Competitive immunoassay for Ochratoxin a based on FRET from quantum dot-labeled antibody to rhodamine-coated magnetic silica nanoparticles

• Published in: Mikrochimica acta (1966) Vol. 183; no. 12; pp. 3093 - 3099
• Main Authors: Mahdi, Mozaffari, Mansour, Bayat, Afshin, Mohsenifar
• Format: Journal Article
• Language: English
• Published: Vienna Springer Vienna 01.12.2016; Springer; Springer Nature B.V
• Subjects: Analytical Chemistry; Antibodies; Cadmium tellurides; Characterization and Evaluation of Materials; Chemistry; Chemistry and Materials Science; Energy measurement; Energy transfer; Fluorescence; Fretting; Immunoassay; Magnetic resonance; Microengineering; Nanochemistry; Nanoparticles; Nanotechnology; Original Paper; Polydispersity; Proximity; Quantum dots; Rhodamine; Silica; Silicon dioxide; Viral antibodies; Capping; Transmission electron microscopy; Nanobiosensor; Dynamic light scattering; Food contamination; Mycotoxin; Magnetic nanoparticles; Core-shell nanoparticles; CdTe
• ISSN: 0026-3672; 1436-5073
• DOI: 10.1007/s00604-016-1951-z

We report on a highly sensitive competitive immunoassay for the mycotoxin Ochratoxin (OTA) using magnetic silica nanoparticles (NPs) fluorescently labeled with rhodamine 123 (Rho123) as signal intensifier. The method is based on the measurement of fluorescence resonance energy transfer (FRET) that occurs from CdTe quantum dots covered with anti-OTA antibody to the dye Rho123 on the surface of the NPs. The immunoreaction between anti-OTA antibody and OTA brings the fluorophore (acting as the acceptor) in close proximity of the QDs (acting as the donor), and this causes FRET to occur upon photo-excitation of the QDs. The size and polydispersity of the silica coated magnetic NPs was studied via TEM. The method has a detection limit of 0.8 pg of OTA per mL. It was applied to the determination of OTA in spiked human serum. A linear relationship is found between the increase in the fluorescence intensity of Rho 123 at 580 nm and the concentration of OTA in spiked samples over the 8 to 48 pg⋅mL −1 concentration range. This highly sensitive homogeneous competitive detection scheme is simple, rapid and efficient. It does not require multiple separation steps and excessive washing. Graphical abstract Following photoexcitation of immobilized quantum dots (QDs), FRET occurs between the QDs and Rhodamine 123. The close proximity of Rho 123 and the magnetic silica core/shell particles leads to strongly intensified emission to result in an assay for Ochratoxin A that has a detection limit as low as 0.8 pg⋅mL -1