Novel Electrochemical Immunosensors For Human Chorionic Gonadotropin Based On Nanomaterials

Human chorionic gonadotropin(hCG), a highly glycosylated protein(37.5 k Da), is produced in pregnancy. During pregnancy, the variation of hCG in the urine or serum of human can cause some diseases, such as ovarian cancer, chorioepithelioma and male sterility. Therefore, there is a pressing need to develop a device that can rapidly measure the hCG concentration.Electrochemical immunosensors have been proved to be ideal methods due to their inherent advantages, such as the high sensitivity, low cost, easy of miniaturization, simple pretreatment procedures, fast analytical time, precise measurement, and small-sized instruments. The modifying technology of the electrode is the crucial step, which affects the signal intensity of the electrochemical detection and the immobilization of biological molecule. It has been proved that the nanomaterials with good biocompatibility and strong electrocatalytic activity are the ideal materials. In this paper, nanomaterials, such as multi-walled carbon nanotubes, nanoporous Pd, gold nanoparticles, are prepared.1. Electrochemical immunosensor for human chorionic gonadotropin based on nanocomposites of multi-walled carbon nanotubes- ionic liquid and nanoporous PdFirstly, a novel composite film consisted of multi-walled carbon nanotubes(MWCNTs) and room temperature ionic liquid(RTIL) of 1-butyl-3-methylimidazolium hexafluorophosphate(BMIMPF6), which combined the advantages of MWCNTs and RTIL, was fabricated onto glassy carbon electrode surface. The mechanism of the synergy of MWCNTs and RTIL has been discussed. Secondly, nanoporous Pd(NP-Pd) prepared by simple dealloying method was modified on the first film. The structure of NP-Pd has been confirmed by EDS, XRD, SEM, TEM and BET analysis. Due to the large specific surface area and excellent electrical conductivity of NP-Pd, K3[Fe(CN)6] as electron transfer mediator was promoted and the amount of h CG antibody was enhanced significantly. Results showed that MWCNTs-BMIMPF6/NP-Pd composites were successfully designed to be a sensitive immunosensor platform for hCG determination. Under the optimum conditions, the immunosensor exhibited high senstitivity and a wide linear range for h CG from 0.05 to 50 ng mL-1 with a detection limit of 3.2 pg m L-1. The prepared immunosensor showed high sensitivity, reproducibility and stability. And this immunosensor preparation strategy was a promising platform for clinical application.2. Sandwich electrochemical immunosensor for human chorionic gonadotropin using nanoporous Pd as labelThe nanoporous Pd(NP-Pd) was prepared by dealloying method and used as electrochemical label due to its wonderful conductivity, good biocompatibility and strong electrocatalytic activity toward antigen-antibody reaction. Results proved that the immunosensor fabricated using the label based on NP-Pd loaded with horseradish peroxidase(HRP) and secondary anti-hCG antibody(Ab2)(NP-Pd-HRP-Ab2) had high sensitivity, and the sensitivity of the label NP-Pd-HRP-Ab2 was much higher than that of HRP-Ab2. Gold nanoparticles(GNPs), Prussian blue(PB) and GNPs as immobilization matrix were not only used to immobilize anti-hCG(Ab1) but also took part in the signal amplification. Under optimized condition, the amperometric signal increased linearly with hCG concentration in the range of 0.5 ng m L-1 to 200 ng mL-1(γ =0.9986) with a low detection limit(3σ) of 9.2 pg mL-1(0.093 mIU mL-1). The immunosensor displayed good sensitivity and selectivity. In addition, the immunosensor was successfully used for the determination of hCG in human serum.