Fig. 1

Characterization of MC-PLGA@Met-CO₂/siFGL1. a Illustrations of the chemical reactions for the modification of Met with guanidine and the pH-triggered CO₂ gas generated by the guanidine-modified Met. b UV absorption spectra of Met and Met-CO₂ in the range of 220–300 nm. c FTIR spectra of Met and Met-CO₂. d The ¹³C-NMR spectrum of Met and Met-CO₂ dissolved in D₂O. e Representative TEM images of PLGA@Met-CO₂/siFGL1 NPs negatively stained with vanadium (scale bar = 100 nm). f Representative TEM images of MC-PLGA@Met-CO₂/siFGL1 NPs at pH 7.4 (a, scale bar = 50 nm), 6.0 (b, scale bar = 100 nm), and 5.0 (c, scale bar = 100 nm), negatively stained with vanadium. g Immunogold TEM images of MC and MC-PLGA@Met-CO₂/siFGL1 NP samples probed for α4 (red arrows, large gold) and vascular cell adhesion molecule-1 (yellow arrows, small gold) after negative staining with 2% sodium phosphotungstate (scale bar = 50 nm). h NP size distribution of PLGA@Met-CO₂/siFGL1 NPs and MC-PLGA@Met-CO₂/siFGL1 NPs at pH 7.4, 6.0, and 5.0, determined by DLS. i NP size distribution of MC-PLGA@Met/siFGL1 NPs (without CO₂) at pH 7.4, 6.0, and 5.0, determined by DLS. j Zeta potential of PLGA@Met-CO₂/siFGL1 NPs and MC-PLGA@Met-CO₂/siFGL1 NPs