Titanium oxide shell coatings decrease the cytotoxicity of ZnO nanoparticles

Area of Science:

• Materials Science
• Nanotechnology
• Biomedical Engineering

Background:

• Nanoparticles of zinc oxide (nano-ZnO) are widely used but can cause significant cellular damage.
• Oxidative stress and DNA damage are key concerns associated with nano-ZnO exposure.
• Developing safer nanomaterials is crucial for their broader application.

Purpose of the Study:

• To reduce the cytotoxicity of nano-ZnO by coating it with a titanium dioxide (TiO2) layer.
• To synthesize and characterize core (nano-ZnO)/shell (TiO2) nanoparticles (NPs).
• To evaluate the effectiveness of the TiO2 coating in mitigating nano-ZnO's harmful effects on mammalian cells.

Main Methods:

• Sol-gel method was used to synthesize core/shell ZnO/TiO2 NPs with varying coating thicknesses.
• Transmission electron microscopy (TEM) and Raman spectroscopy confirmed the core/shell structure.
• X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) spectroscopy provided detailed structural information.
• Cytotoxicity assays (MTT, IL-8, LDH, DCFH-DA) were performed on A549 lung cells to assess toxicity, inflammation, membrane damage, and reactive oxygen species (ROS) production.

Main Results:

• Characterization confirmed the successful formation of ZnO/TiO2 core/shell nanostructures.
• The TiO2 shell was amorphous and showed slight intrinsic cytotoxicity.
• Core/shell nanostructures exhibited significantly less oxidative stress and cytotoxicity compared to physical mixtures of ZnO and TiO2 NPs.
• Increased TiO2 coating thickness correlated with reduced nano-ZnO toxicity.

Conclusions:

• The ZnO/TiO2 core/shell nanostructure effectively moderates the cytotoxicity of nano-ZnO.
• This moderation is achieved by limiting zinc ion release and reducing the direct contact area of the ZnO core.
• Core/shell nanoparticle design offers a promising strategy to enhance the safety of nanomaterials for biological applications.