Research On Key Technology Of Thermal Cycle System Of Fluorescence Quantitative PCR Instrument

Fluorescence quantitative PCR instrument is based on the principle of large-scale amplification of trace DNA fragments in vitro-polymerase chain reaction(Polymerase Chain Reaction:PCR),after undergoing high-temperature denaturation,lowtemperature annealing,extension temperature thermal cycle(25-45 times),combined with fluorescence detection and fluorescent probes and other technologies,which is referred to as qPCR instrument.The core technology of qPCR instrument includes two aspects:"fluorescence detection system" and "thermal cycle temperature control system",which are important factors that directly affect the length of gene detection and amplification efficiency,and are also technical difficulties in the product development.In PCR gene amplification experiments,the thermal cycling reaction takes more than one hour,and the amplification efficiency is low and false positives are high,which is drawback and defect for the detection of a large number of samples and the prevention and control of infectious diseases.Shortening the PCR reaction time and improving the amplification efficiency have become current research hotspots.Generally,we start with the development of high-efficiency fluorescent reagents to increase the fluorescence efficiency and optimize the temperature control system to increase the detection time.The research content of this subject focuses on:Propose a high-power and high-efficiency temperature control circuit of thermoelectric cooler,and research on the key technology of the thermal cycle temperature control system of the fluorescent quantitative PCR instrument,which aims to solve the problem that the existing thermal cycle temperature control technology is difficult to meet various new development requirements such as rapid,high-efficiency and miniaturization of PCR.The main work of the paper is as follows.First of all,a thermal cycle temperature control system platform is designed and built.According to the characteristics of thermal reaction cycle,design each module and index parameters.According to the calculation of the temperature control power,the selection of thermoelectric cooler is carried out.Design a heat dissipation scheme to improve work efficiency and provide a good experimental platform for thermal cycling reactions.Secondly,propose a high-power drive circuit based on Buck+H bridge.A semiconductor refrigeration chip temperature control circuit that can accurately control temperature,improve work efficiency,protect and extend the service life of TEC is proposed,which solves the technical difficulties of its high-power drive and highefficiency operation.The overall control circuit is designed,and the PWM technology is adopted to realize the heating and cooling switching and power control of the refrigeration plate,which effectively guarantees the efficient,reliable and stable operation of the temperature control system.Thirdly,study the control algorithm and performance analysis.According to the response characteristics of the thermal cycle system,the system model identification is established.Aiming at the problems of temperature overshoot and hysteresis in the system,fuzzy PID control algorithm is designed on the basis of PID and simulated and compared,which effectively improves the temperature response and stability of thermal cycle.Simulate and analyze the uniformity of the temperature field of the sample block,improve and increase the heat transfer efficiency of the system and reduce the heat loss,So as to obtain a reaction module with uniform temperature distribution,which is helpful to improve the efficiency of PCR gene amplification experiment.This article conducts an in-depth research on the thermal cycle system of PCR.The thermal cycle system designed effectively solves the technical difficulties in temperature control of thermoelectric coolers,which has the characteristics of wide range,rapid temperature change,efficient and stable operation.It is suitable for the thermal cycle of fluorescent quantitative PCR instrument.The thermal cycle temperature control system has a good market prospect and is conducive to improving the market competitiveness of domestic PCR instruments.