Research On Automatic Nucleic Acid Extraction System

With the development of molecular biology,molecular diagnosis has become one of the basic technologies of biology,and has played an increasingly prominent role in the fields of infectious disease prevention and control,malignant disease prevention and diagnosis,and species identification.Molecular diagnosis mainly includes nucleic acid extraction,nucleic acid amplification and nucleic acid hybridization,and its primary task is nucleic acid extraction.The outbreak of the new crown epidemic in 2020 has greatly stimulated the development and application of molecular diagnostics,and a large-throughput,fast and efficient nucleic acid extraction technology is urgently needed.In this paper,combining biological,mechanical,electronic,computer and other technologies,in order to meet the needs of rapid processing and extraction of large-throughput samples to be tested,the two functions of sample transfer and nucleic acid extraction involved in the automatic nucleic acid extraction system are studied.In terms of pipetting function,a motion platform is built based on the Cartesian coordinate system,and functional mechanisms such as a sampling manipulator that can freely change the spacing,a syringe pump driven by a stepper motor,etc.are designed.At the same time,according to the needs of each functional mechanism,STM32 is used as the main control.The chip designs the hardware circuit,uses the C/C++ language to write the embedded software based on STM32,and designs the corresponding human-computer interaction interface,which realizes the rapid transfer of samples between containers of different specifications.In terms of extraction device,using the principle of nucleic acid extraction by magnetic bead method,a motion platform is built based on the cylindrical coordinate system,and a horizontal rotating feeding mechanism,a vertical extraction mechanism and a constant temperature pyrolysis mechanism located below are designed.For the hardware circuit of the main control chip,the embedded software based on STM32 is written in C/C++ language and the corresponding human-computer interaction interface is designed,which realizes the rapid extraction of 96 samples.Combined with the operational requirements of biological detection,the performance test and biological test of the principle prototype of the nucleic acid extraction system built in this study were carried out.Among them,the repeated positioning accuracy of long-distance linear motion is ±0.11 mm,the accuracy of circular motion is ±0.035°,the pipetting error is less than 5%,and the maximum surface temperature difference of the pyrolysis mechanism is 0.9°C.The nucleic acid extraction device was tested for nucleic acid extraction using blood samples stored in the laboratory,and the extraction results were tested by fluorescence quantitative PCR.The Cq values were all between 11 and 14,and the CV value was 3.2%.The test results show that the performance indicators of the system meet the design and use requirements,and the nucleic acid extraction test is compared with manual and existing instruments on the market,indicating that the extraction quality is basically consistent with manual and existing products in the market,and meets the requirements of fluorescence quantitative PCR.testing requirements.This paper studies the two functions of pipetting and extraction included in the automatic nucleic acid extraction system,realizes the automatic operation of the nucleic acid extraction process,and provides a theoretical and practical basis for the integration of molecular diagnostic equipment.