SCHEDULED MAINTENANCE
Microwave-assisted synthesis of Gd(iii)-loaded nanozeolite SOD as MRI contrast agent with remarkable stability in vivo†
Abstract
Gd3+-loaded nanozeolite sodalite (SOD) is fast prepared through sequential hydrothermal synthesis, detemplation, and Gd3+ ions exchange under microwave irradiation. This microwave-assisted synthesis procedure provides nanozeolite Gd3+-SOD with a uniform particle size of 30 ± 2 nm and well framework structure. The result of its water proton relaxation rate indicates that its positive relaxivity per Gd3+ ion or per nanozeolite particle is relatively high, due to the efficient immobilization and enrichment of Gd3+ ions in the micropores as well as the large surface-to-volume ratio of nanozeolite. Furthermore, the relaxivity per Gd3+ ion displays clear position dependence, i.e., the exchanged Gd3+ ions near the external surface of nanozeolite pay major contribution to the total relaxivity. Moreover, the irreversible ion exchange process indicates that leaching of Gd3+ ion from nanozeolite Gd3+-SOD can be suppressed. The cell viability test shows low toxicity of nanozeolite Gd3+-SOD in vitro. The biodistribution and clearance data demonstrate the fast elimination of nanozeolite Gd3+-SOD by the reticuloendothelial system and steady accumulation in the liver and spleen for a long time, which indicates the negligible leaching of Gd3+ ion in vivo considering the highly stable framework structure of zeolite. In addition, the in vivo MRI demonstrates a brighter contrast enhancement in T1-weighted image compared to the pre-contrast image in the liver. This remarkable stable nanozeolite Gd3+-SOD with a positive relaxivity not only is a potential contrast agent for magnetic resonance imaging but also provides new insight into the utilization of nanozeolite with a unique framework structure.
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