Magnetic resonance imaging Magnetic resonance imaging experiments were performed with a 1.5-T clinical MRI instrument with a Micro-47 surface coil (Intera, Philips Medical Systems, Amsterdam, The Netherlands). T2 relaxivity (r2 (s−1 mM−1); ratio of R2 (1/T2) to iron concentration)
of MNCs was measured at room temperature by the Carr-Purcell-Meiboom-Gill sequence: TR = 10 s, 32 echoes, with 12 ms even echo space, number of acquisitions = 1, point resolution 156 × 156 μm, section thickness 0.6 mm. Characterization The morphology and the size of MNPs were analyzed using a transmission electron microscope (JEM-2100 LAB6, JEOL Ltd., Akishima-shi, Japan), and the crystallographic structure of MNPs was obtained from X-ray diffraction patterns (D/MAX Ultima III, Rigaku Co., Shibuya-ku, Japan). The characteristic bands of pure oleic acid and MNPs were evaluated by Fourier transform infrared spectroscopy (FT-IR; Excalibur Series, Selleckchem BLZ945 Varian Inc., Palo Alto,
CA, USA) to PARP signaling confirm the existence of oleic acid on the MNPs. The amount of oleic acid on the MNPs was quantified using a thermogravimetric analyzer (SDT-Q600, TA Instruments, New Castle, DE, USA). The MNC size (hydrodynamic diameter) was analyzed by laser scattering (ELS-Z, Otsuka Electronics, Hirakata-shi, Japan). The Fe concentration in MNCs was quantified by inductively coupled plasma atomic emission spectrometry (Thermo Electron Corporation, Waltham, MA, USA). Results and discussion High-quality MNPs in terms of size uniformity, single crystallinity, and high magnetism should be verified first as a part of the building blocks aminophylline that comprise the MNCs. This guarantees repeatability in experiments aimed to determine optimal GSI-IX enhancement of MNC T2 relaxivity. For particle uniformity, MNPs were synthesized by a thermal decomposition method using an iron-oleate as the precursor and oleic acid as the primary ligand . The narrow size distribution (7.8 ± 0.5 nm) and the spherical morphology of the MNPs were ascertained by transmission electron microscopy (Figure 2a). The highly crystalline MNP structure was confirmed by the X-ray powder diffraction pattern
assigned at 2θ values of 30° (220), 36° (311), 44° (400), 58° (511), and 63° (440), which indicated the inverse spinel structure of magnetite (Fe3O4; JCPDS no. 19–0629; Additional file 1: Figure S1a). Moreover, the MNPs exhibited the saturation magnetization value of 87 emu g−1 Fe at 1.0 T without magnetic hysteresis (Additional file 1: Figure S1b). Figure 2 Characterization of PMNPs. (a) Transmission electron microscopy image of MNPs. (b) Thermogravimetric analysis shows weight change in relation to temperature of the three PMNPs containing different amounts of primary ligand (oleic acid). (c) Derivative weight curves of the three PMNPs (LMNPs, MMNPs, and HMNPs). (d) Illustration of the interactions of oleic acid on MNPs.