Donor platelets can be transfected with mRNA-LNP while in plasma and PAS. (A) Schematic describing platelet transfection in PAS₁₀₀, or in clinical storage solutions of PAS_70:30 or plasma. (B) Relative NanoLuc expression, measured as the normalized luminescence per platelet donor unit, using mRNA-LNP containing the ionizable lipid ALC-0315 or NTX-001 in PAS₁₀₀, PAS_70:30, and in plasma. (C and D) Quantification of median fluorescence intensity (MFI) (bars, left y-axis) and percentage of platelets (yellow circles, right y-axis) positive for the platelet activation marker CD62P (C) and representative flow cytometry plots (D). (E and F) Quantification of DiD MFI of platelets positive for DiD-labeled mRNA-LNP with statistical significance (bars, left y-axis) and percentage of platelets (red circles, right y-axis) positive for DiD (E) and representative flow cytometry plots (F). (G) NanoLuc expression in platelets transfected in PAS with increasing percentages of plasma present (v/v) (bars, left y-axis) and percentage of platelets (red circles, right y-axis) positive for DiD-labeled mRNA-LNP. Platelets were transfected at a concentration of 50 × 10⁶ mL⁻¹. P values were determined by 2-way analysis of variance. Values reported as mean ± standard error of the mean. ∗∗P < .01; ∗∗∗∗P < .0001. n = 3. Ns, not significant.