Investigation of Magnetic Nanoparticles for the Rapid Extraction and Assay of Alpha-Emitting Radionuclides From Urine: Demonstration of a Novel Radiobioassay Method

Abstract

In the event of an accidental or intentional release of radionuclides into a populated area, massive numbers of people may require radiobioassay screening as triage for dose-reduction therapy or identification for longer-term follow-up. If the event released significant levels of beta- or alpha-emitting radionuclides, in vivo assays would be ineffective. Therefore, highly efficient and rapid analytical methods for radionuclide detection from submitted spot urine samples (≤50 mL) would be required. At present, the quantitative determination of alpha-emitting radionuclides from urine samples is highly labor intensive and requires significant time to prepare and analyze samples. Sorbent materials that provide effective collection and enable rapid assay could significantly streamline the radioanalytical process. The authors have demonstrated the use of magnetic nanoparticles as a novel method of extracting media for four alpha-emitting radionuclides of concern (polonium, radium, uranium and americium) from chemically-unmodified and pH-2 human urine. Herein, the initial experimental sorption results are presented along with a novel method that uses magnetic nanoparticles to extract radionuclides from unmodified human urine and then collect the magnetic field-induced particles for subsequent alpha-counting-source preparation. Additionally, a versatile human dose model is constructed that determines the detector count times required to estimate dose at specific protective-action thresholds. The model provides a means to assess a method's detection capabilities and uses fundamental health physics parameters and actual experimental data as core variables. The modeling shows that, with effective sorbent materials, rapid screening for alpha-emitters is possible with a 50-mL urine sample collected within 1 wk of exposure/intake.

Magnetic iron oxide and manganese-doped iron oxide nanoparticles for the collection of alpha-emitting radionuclides from aqueous solutions

“…Transmission electron microscope (TEM) and scanning transmission electron microscope (STEM) images of the materials used in this study were presented by O’Hara et al . 27 and Warner et al , 24 respectively.…”

“…O’Hara et al explored the use of MNPs (unmodified Fe 3 O 4 NPs and the Mn-doped Fe 3 O 4 NPs synthesized by Warner et al ) in the collection of alpha-emitting radionuclides ( 210 Po, 226 Ra, 233 U, and 241 Am) from human urine at its natural pH and at pH ~2. 27 Additionally, they demonstrated a simplified and fast in vitro radiobioassay method wherein the MNPs were used to scavenge radionuclides from urine prior to magnetic capture, dissolution of the concentrated MNPs, and subsequent counting source preparation for alpha energy spectroscopy (AES). More recently, members of this research team explored the use of Fe 3 O 4 , Mn-doped Fe 3 O 4 , and other metal oxide sorbent structures for the collection of U from seawater.…”

Nanostructured Metal Oxide Sorbents for the Collection and Recovery of Uranium from Seawater

“…29,30 Moreover, iron oxide is also intrinsically a relatively good uranium sorbent. 5,25,45 It can be seen from Table 3 that bare Fe 3 O 4 magnetic nanoparticles (MNP) and clusters showed only moderate uptake of uranium, especially considering the very high surface area of 8 nm Fe 3 O 4 MNP. Manganese doping on the Fe 3 O 4 significantly improved the performance of all materials (∼10−20%).…”

Magnetic iron oxide nanoparticles for the collection and direct measurement of adsorbed alpha-emitting radionuclides from environmental waters by liquid scintillation analysis

“…The described method is capable of concentrating a range of naturally occurring or man-made radionuclides from environmental waters and urine onto a small mass of relatively non-toxic Fe 3 O 4 NPs, 63,64 which in turn can be isolated from the bulk solution by application of a strong magnet. 40,59 This resulting concentrated metal oxide suspension can then be introduced directly into the scintillation cocktail, or the MNPs can be dissolved prior to scintillation cocktail addition (see ESI† for process flow schematic and table).…”

“…Then, the radio-nuclide-sorbed MNPs were magnetically concentrated from urine and then used to prepare alpha counting sources for AEA. 59 The concentrated MNPs were dissolved in acid prior to counting source preparation via (1) spontaneous deposition onto metal discs ( 210 Po) and (2) NdF 3 co-precipitation and capture on a filter membrane ( 226 Ra and 241 Am).…”