Improvement of Localization of Radiation-Resistant Tumor Areas with MesoporousSilicon Nanotube-Based Intracellular Electron Paramagnetic Resonance pO2 Imaging

Hypoxic tumors consist of areas that have reduced oxygen levels in the tissue due to insufficient blood flow or poor vascularization. As a result, the tumor becomes more aggressive, spreading to other parts of the body, and being harder to treat with chemotherapy or radiation. Determining the oxygenation at the time of diagnosis will enable more effective treatment planning and therapeutic effect. Electron Paramagnetic Resonance Imaging (EPRI) with a sensor to measure oxygen was utilized to assess tumor oxygenation in vivo. The triarylmethyl (trityl) radical is good for measuring oxygen. However, it faced challenges from high dosage requirements, a short half-life, and poor intracellular permeability. The goal of this study is to develop mesoporous silica nanoparticles (MSNs) as carriers, which allows for an effective targeted delivery of the trityl radicals without being destroyed by dilution or environment. The synthesis of such a nanoplatform for tumor targeting was performed without losing oxygen- sensing capacity due to self-relaxation or broadening effects. The results indicated a high sensitivity to oxygen within the partial oxygen pressure range between 0 and 155 mmHg. MSN- trityl showed the best intracellular oxygen mapping in both in-vitro and in-vivo studies. MSN- trityl provides high-value oxygenation information for in-situ diagnostic imaging in potentialclinical applications.