عنوان مقاله [English]
In this research, using FRET (fluorescence resonance energy transfer) from Cd/Te quantum dot (anti Ochratoxin A antibody immobilized on the external surface of quantum dot or QDs) to (Ochratoxin A labeled with Rhodamine 123 bound to albumin), a sensitive competitive immunoassay was developed for measuring Ochratoxin A. The highly specific immune-reaction between anti-Ochratoxin A antibody on the QDs and labeled Ochratoxin A brings the Rho fluorophore and the QDs in close spatial proximity, and following photo-excitation of the QDs, causes FRET to occur between the Rho fluorophore (acting as the acceptor) and the QDs (acting as the donor). In the absence of free Ochratoxin A, the immune reaction between labeled Ochratoxin and the anti-Ochratoxin antibody on the QDs induces emission and causes FRET to occur. In the presence of free Ochratoxin A, it competes with the labeled Ochratoxin A-albumin complex for binding to the antibody-QDs conjugate in the Nanobiosensor, leading to reduction in Rhodamine emission after FRET. The reduction in the fluorescence intensity of the Rhodamine acceptor directly correlates with the concentration of free Ochratoxin A in the sample. This method has a detection limit of 220pg per ml. It has also been used to measure Ochratoxin A in human serum samples. A linear relationship is found between the increase in the fluorescence intensity of Rho 123 at580 nm and the concentration of OTA in spiked samples over the 100-800 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.
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