Transfection of platelets with PO-mRNA-LNP is scalable to physiological and supraphysiological concentrations in PAS_70:30 and plasma. (A-B) Relative NanoLuc expression per unit platelet transfected with mRNA-LNP at various doses suspended at physiological (250 × 10⁶ mL⁻¹) and supraphysiological concentration (800 × 10⁶ mL⁻¹) in PAS_70:30 (A) and plasma (B) at 4 hours. (C-D) Quantification of MFI (bars, left y-axis) and percentage of platelets (yellow circles, right y-axis) positive for the platelet activation marker CD62P in PAS_70:30 (C) and plasma (D). (E-F) Quantification of MFI of platelets positive for DiD-labeled mRNA-LNP (bars, left y-axis) and percentage of platelets (yellow circles, right y-axis) positive for DiD in PAS_70:30 (E) and plasma (F). (G) Percentage of platelets positive for the platelet activation marker CD62P when activated with ADP (10 μM) or unactivated. P values were determined by the unpaired Student t-test (2-tailed) or the 1-way analysis of variance. Values are reported as mean ± standard error of the mean. ∗P < .05; ∗∗P < .01; ∗∗∗P < .001; ∗∗∗∗P < .0001. n = 3. Ns, not significant.