Abstract
A surface-enhanced Raman scattering (SERS) tag is proposed for high-sensitivity detection of gibberellin A(3) (GA(3)). Silver nanoparticles (AgNPs) were synthesized using citrate reduction. 4-Mercaptobenzoic acid (MBA) was used for the Raman-labeled molecules, which were coupled to the surface of the AgNPs using sulfydryls. MBA was coated with silica using the Stöber method to prevent leakage. GA(3) antibodies were attached via the active functional groups N-Hydroxysuccinimide (NHS) and N-Ethyl-N'-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC) to construct a novel immuno-AgNPs@SiO(2) SERS tags. The captured SERS substrates were fabricated through Fe(3)O(4) nanoparticles and gold nanoparticles (AuNPs) using chemical methods. These nanoparticles were characterized using ultraviolet-visible spectroscopy (UV-Vis), dynamic light scattering, Raman spectroscopy, transmission electron microscope (TEM), and X-ray diffraction (XRD). This immuno-AgNPs@SiO(2) SERS tags has a strong SERS signal based on characterizations via Raman spectroscopy. Based on antigen-antibody reaction, the immuno-Au@Fe(3)O(4) nanoparticles can capture the GA(3) and AgNPs@SiO(2) SERS tags. Due to the increasing number of captured nanoprobes, the SERS signal from MBA was greatly enhanced, which favored the sensitive detection of GA(3). The linear equation for the SERS signal was y = -13635x + 202211 (R(2) = 0.9867), and the limit of detection (LOD) was 10(-10) M. The proposed SERS tags are also applicable for the detection of other food risk factors.