title: 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.
authors.affiliation: Department of Aerospace and Mechanical Engineering, Bioengineering Graduate Program, University of Notre Dame, Notre Dame, IN 46556, USA. rroeder@nd.edu and Harper Cancer Research Institute, University of Notre Dame, Notre Dame, IN 46556, USA.
authors.forename: Tracie L
authors.initials: TL
authors.lastname: McGinnity
authors.affiliation: Department of Electrical Engineering, University of Notre Dame, Notre Dame, IN 46556, USA and Notre Dame Center for Nanoscience and Nanotechnology (NDnano), University of Notre Dame, Notre Dame, IN 46556, USA.
authors.forename: Owen
authors.initials: O
authors.lastname: Dominguez
authors.affiliation: Department of Aerospace and Mechanical Engineering, Bioengineering Graduate Program, University of Notre Dame, Notre Dame, IN 46556, USA. rroeder@nd.edu.
authors.forename: Tyler E
authors.initials: TE
authors.lastname: Curtis
authors.affiliation: Department of Aerospace and Mechanical Engineering, Bioengineering Graduate Program, University of Notre Dame, Notre Dame, IN 46556, USA. rroeder@nd.edu and Harper Cancer Research Institute, University of Notre Dame, Notre Dame, IN 46556, USA.
authors.forename: Prakash D
authors.initials: PD
authors.lastname: Nallathamby
authors.affiliation: Department of Electrical Engineering, University of Notre Dame, Notre Dame, IN 46556, USA and Notre Dame Center for Nanoscience and Nanotechnology (NDnano), University of Notre Dame, Notre Dame, IN 46556, USA.
authors.forename: Anthony J
authors.initials: AJ
authors.lastname: Hoffman
authors.affiliation: Department of Aerospace and Mechanical Engineering, Bioengineering Graduate Program, University of Notre Dame, Notre Dame, IN 46556, USA. rroeder@nd.edu and Department of Electrical Engineering, University of Notre Dame, Notre Dame, IN 46556, USA and Harper Cancer Research Institute, University of Notre Dame, Notre Dame, IN 46556, USA and Notre Dame Center for Nanoscience and Nanotechnology (NDnano), University of Notre Dame, Notre Dame, IN 46556, USA.
authors.forename: Ryan K
authors.initials: RK
authors.lastname: Roeder
mesh_terms: D015374:Biosensing Techniques; D003287:Contrast Media; D006195:Hafnium; D053768:Metal Nanoparticles; D010087:Oxides; D014057:Tomography, X-Ray Computed; D014965:X-Rays
chemical_list: D003287:Contrast Media; D010087:Oxides; C545179:hafnium oxide; D006195:Hafnium