Oxygen Vacancy Enables Markedly Enhanced Magnetic Resonance Imaging-Guided Photothermal Therapy of a Gd³⁺-Doped Contrast Agent

Gd³⁺-based contrast agents (CAs) are the most prevailing and widely used for enhanced magnetic resonance imaging (MRI). Numbers of approaches have been developed to regulate the key parameters in order to obtain high-relaxivity CAs, according to the classic Solomon-Bloembergen-Morgen theory. Herein, a method of controlling oxygen vacancies in inorganic nanosized CAs has been developed for largely accelerated proton relaxation to obtain a high r₁ value. Such a strategy is verified on oxygen-deficient PEG-Na_xGdWO₃ nanorods, which exhibit a remarkable r₁ value up to 80 mM^-1 s^-1 (at 0.7 T) and a high r₁ value of 32.1 mM^-1 s^-1 on a clinical 3.0 T scanner, offering an excellent blood pool MRI performance at a low dose. Meanwhile, free electrons and/or oxygen-vacancy-induced small polarons can endow PEG-Na_xGdWO₃ nanorods with significant photothermal conversion for MRI-guided photothermal therapy.