Finely crafted quasi-core-shell gadolinium/layered double hydroxide hybrids for switching on/off bimodal CT/MRI contrasting nanodiagnostic platforms

We successfully synthesized a size-controlled hybrid of layered double hydroxide (LDH) platelets and Gd(OH)₃ nanorods through the reverse micelle method. Under controlled synthetic conditions, the hybrid was developed to a quasi-core-shell structure, where the Gd(OH)₃ nanorods were covered by the LDH platelet assembly, and this was investigated by X-ray diffraction and high-resolution transmission electron microscopy. The zeta potential measurement for the hybrid revealed that Gd(OH)₃ was surrounded by LDH moieties. According to dynamic light scattering, the hydrodynamic radius of the hybrid was uniformly controlled under 150 nm, which was comparable to that of one Gd(OH)₃ nanorod surrounded by an LDH moiety. Thus, the obtained hybrid exhibited a maximum Hounsfield unit of 180 at a concentration of 5 mg mL^-1, implying its potential as a computed tomography contrast agent. The magnetic resonance relaxivities of the hybrid were examined at pH 5 and 7, simulating lysosomal and plasma conditions; the r₁ values were 7.3 and 2.9, respectively, which were highly dependent on the physiological conditions.