The unsatisfactory performance of current gadolinium chelate based T1 contrast agents (CAs) for magnetic resonance imaging (MRI) stimulates the search for better alternatives. Herein, we report a new strategy to substantially improve the capacity of nanoparticle-based T1 CAs by exploiting the photoinduced superhydrophilic assistance (PISA) effect. As a proof of concept, we synthesized citrate-coated Gd-doped TiO2 ellipsoidal nanoparticles (GdTi-SC NPs), whose r1 increases significantly upon UV irradiation. The reduced water contact angle and the increased number of surface hydroxyl groups substantiate the existence of the PISA effect, which considerably promotes the efficiency of paramagnetic relaxation enhancement (PRE) and thus the imaging performance of GdTi-SC NPs. In vivo MRI of SD rats with GdTi-SC NPs further demonstrates that GdTi-SC NPs could serve as a high-performance CA for sensitive imaging of blood vessels and accurate diagnosis of vascular lesions, indicating the success of our strategy.
Keywords: T1 relaxivity; gadolinium-based contrast agents; magnetic resonance angiography; photoinduced superhydrophilicity; titanium dioxide nanoparticles.