title: Detection of cortisol at a gold nanoparticle|Protein G-DTBP-scaffold modified electrochemical immunosensor.
abstract: An ultrasensitive electrochemical immmunosensor was demonstrated to be capable of detecting the hormone cortisol down to concentrations as low as 16 pg mL(-1). In addition, the immunosensor displayed a sensitivity of 1.6 μA pg(-1) mL(-1) and a linear range up to ∼2500 pg mL(-1) of cortisol. This immunosensor was constructed based on a Au nanoparticle|dimethyl 3,3'-dithiobispropionimidate·2HCl (DTBP)-Protein G scaffold-modified Au electrode. In this work, the Au nanoparticles were used to increase the electrochemically active surface area by 28% (with a standard deviation of 3%) to enhance the quantity of the Protein G scaffold on the electrode. Thiolation of Protein G by DTBP aided in avoiding the confirmation change of Protein G, while this Protein G-DTBP component offered an orientation-controlled immobilisation of the capture antibody on the Au electrode. In this immunosensor, a monoclonal anti-cortisol capture antibody was optimally aligned by the scaffold before a competitive immunoassay between sample cortisol and a horseradish peroxidase-labelled cortisol conjugate was conducted. For quantitative analysis, square wave voltammetry was used to monitor the reduction current of benzoquinone produced from a horseradish peroxidase catalysed reaction. The improved analytical performance of our immunosensor was attributed to the synergetic effect of Au nanoparticles and the Protein G-DTBP scaffold.
authors: Institute of Environmental and Analytical Sciences, College of Chemistry and Chemical Engineering, Henan University, Kaifeng, PR China.
authors: Xiaoqiang
authors: X
authors: Liu
authors: Ruoxia
authors: R
authors: Zhao
authors: Wenling
authors: W
authors: Mao
authors: Heqing
authors: H
authors: Feng
authors: Xiuhua
authors: X
authors: Liu
authors: Danny K Y
authors: DK
authors: Wong
mesh_terms: D000911:Antibodies, Monoclonal / Q000276:immunology; D016227:Benzoquinones / Q000378:metabolism; D055162:Biocatalysis; D015374:Biosensing Techniques; D058266:Dielectric Spectroscopy; D004566:Electrodes; D006046:Gold / Q000737:chemistry*; D006735:Horseradish Peroxidase / Q000737:chemistry / Q000378:metabolism; D006854:Hydrocortisone / Q000032:analysis* / Q000276:immunology; D007096:Imidoesters / Q000737:chemistry*; D007118:Immunoassay / Q000295:instrumentation*; D053768:Metal Nanoparticles / Q000737:chemistry*; D009419:Nerve Tissue Proteins / Q000737:chemistry*; D013438:Sulfhydryl Compounds / Q000737:chemistry
chemical_list: D000911:Antibodies, Monoclonal; D016227:Benzoquinones; C029152:G-substrate; D007096:Imidoesters; D009419:Nerve Tissue Proteins; D013438:Sulfhydryl Compounds; C004532:quinone; C007471:dimethyl dithiobispropionimidate; D006046:Gold; D006735:Horseradish Peroxidase; D006854:Hydrocortisone