RESUMEN
The controlled preparation of chitosan particles is far from being trivial due to a considerable number of experimental parameters. For chitosan-tripolyphosphate (TPP) particles we evaluate the impact of chemical (type of chitosan, concentration, chitosan to TPP ratio, pH, ionic strength) and process factors (dialysis, stirring rate, rate of TPP addition, temperature, needle diameter) on the size and colloidal stability. The particles were prepared at pH=6.0 at which chitosan adopts the coiled conformation that is discussed as the dominant factor in controlling the stoichiometry of crosslinking reaction shifted towards TPP. These conditions result in identical particle size around 400nm and zeta potential around 22mV. The colloidal stability evaluated 24 hours after preparation depends on the amount of TPP during crosslinking. Under the same conditions, the colloidal stability up to 1 month is demonstrated. Several recommendations are provided to increase the control over formation of chitosan-TPP particles.
RESUMEN
The generation of reactive oxygen species (ROS) has been proposed as the underlying mechanism involved in the genotoxicity of iron oxide nanoparticles. The data published to date are, however, inconsistent, and the mechanism underlying ROS formation has not been completely elucidated. Here, we investigated the capacity of several surface-modified magnetite nanoparticles (MNPs) to generate ROS in A549 human lung adenocarcinoma epithelial cells and HEL 12469 human embryonic lung fibroblasts. All MNPs, regardless of the coating, induced significant levels of DNA breakage in A549 cells but not in HEL 12469 cells. Under the same treatment conditions, variable low levels of intracellular ROS were detected in both A549 and HEL 12469 cells, but compared with control treatment, none of the coated MNPs produced any significant increase in oxidative damage to DNA in either of these cell lines. Indeed, no significant changes in the total antioxidant capacity and intracellular glutathione levels were observed in MNPs-treated human lung cell lines regardless of surface coating. In line with these results, none of the surface-modified MNPs increased significantly the GPx activity in A549 cells and the SOD activity in HEL 12469 cells. The GPx activity was significantly increased only in SO-Fe3O4-treated HEL 12469 cells. The SOD activity was significantly increased in SO-PEG-PLGA-Fe3O4-treated A549 cells but significantly decreased in SO-Fe3O4-treated A549 cells. Our data indicate that oxidative stress plays, at most, only a marginal role in the genotoxicity of surface-modified MNPs considered in this study in human lung cells.
