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Preparation and Evaluation of a Radioisotope-Incorporated Iron Oxide Core/Au Shell Nanoplatform for Dual Modality Imaging

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Magnetic gold-coated iron oxide nanoparticles (Fe@Au NPs) have recently emerged as a new type of iron oxide nanoparticle based magnetic resonance imaging (MRI) contrast agents, in which the gold shell provides a conveniently tunable surface for the presentation of multiple functional molecules. Given the versatility of this nanoplatform and the intrinsic sensitivity limitation of MRI contrast agents, a new approach was developed in this work to incorporate radioisotopes with suitable half-lives into the iron oxide core of Fe@Au NPs and impart the superior sensitivity of nuclear imaging to the nanoplatform. The incorporation of 67Ga was successfully accomplished by co-precipitation of 67Ga3+ with Fe3+/Fe2+ ions at a pH ranging from 4–10. The gold coating procedure was carried out by an iterative hydroxylamine seeding process. Upon the gold deposition, the hydrodynamic radius of the nanoparticles was changed from 23.2±2.2 nm to 31.7±2.3 nm, indicating an 8-nm thickness for the gold shell. The Fe@Au NPs were functionalized by lipoic acid (LA) and further conjugated with a polyarginine cell permeation peptide, NH2GR11. All the Fe@Au NPs stayed nearly 100% intact in either PBS or rat serum within 72 h. Cell labeling with the LA-modified Fe@Au NPs and NH2GR11-conjugated Fe@Au NPs was conducted by using a human prostate cancer cell line (PC-3). It was shown that NH2GR11 was able to increase the nanoparticle loading to PC-3 cells by 2–3 times. Shown in a pilot dual-modality imaging study, the LA-modified Fe@Au NP labeled cells could be visualized by both MRI and autoradiography imaging if the labeled PC-3 cell concentrations were above 1 × 105 cells/mL. The cell permeation peptide, NH2GR11, could significantly enhance the dual-modality detection sensitivity of the nanoplatform labeled PC-3 cells.


Document Type: Research Article


Publication date: 2008-12-01

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  • Journal of Biomedical Nanotechnology (JBN) is a peer-reviewed multidisciplinary journal providing broad coverage in all research areas focused on the applications of nanotechnology in medicine, drug delivery systems, infectious disease, biomedical sciences, biotechnology, and all other related fields of life sciences.
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