Sodium lanthanide tungstate-based nanoparticles as bimodal probes for T₁-T₂ magnetic resonance imaging and X-ray...

Magnetic resonance imaging (MRI) is one of the most commonly used imaging techniques for diagnosis in clinics. Often, magnetically-active substances, called contrast agents (CAs), have to be used, which increase contrast by shortening the longitudinal (T₁) (resulting in signal enhancement in T₁-weighted images) and/or transverse (T₂) (resulting in signal decay in T₂-weighted images) relaxation times of the water protons present in biological tissues. A further strategy to improve diagnostic accuracy is recording both kinds of images (T₁-weighted and T₂-weighted) using dual T₁-T₂ CAs, which facilitates the exclusion of false positives. The traditional T₁ or T₂ contrast agents are not suitable for such a purpose. This paper deals with the development of double sodium lanthanide tungstate-based nanoparticles containing Gd³⁺ and Dy³⁺ cations, which are dispersible in physiological media, do not show appreciable in vitro (for human fibroblast cells) and in vivo (for C. elegans) toxicity and present appropriate relaxivity values for their use as a dual T₁-T₂ contrast agent for magnetic resonance imaging. In addition, they show an excellent X-ray attenuation capacity, thanks mainly to their tungsten content, which makes them also useful for X-ray computed tomography. Hence, the developed nanoparticles are ideal multimodal probes to be used as a dual T₁-T₂ contrast agent for magnetic resonance imaging and as a contrast agent for X-ray computed tomography.