Zeolitic imidazolate framework nanoparticles loaded with gadolinium chelate as efficient T 1 MRI contrast agent

Gd–chelate magnetic resonance imaging (MRI) contrast agents used in conventional clinical medicine still have some shortcomings, such as their low relaxation rates and poor imaging sensitivity. In this work, a Gd–chelate (Gd–DTPA), with a comparison made to the commercial contrast agent Magnevist was loaded into a zeolitic imidazolate framework (ZIF-8) to construct the efficient T1 MRI contrast agent Gd–DTPA@ZIF-8. At 0.5 T, the longitudinal relaxivity value (r1) of Gd–DTPA@ZIF-8 reaches 29.60 mM−1 s−1, which is about 6 times higher than that of Gd–DTPA. In terms of the retention of Gd–DTPA in ZIF-8, no obvious Gd3+ ions are released in water and complete culture solution over a long time period. Haemolysis and cytotoxicity experiments revealed that Gd–DTPA@ZIF-8 has good biocompatibility. In addition, the in vivo MRI results prove that Gd–DTPA@ZIF-8 can significantly enhance the T1-weighted MRI contrast effect of the tumour site. These advantages make Gd–DTPA@ZIF-8 a potential candidate for biomedical applications.