Analysis of Stable Chelate-free Gadolinium Loaded Titanium Dioxide Nanoparticles for MRI-Guided Radionuclide Stimulated Cancer Treatment

Title:Analysis of Stable Chelate-free Gadolinium Loaded Titanium Dioxide Nanoparticles for MRI-Guided Radionuclide Stimulated Cancer Treatment

Volume: 18 Issue: 7

Author(s): Lei Fang, Hengbo Huang, James D. Quirk, Jie Zheng, Duanwen Shen, Brad Manion, Matthew Mixdorf, Partha Karmakar, Gail P. Sudlow, Rui Tang and Samuel Achilefu*

Affiliation:

• School of Medicine, Mallinckrodt Institute of Radiology, Washington University in St. Louis, Saint Louis, United States
• Department of Biomedical Engineering, School of Engineering, Washington University in St. Louis, Saint Louis, United States
• Department of Biochemistry and Molecular Biophysics, School of Medicine, Washington University in St. Louis, Saint Louis, United States
• Department of Biomedical Engineering, University of Texas Southwestern, Dallas, United States

Keywords: Titanium dioxide, colorimetric assay, MRI, relaxivity, cerenkov radiation, reactive oxygen species, magnetic resonance imaging, cancer.

Abstract:

Background: Recent studies demonstrate that titanium dioxide nanoparticles (TiO2 NPs) are an effective source of reactive oxygen species (ROS) for photodynamic therapy and radionuclide stimulated dynamic therapy (RaST). Unfortunately, tracking the in vivo distribution of TiO2 NPs noninvasively remains elusive.

Objective: Given the use of gadolinium (Gd) chelates as effective contrast agents for magnetic resonance imaging (MRI), this study aims to (1) develop hybrid TiO₂-Gd NPs that exhibit high relaxivity for tracking the NPs without loss of ROS generating capacity; and (2) establish a simple colorimetric assay for quantifying Gd loading and stability.

Method: A chelate-free, heat-induced method was used to load Gd onto TiO₂ NPs, which was coated with transferrin (Tf). A sensitive colorimetric assay and inductively coupled plasma mass spectrometry (ICP-MS) were used to determine Gd loading and stability of the TiO₂-Gd-Tf NPs. Measurement of the relaxivity was performed on a 1.4 T relaxometer and a 4.7 T small animal magnetic resonance scanner to estimate the effects of magnetic field strength. ROS was quantified by activated dichlorodihydrofluorescein diacetate fluorescence. Cell uptake of the NPs and RaST were monitored by fluorescence microscopy. Both 3 T and 4.7 T scanners were used to image the in vivo distribution of intravenously injected NPs in tumor-bearing mice.

Results: A simple colorimetric assay accurately determined both the loading and stability of the NPs compared with the expensive and complex ICP-MS method. Coating of the TiO₂-Gd NPs with Tf stabilized the nanoconstruct and minimized aggregation. The TiO₂-Gd-Tf maintained ROS-generating capability without inducing cell death at a wide range of concentrations but induced significant cell death under RaST conditions in the presence of F-18 radiolabeled 2-fluorodeoxyglucose. The longitudinal (r1 = 10.43 mM^-1s^-1) and transverse (r2 = 13.43 mM^-1s^-1) relaxivity of TiO₂-Gd-Tf NPs were about twice and thrice, respectively, those of clinically used Gd contrast agent (Gd-DTPA; r1 = 3.77 mM^-1s^-1 and r2 = 5.51 mM^-1s^-1) at 1.4 T. While the r1 (8.13 mM^-1s^-1) reduced to about twice that of Gd-DTPA (4.89 mM^-1s^-1) at 4.7 T, the corresponding r2 (87.15 mM^-1s^-1) increased by a factor 22.6 compared to Gd-DTPA (r2 = 3.85). MRI of tumor-bearing mice injected with TiO₂-Gd-Tf NPs tracked the NPs distribution and accumulation in tumors.

Conclusion: This work demonstrates that Arsenazo III colorimetric assay can substitute ICP-MS for determining the loading and stability of Gd-doped TiO₂ NPs. The new nanoconstruct enabled RaST effect in cells, exhibited high relaxivity, and enhanced MRI contrast in tumors in vivo, paving the way for in vivo MRI-guided RaST.

Cite this article as:

Fang Lei, Huang Hengbo, Quirk D. James, Zheng Jie, Shen Duanwen, Manion Brad, Mixdorf Matthew, Karmakar Partha, Sudlow P. Gail, Tang Rui and Achilefu Samuel*, Analysis of Stable Chelate-free Gadolinium Loaded Titanium Dioxide Nanoparticles for MRI-Guided Radionuclide Stimulated Cancer Treatment, Current Analytical Chemistry 2022; 18 (7) . https://dx.doi.org/10.2174/1573411018666220321102736