SiO2-coated layered gadolinium hydroxides for simultaneous drug delivery and magnetic resonance imaging

Layered gadolinium hydroxides (LGdH) have significant potential in simultaneous drug delivery and magnetic resonance imaging (MRI). In this work, we synthesized LGdH nanocomposites surface functionalised with SiO2 nanodots (LGdH@SiO2). We find these to have good dispersibility in cell culture medium, and a reduced tendency to aggregate compared to their uncoated analogue. Under the optimal reaction conditions, SiO2 nanodots were evenly spread across the surface of the LGdH particles. We further intercalated ibuprofen (Ibu) and 5-fluorouracil (5FU) into LGdH@SiO2, and explored the use of the resultant composites for drug delivery in vitro. While the SiO2 coating could effectively reduce aggregation of the Ibu intercalate prepared by ion exchange from the parent LGdH, it was noted to increase aggregation in the case of the 5FU-loaded systems produced by coprecipitation. With a SiO2 coating, 5FU release from the composite was almost zero-order at pH 7.4. The LGdH-5FU@SiO2 composites can effectively inhibit the growth of A549 ​cells (a human adenocarcinoma cell line). In contrast, the Ibu-loaded materials are highly biocompatible. After SiO2 modification, LGdH-5FU@SiO2 retains the same proton relaxivity properties as LGdH-5FU, while LGdH-Ibu@SiO2 becomes suitable for use as a negative contrast agent in MRI.