The homogenized mixture was prepared by repeated and gently pipetting

The homogenized mixture was prepared by repeated and gently pipetting. Cd/Te QDs were synthesized by the simultaneous reduction of cadmium chloride and tellurium in the presence of sodium borohydride under nitrogen atmosphere. Magnetic nanoparticles were synthesized using FeSO4 and FeCl3 (1:2 molar ratio) and ammonia as an oxidizing agent under nitrogen atmosphere. The prepared magnetic nanoparticles shelled by silica using tetraethoxysilane in the presence of ammonia. Nanoparticles synthesis and monodispersity confirmed by TEM. Immobilization of Cd/Te Zinc Protoporphyrin QDs to antibodies and labeling of aflatoxin B1-albumin by Rho 123 were performed by EDC/NHS reaction in reaction mixture buffer, pH 6, at room temperature. Results By using the magnetic/silica core shell sensitivity of the system changed from 210-11 in our previous study to 210-12 in this work. The feasibility of the method established by the detection of aflatoxin B1 in spiked human serum. There is a linear relationship between the decreased fluorescence intensity of Rho 123 with increasing concentration of aflatoxin B1 in spiked samples, over the range of 0.01-0.06 mol.mL-1. Conclusions This homogeneous competitive detection scheme is simple, rapid and efficient, and does not require multiple separation steps and excessive washing. and (1, 2). There are reasonable Zinc Protoporphyrin economic and safety reasons for establishing highly sensitive, selective, cost-effective and rapid analytical methods for regular screening of aflatoxin B1 in a range of specimens (3, 4). Several methods such as high performance liquid chromatography, thin layer chromatography, enzyme-linked immunosorbent assay have currently used for detection of aflatoxin B1 in different specimens. Recently, some new nanobiosensors using different nanoparticles or microarray systems for detection of mycotoxins have been designed (5-10). However, rapid, sensitive and early detection of aflatoxicosis would be Zinc Protoporphyrin very helpful to distinguish high-risk persons. In recent years, based on such characteristics as easy handling, fast and high sensitivity, QDs in FRET-based nanobiosensor have extensively studied for the detection and diagnosis of different kinds of molecules and diseases (11-13). Unique optical properties have made QDs one of the most important labeling materials for biological and medical diagnostic applications. QDs are approximately spherical, the shell of which can be capped with various water-soluble functional groups, and are easily dispersed in water (14, 15). These surface functional groups could attach to biomolecules to form QD-nanobioconjugate. An example for this case is the terminal carboxylic groups Zinc Protoporphyrin of thioglycolic acid linked to various biomolecules (16, 17). Moreover, QDs as ideal donors possess many advantages in Zinc Protoporphyrin fluorescence resonance energy transfer (FRET) applications (18, 19). FRET occurs when the electronic excitation energy of a donor fluorophore is transferred to a nearby acceptor molecule. In this study, a very high sensitive, simple and rapid FRET-based nanobiosensor designed to detect aflatoxin B1 (Scheme 1). The QDs-labeled anti-aflatoxin B1 antibody and Rho 123-labeled aflatoxin B1-albumin considered as main parts of the nanobiosensor. We also used a novel magnetic/silica core shell that interestingly acts as an intensifier of the related signals. In this study, we decided to make a highly sensitive nanobiosensor to detect aflatoxin B1 in real samples. Open in a separate window Scheme 1 Excitation light passes through the magnetic/silica core shell, 2. Excitation light was intensified in contact with the magnetic/silica core shell and excited the Cd/Te QDs, 3. FRET was occurred because of close proximity of the QDs and the Rho 123, 4. Emission of the Rho 123 passes through magnetic/silica core shell, 5. Emission light was intensified 2. Materials and Methods Aflatoxin B1, aflatoxin B1-albumin conjugate, anti-aflatoxin B1 antibody, cadmium chloride (CdCl2), sodium borohydride (NaBH4), tellurium powder (Te), 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hy- drochloride (EDC), N-hydroxysuccinimide (NHS) purchased from Sigma MAPK3 chemical company (St. Louis, Mo, http://www.sigmaaldrich.com). Thioglycolic acid (TGA), FeSO4, FeCl3, tetraethoxysilane (TEOS) and all.