Gold-Nanocluster-Mediated Delivery of siRNA to Intact Plant Cells for Efficient Gene Knockdown

RNA interference, which involves the delivery of small interfering RNA (siRNA), has been used to validate target genes, to understand and control cellular metabolic pathways, and to use as a "green" alternative to confer pest tolerance in crops. Conventional siRNA delivery methods such as viruses and Agrobacterium-mediated delivery exhibit plant species range limitations and uncontrolled DNA integration into the plant genome. Here, we synthesize polyethylenimine-functionalized gold nanoclusters (PEI-AuNCs) to mediate siRNA delivery into intact plants and show that these nanoclusters enable efficient gene knockdown. We further demonstrate that PEI-AuNCs protect siRNA from RNase degradation while the complex is small enough to bypass the plant cell wall. Consequently, AuNCs enable gene knockdown with efficiencies of up 76.5 ± 5.9% and 76.1 ± 9.5% for GFP and ROQ1, respectively, with no observable toxicity. Our data suggest that AuNCs can deliver siRNA into intact plant cells for broad applications in plant biotechnology.