A simple and rapid optical biosensor for detection of aflatoxin B1 based on competitive dispersion of gold nanorods

• A one-step and label-free optical biosensor based on competitive dispersion of gold nanorods was developed for aflatoxin B1.
• The increase of AFB1 concentration in samples will increase dispersion of nanorods in solution.
• False results caused by undesirable aggregation could be effectively reduced based on dispersion of gold nanorods.
• The changes in absorption intensity of UV–vis spectra and the average hydrodynamic size of nanorods were employed as sensing indicator.
• Sensitivity, selectivity and feasibility of proposed biosensor were evaluated.

This report illustrates a promising one-step and label-free optical biosensor for determination of aflatoxin B1 (AFB1) that is most commonly found in foods and highly dangerous even at very low concentrations. In this research, gold nanorods (GNRs) were employed as a sensing platform, which showed high stability under high ionic strength conditions without addition of any stabilizing agent. GNR-AFB1–BSA (bovine serum albumin) conjugates aggregated after mixing with free antibodies, resulting in significant changes in absorption intensity. At the same time the existence of AFB1 molecules in samples caused dispersion of nanorods, as a result of competitive immune-reaction with antibodies. By taking advantages of the competitive dispersion of GNRs, the developed method could effectively reduce false results caused by undesirable aggregation, which is a big problem for spherical gold nanoparticles. Absorption intensity of UV–vis spectra served as the sensing indicator, with dynamic light scattering (DLS) measurement as another sensing tool. The designed biosensing system could detect AFB1 in a linear range from 0.5 to 20 ng mL−1, with a good correlation coefficient of 0.99. And the limit of detection (LOD) was 0.16 ng mL−1, indicating an excellent sensitivity with absorbance result. The recoveries of the spiked AFB1 in real peanut samples ranged from 94.2% to 117.3%. Therefore the proposed nano-biosensor was demonstrated to be sensitive, selective, and simple, providing a viable alternative for rapid screening of toxins in agriculture products and foods.