The Assembly Of Functional DNA Nanostructures And Studies For The Detection Of Cancer Cells

Cancer is a serious threat to human health and life.The early diagnosis and treatment is a key factor to improve its clinical efficacy and decrease death rate.Therefore,the sensitive and accurate detection of tumor at an early stage has the vital practical significance.Traditional approaches to detect cancer are limited in specificity and sensitivity and are harmful to patients,thus they can not meet the requirements of early cancer detection.In recent years,a series of new molecules for tumor biomarkers(such as mRNA,membrane protein,etc.)detection have been developed,providing new opportunities for early cancer diagnosis.Since DNA nanotechnology put forward,it has attracted wide attention in the field of biological medicine and has been used in cancer detection and imaging.Because DNA nanostructures have good programmability,biocompatibility and no obvious cytotoxicity and immunostimulatory.Based on the discussion above,this thesis use DNA nanotechnology to built new cancer cell detection systems for the logic detection of mRNAs and label-free and sensitive detection of membrane protein,realizing the sensitive and accurate detection of tumour cells.We wish that our systems can provide the basis for early clinical detection of malignant tumor.This thesis constructed double recognition probe-conjugated DNA tetrahedron for accurate detection of HepG2 cancer cells by "in situ" logic detection of mRNAs.The construction included:(1)the double recognition probe for the logic detection of two mRNAs--GalNAc-T mRNA and TK1 mRNA.Only two specific mRNAs exist,can the construction output a fluorescence signal.Thus this method can accurately distinguish HepG2 liver cancer cells with HL7702 normal hepatocyte;(2)DNA tetrahedron structure.It has good biocompatibility,easiness of synthesis and modification,stabilization and the ability to enter cell.To be the carrier of the probe,it can transport probe into cell and protect the probe from enzyme digestion.And as a result,this construction successfully distinguished HepG2 liver cancer cells with HL7702 normal hepatocyte,avoiding false signal by detecting only one kind of mRNA.Meanwhile,the logic detection method is more simple and intuitive and can avoid fluorescence spectrum overlap and channel number limit by multicolor detection way.This thesis also constructed "colocalize on" aptamer probe-triggered signal amplification device on Hela cell membrane for its label-free and sensitive detection.Besides the design of "colocalize on" aptamer probe,we also combined the classic HCR reaction to produce DNA ribbon on Hela cell membrane.When the dye--Eve Green insert into the double-stranded DNA ribbon,it can output fluorescent signal.This strategy can detect Hela cells with a limit of 100 cells.In addition,the dye’s insertion was after the identification and signal amplification process,which could not interfere with the identification and signal amplification process.