Block copolymer-dsRNA complexes for crop protection

在过去60年里，农药的使用使作物产量增加了一倍多，2018年达到90亿吨，满足了人口增长带来的粮食和植物性产品需求的增长。然而，它们的过度使用对环境和人类健康造成了负面影响，并对脱靶物种造成了危害。这有助于发展替代虫害防治措施，这些措施只针对特定物种，同时尽量减少脱靶毒性作用。其中一种替代方案是基于rna的生物农药，它可以调整以匹配特定的害虫基因，并减少非目标损害的可能性。在这种方法中，将双链RNA分子（dsRNA）传递给害虫，通过选择性基因沉默来阻碍它们的生长或可能导致害虫死亡。递送载体已经被开发出来，以保护RNA在到达害虫体内的目标位点之前，在许多环境中不被降解。最近，人们为此目的合成了一种亲水双嵌段共聚物，其中带阳离子的PQDMAEMA嵌段与带负电荷的dsRNA结合，而中性的PDMA嵌段提供了空间稳定性，以防止所产生的聚合物-dsRNA复合物的聚集，这被证明可以有效地结合并保护dsRNA[2]。除了保护dsRNA，复合体应该允许dsRNA在害虫的细胞内释放。为此，该项目将以先前合成的共聚物为基础，将ph响应性纳入聚合物设计中。更具体地说，永久季铵化（QDMAEMA）和ph依赖性季铵化（DMAEMA）单体将用于合成阳离子块。然后，该块将根据其环境的pH值具有可变的正电荷，这有望在目标条件下诱导触发dsRNA的释放。预期的结果包括重现以前聚合物和复合物的合成和表征技术，以及测试机器学习算法，以基于合作者数据将聚合物性质与复合物的性能联系起来。

The use of pesticides has allowed crop production to more than double over the last 60 years, reaching 9 billion tonnes in 2018 and keeping up with increasing food and plant-derived products demand due to population growth [1]. However, their excessive use has led to negative impacts on the environment and to human health and off-target species [1]. This has contributed to the development of alternative pest control measures that target only specific species while minimising off-target toxicity effects.One such alternative is RNAi-based biopesticides that can be tuned to match specific pest genes and reduce the possibility of non-target damage. In this method, a double-stranded RNA molecule (dsRNA) is delivered to pests, stunting their growth or potentially causing pest death by selective gene silencing. Delivery vectors have been developed to protect RNA from degradation in the many environments it encounters before reaching the target sites within the pests. Recently a hydrophilic di-block copolymer has been synthesised for this purpose, where the cationic PQDMAEMA block binds to the negatively charged dsRNA and the neutral PDMA block provides steric stabilisation to prevent aggregation of the resulting polymer-dsRNA complexes, which were shown to effectively bind to and protect dsRNA [2].In addition to protecting dsRNA, complexes should allow dsRNA release once within the pest's cells. To this end, this project will build upon the previously synthesised copolymer to include pH-responsiveness into polymer design. More specifically, both permanently quaternised (QDMAEMA) and pH-dependently quaternised (DMAEMA) monomers will be used to synthesise the cationic block. This block will then have a variable positive charge depending on the pH of its environment, which is expected to induce the triggered release of dsRNA under targeted conditions. Anticipated results include reproducing synthesis and characterisation techniques of previous polymers and complexes and testing a machine learning algorithm to relate polymer properties to complexes' performance based on collaborator data.