K₂Mn₃[Fe^II(CN)₆]₂ NPs with High T₁‐Relaxivity Attributable to Water Coordination on the Mn(II) Center for Gastrointestinal Tract MR Imaging

Abstract

The lack of acid stability in the stomach and of temporal stability when moving through the gastrointestinal (GI) tract has made the development of oral magnetic resonance imaging (MRI) contrast agents based on the platform of Gd 3+ -complexes problematic.On the other hand, the negative contrast enhancement produced by the T 2 -weighted magnetic metal oxide nanoparticles (NPs) often renders the image readout difficult. Biocompatible NPs of the manganese Prussian blue analog K 2 Mn 3 [Fe II (CN) 6 ] 2 exhibit extremely high stability under the acidic conditions of the gastric juice. Additionally, the high r 1 relaxivity, low toxicity, and high temporal stability of such NPs offer great potential for the development of a true T 1 -weighted oral contrast agent for MRI of the entire GI tract.

Rational Atomic Engineering of Prussian Blue Analogues as Peroxidase Mimetics for Colorimetric Urinalysis of Uric Acid

“…73-0687), implying a face-centered cubic structure. The NPs exhibit intense absorption in the FT-IR spectra identically at 2072 cm –1 (Figure C), attributed to the CN stretching vibration in the Fe 2+ –CN–Fe 3+ of PB, and the stretching vibration relative to the carboxylate group of citrate anion is located at 1605 cm –1 , suggesting surface modification of the NPs by citrate due to its strong metal coordination property . Besides, the strong absorption at around 3435 cm –1 indicative of water implies the presence of bound water molecules in the framework of the NPs.…”

Prussian Blue and Its Analogues: From Properties to Biological Applications

“…[38] Dopting heavy metal ions to form PBA can raise the performance greatly. Murthi and coworkers [39] have reported a Mn-dopting PBA for gastrointestinal (GI) tract imaging. In this work, Mn-based PBA showed a large r 1 relaxivity value and extremely high stability under acidic conditions with the presence of Mn.…”

“…In order to make up the shortcoming of lacking acid and temporal stability, it is a good idea to introduce PB analogues. [39] So, it seems meaningful that combining the absorption capacity of small intestinal villi with biosafety to develop a new bioimaging agent like PBA using in gastrointestinal diseases like IBD.…”

“…However, the weaker value of relaxivity limits it applications. One effective method is doping high‐spin transition metal ions to PB nanostructure such as Mn 2+ and Gd 3+ , [16b,39,107] the gradient particles show higher value of r1 relaxivity, which from 4.3 mM −1 s −1 for Gd‐DTPA to 12.3 mM −1 s −1 for GDPB [107b] . It is known to all that Gd‐based contrast agents play a key role in the diagnosis of MRI, which can also act as Ca(II) antagonist to combine with correlative enzymes and restrain voltage‐gated calcium channels [108] .…”

“…Intravenous injection is indeed a common mode of administration, however, oral administration maybe a potential way guide to imaging for the gastrointestinal tract. In order to make up the shortcoming of lacking acid and temporal stability, it is a good idea to introduce PB analogues [39] . So, it seems meaningful that combining the absorption capacity of small intestinal villi with biosafety to develop a new bioimaging agent like PBA using in gastrointestinal diseases like IBD.…”