Fig. 3.

The interaction of silica particles with self-assembled DOPC, but not DOPS, is irreversible and specific for NFS. (A) Hemolytic activity of the silica particles in presence of self-assembled DOPC or DOPS. Hemolytic particles, i.e., gQ-f, gQ-ff, cQ-f (positive reference quartz), and aS were pre-incubated with just the vehicle (0.01 M PBS), or 0.1 mg mL⁻¹ of DOPC or DOPS for 30 min. A suspension of 5% RBC was added and the hemolytic activity assessed after a further incubation of 30 min. Data are the mean ± SEM of three independent experiments and were compared with a two-tailed Student’s t test. * **p < 0.001 vs. group without PLs, containing only silica. (B) Irreversible adsorption of DOPC inhibits the hemolytic activity of the silica particles. Hemolytic particles, i.e., gQ-f, gQ-ff, cQ-f (positive reference quartz), and aS were pre-incubated with the vehicle or 0.1 mg mL⁻¹ of DOPC for 30 min. The mixture was centrifuged, supernatant removed, particles washed three times with PBS, and hemolysis assessed. Data are the mean ± SEM of three independent experiments and were compared with a two-tailed Student’s t test. * **p < 0.001 vs. group without PLs, containing only silica. (C) Surface silanol distribution (transmittance IR spectra reported in absorbance) in the νOD spectral region (after H/D isotopic exchange and νOH spectra subtraction) of aS incubated with just the vehicle (0.01 M PBS), or 0.1 mg mL⁻¹ of DOPC or DOPS for 30 min, washed three times with PBS, and dried. (D) Correlation between % NFS and adsorbed self-assembled PLs (molecules nm⁻²) for silica particles. Percent NFS relative to total silanols as calculated from deconvolution of IR spectroscopic features were compared by linear regression analysis with DOPC or DOPS (molecules nm⁻²) adsorption for each silica sample. Parametric linear regression analysis (DOPC: Pearson’s coefficient = 0.99; R² = 0.97; DOPS: Pearson’s coefficient = 0.92; R² = 0.78) was applied.