| Nucleic Acids aptamers are single-stranded DNA/RNA molecules that tend to form specific secondary structures capable of binding to various targets,such as small molecules,proteins,nucleic acids,and even cells,and are increasingly used to detect the changes of diseased cells at the molecular level.In recent years,a new screening technology called cell-SELEX has been developed to apply the whole living cells as targets to find aptamers capable of recognizing specific diseased cells at molecular level and has shown great potential for applications in cancer diagnosis and treatment.However,a whole cell-SELEX experiment involves a series of complicated operations,and it is often time-consuming to conduct experiments manually.Therefore,the automation of cell-SELEX screening process is very important for accelerating the screening and application of nucleic acid aptamers.Therefore,our research group is developing a cell-SELEX-based aptamers screening machine based on a fully enclosed cartridge.In this paper,we are focused on the temperature control of the polymerase chain reaction(PCR)used for the rapid cell-SEl EX screening of aptamers.We had designed a special PCR reaction chamber with 500 ?L corresponding to the cell-SELEX experimental protocols.Based on the design of a large-volume hardware system,a cascade temperature control system has been developed,including a fuzzy PID controller and a PI controller,which were used to control the PCR chamber and the metal module respectively.To verify the performance of the temperature control system,two temperature control experiments have been performed on our designed hardware system through the traditional PID and cascade PID methods,respectively.Compared with the traditional PID controller,our proposed cascade controller shows much better performance in terms of speed,accuracy and stability,and thus can better satisfy the requirement of the cell-SELEX screening of nucleic acid aptamers. |
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