a, b, Mean diameter (a) (nm) and Zeta potential (b) (mv) of different nanoparticles with or without encapsulation of replicon RNA. Shown are mean (box) of three different measurements from one of two independent experiments. (c) RNA encapsulation efficiency of DOTAP, Lipofectamine, and TT3 nanoparticles. Shown are mean (box) of 3 different measurements from one of two independent experiments. n.d. means non-detectable. d–g, morphologies of DOTAP and TT3 lipid nanoparticles without (d, f) or with replicon RNA (e, g) were imaged by Cryo-TEM. Shown are representative images from one of three independent fields of view in a single experiment. Scale bar (100 nm) is indicated. The source data are provided with this paper; the source data for d–g are also stored at https://doi.org/10.6084/m9.figshare.12498047.