Albumin-Coated Single-Core Iron Oxide Nanoparticles for Enhanced Molecular Magnetic Imaging (MRI/MPI)

Abstract

Colloidal stability of magnetic iron oxide nanoparticles (MNP) in physiological environments is crucial for their (bio)medical application. MNP are potential contrast agents for different imaging modalities such as magnetic resonance imaging (MRI) and magnetic particle imaging (MPI). Applied as a hybrid method (MRI/MPI), these are valuable tools for molecular imaging. Continuously synthesized and in-situ stabilized single-core MNP were further modified by albumin coating. Synthesizing and coating of MNP were carried out in aqueous media without using any organic solvent in a simple procedure. The additional steric stabilization with the biocompatible protein, namely bovine serum albumin (BSA), led to potential contrast agents suitable for multimodal (MRI/MPI) imaging. The colloidal stability of BSA-coated MNP was investigated in different sodium chloride concentrations (50 to 150 mM) in short- and long-term incubation (from two hours to one week) using physiochemical characterization techniques such as transmission electron microscopy (TEM) for core size and differential centrifugal sedimentation (DCS) for hydrodynamic size. Magnetic characterization such as magnetic particle spectroscopy (MPS) and nuclear magnetic resonance (NMR) measurements confirmed the successful surface modification as well as exceptional colloidal stability of the relatively large single-core MNP. For comparison, two commercially available MNP systems were investigated, MNP-clusters, the former liver contrast agent (Resovist), and single-core MNP (SHP-30) manufactured by thermal decomposition. The tailored core size, colloidal stability in a physiological environment, and magnetic performance of our MNP indicate their ability to be used as molecular magnetic contrast agents for MPI and MRI.

Magnetic particle imaging: tracer development and the biomedical applications of a radiation-free, sensitive, and quantitative imaging modality

“…Similar to when SPION contrast agents were first realised for MRI in the 1980s, 212 research on the development and synthesis of monodispersed novel MPI-tailored SPIONs has recently become an important area of research. 5,63,188,213–216 These new particles can be functionalised and optimised for improved performance in specific applications, like for increased circulation time or for more efficient cell targeting. Whilst MPI-optimised tracers will have to undergo a lengthy evaluation before clinical approval, the exploration and development of better performing SPIONs should spur further work towards clinical applications.…”

Advances in Magnetic Nanoparticles Engineering for Biomedical Applications—A Review

“…Coating the surface of MNPs prevents aggregation in physiological tissue and bloodstream and enhances the biocompatibility. Often, it is a crucial step to prevent unwanted interactions of MNPs with their local biological environment as proteins and cells, and thus avoid their toxicity [132,133]. Commonly used coating materials are dextran [134][135][136] polyethylene glycol (PEG) [50,137] peptides [138] and serum albumin [132,139,140].…”

“…Often, it is a crucial step to prevent unwanted interactions of MNPs with their local biological environment as proteins and cells, and thus avoid their toxicity [132,133]. Commonly used coating materials are dextran [134][135][136] polyethylene glycol (PEG) [50,137] peptides [138] and serum albumin [132,139,140]. In this section, we present the latest developments in the translation of MNPs into biomedical applications like magnetic imaging, drug delivery, hyperthermia, and magnetic actuation.…”

“…Thus, imaging modalities have recently gained significant attention and are still developing. Magnetic resonance imaging (MRI) and magnetic particle imaging (MPI) are non-invasive imaging techniques that uses MNPs as contrast agents to deliver a high-resolution image without using ionizing radiation [132,141]. MRI detects the nuclear magnetic resonance signal of 1 H atoms after applying radiofrequency pulses.…”

“…After stabilization with tannic acid, the MNPs were coated with albumin which enhanced their colloidal stability in a physiological environment like a bloodstream. The MNPs exhibit diameters of dc = 27.7 nm and dh = 42 nm and relaxivity values r1 = 6.2 L•mmol −1 s −1 and r2 = 600 L•mmol −1 s −1 , r2 and a r1/r2 ratio and for MPI, a higher value for A3* = 26 Am 2 /kg(Fe), A5/A3 ratio compared to Resovist (Table 2), which makes these MNPs promising for clinical applications in the above-mentioned hybrid MP/MR imaging modality [132].…”