In vitro assessment of CeO₂ nanoparticles effects on intestinal microvilli morphology

Some nanoparticles (NPs) have been shown to disrupt intestinal microvilli morphology in vitro, an alteration that could potentially affect nutrient absorption and barrier properties. This study aimed at evaluating the potential effect of CeO₂ NPs (4-8 nm, citrate stabilized) on Caco-2 microvilli morphology. In addition to the standard Caco-2 cell clone, the C2BBe1 clone was used, as it is considered to develop a more homogeneous cellular morphology. Semiautomated microvilli density quantification and a new cell scoring approach were used to evaluate scanning electron microscopy (SEM) images. The quantification method made use of the whole micrograph surface, avoiding the need to choose subareas for analysis, and increasing the representativeness of the results when compared to previous studies. The main advantage of the scoring system is that it informs on the intercellular variability within a cell preparation. Benzalkonium was used as a positive control inducing toxicity and morphological alterations on microvilli. After three-week differentiation, Caco-2 cells were exposed to 100 μg/mL of CeO₂ NPs for 24 h. The integrity of the membrane was evaluated by transepithelial electrical resistance (TEER) and thereafter processed for its observation by SEM. Results showed that both the standard Caco-2 clone and the C2BBe1 clone present notable morphological heterogeneity. The two evaluation approaches were able to identify morphological effects caused by the positive control, but did not detect statistically significant morphological alterations after exposure to CeO₂ NPs.