title: Disposable electrochemical immunosensor by using carbon sphere/gold nanoparticle composites as labels for signal amplification.
abstract: This work designed a simple, sensitive, and low-cost immunosensor for the detection of protein marker by using a carbon sphere/gold nanoparticle (CNS/AuNP) composite as an electrochemical label. The nanoscale carbon spheres, prepared with a hydrothermal method by using glucose as raw material, were used to load AuNPs for labeling antibody by electrostatic interaction, which provided a feasible pathway for electron transfer due to the remarkable conductivity. The disposable immunosensor was constructed by coating a polyethylene glycol (PEG) film on a screen-printed carbon-working electrode and then immobilizing capture antibody on the film. With a sandwich-type immunoassay format, the analyte and then the CNS/AuNP-labeled antibody were successively bound to the immunosensor. The bound AuNPs were finally electro-oxidized in 0.1  M HCl to produce AuCl(4)(-) for differential pulse voltammetric (DPV) detection. The high-loading capability of AuNPs on CNS for the sandwich-type immunorecognition led to obvious signal amplification. By using human immunoglobulin G (IgG) as model target, the DPV signal of AuNPs after electro-oxidized at optimal potential of +1.40 V for 40 s showed a wide linear dependence on the logarithm of target concentration ranging from 10 pg  mL(-1) to 10 ng  mL(-1). The detection limit was around 9 pg  mL(-1). The immunosensor showed excellent analytical performance with cost effectivity, good fabrication reproducibility, and acceptable precision and accuracy, providing significant potential application in clinical analysis.
authors.affiliation: State Key Laboratory of Analytical Chemistry for Life Science, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210093, PR China.
authors.forename: Qiunan
authors.initials: Q
authors.lastname: Xu
authors.forename: Feng
authors.initials: F
authors.lastname: Yan
authors.forename: Jianping
authors.initials: J
authors.lastname: Lei
authors.forename: Chuan
authors.initials: C
authors.lastname: Leng
authors.forename: Huangxian
authors.initials: H
authors.lastname: Ju
mesh_terms: D004563:Electrochemistry / Q000379:methods*; D004566:Electrodes; D006046:Gold / Q000737:chemistry*; D006801:Humans; D007118:Immunoassay / Q000379:methods*; D007074:Immunoglobulin G / Q000032:analysis* / Q000737:chemistry*; D053768:Metal Nanoparticles / Q000737:chemistry*; D053758:Nanoparticles / Q000737:chemistry*; D010084:Oxidation-Reduction; D015203:Reproducibility of Results
chemical_list: D007074:Immunoglobulin G; D006046:Gold