Highly sensitive electron paramagnetic resonance nanoradicals for quantitative intracellular tumor oxymetric images

Figures & data

Figure 1 (A) Illustration of trityl-loaded FMSNs for electron paramagnetic resonance imaging. FMSN with targeting moiety, TAG72mAb, as a carrier for trityl radical for in vivo tumor oxygen measurement. (B) Transmission electron microscope (TEM) image of mesoporous silica nanoparticles. (C) Thermogravimetric analysis of FMSN, FMSN-PEG, and FMSN-PEG-TAG72. (D) EPR spectrum of trityl (black), FMSN-trityl (red), and overlay.

Figure 2 Oxygen response of FMSN-trityl. (A) EPR spectrum of trityl and FMSN-trityl at various oxygen concentrations. The spectra are scaled to the same maximum amplitude height in the plots. (B) The dependence of peak-to-peak EPR spectrum line width of trityl/FMSN-trityl on oxygen partial pressure. (C) The dependence of peak-to-peak EPR spectrum line width of FMSN-trityl at different pH levels.

Figure 3 Cell uptake of FMSN-trityl. Fluorescent confocal images of cells treated with (A) PBS, (B) trityl-loaded FMSN-PEG, (C) trityl-loaded FMSN-PEG-TAG72. Trityl-loaded FITC-MSNs (green); nucleus stain, DAPI (blue); and cell membrane stain, WGA647 (red). (D) Histogram of cell counts from flow cytometer. X-axis shows the intensity of FITC.

Figure 4 Cell oxygen consumption. (A) EPR spectra of cells treated with trityl-loaded FMSN-PEG-TAG72 at various time points. (B) The peak-to-peak line width of EPR spectra was converted to pO₂ (mmHg) and plotted with time. Dwell time per scan is 5.12 s.

Figure 5 In vivo tumor oxygen images. Nude mice with LS-174T xenograft tumor on leg flank were used to monitor in vivo oxygen measurements. pO₂ of tumor was first imaged by intravenously injected trityl. After half-hour washout, tumor mice were injected with 3.36 mg of FMSN-trityl and the intracellular pO₂ levels were monitored by EPRI. Tumor outlines obtained from MRI were illustrated in pink. Color bar showed pO₂ scale in the range 0–60 mmHg. (A) pO₂ image measured from FMSN-trityl via IT injection. (B) Signal amplitude acquired from FMSN-trityl via IT injection. (C) pO₂ image measured from trityl via IV injection.