Sensitive immunoassay of human chorionic gonadotrophin based on multi-walled carbon nanotube–chitosan matrix

Abstract

A novel amperometric immunosensor for human chorionic gonadotropin (HCG) assay has been fabricated through incorporating toluidine blue (TB) and hemoglobin (Hb) on the multiwall carbon nanotube (MWNT)-chitosan (CS) modified glassy carbon electrode, followed by electrostatic adsorption of a conducting gold nanoparticles (nanogold) film as sensing interface. The MWNT-CS matrix provided a congenial microenvironment for the immobilization of biomolecules and promoted the electron transfer to enhance the sensitivity of the immunosensor. Due to the strong electrocatalytic properties of Hb and MWNT toward H(2)O(2), the Hb and MWNT significantly amplified the current signal of the antigen-antibody reaction. The immobilized toluidine blue as an electron transfer mediator exhibited excellent electrochemical redox property. After the immunosensor was incubated with HCG solution, the access of activity center of the Hb to toluidine blue was partly inhibited, which leaded to a linear decrease in the catalytic efficiency of the Hb to the oxidation of immobilized toluidine blue by H(2)O(2) over HCG concentration ranges from 0.8 to 500 mIU/mL. Under optimal condition, the detection limit for the HCG immunoassay was 0.3 mIU/mL estimated at a signal-to-noise ratio of 3. Moreover, the proposed immunosensor displayed a satisfactory stability and reproducibility.

Review: Carbon nanotube based electrochemical sensors for biomolecules

“…Also, 1 h incubation times were used, which is much longer than conventional tests. Another immunosensor that incorporates toluidine blue and hemoglobin on a MWCNT-chitosan modified GCE was also designed to detect ␤-hcG [104]. When hcG bound to antibodies incorporated on the electrode, it inhibited access of hemoglobin to toluidine blue, decreasing the efficiency of oxidation of TB after H 2 O 2 addition.…”

Glucose biosensor based on titanium dioxide-multiwall carbon nanotubes-chitosan composite and functionalized gold nanoparticles

“…Organic membranes show good chemical and thermal stability improved by an inorganic phase. For example, chitosan (CS) was usually combined with TiO 2 nanoparticles [8,9], ZnO nanoparticles [10,11], and carbon nanotubes [12,13]. Nowadays, there are few reports about titanium dioxide-multiwall carbon nanotubes-chitosan (TiO 2 -MWNTs-CS) composite.…”

Kinetic studies of HRP adsorption on ds-DNA immobilized on gold electrode surface by EIS and SPR

“…This should be attributed to the repulsive electrostatic interaction increasing the resistance of charge transfer due to the anionic charge of the film and probe. [39][40][41] After the HRP adsorption, there is a new increase in the R ct due to formation of a nonconducting layer. Thus, these data confirm the layers formation.…”