Evaluating the Use of Ti[O.sub.2] Nanoparticles for Toxicity Testing in Pulmonary A549 Cells

Purpose: Titanium dioxide nanoparticles, 25 nm in size of crystallites (Ti[O.sub.2] P25), are among the most produced nanomaterials worldwide. The broad use of Ti[O.sub.2] P25 in material science has implied a request to evaluate their biological effects, especially in the lungs. Hence, the pulmonary A549 cell line has been used to estimate the effects of Ti[O.sub.2] P25. However, the reports have provided dissimilar results on caused toxicity. Surprisingly, the physicochemical factors influencing Ti[O.sub.2] P25 action in biological models have not been evaluated in most reports. Thus, the objective of the present study is to characterize the preparation of Ti[O.sub.2] P25 for biological testing in A549 cells and to evaluate their biological effects. Methods: We determined the size and crystallinity of Ti[O.sub.2] P25. We used four techniques for Ti[O.sub.2] P25 dispersion. We estimated the colloid stability of Ti[O.sub.2] P25 in distilled water, isotonic NaCl solution, and cell culture medium. We applied the optimal dispersion conditions for testing the biological effects of Ti[O.sub.2] P25 (0-100 [micro]g.[mL.sup.-1]) in A549 cells using biochemical assays (dehydrogenase activity, glutathione levels) and microscopy. Results: We found that the use of fetal bovine serum in culture medium is essential to maintain sufficient colloid stability of dispersed Ti[O.sub.2] P25. Under these conditions, Ti[O.sub.2] P25 were unable to induce a significant impairment of A549 cells according to the results of biochemical and microscopy evaluations. When the defined parameters for the use of Ti[O.sub.2] P25 in A549 cells were met, similar results on the biological effects of Ti[O.sub.2] P25 were obtained in two independent cell laboratories. Conclusion: We optimized the experimental conditions of Ti[O.sub.2] P25 preparation for toxicity testing in A549 cells. The results presented here on Ti[O.sub.2] P25-induced cellular effects are reproducible. Therefore, our results can be helpful for other researchers using Ti[O.sub.2] P25 as a reference material. Keywords: titanium dioxide, nanoparticles, P25, nanotoxicity, A549 cells, dispersion