Fig. 7: Reversible siRNA interaction with albumin, enabled by siRNA-lipid conjugation, enhances siRNA circulation and in vivo bioactivity.

a Schematic model describing how siRNA conjugated to lipid enables reversible albumin interactions, as opposed to the irreversible nature of siRNA covalently linked with albumin. b Confirmation of conjugation of siRNA to albumin visualized using an Agilent 2100 Bioanalyzer. c Cy5-labeled siRNA-lipid conjugates or siRNA-albumin were delivered i.v. (1 mg/kg siRNA). Size exclusion chromatographic measurements of Cy5 fluorescence in albumin-containing plasma fraction (n = 3). d Intravascular Cy5 fluorescence measured through ~1 h was used to calculate siRNA circulation half-life (n = 4). e Cy5 fluorescence in kidneys, lungs, liver, spleen, and heart was measured 1 h after treatment. Fluorescence values in kidneys relative to the total fluorescent values of all organs combined is shown (n = 3–5). f Schematic showing treatment schedule for i.v. delivery of siRNA-lipid conjugates to tumor-bearing mice. g Dissociated tumors collected on treatment day 7 were assessed for Cy5 fluorescence by flow cytometry or (h) lysed and assessed for luciferase activity (n = 5–6). For (c–e, g, h), each bar represents the average value (± S.D.), and each point represents values measured for each individual sample. Significance was assigned by one-way ANOVA with Tukey’s multiple comparisons test.