9.4 t magnet

For in vivo MR imaging studies, cultured HCT116 cancer cells (2 × 10⁶ cells) were injected into the right thigh regions of mice (n = 3) to establish the tumors. Note that these three mice were used for proof-of-concept experiments in this study. After the tumors developed up to a size of approximately 200 mm³, mice were deeply anesthetized with isoflurane (1–4%) using an inhalation device and placed on a heating pad. Then, 500 µg of HA-MnO@MSN was injected intratumorally. MRI acquisitions were performed on a 9.4 T magnet (Bruker-Biospin, Billerica, MA, United States) using a 35-mm volume quad-coil (Bruker-Biospin, Billerica, MA, United States). T1 relaxation times were calculated using a RAREVTR inversion recovery sequence. The baseline image was acquired preinjection and following measurements at various time points postinjection. The MR parameters were set up as TR = 600 ms, TE = 10.5 ms, FOV = 4 × 4 cm, slice thickness = 1 mm, 20 slices, NEX = 8, and matrix size = 256 × 128 recovered to 256 × 256.

The morphology of the samples was characterized using a transmission electron microscope (TEM) (Hitachi, H-7650), operating at an accelerated voltage of 80 kV. Fourier transform infrared spectroscopy (FTIR) was recorded on a Nicolet 550 spectrometer using KBr pellets (approximately 1 mg of the sample was pressed with 300 mg KBr). ZetaSizer Nano was used to measure the hydrodynamic size of the nanoparticles. MRI acquisitions were performed on a 9.4 T magnet (Bruker-Biospin, Billerica, MA, United States) using a 35-mm volume quad-coil (Bruker-Biospin, Billerica, MA, United States). Mn concentrations were based on the molar concentration of manganese atoms measured using ICP-MS (Perkin Elmer Elan 6100).