Colloidal stability, cytotoxicity, and cellular uptake of HfO2 nanoparticles

The colloidal stability, cytotoxicity, and cellular uptake of hafnium oxide (HfO2) nanoparticles (NPs) were investigated in vitro to assess safety and efficacy for use as a deliverable theranostic in nanomedicine. Monoclinic HfO2 NPs, similar to 60-90 nm in diameter and ellipsoidal in shape, were directly prepared without calcination by a hydrothermal synthesis at 83% yield. The as-prepared, bare HfO2 NPs exhibited colloidal stability in cell culture media for at least 10 days without significant agglomeration or settling. The viability (live/dead assay) of human epithelial cells (HeLa) and monocyte-derived macrophages (THP-1) did not fall below 95% of untreated cells after up to 24 h exposure to HfO2 NPs at concentrations up to 0.80 mg/ml. Similarly, the mitochondrial activity (MTT assay) of HeLa and THP-1 cells did not fall below 80% of untreated cells after up to 24 h exposure to HfO2 NPs at concentrations up to 0.40 mg/ml. Cellular uptake was confirmed and visualized in both HeLa and THP-1 cells by fluorescence microscopy of HfO2 NPs labeled with Cy5 and transmission electron microscopy (TEM) of bare HfO2 NPs. TEM micrographs provided direct observation of macropinocytosis and endosomal compartmentalization within 4 h of exposure. Thus, the HfO2 NPs in this study exhibited colloidal stability, cytocompatibility, and cellular uptake for potential use as a deliverable theranostic in nanomedicine.

Automated summary

The study demonstrated that hafnium oxide nanoparticles exhibit colloidal stability, cytocompatibility, and cellular uptake in vitro, making them a promising candidate for deliverable theranostics in nanomedicine.