Mn() complex impregnated porous silica nanoparticles as Zn()-responsive "Smart" MRI contrast agent for pancreas imaging

Type-1 and type-2 diabetes mellitus are metabolic disorders governed by the functional efficiency of pancreatic β-cells. The activities of the cells toward insulin production, storage, and secretion are accompanied by Zn( ii ) ions. Thus, for non-invasive pathology of the cell, developing Zn( ii ) ion-responsive MRI-contrast agents has earned considerable interest. In this report, we have synthesized a seven-coordinate, mono(aquated) Mn( ii ) complex ( 1 ), which is impregnated within a porous silica nanosphere of size 13.2 nm to engender the Mn( ii )-based MRI contrast agent, complex 1 @SiO 2 NP. The surface functionalization of the nanosphere by the Py 2 Pic organic moiety for the selective binding of Zn( ii )-ions yields complex 1 @SiO 2 -Py 2 PicNP, which exhibits r 1 = 13.19 mM −1 s −1 . The relaxivity value elevates to 20.38 mM −1 s −1 in the presence of 0.6 mM BSA protein at pH 7.4. Gratifyingly, r 1 increases linearly with the increase of Zn( ii ) ion concentration and reaches 39.01 mM −1 s −1 in the presence of a 40 fold excess of the ions. Thus, Zn( ii )-responsive contrast enhancement in vivo is envisaged by employing the nanoparticle. Indeed, a contrast enhancement in the pancreas is observed when complex 1 @SiO 2 -Py 2 PicNP and a glucose stimulus are administered in fasted healthy C57BL/6 mice at 7 T. Mn( ii )-based porous silica nanoparticle encapsulated Zn( ii )-responsive MRI contrast agent has been investigated to examine the pathological condition of pancreatic β-cells whose functional efficiency is related to type-1 and type-2 diabetes mellitus.