碳纳米管在植物遗传物质递送中的研究进展

Research progress of carbon nanotubes in delivery of plant genetic materials

  • 摘要: 植物基因工程赋予了植物高产、抗逆等优良性状, 为保障粮食安全提供了解决思路。但目前植物转基因主要依赖于根瘤农杆菌侵染法和基因枪法, 这些方法存在转基因效率低和物种依赖等一些局限性。近年来, 纳米载体在植物基因工程领域引起了较大的关注。多项研究表明, 纳米载体能够携带核酸分子(DNA、RNA)进入植物细胞。因此利用纳米载体递送遗传物质已成为提高植物转基因或基因编辑效率的可行策略之一。在这些纳米载体中, 碳纳米管(carbon nanotubes, CNTs)具有高稳定性、高生物相容性、高比表面积等优点, 显示出了巨大的应用潜力。同时, 高长径比赋予了CNTs穿过细胞膜和叶绿体膜的能力。多种表面修饰也使得CNTs能够携带核酸分子靶向递送到不同细胞器中。聚乙烯亚胺(PEI)修饰的CNTs能搭载质粒进入细胞核, 在非转基因的前提下瞬时表达外源基因, 且突破宿主特异性的限制。壳聚糖修饰的CNTs利用脂质交换包膜穿透机制选择性地将质粒DNA递送到叶绿体中进行表达。除此之外, 基于π-π堆积的原理, CNTs还被设计为siRNA递送平台, 以高效、特异性地沉默内源性基因。值得注意的是, CNTs还可以保护所搭载的核酸在递送过程中不被核酸酶所降解, 保障了递送物质的完整性, 为后续高效表达打下了基础。CNTs还将与基因组编辑技术CRISPR相结合, 通过递送并瞬时表达含有Cas9蛋白原件的质粒实现无外源基因插入的基因组编辑。然而, 作为一种新型的核酸递送技术, CNTs仍然存在许多不足。CNTs介导的外源质粒瞬时表达效率较低, 该递送体系仍需要进一步优化改进。CNTs在携带并表达较大的DNA元件方面仍然存在一定的技术限制。此外, 细胞如何高效吸收CNTs的机制仍需要进一步研究, 这对于未来定向递送CNTs到特定植物细胞和细胞器中有重大意义。总之, 本文针对CNTs递送遗传物质进入植物细胞提供了一个较为全面的综述, 不仅涵盖了CNTs的结构属性, 并概述了用于CNTs表面功能化的主要技术, 以及CNTs递送遗传物质的研究进展。此外, 我们还探讨了CNTs应用的限制因素和未来的一些应用前景, 旨在为植物遗传转化技术和方法提供一些新思路或参考。

     

    Abstract: Population expansion, climate change, and growing scarcity of arable land threaten global food security. With the development of biotechnology, transgenic crops with superior features, such as high yield and stress resistance, can ensure food security. Despite decades of progress in biotechnology, genetic modification of most plant species remains challenging. Currently, plant transgenic technologies that rely on Agrobacterium tumefaciens and gene guns are limited by low transfer efficiencies and species dependence. Recently, nanocarriers have received significant attention in the field of plant genetic engineering. Multiple studies have found that nanoparticles can carry nucleic acids (DNA, RNA) and proteins into plant cells. The use of nanomaterials to enhance the efficiency of genetic biomolecule delivery into plant cells is a useful strategy for efficient plant genetic modification. Among the nanomaterials possessing the advantages of stability, biocompatibility, and a high surface-area-to-volume ratio, carbon nanotubes (CNTs) have shown great application potential. Meanwhile, a high aspect ratio causes CNTs to passively traverse the extracted chloroplasts and plant membranes. Various surface modifications render CNTs capable of carrying a range of cargoes and target different organelles, such as the nucleus or chloroplasts. Polyethyleneimine (PEI)-modified CNTs loaded with plasmids enter the nucleus and transiently express exogenous genes without transgene or host range limitations. Using the lipid exchange envelope penetration mechanism, chitosan-complexed CNTs selectively delivered plasmid DNA to chloroplasts. Based on π-π adsorption, CNTs have been designed as an siRNA delivery platform to silence endogenous genes with high efficiency and specificity. Modified CNTs can also protect nucleic acid cargo from degradation by nucleases during delivery. CNTs combine with genome-editing tools, such as clustered regularly interspaced short palindromic repeats (CRISPR), producing a new opportunity to achieve permanent genome editing through independent DNA delivery without transgene integration. However, as a novel nucleic acid delivery technique, CNTs have several drawbacks. CNT-mediated delivery of plasmids into cells exhibits relatively low expression efficiency, which warrants further improvement. There are still technical limitations in carrying large DNA units, such as the CRISPR-associated protein 9 (Cas9) expression box, for gene editing. Furthermore, the cellular uptake mechanism and techniques of CNT modification require further investigation, which will have a significant influence on the targeted delivery to plant cells and organelles. This review provides a comprehensive summary of the structural attributes of CNTs and offers an overview of the primary techniques employed for the surface functionalization of CNTs and advancements in nucleic acid delivery into plants via surface-modified CNTs. In this review, we explored the limiting factors and prospects for the application of CNTs, which will provide new insights for plant genetic transformation technologies and methods.

     

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