Magnetic relaxation switching assay based on three-dimensional assembly of Fe3O4@ZIF-8 for detection of cadmium ions

The design and construction of a novel magnetic resonance switch (MRS) sensor for cadmium ion (Cd2+) detection is described. Fe3O4@ZIF-8 was synthesized through seed-mediated growth of dimercaptosuccinic acid-coated Fe3O4. Fe3O4@ZIF-8 with high relaxation value (163.086 mM−1 s−1) and large negative zeta potential (−20.69 mV) exhibited good magnetic relaxation performance and water solubility. The successfully synthesized Fe3O4@ZIF-8 was used to develop an immune recognition-based MOFs-MRS sensor for highly sensitive detection of Cd2+. The proposed MRS detected a wide linear range of Cd2+ concentration from 2 to 200 ng mL−1 with a low limit of detection of 0.65 ng mL−1 (S/N = 3), and displayed high selectivity towards matrix interference. The robust sensing system was effective even in a complex sample matrix, enabling the quantitative analysis of Cd2+ content in rice samples and drinking water samples with good reliability. Recoveries of Cd2+ ranged from 91.50 to 112.05% for spiked drinking water and from 95.86 to 110.45% for spiked rice samples. The versatility of Fe3O4@ZIF-8 with customized relaxation responses could allow the adaptation of magnetic resonance platforms for food safety purposes.