An aptamer based method for small molecules detection through monitoring salt-induced AuNPs aggregation and surface plasmon resonance (SPR) detection

A simple, rapid and sensitive method for small molecules detection based on surface plasmon resonance (SPR) is presented. In this work, aptamer and unmodified gold nanoparticles (AuNPs) were combined to construct a sensor for small molecules detection. The AuNPs/ssDNA complexes display excellent stability under high salt condition. However, in the presence of target molecules, the binding of aptamers/AuNPs would be broken, thus resulting in the aggregation of AuNPs due to the loss of protection by the aptamers. The aggregation of the unmodified AuNPs led to a change of refractive index of the solution. Thus, assay results can be obtained by a fiber optic surface plasmon resonance (FOSPR) probe. In order to improve the detection sensitivity, U-shaped fiber optic probe silver film coating was employed. This new method shows excellent analytical performance for bisphenol A (BPA) in the range of 0.01-50 ng/mL (ppb) with a limit of detection (LOD) of 0.0037 ng/mL (ppb), which is about 30 times better than that of conventional enzyme-linked immunosorbent assay (ELISA). In addition, the proposed method exhibited excellent specificity, acceptable precision, and good accuracy. The proposed SPR assay was successfully applied to BPA determination in actual samples. Therefore, the present method was demonstrated to be promising for effective detection of small molecules.