TY - JOUR T1 - Markedly Enhanced Magnetic Resonance Imaging-Guided Photothermal Therapy with Oxygen Vacancy Regulation JF - Journal of Nuclear Medicine JO - J Nucl Med SP - 1253 LP - 1253 VL - 59 IS - supplement 1 AU - Dalong NI AU - Dawei Jiang AU - Bo Yu AU - Lei Kang AU - Weijun Wei AU - Carolina Ferreira AU - Weibo Cai Y1 - 2018/05/01 UR - http://jnm.snmjournals.org/content/59/supplement_1/1253.abstract N2 - 1253Objectives: Gd3+-based contrast agents (CAs) are widely used for enhanced magnetic resonance imaging (MRI). A number of approaches have been developed to regulate the key parameters to obtain high-relaxivity CAs by controlling the nanoparticles’ size, regulating their shape, or tuning the surface modification. However, these methods are usually confined to the optimization of nanoparticles’ morphological features, and the r1 enhancement is rather limited at a clinical strength of 3.0 T. Our goal is to develop a novel strategy for accelerating water proton relaxation to obtain a high r1 value. Meanwhile, integrating CAs with therapeutic function for MRI-guided cancer therapy can simultaneously reduce the damage to normal tissues and improve their therapeutic efficacy. Methods: Oxygen-deficient tungsten oxides and tungsten bronzes are promising photothermal agents because of their strong near-infrared (NIR) photothermal conversion. Their critical feature of tunable oxygen vacancy concentrations triggered our interest to develop Gd3+-doped tungsten bronzes for investigating the proton relaxation behavior and photothermal conversion properties. In this work, oxygen-deficient PEGylated Gd3+-doped NaxWO3 (PEG-NaxGdWO3) nanorods were synthesized to explore its properties and applications as a MRI-guided photothermal agent. Results: The PEG-NaxGdWO3 nanocrystals were rod-like in shape and were about 140 nm in length and 80 nm in width. The r1 value of PEGNaxGdWO3 nanorods was calculated to be 32.1 mM−1 s−1 at 3.0 T, which is a high value among the reported relaxivities of nanosized Gd3+-based CAs and is 8-fold larger than that of commercial Gd3+-chelates. Importantly, the r1 value decreased with the reduced oxygen vacancy concentration, verifying that the oxygen vacancy would lead to efficient enhancement of MR relaxivity of PEG-NaxGdWO3 nanorods. Excellent blood pool MR images were obtained after the injection of PEG-NaxGdWO3 nanorods at a low injection dose, with the jugular vein and carotid artery being clearly delineated. Furthermore, MRI-guided photothermal therapy of tumors was successfully achieved on the 4T1 tumor-bearing mice after the injection of PEG-NaxGdWO3 nanorods, which substantially inhibited the tumor growth upon 980 nm laser irradiation, whereas the control groups show rapid tumor growth. CONCLUSION: In summary, we presented here the paradigm of oxygen-vacancy enhanced relaxivity of a Gd3+-doped tungsten bronze (PEGNaxGdWO3) nanorod. Excellent blood pool MR images have been achieved at rather low doses using these high-performance CAs. The oxygen vacancies are deemed to be responsible for both the high MR relaxivity and the outstanding photothermal therapy performance, which enabled these nanorods as an efficient theranostic platform for MRI-guided photothermal therapy by simply regulating the oxygen vacancy. ER -