Block copolymer-dsRNA complexes for crop protection

杀虫剂的使用使作物产量在过去60年里翻了一番以上，2018年达到90亿吨，跟上了人口增长对粮食和植物衍生产品日益增长的需求[1]。然而，它们的过度使用导致了对环境和人类健康的负面影响和目标外物种[1]。这有助于开发仅针对特定物种的替代虫害控制措施，同时将非靶标毒性影响降至最低。其中一种替代方案是基于RNAi的生物杀虫剂，它可以进行调整，以匹配特定的害虫基因，并减少非靶标损害的可能性。在这种方法中，双链RNA分子(DsRNA)被传递给害虫，通过选择性的基因沉默阻碍它们的生长或潜在地导致害虫死亡。已经开发了传递载体来保护RNA在到达害虫内的目标位置之前在许多环境中不被降解。最近为此目的合成了一种亲水性双嵌段共聚物，其中阳离子PQDMAEMA嵌段与带负电荷的dsRNA结合，而中性PDMA嵌段提供空间稳定以防止所产生的聚合物-dsRNA复合物的聚集，这被证明是有效地结合和保护dsRNA[2]。除了保护dsRNA，复合体应该允许dsRNA在害虫的细胞内一次释放。为此，该项目将在以前合成的共聚物的基础上，将pH响应性纳入聚合物设计。更具体地说，永久季节化(QDMAEMA)和pH依赖季节化(DMAEMA)单体都将用于合成阳离子嵌段。然后，这个区块将具有可变的正电荷，这取决于其环境的pH值，这有望在目标条件下诱导dsRNA的触发释放。预期的结果包括复制以前聚合物和络合物的合成和表征技术，以及测试一种机器学习算法，以基于合作者数据将聚合物属性与络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.