Fluorescent Heterodoped Nanotetrapods as Synergistically Enhancing Positive and Negative Magnetic Resonance Imaging Contrast Agents

Abstract

In this work, we report Mn−Fe heterodoped ZnSe tetrapod nanocrystals (NCs) synthesized to synergistically enhance contrast in both T 1 -and T 2 -weighted magnetic resonance imaging (MRI). The proposed NCs were prepared using a customized heteroarchitecture such that the manganese (Mn) is confined in the core and iron (Fe) in the branches of the tetrapods. The elemental composition and profile of these NCs were studied using X-ray photoelectron spectroscopy, energy-dispersive X-ray spectroscopy, and inductively coupled plasma mass spectroscopy. Photoluminescence quantum yield of these heterodoped NCs in water is ∼30%. Magnetic measurements reveal the simultaneous presence of superparamagnetic and paramagnetic behavior in these NCs because of the coexistence of Mn 2+ and Fe 2+ dopants. Their potential as simultaneous positive and negative MRI contrast agents was demonstrated by relaxivity measurements and in vivo MRI. From the in vivo studies, we also found that these NCs (with a hydrodynamic diameter of 20 nm) are excreted from the body within 24 h after the injection. Therefore, these heterodoped tetrapods NCs, while being fluorescent and safe, hold great future as a synergistically enhancing dual-modal MRI contrast agent.

A new class of cubic SPIONs as a dual-mode T1 and T2 contrast agent for MRI

“…The need for a synergistic positive and negative contrast enhancing and safe MRI contrast agent that can be utilized in clinical diagnosis has attracted the interest of many research groups [18,19]. The combination of both T 1 -contrast-enhanced image with high spatial resolution and T 2 -contrast-enhanced image with increased lesion detection capability allows complementary anatomic and pathologic information [20]. In this study, by controlling the shape and size of the SPIONs, we targeted a new class of synergistic MRI contrast agents.…”

“…For this purpose, hybrid nanoparticles have recently been developed, where the Gadolinium species integrated with iron oxide nanoparticles in a coreshell format systematically demonstrated the feasibility of such hybrid probes [19]. In another study, Mn-Fe heterodoped ZnSe tetrapod nanocrystals were proposed to simultaneously enhance contrast in both T 1 -and T 2 -weighted MRI [20]. However, the use of hybrid materials as in these two examples may cause magnetic interactions of nanoparticles, which in turn result in the perturbation of the relaxation process [21].…”

Heterodoped Nanoparticles as Dual-Mode Contrast Agent for MRI

“…T2 contrast agents are generally used for lesion detection [2]. T1-T2 dual-modal imaging can result in complementary diagnosis information by the advantages of positive and negative contrast effect [3].…”