Hafnia (HfO₂) nanoparticles as an X-ray contrast agent and mid-infrared biosensor

Abstract

The interaction of hafnium oxide (HfO2) nanoparticles (NPs) with X-ray and mid-infrared radiation was investigated to assess the potential as a multifunctional diagnostic probe for X-ray computed tomography (CT) and/or mid-infrared biosensing. HfO2 NPs of controlled size were prepared by a sol-gel process and surface functionalized with polyvinylpyrrolidone, resulting in relatively spherical and monodispersed NPs with a tunable mean diameter in the range of ∼7-31 nm. The X-ray attenuation of HfO2 NPs was measured over 0.5-50 mM concentration and compared with Au NPs and iodine, which are the most prominent X-ray contrast agents currently used in research and clinical diagnostic imaging, respectively. At clinical CT tube potentials >80 kVp, HfO2 NPs exhibited superior or similar X-ray contrast compared to Au NPs, while both exhibited significantly greater X-ray contrast compared to iodine, due to the favorable location of the k-shell absorption edge for hafnium and gold. Moreover, energy-dependent differences in X-ray attenuation enabled simultaneous quantitative molecular imaging of each agent using photon-counting spectral (multi-energy) CT. HfO2 NPs also exhibited a strong mid-infrared absorption in the Reststrahlen band from ∼250-800 cm(-1) and negative permittivity below 695 cm(-1), which can enable development of mid-infrared biosensors and contrast agents, leveraging surface enhanced mid-infrared and/or phonon polariton absorption.

Evaluation of spectral photon counting computed tomography K-edge imaging for determination of gold nanoparticle biodistribution in vivo

“…First, the detection of AuNP in the bone marrow is remarkable, since contrast arising in that tissue would likely have gone unnoticed or be undetectable on conventional images due to the nearby presence of bone, although the accuracy of detection in the bone marrow is not as good as for other organs as can be seen in Figure 7, which may be due to factors such as beam hardening 34 . This highlights the strength of SPCCT, i.e.…”

Small, Long Blood Half-Life Iodine Nanoparticle for Vascular and Tumor Imaging

“…A standard calibration curve is shown in Supplementary Fig. S6 44 . HU values were calculated by measuring the 3-D reconstructed voxel values in a 3-D region as well as in water and air, and using the formula for Hounsfield Units: HU = 1000 × (µ − µ water )/(µ water − µ air ).…”

Metal-based NanoEnhancers for Future Radiotherapy: Radiosensitizing and Synergistic Effects on Tumor Cells

“…Hafnium oxide (hafnia, HfO 2 ) has been shown to possess photo-luminescent properties 132 and HfO 2 nanoparticles (HfO 2 NPs) exhibit chemical inertness in cellular and subcellular systems 133 - 135 . Hence, owing to the high atomic number, electron density, and chemical stability of hafnium/hafnia, HfO 2 NPs show promising potential as sensitizers for radiation therapy as well as X-ray contrast agents 136 .…”