Comparison methods of immunoassay cadmium telluride quantum dot and magnetic silica nanoparticle for detection of ochratoxin based on FRET

The purpose of present research is the comparison of two new methods of ochratoxin detection i.e. cadmium tellutide quantum dot and nanoparticle magnetic silica based on fluorescence resonance energy transfer (FRET) from cadmium telluride quantum dot to RHo123. Nano particle magnetic silica was synthesized using FeCl3 and FeSO4 under nitrogen flow, alkaline pH and addition of TEOS solution. As a new method, in order to add a functional group, we used APTES, and to increase these groups and elevate its effectiveness, it was subjected to glutaraldehyde. The specific immune-reaction between the anti-ochratoxin antibody on the quantum dot and the labeled-ochratoxin brings the Rho 123 fluorophore (the acceptor), and the quantum dot (the donor (in close spatial proximity and causes FRET to occur upon photo-excitation of the quantum dot. In the absence of unlabeled ochratoxin, the antigen-antibody complex is stable and strong emission of quantum dot is observed. In the presence of free ochratoxin, it will compete with the rhodamine labeled ochratoxin -albumin complex (as a bionanosensor) for binding to the antibody- quantum dot conjugate, and thus, FRET is increasingly suppressed. There is a linear relationship between the decreased fluorescence intensity of Rho 123 in 580nm with increasing concentration of ochratoxin present in the sample in the range 8 - 48 pg /ml. By using the magnetic silica Nano particle, a signal intensifier rise sensitivity of the system from 22 to 0.8pg/ml, which is a 275-fold increase. This highly sensitive homogenous competitive detection is simple, rapid and efficient. It does not require multiple separation steps as well as excessive washing.