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    Home > New work of nano Daniel Chad a. Mirkin JACS: a new method to stabilize responsive DNA engineering colloidal crystals

    New work of nano Daniel Chad a. Mirkin JACS: a new method to stabilize responsive DNA engineering colloidal crystals

    • Last Update: 2019-07-29
    • Source: Internet
    • Author: User
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    DNA programmable assembly can be used to precisely control particle composition, crystal symmetry, lattice parameters and other properties At present, scientists have used DNA programming to synthesize more than 50 kinds of colloidal crystals with different symmetry and hundreds of different types The reversible base pairing interaction between single stranded DNA and DNA modified nanoparticles drives the formation of colloidal crystals Because this interaction is related to pH and dielectric strength of solvents, the environment can be used to regulate lattice parameters to obtain responsive materials At the same time, this system can also be used in photolithography, so it has a broad prospect in the development of new 2D and 3D nano materials Of course, one of the preconditions for the preparation and application of responsive colloidal crystals is to ensure the flexibility and integrity of DNA molecules Researchers have proposed different stabilization methods, including silicon embedding or silver ion post-treatment, using polyethylene glycol molecules instead of DNA, photocrosslinking But these methods are not perfect, either can not completely solve the stability problem, or sacrifice the flexibility of DNA Based on this, the research team of Chad a Mirkin, a nanomaterial from Northwest University, put forward a strategy of covalently crosslinking DNA with DNA cross linker, which solved this problem perfectly It not only obtained stable colloidal crystal, but also maintained the solvent dependent response of colloidal crystal The relevant research results were published on J am Chem SOC( DOI:10.1021/jacs.9b06106 )。
    DNA cross-linking agents have been used to cross-link hybrid DNA double strands, and have also been developed to inhibit DNA replication Therefore, the authors suspect that the same strategy can be used to enhance the thermal stability of colloidal crystals, while maintaining their solvent dependent response BCNU and 8-MOP were selected as crosslinking agents They used DNA modified gold nanoparticles to prepare BCC and FCC colloidal crystals, and then BCNU or 8-MOP were used to crosslink DNA SEM analysis shows that these crystals have the characteristics of long-range ordered programmable atomic equivalent (PAEs) After washing with water and ethanol, the morphology has no obvious change, but the non crosslinked colloidal crystals become unstable after leaving the salt solution, and there is no longer long-range ordered structure after washing The crystallinity of these crystals was analyzed by SAXS The results show that the lattice parameters of BCC crystal are reduced by 16.1% and FCC crystal by 12.9% after crosslinking These results show that this crosslinking method can obtain stable crystal and keep crystal properties (photo source: J am Chem SOC.) in order to further study the stability of these crystals, the author replaced the original PBS salt solution with a series of commonly used organic solvents (ethanol, dimethylformamide, dichloromethane, n-hexane), and then shook it at 25 ℃ for 24 hours The subsequent SAXS analysis (Figure 2) shows that the crystallinity of the crystals before and after treatment has basically no change, in addition, strong acid and alkali will not damage the structure of these crystals These results show that these crosslinked crystals can maintain stability and structural characteristics in the common solvents which destroy DNA interaction (photo source: J am Chem SOC.) next, the author analyzed the thermal stability of the crosslinked crystal The melting temperature measurement results show that the uncrosslinked crystals start to melt at about 45 ℃, and the crosslinked crystals do not melt at 90 ℃ The SEM test after the experiment shows that these crystals still maintain the characteristics of long-range order (Figure 3) (photo source: J am Chem SOC.) finally, the authors tested the stimulus response characteristics of these crystal structures (Figure 4) The crystal was treated with PBS and pure water in turn, and SAXS was detected after each treatment The results showed that the crystal lattice parameters would change reversibly In addition, similar results were obtained by alternative treatment with other commonly used solvents This shows that the cross-linked DNA in these crystals still maintains flexibility and can change reversibly in different solvents, which is a feature that previous stabilization methods cannot achieve (photo source: J am Chem SOC.) to sum up, this study developed a new method to stabilize DNA colloidal crystal based on DNA covalent cross-linking, which is convenient and reliable, and does not need special DNA sequence or other special groups before crystallization In this way, colloidal crystals with abnormal stability can be obtained, and the structural characteristics and crystallization properties of these crystals can be maintained The most important thing is that this method also maintains the flexibility of DNA in the cross-linked crystal, thus maintaining the response of colloidal crystal dependent on solvent.
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