Construction Of DNA Nano-self-assembly Structure And Its Application In Tumor Marker Detection

The aberrant expression of micro RNA(mi RNA)are closely associated with the occurrence and development of various diseases and genetic diseases.Therefore,it is necessary to detect mi RNA sensitively and accurately,especially to monitor mi RNA expression in living cancer cells.However,due to the low abundance of mi RNA in cells and the complex in vivo environment,and efficient amplification strategy is essential for intracellular mi RNA imaging.To address the above issues,this paper adopts DNA tetrahedra as the basic backbone to achieve imaging analysis of intracellular mi RNA in tumor cells by modifying different functionalized hairpin structures and p H-sensitive DNA sequences and then combining with signal amplification strategies(hybridization chain reaction and catalytic hairpin assembly).The main elements are as follows.(1)DNA self-assembling nanoprobes with self-transferability and resistance to nuclease degradation have been developed and applied to biological imaging of living cells.In this work,we constructed a hairpin-functionalized DNA tetrahedron(HFDT)intramolecular catalytic self-assembly platform to detect low-abundance mi RNA by the catalyzed hairpin assembly(CHA).The designed HFDT enhances CHA reaction efficiency and aggregates into dendrimers structures in the presence of mi RNA.This innovative strategy "small to large" can effectively change the distribution and properties of biomaterials in the organism,thus effectively retaining them inside the tumor and reducing the reflux of nanomaterials,increasing their accumulation in the tumor site and protecting them from the complex physiological environment,which has promising applications in tumor imaging.(2)Design of a pH-sensitive hairpin-functionalized DNA tetrahedron for monitoring p H and mi RNA in living cells.Different from conventional DNA tetrahedral nanoprobes,G-quadruplexes and i-motif structures act as important conformational switching elements.Inspired by the different p H values inside and outside tumor cells,a p H-sensitive hairpin-functionalized DNA tetrahedron(p SHFDT)was formed by hybridizing the G-quadruplex structure with hairpins H1 and H2 and assembling them at the apex DNA tetrahedron.Due to the low p H within the lysosomes in tumor cells,i-motif DNA structures are formed between p SHFDT,leading to aggregation and the generation of dendritic structures,with concomitant dissociation releasing hairpin H1 and H2,triggering a hybridization chain reaction(HCR)in the presence of mi RNA,and the resulting long-stranded DNA leading to fluorescence recovery.Combining the i-motif structure of DNA(p H-sensitive)and the characteristics of HCR enables imaging analysis of low-abundance mi RNA in tumor cells.We hope that this constructed nanoprobe will provide a new approach to tumor marker imaging,even at generally low levels,using a nanoprobe that offers potential for early diagnosis and treatment of disease.