofCortex-M3as a core processor and realized the temperature acquisition, temperaturecontrol, photoelectric signal detection, LCD display, serial ports, key and other functions.The software design of system used standard peripherals library which greatly improveddevelopment efficiency. Temperature accuracy was the key to the success of nucleic acidamplification. We used the incremental PID temperature control algorithm and PWMtechnology to achieve precise control of temperature and the Genetic Algorithm andParticle Swarm Optimization algorithm for online self-tuning PID parameters.The temperature control solution of this system can carry out accurate control ofnucleic acid reaction temperatures and the system can also detect weak fluorescencesignals online, enabling the portable POCT devices for nucleic acid detection.