title: Picogram-detection of estradiol at an electrochemical immunosensor with a gold nanoparticle|Protein G-(LC-SPDP)-scaffold.
abstract: Low picograms of the hormone 17beta-estradiol were detected at an electrochemical immunosensor. This immunosensor features a gold nanoparticle|Protein G-(LC-SPDP)(1)-scaffold, to which a monoclonal anti-estradiol capture antibody was immobilised to facilitate a competitive immunoassay between sample 17beta-estradiol and a horseradish peroxidase-labelled 17beta-estradiol conjugate. Upon constructing this molecular architecture on a disposable gold electrode in a flow cell, amperometry was conducted to monitor the reduction current of benzoquinone produced from a catalytic reaction of horseradish peroxidase. This current was then quantitatively related to 17beta-estradiol present in a sample. Calibration of immunosensors in blood serum samples spiked with 17beta-estradiol yielded a linear response up to approximately 1200 pg mL(-1), a sensitivity of 0.61microA/pg mL(-1) and a detection limit of 6 pg mL(-1). We attribute these favourable characteristics of the immunosensors to the gold nanoparticle|Protein G-(LC-SPDP) scaffold, where the gold nanoparticles provided a large electrochemically active surface area that permits immobilisation of an enhanced quantity of all components of the molecular architecture, while the Protein G-(LC-SPDP) component aided in not only reducing steric hindrance when Protein G binds to the capture antibody, but also providing an orientation-controlled immobilisation of the capture antibody. Coupled with amperometric detection in a flow system, the immunosensor exhibited excellent reproducibility.
authors.affiliation: Department of Chemistry and Biomolecular Sciences, Macquarie University, Sydney, NSW 2109, Australia.
authors.forename: Xiaoqiang
authors.initials: X
authors.lastname: Liu
authors.forename: Danny K Y
authors.initials: DK
authors.lastname: Wong
mesh_terms: D015374:Biosensing Techniques / Q000295:instrumentation* / Q000379:methods; D002138:Calibration; D002623:Chemistry Techniques, Analytical / Q000379:methods*; D002853:Chromatography, Liquid / Q000379:methods; D004563:Electrochemistry / Q000379:methods*; D004566:Electrodes; D004958:Estradiol / Q000032:analysis* / Q000378:metabolism; D006046:Gold / Q000737:chemistry*; D006735:Horseradish Peroxidase / Q000378:metabolism; D007118:Immunoassay; D053768:Metal Nanoparticles / Q000737:chemistry*; D009419:Nerve Tissue Proteins / Q000032:analysis*; D015203:Reproducibility of Results; D013438:Sulfhydryl Compounds
chemical_list: C029152:G-substrate; D009419:Nerve Tissue Proteins; D013438:Sulfhydryl Compounds; D004958:Estradiol; D006046:Gold; D006735:Horseradish Peroxidase