*2.1. Materials*

The pH-sensitive cationic lipid, 7-(4-(dipropylamino)butyl)-7-hydroxytridecane-1,13 diyl dioleate (CL4H6), was synthesized as described previously [38]. 7-Hydroxy-7-(4 morpholinobutyl)tridecane-1,13-diyl dioleate (CL7H6) was synthesized as described in the Supplementary Method. Chol was purchased from SIGMA Aldrich (St. Louis, MO, USA). DOTMA, 1,2-distearoyl-*sn*-glycero-3-phosphocholine (DSPC), DOPE, 1,2-dimirystoyl-*rac*glycero, methoxyethyleneglycol 2000 ether (PEG-DMG), and 1,2-distearoyl-*rac*-glycero, methoxyethyleneglycol 2000 ether (PEG-DSG) were obtained from the NOF Corporation (Tokyo, Japan). DLin-MC3-DMA was purchased from Selleck Biotech (Houston, TX, USA). 3,30 -Dioctadecyloxacarbocyanine perchlorate (DiO) and Ribogreen were purchased from ThermoFisher Scientific (Waltham, MA, USA). Purified anti-mouse CD16/32 antibody (clone 93), PE Anti-mouse CD40 antibody (clone FGK45), FITC anti-mouse CD80 antibody (clone 16-10A1), phycoerythrin (PE) anti-mouse CD86 antibody (clone A17199A), allophycocyanin (APC) anti-mouse CD69 antibody (clone H1.2F3), PE anti-mouse CD3 antibody (clone 17A2), peridinin-chlorophyll-protein (PerCP)/Cyanine 7 anti-mouse CD19 antibody (clone 6D5), FITC anti-mouse NK1.1 antibody (clone PK136), APC anti-mouse CD11c antibody (clone N418), PerCP/Cyanine 5.5 anti-mouse I-A/I-E antibody (clone M5/114.15.2), and propidium iodide (PI) were purchased from BioLegend (San Diego, CA, USA). Anti-human polo-like kinase 1 (hPLK1) siRNA (siPLK1, sense: 50 -AGA uCA CCC uCC UUA AAu AUU-30 ; antisense; 50 -UAU UUA AGG AGG GUG AuC UUU-30 , 2 0 -OMe-modified nucleotides are in lower case) was purchased from Hokkaido System Science Co., Ltd. (Sapporo, Japan). The ovalbumin (OVA)-encoding mRNA (cat# L-7610) and enhanced green fluorescent protein (EGFP)-encoding mRNA (cat# L-7601) were purchased from Trilink BioTechnologies (San Diego, CA, USA). A microfluidic device, an invasive lipid nanoparticle production (iLiNP) device, was fabricated as described previously [40].
