Self-assembly Of DNA-templated Nanomachine For Circulating Tumor Cells Recognition Isolation And Imaging

Circulating tumor cells(CTC)are tumor cells present in the peripheral blood of cancer patients.Studies have shown that the main reason of death in cancer is the spread of cancer cells.However,due to the extremely low content of CTC in the early stages of cancer and the difficulty of separation,the detection and analysis of CTC separation is still a huge challenge.With the development of nanomedicine technology,the use of same probe for the separation and detection of CTC has achieved certain results,but few articles have reported the application of using same probe for specific recognition,isolation and detect miRNA-21.The functionalized nanomaterials introducing DNA as a template have been more widely used in biomedicine on account of the development of nanotechnology and nucleic acid technology.In this paper,CTC was specifically recognized by the DNA aptamers and separated by the DNA-functionalized Fe3O4 magnetic nanoparticles(MNP)which had typical magnetism.Moreover,an entropy-driven catalytic amplification system was successfully constructed based on the DNA-functionalized quantum dots(QDs)and DNA-functionalized gold nanoparticles(AuNPs)which was utilized to detect the cancer marker miRNA-21 in CTC.The experiment involved in this work is mainly divided into three parts.First of all,DNA-functionalized CdTe QDs with prominent biocompatibility was synthesized by one-step method.Spherical AuNPs particles with particle size of 50 nm was prepared by seed growth method and functionalized with DNA through low pH method.EDC/NHS reduction method was applied to functionalize MNP with DNA.Then,DNA-functionalized MNP and AuNPs and DNA aptamers were self-assembled to form aptamers-AuNPs-MNP satellite structure probes.Moreover,CdTe QDs and AuNPs,both of which were functionalized with DNA,were used to connect DNA strands to obtain the AuNPs-QDs satellite structure with entropy-driven catalytic amplification system.In the end,DNA-functionalized CdTe QDs,DNA-functionalized MNP,DNA-functionalized AuNPs and DNA aptamers were used to synthesize aptamers-MNP-AuNPs-QDs satellite structure probes through self-assembly process and some characterization experiments was conducted to verify the above probes.The aim of this dissertation is to design different DNA sequences and achieve self-assembly which rely on the complementary base pairing between DNA bases.In addition,a satellite-structured probe was synthesized for analysis which formed by large-sized AuNPs as the core,DNA-functionalized QDs,DNA functionalized MNP and DNA ligands.This paper has verified the specificity of the selected DNA aptamers for MCF-7 tumor cells as well as assembled the aptamers-AuNPs-MNP satellite structure and proved its magnetic separation effect.An entropy-driven AuNPs-QDs catalytic amplification system was also successfully assembled and its feasibility was testified in vitro by antisense miRNA-21 and in fixed cells to detect miRNA-21.Particularly,the aptamers-MNP-AuNPs-QDs probes for identification,separation and detection were successfully assembled.Although the current work so far is not perfect,it has also achieved certain satisfactory results,and our experimental design strategy is very innovative.It is convincing that the above strategy will be of great significance for the identification,isolation and detection of CTC in patients with early cancer.