Application Of DNA Nanotechnology In Dynamic Control And Imaging Of Cells

To better understand cell behaviors on substrates, the precise control of density and orientation of cell specific ligands remains a great challenge. In this study, we established an easy-to-use approach to manipulate the adhesion and patterning of mammalian cells on gold substrates. We prepared DNA self-assembled monolayers(DNA-SAMs) on gold substrates and found that the sequence-specific orientation of DNA-SAMs played an important role in modulating cell adhesion. We also found that the DNA-SAMs on gold substrates could be used as a potentially universal cell culture substrate, which showed properties similar to cationic polymers(e.g. poly-L lysine, PLL) substrates. Furthermore, we could manipulate cell adhesion by tuning the length of poly adenine(polyA) in the DNA sequence. We also prepared a DNA aptamer-based SAM to regulate cell adhesion by exploiting stimuli-responsive conformational change of the aptamer. By using the well-established DNA spotting technology, we patterned cells on DNA-SAMs to form a spot matrix and four English letters “CELL”. Our findings suggest that DNA-SAMs on gold substrates are potentially useful for making smart surfaces for cell studies, thus introducing a new platform for cell/tissue engineering research.Control cell release is a crucial step in cell culture and it is also involved in many physical and pathological processes. So it possess great significance in biological and biomedical studies. In vivo, this process is regulated by many factors. Here, we developed a substrate by grafting RGD coupled double strand DNA on biotin modified coverslip. By utilizing DNA toehold-mediated strand displacement reactions, a series logic operations, AND, OR, and XOR logic gates as well as logistic circuits were designed to release cells which were adhered on the RGD substrate to mimic the interaction between different factors.CRISPR(clustered regularly interspaced short palindromic repeats)-Cas9 endonuclease system, which is initially found as an antiviral immune system widely existing in bacterial genomes, has been developed as a powerful tool of genome editing due to its high specificity and efficiency and is used in a large variety of organisms. On the other hand, with deactivated Cas9(dCas9, whose nuclease activity is disabled) protein and single-stranded guide RNAs(sgRNAs), this system has also been proved powerful to label and visualize specific loci in live cells owing to its capability to target almost arbitrary DNA sequence on chromatin without irreversible damage. In this paper, we proposed a new strategy for multicolor imaging and tracking specific gene loci in living cells by utilizing in vitro transcribed sgRNAs labeled with different chemical fluorescence dyes. We believe that it will be a powerful tool to understand the gene spatial organization and it dynamic propriety.The significant role of telomeres in cells has attracted much attention since they were discovered. Fluorescence microscopic imaging is an effective method been used to study subcellular structures like telomeres. However, the optic diffraction limit of traditional optical microscopy hampers deep investigation on them. Recent progress on superresolution fluorescence microscopy makes it possible to visualize structures with a much higher resolution. In this work, we used stimulated emission depletion(STED) microscopy to observe fluorescence-labeled telomeres in interphase cell nuclei. Results showed that the size of fluorescent puncta representing telomeres under STED microscope was much smaller than that under confocal microscope. Two adjacent telomeres whose distance between each other was around the optic diffraction limit could hardly be discriminated by confocal microscopy, but could be clearly separated by STED imaging. We conclude that as compared to traditional confocal microscopy, STED microscopy is a more powerful tool that can help us obtain more detailed information about telomeres.