Impact of titanium dioxide particle size on macrophage production of intracellular reactive oxygen species.

OBJECTIVES

The aim of this study was to investigate the response of THP-1 monocyte-derived macrophages following exposure to titanium dioxide nanoparticles (TiO NPs) and microparticles (TiO MPs) in an in vitro system.

DESIGN

THP-1 monocytes were maintained in RPMI medium and transformed into M0 macrophages using Phorbol 12-myristate 13-acetate (PMA). TiO particle size characterization was performed using scanning electron microscopy (SEM) and dynamic light scattering (DLS) technology. A viability study using an XTT assay was performed by treating THP-1-derived macrophages with TiO NPs (<100 nm) and TiO MPs (<5 μm) at concentrations ranging from 100, 50, 25, 12.5, 6.25 and 3.125 μg/mL. Macrophages were then treated with three different concentrations of NPs and MPs (5, 20 or 100 μg/mL) for 24 h, and ROS production and TiO particle cellular uptake were measured using ROS assays and flow cytometry, respectively.

RESULTS

There was no significant change in the viability of THP-1 monocytes after treatment with TiO NPs and MPs. The uptake of both particles was confirmed and showed an increase in ROS generation, and the MPs produced more ROS than NPs. The increase in ROS generation with NPs was concentration-dependent.

CONCLUSION

Uptake of TiO NPs and MPs in macrophages at subcytotoxic levels generate ROS in a size- and dose-dependent manner.