基于角度可控DNA镊子的多边形纳米结构自组装及其细胞摄取效率研究

DNA nanotechnology has shown great potential in the application of drug delivery recently. Since shapes and sizes of DNA nanostructures severely affect their cellular uptake efficiency, construction of shape- and size- tunable DNA nanostructures has great value of application in drug delivery. First, a tweezer-shaped DNA nanostructure (named as DNA tweezer) is designed by single-stranded DNA brick strategy. The DNA tweezer is composed of two arms, which are connected with a certain angle by the hybridization of sticky ends on the heads of two arms (named as Sticky End I). Adjustment of Sticky End I position on the arms achieves the angle control of the DNA tweezer. Furthermore, by adding another set of sticky ends on the tails of two arms (named as Sticky End II), DNA tweezers are used as monomers to hierarchically assemble into polygonal nanostructures by the hybridization of Sticky End II, and the shape of the polygonal structure is determined by the angle of DNA tweezer. In addition, the size of the polygonal structure is precisely programmed by moving Sticky End II along the DNA helical axis. Finally, we are going to investigate the cellular uptake efficiency of polygonal structures with different shapes and sizes, among which a structure with highest cellular uptake efficiency is obtained. The new and general angle control principle developed for monomers with large molecular weight (>1.5 MDa) in this program, allows the fabrication of DNA nanostructures with tunable shapes and sizes, providing not only theoretical direction but practical foundation for the construction and application for DNA nanostructures as effective drug carriers.

近年来DNA纳米结构在药物运载方面展现出广阔的应用前景，但其形状及尺寸严重影响着运载过程中的细胞摄取效率，因此构建形状及尺寸可调的DNA纳米结构具有非常重要的应用价值。本项目拟首先利用单链DNA模块技术设计出镊子状纳米结构（称为DNA镊子），该结构由两个长方体形悬臂组成，两悬臂通过头部的粘性末端连接成一定角度；基于DNA纳米结构的空间可寻址性，可通过精确调节粘性末端的位置，实现对DNA镊子的角度控制。然后可将DNA镊子作为单体，通过分级组装构建不同形状的多边形纳米结构，其中目标结构的形状由单体的角度决定；同时实现对每种多边形结构的尺寸调节。最后比较细胞对不同形状及尺寸的多边形纳米结构的摄取情况，得到摄取效率最高的DNA纳米结构。利用本项目建立的针对大分子量单体的创新型角度控制方法，可实现形状及尺寸可调的DNA纳米结构的构建，为更高效DNA纳米结构药物载体的设计及应用提供理论指导及实践基础。

由于DNA自身良好的生物相容性，使得DNA纳米管在药物运载、生物反应器等方面有着可观的应用前景。自从20世纪80年代DNA纳米技术的概念提出以来，利用DNA模块、DNA折纸及环状DNA等多种方法都可实现DNA纳米管的自组装，但其尺寸均受到了严重限制，目前报道的DNA纳米管直径大多小于100 nm。制备大尺寸DNA纳米管一直是科学家们面临的重大挑战。因此，发展一种系统性、通用性的DNA纳米管构建策略尤为重要。聚焦于此问题，该项目对于大尺寸DNA纳米管自组装进行了深入研究。研究发现通过对DNA结构重复单元的刚性和曲率进行调节，可以构建不同直径的纳米管,范围可从50 nm 调节至550 nm。实验结果表明，刚性大、曲率小的DNA结构重复单元有利于大直径纳米管的生成。同时DNA双链扭转密度的调节实现了纳米管手性的控制，为纳米材料构建手性支架平台奠定了良好的基础。

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