Tailoring magnetic resonance imaging relaxivities in macroporous Prussian blue cubes.

In order to unravel the relationship between zeta potential values and r2/r1 ratios for contrast agents in MRI application, a series of macroporous Prussian blue cubes were successfully synthesized by HCl etching and used as model samples for relaxivity investigation. It was found that their r2/r1 ratios firstly decreased and then increased with the increasing HCl concentration, while the variation trend for zeta potential is quite the opposite. By employing Gauss fitting and eliminating the HCl concentration in the resultant equations, a relationship between zeta potential values and r2/r1 ratios, i.e. ζ = 229 × (563 -r2/r1)0.012- 267, was finally obtained. This result showed that magnetic resonance imaging relaxivities (viz. r2/r1) could be tailored through altering zeta potential values (surface charges) of the contrast agent.