Figure 1. Firm adhesion of amorphous silica to alveolar epithelial cells (AEC) is energy and caveolin dependent. ( A ) Adhesion force between an amorphous silica probe tip and A549 cells was measured by force spectroscopy. Interfering with ATP production (NaN 3 and 2-deoxy-D-glucose), lipid microdomains (LM, methyl-β-cyclodextrin MBCD) or caveolin (Filipin III) but not with clathrin-mediated endocytosis (chlorpromazine) diminished adhesion strength at 120 s, but not at the earlier time points. For each time point the data is collected from 10 different cells with an average 15 repeats on every cell with at least three independent experiments for each group (mean ± SEM; **p < 0.01 compared to matching untreated control). ( B ) Polynomial curve fitting of the dataset (from the initial 120 s and beyond) revealed biphasic process with the adhesion strength increasing between 0 and 30 s (not affected by the inhibitors) and 60–120 s (ATP-, LM- and caveolin-dependent). ( C ) Validation of the most important findings in primary human AEC (hAEC) at 120 s with no effect of chlorpromazine and significant suppression of the adherence strength by Filipin III (≥ 3 independent experiments with n = 10 different cells and an average 15 repeats on every