Abstract
Purpose: Magnetic targeting refers to the attachment of therapeutic agents to magnetizable particles such as magnetic nanoparticles (MNPs) and then applying magnetic fields to concentrate them to the targeted region such as solid tumors. The purpose of this study was to investigate the usefulness of magnetic particle imaging (MPI) for monitoring the effect of magnetic targeting using tumor-bearing mice. Materials and Methods: Colon-26 cells (1 × 106 cells) were implanted into the backs of eight-week-old male BALB/c mice. When the tumor volume reached approximately 100 mm3, the mice were divided into treated (n = 8) and untreated groups (n = 8). The tumors in the treated group were directly injected with MNPs (Resovist?, 250 mM) and a neodymium magnet was attached to the tumor surface, whereas the magnet was not attached to the tumor in the untreated group. The mice were imaged using our MPI scanner and the average and maximum MPI values were obtained by drawing a region of interest (ROI) on the tumor, with the threshold value for extracting the contour of the tumor being taken as 40% of the maximum MPI value in the ROI. The relative tumor volume growth (RTVG) was calculated from (V ? V0)/V0, where V0 and V represented the tumor volume immediately before and after the injection of MNPs, respectively. Results: The average and maximum MPI values in the treated group were significantly higher than those in the untreated group 3 days after the injection of MNPs, suggesting the effectiveness of magnetic targeting. There were no significant differences in RTVG between the two groups. Conclusion: Our preliminary results suggest that MPI is useful for monitoring the effect of magnetic targeting.
Highlights
Molecular transport based on magnetic nanoparticles (MNPs) has been the subject of recent strategies to enhance drug delivery and reduce drug toxicity in diverse medical fields [1] [2]
Magnetic targeting refers to the attachment of therapeutic agents to magnetizable particles such as MNPs and applying magnetic fields to concentrate them to the targeted region such as solid tumors and regions of infection [4]
We have developed a system for magnetic particle imaging (MPI) with a field-free-line encoding scheme, in which the field-free line is generated using two opposing neodymium magnets, and transverse images are reconstructed from the third-harmonic signals received by a gradiometer coil using the maximum likelihood-expectation maximization (ML-EM) algorithm [9] [10]
Summary
Molecular transport based on magnetic nanoparticles (MNPs) has been the subject of recent strategies to enhance drug delivery and reduce drug toxicity in diverse medical fields [1] [2]. MNPs are actively being developed based on their unique properties to respond to magnetic fields including static and alternating magnetic fields [2] [3]. Magnetic targeting refers to the attachment of therapeutic agents to magnetizable particles such as MNPs and applying magnetic fields to concentrate them to the targeted region such as solid tumors and regions of infection [4]. Accurate knowledge of the distribution and quantity of MNPs within the targeted tumor is crucial for effective and safe treatment planning of cancer therapy based on magnetic targeting [6]. We have developed a system for MPI with a field-free-line encoding scheme, in which the field-free line is generated using two opposing neodymium magnets, and transverse images are reconstructed from the third-harmonic signals received by a gradiometer coil using the maximum likelihood-expectation maximization (ML-EM) algorithm [9] [10]
Sign-in/Register to view highlights & summary 
Published Version (
Free)
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call