We report the development of a multimodal lanthanide vanadate system suitable as dual T1-T2 MRI contrast agent as well as a luminescent imaging probe in the near-infrared region, using Dy3+ and Gd3+ as T2 and T1 components, respectively, and Nd3+ as the luminescent center. The vanadate matrix was chosen to avoid the undesired solubility associated to previously reported fluoride-based contrast agents. With such aim, we first optimized the design of the MRI system by comparatively evaluating the magnetic relaxivities of two different architectures consisting of i) uniform NPs incorporating both paramagnetic cations in solid solution (single-phase NPs), and ii) core-shell NPs consisting of a DyVO4 core coated with a homogeneous GdVO4 shell (DyVO4@GdVO4). We found that, although both samples presented magnetic relaxivity properties that make them adequate for their use as dual T1-T2 contrast agents for magnetic resonance imaging, the core-shell architecture would be more suitable because of their higher magnetic relaxivity values. Secondly, to prepare the multimodal system, the GdVO4 layer of such optimal dual T1-T2 MRI probe was doped with Nd3+ cations. An inert YVO4 intermediate shell was also introduced between the cores and the outer layer aiming to avoid energy transfer from Nd3+ to Dy3+, which would cause luminescence quenching. These core-shell-shell nanoparticles showed magnetic relaxivity values similar to those of the core-shell system and an intense luminescence in the near-infrared region. Moreover, they were dispersible and chemically stable under conditions that mimic the physiological media, and they were nontoxic for cells. Therefore, such multimodal nanoparticles meet the main requirements for their use as a dual T1-T2 contrast agent for magnetic resonance imaging and as a probe for luminescent imaging in the near-infrared region.

This publication is part of the I + D + I Grants PID2021-122328OB-I00 and PID2020-118448RB-C21, funded by MCIN/AEI/10.13039/501100011033 and by “ERDF A way of making Europe”. This work was supported as well by Junta de Andalucía under grant no. P20_00182, co-financed by EU FEDER funds. Grant PRE2019-090170 funded by MCIN/AEI/10.13039/501100011033 and by “ESF Investing in your Future” is also acknowledged. Relaxivity measurements were performed at the ICTS “NANBIOSIS”, specifically in Unit 28 at the “Instituto de Investigación Biomédica de Málaga y Plataforma en Nanomedicina (IBIMA Plataforma BIONAND)”.

Peer reviewed