Development of Iron Oxide Nanochains as a Sensitive Magnetic Particle Imaging Tracer for Cancer Detection

Abstract

The advancement of imaging technologies plays a crucial role in improving the diagnosis and monitoring of diseases, including cancer. This study introduces a new design of iron oxide-based nanoparticles specifically developed for magnetic particle imaging (MPI), aimed at tracking and diagnosing breast cancer more effectively. By precisely controlling the size, shape, and magnetic properties of these nanoparticles, we enhance the responsiveness of MPI, resulting in an increased signal. In our research, we established a novel synthetic route for fabricating iron oxide nanochains (FeONCs) characterized by their uniform shape and size, which contribute to high magnetic properties suitable for MPI applications. Initial results indicate these FeONCs exhibit superior magnetic properties compared to conventional spherical superparamagnetic iron oxide nanoparticles, nanocubes, and reported nanoworm-type structures. Magnetic relaxometry studies revealed that FeONCs provide higher sensitivity than the commonly used VivoTrax Synomag D50 and D70 in MPI. Further, the size and shape of FeONCs significantly influence cellular uptake. In vivo experiments using orthotopic breast cancer mouse models allow us to assess the biocompatibility and magnetic characteristics of the nanoparticles, confirming their imaging efficacy. Furthermore, by conjugating these nanoparticles with the RGD peptide, we enhance their ability to specifically target breast cancer, establishing them as promising tracers for in vivo MPI applications characterized by high sensitivity. Thus, our findings highlight that FeONCs significantly improve imaging quality, facilitating the early detection and accurate monitoring of breast cancer. This paves the way for innovative diagnostic strategies and personalized treatment options. Future research will focus on fine-tuning the surface chemistry of these nanoparticles to further enhance the targeting efficiency and optimization of their practice in clinical applications, particularly for MPI-based hyperthermia therapy.

Keywords: SPION; breast cancer imaging; contrast agents; iron oxide nanochain; magnetic moment; magnetic particle imaging.

Scheme 1. Schematic Representation for the Synthesis, Magnetic Properties, and MPI Imaging Application of FeONCs

Figure 1

Characterization of prepared iron oxide nanochains and nanoparticles. (A) TEM images for (i) FeONCs, (ii) DSPE-PEG FeONCs, (iii) DSPE-PEG FeONPs, (iv) RGD FeONCs, (v) RGD FeONPs, and (vi) FeONCB. Scale bar = 100 nm. The inset in figure (i) shows the high-resolution TEM images for FeONCs, with the d spacing value of 0.30 nm, which corresponds to the (220) plane. Scale bar = 1 nm. (B) Dynamic light scattering experiments for prepared nanochains and nanoparticles using DSPE-PEG and RGD surface modifications. The concentration of Fe is made to 50 μg/mL for the DLS measurements. (C) SQUID magnetometry measurements for the prepared FeONCs, FeONCBs, and FeONPs at room temperature. Magnetization curves were obtained from −50,000 to 50,000 (Oe).

Figure 2

Cell viability and cellular uptake of NPs. (A,B) MTT assay for DSPE-PEG FeONCs and RGD FeONCs using 4T1 breast cancer cells with varying concentrations of [Fe]. (C) Fluorescence microscopic images for nontreated control, DSPE-PEG/RGD-FeONC and DSPE-PEG/RGD-FeONPs. Blue = DAPI, RITC = NPs. The concentration of Fe used is 25 μg/mL for the cellular uptake studies. Scale bar = 50 μm.

Figure 3

Comparison of sensitivity and spatial resolution of NPs. (A) PSF for DSPE-PEG FeONCs, RGD FeONCs, VivoTrax, Synomag D70, and Synomag D50. RGD FeONCs showed higher signal sensitivity than all other tracers studied for the same iron content [Fe, 100 μg/mL]. (B) Normalized signal resolution for DSPE-PEG FeONCs, RGD FeONCs, VivoTrax, Synomag D70, and Synomag D50. (C) Table to represent the sensitivity and resolution of each nanoparticle for the same concentration of iron [Fe, 100 μg/mL]. (D) 2D MPI images for DSPE-PEG FeONCs, RGD FeONCs, VivoTrax, Synomag D70, and Synomag D50 for 100 μg/mL iron content. (E) Linear correlation for the MPI signal intensity with varying iron content for the NPs and commercial tracers studied.

Figure 4

2D MPI images for various NPs used for the study. 2D MPI images for various NPs and commercial tracers used for the study. (A) 2D MPI images for (a) DSPE-PEG FeONCs, (b) RGD FeONCs, (c) DSPE-PEG FeONP, (d) RGD FeONP, (e) VivoTrax, (f) Synomag-D70, and (g) Synomag-D50, respectively. The concentration of Fe is 100 μg/mL. (B) Linear correlation curve for the MPI signal intensity with varying [Fe] content in different nanoparticles studied.

Figure 5

In vivo 3D MPI images for the orthotopic breast cancer mice model. 3D MPI images for (A) DSPE-PEG FeONCs, (B) RGD FeONCs, (C) DSPE-PEG FeONPs, and (D) RGD FeONPs using orthotopic 4T1 mammary fat pad (MFP) mice. A-B show the CT overlay images with MPI for DSPE-PEG and RGD FeONCs after 24 h of particle injection. (E) Quantitative measurement for the MPI signals in the tumor regions for various NPs studied in the breast cancer model, where n = 3, *P < 0.05, **P < 0.01, ***P < 0.001.

Figure 6

Ex vivo analysis of DSPE-PEG FeONCs and RGD FeONCs using MPI. (A) Digital photographs and (B) 2D MPI images showing the excised organs from mice injected with DSPE-PEG FeONCs [Fe, 100 μg/mL]. (C) Digital photographs and (D) 2D MPI images showing the excised organs from mice injected with RGD FeONCs [Fe, 100 μg/mL]. The mice are sacrificed after 24 h of injection of NPs through I V injection. (E,F) Quantification of Fe in the main organs of mice after DSPE-PEG and RGD FeONCs injection using MPI and ICP–OES, respectively (n = 3). Prussian blue stained (iron showed blue) followed by nuclear fast red counterstain for (G) DSPE-PEG FeONC and (H) RGD FeONCs, respectively. Scale bar 100 μm. All the data were analyzed by t-test using Graph Pad (***p ≤ 0.001; *p ≤ 0.01).