Colloidal stability, cytotoxicity, and cellular uptake of HfO₂ nanoparticles

Abstract

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, ~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.

The Surface Chemistry of Colloidal Nanocrystals Capped by Organic Ligands

“…To some extent this is related to the biological relevance of iron oxide and its incompatibility with NMR spectroscopy. However, hafnium oxide is also a valuable nanocrystal for biomedicine, − and it is compatible with NMR. This is currently the focus in our own research group.…”

Effect of Hafnium Coating on Osseointegration of Titanium Implants: A Split Mouth Animal Study

“…In the current study, hafnium coating appears to have offered similar biocompatibility (aspartate transaminase (AST), alanine aminotransferase (ALT), and creatine kinase (CK) enzyme assay), statistically significant improvement (independent Student's t-test, p < 0:05) in insertion torque (25:42 ± 3:96) and removal torque (29:17 ± 2:88) than commercially pure titanium with insertion torque (22:08 ± :57) and removal torque (25:42 ± 2:57). Hafnium has proved to have good tissue response and osseointegration, along with required mechanical properties [39][40][41][42][43][44][45][46][47][48]. Though these results seem to favour hafnium, it is necessary to analyse the factors that could have confounded our study.…”

Harnessing HfO2 Nanoparticles for Wearable Tumor Monitoring and Sonodynamic Therapy in Advancing Cancer Care

“…To visualize the cellular uptake of HfO 2 NPs, CT26 cells were incubated with Alexa Fluor 633-conjugated HfO 2 NPs (f-HfO 2 NPs) at a concentration of 200 μg/mL. The preparation of f-HfO 2 NPs followed a previously reported procedure . Briefly, a solution of (3-aminopropyl)­triethoxysilane (APTES)-Alexa Fluor 633 was prepared by mixing 3 mL of cyclohexane, 100 μL of APTES, and 0.1 mg of Alexa Fluor 633, followed by stirring for 24 h. The HfO 2 NPs (8 mM in 90% ethanol) were mixed with the prepared APTES-Alexa Fluor 633 under rapid stirring for 6 h at room temperature.…”