Figure 6. Conjugation of FA with PSiO₂ nanoparticle showed improved endocytosis in HeLa cells. HeLa cells treated with PSiO₂ nanoparticles at 10 µg/ml for 2 h and the extracellular binding of the nanoparticles was quenched with trypan blue (FITC, pristine FITC-labeled particle; FITC/PEI, PEI-functionalized FITC-labeled particle; FITC/PEI/FA, FA-conjugated PEI-functionalized FITC-labeled particle). Fluorescence microscopy was used to image FITC-labeled particles inside the cells and differential interference contrast microscopy for cellular morphology evaluations (A). Flow cytometry was used to detect the number of HeLa cells with endocytosed PSiO₂ nanoparticles in control or trypan blue quenched cells (B). Reprinted with permission from reference 53.