Magnetic aptasensor with UiO-MOFs-mediated orientation-ordered aptamers for sensitive portable test of okadaic acid toxin

Background Shellfish toxin residues (e.g., okadaic acid, OA) in seafood are a global concern, and the development of precise, sensitive portable test kits is therefore necessary. Magnetic nanoparticle-aptasensors (MNAS) are attractive for specific recognition and sensitive assay, yet direct epitaxial aptamer immobilization on Fe 3 O 4 causes thin, scattered coatings, leading to limited probe capacity and non-specific adsorption. Fabricating high-efficiency MNAS with dense, ordered aptamer arrays for precise detection thus remains a challenging yet promising goal. Results We propose a high-performance magnetic nanoparticle-aptasensor (MNAS) mediated by UiO-66-NH 2 MOFs prepared with a secondary growth strategy (denoted as UiO/UiO-MOFs), in which AuNPs were uniformly anchored on MOF and facilitated the orientation-ordered nucleic acid aptamers enabling specific test of trace OA. The UiO/UiO-MOFs served as a scaffold with ordered amino group arrays, facilitating the construction of a homogeneous AuNPs interface and thus the tethering of high-density aptamers (up to 12.5 μmol/kg). This sensing platform synergistically integrated the advantages of ordered UiO/UiO-MOF self-assembly, robust AuNPs bridging, and the spherically ordered configuration of dense aptamers, thereby achieving efficient target OA recognition with minimal non-specific cross-reactivity. Coupled with laser-induced fluorescence (LIF) detection, the sensor exhibited excellent specificity, ultra-high sensitivity (limit of detection, LOD = 30 pg/mL), and outstanding stability. Notably, the sensor was successfully applied for the accurate on-site detection of OA residues in real mussel and clam samples, with satisfactory recovery rates ranging from 83.0±3.3% to 107.7±1.3%. Significance This study posed an affordable yet powerful strategy capable of simultaneously realizing efficient UiO/UiO-MOFs surface mediation surface mediation and high capacity of spherical orientation-ordered aptamers. It expands the toolkit for epitaxial aptamer immobilization on MNAS, facilitates the ordered anchoring of aptamers, and thus enables the construction of advanced MNAS tailored for shellfish toxin detection.