Normalized Nucleic Acid Payload in Lipid Nanoparticles: A Perspective on the Harmonization of Published Data

Precise and consistent reporting of the nucleic acid payload per lipid nanoparticle (LNP) is important for advancing the understanding and development of nanomedicines. However, the reported number of RNA molecules ranges between ∼1-300 in recent investigations. To evaluate the RNA payload across investigations, we introduce and apply a normalized nucleic acid payload metric which accounts for differences in LNP size, nucleotides per RNA and N/P charge ratio. The normalized payload results in a similar value for siRNA-and mRNA-containing LNPs of different LNP sizes, where the average value of 71± 16 nucleotides/zeptoliter agrees well with the expected payload density based on molecular packing arguments. The use of normalized payload harmonizes the reported payload, complements existing payload metrics and enables comparison across samples and measurement techniques at both the single-particle and ensemble-average level.