Microfluidic process-property correlations of dsRNA lipid nanoparticle formulations

The control of agricultural pest insects currently relies on broad-spectrum insecticides, which select for resistance in pest populations while also harming non-target species. In contrast, RNA interference (RNAi) has a species-dependent mode of action based on the delivery of double-stranded RNA (dsRNA) that precisely matches essential genes in pests, minimizing off-target effects. The successful application of RNAi requires the development of sprayable formulations that temporarily protect the dsRNA from environmental degradation (allowing uptake by pest insects) but also ensure the efficient release of the dsRNA within insect cells. Lipid nanoparticles (LNPs) based on pharmaceutical-grade lipids are currently too expensive for agricultural use, making the development of affordable and scalable dsRNA-LNP formulations essential for spray-induced gene silencing. Here we used technical-grade lipid components (available at the ton scale) and demonstrated the cost-effective production of structurally controlled dsRNA-LNP formulations by optimizing formulation recipes and scaling up the microfluidic mixing process. The dispersions contained spherical nanoparticles less than 100 nm in diameter, with a zeta potential exceeding + 20 mV, and an entropy-driven Gibbs free energy change for dsRNA-LNP decomplexation in the moderate range of approximately – 20 kJ/mol. The formulations protected dsRNA from RNase III degradation and hydrolysis at pH 4–11 for at least 24 h while allowing SDS-mediated dsRNA release. Our work provides insight into the structure–property correlations of inexpensive dsRNA-LNP formulations for sustainable RNAi-based pest management systems.