Preparation, characterization and application of manganese ferrite nanoparticles for hepatoma receptor specific MR molecular imaging

Abstract

To achieve a molecular imaging with high spatial resolution, in particular, biomarker-targetable imaging probes based on magnetic nanoparticles have been designed and manufactured. In addition, recent researches reported that manganese ferrite nanoparticles (MFNPs) synthesized by a thermal decomposition method exhibit, large magnetic susceptibility rather than magnetite nanoparticles. Prior to the application of manganese ferrite, first we studied correlation of surface charge and cellular interaction of MFNPs. For investigation of the interactions of cells with magnetic nanoparticles in a biological medium, we selected the amphiphilic surfactant most commonly used for nanoemulsions, non-ionic polysorbate 80 (P80). The hydroxyl terminals of P80 were modified to carboxyl or amine terminals respectively. The MFNPs were synthesized by nanoemulsion method involving sonication and stirring with three types of polysorbate 80. Colloidal size, morphology, monodispersity, solubility, and T2 relaxivity were found to be similar between the three types of MFNPs. However, cationic MFNPs exhibited greater cytotoxicity than anionic and non-ionic MFNPs, and Raw264.7 cell uptake of cationic MFNPs was greater than that of anionic or non-ionic MFNPs under the same conditions. Next, we thus fabricated Hepatocelluar carcinoma (HCC)-specific MR imaging probes using a lactobionic acid (LBA) as a targeting moiety and. HepG2, human HCC cell line, were selected as a model cell due to the expression of abundant asialoglycoprotein receptor (ASGPr) interact-able with galactoses or n-acetyl-galactosamines. For the targeted MR imaging of ASGPr-expressed HepG2 cells, LBA molecules were conjugated with MFNPs. Subsequently, the carboxyl group of LBA was conjugated with amine group of polysorbate 80 on MFNPs using carboimide chemistry. The colloidal size of the prepared LBA-MFNPs was 30.7 ± 7.6 nm and the surface potential was 0.5 ± 1.3 mV. Significant cytotoxicity of LBA-MFNPs was observed and the targeting ability of LBA-MFNPs was investigated by dark-field microscopy, Prussian blue staining, cellular transmission electron microscopy, and MR imaging. Thus, LBA-MFNPs were successfully attached with ASGPr-expressed HepG2 cell (ASGPr-deficient MCF7 cells was used as a control cell line). In conclusion, the results of our study indicate that high specificity to HCC as compared to non-HCC cells. Thus such an approach may provide a promising strategy for tumor-specific MR imaging.