Ling Zou,Yulan Tian,Xi Zhang,Jiaru Fang,Ning Hu,Ping Wang
This work describes an immunosensor for the determination of okadaic acid (OA) using a Love-wave sensor with the immunogold staining method. In this assay, OA-BSA was captured by the anti-BSA antibody (BSA-MAb) bond with staphylococcal protein A (SPA) on the sensor surface via Fc regions. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were employed to monitor the fabrication steps of immunosensor using the redox probe of K 3 Fe(CN) 6 . An indirect competitive immunoassay format was employed to detect OA after the immunosensor was prepared and gold nanoparticles (AuNPs) were introduced to amplify the phase signal. The results demonstrated that developed immunosensor was able to specifically respond to OA ranging from 10 to 150 ng/mL, providing limit of detection of 5.5 ng/mL. When applied to determine OA concentration in real sample, the results agreed well with those obtained by the commercial ELISA assay. The developed immunosensor is therefore suitable and has great application potential in detection of OA in shellfish.
Lou Doudou,Tian Yanyan,Zhang Yu,Yin Junjie,Yang Ting,He Chuan,Ma Ming,Yu Wei,Gu Ning
We found that the peroxidase-like activity of gold nanoparticles (GNPs) followed the Michaelis-Menten kinetic model and was dependent on environmental pH and temperature, which was very similar to natural Horseradish Peroxidase (HRP). However, unlike HRP, which needs a lower H2O2
concentration with a very narrow range to reach a maximum reaction rate and avoid enzyme poisoning, GNPs have very high activity, even at an H2O2 concentration two orders of magnitude higher than HRP. It was demonstrated that H2O2 treatment could
enhance the peroxidase-like activity of GNPs, resulting thus in the activity increase in a circular catalytic reaction by the reduplicative use of GNPs. It was also found that the peroxidase-like activity of GNPs responded sensitively to nanoparticle size and surface modifications. When used
in an immunoassay, GNPs were generally conjugated with antibody and blocked with hydrophilic macromolecules to construct a nanoprobe. This strongly reduced the peroxidase-like activity and detection sensitivity of GNPs, therefore, restricting their use as peroxidase mimetics. We presented
a novel strategy that combined the nanoprobes with gold staining to expose fresh catalytic gold surfaces and obtained a great increase in detection sensitivity.
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