科研之友
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摘要
Herein, we demonstrate the protocol of a label-free photoelectrochemical (PEC) immunoassay on the basis of ordered mesoporous carbon (CMK-3) and water-soluble CdSe@2nS core-shell quantum dots (ODs) coupled with a biospecific interaction for the ultrasensitive detection of human immunoglobulin (antigen, H-IgG) as a model protein. The CMK-3 was dispersed with chitosan (CS-CMK-3), which contains a large amount of amino groups (-NH2), and the CdSe(aZnS ODs were treated with thioglycolic acid, which contains carboxylic acid groups (-COOH). The layer-by-layer assembling of CdSe(aZnS QDs and CS-CMK-3 achieved through the covalent bonding of -COOH and -NH2 was employed as a photoactive antibody (Ab) immobilization matrix. Improved sensitivity was achieved through the synergistic effect of the excellent electrical conductivity and high specific surface area of CMK-3, as well as the high photon-to-electron conversion efficiency of CdSe@ZnS ODs. The photoexcitation of a CMK-3/CdSe(aZnS QDs-modified ITO electrode potentiostated at 0 V (vs. Ag/AgCl) under white light led to a stable anodic photocurrent. To perform the immunoassay, anti-human immunoglobulin (antibody, anti-H-IgG) was conjugated onto the CdSe(aZnS QDs-modified electrode by using EDC-NHS coupling reactions between -COOH of CdSe@ZnS QDs and -NH2 of the antibody. The concentrations of H-IgG were measured through the decrease in photocurrent intensity resulting from the increase in steric hindrance due to the formation of the immunocomplex. Under the optimal conditions, a linear relationship between photocurrent decrease and H-IgG concentration was obtained in the range 10 pg mL(-1)-100 ng m1: L-1 with a detection limit of 5 pg mL(-1). This strategy opens a simple perspective for the application of mesoporous conductive material and core-shell QDs as light-harvesting architecture, which might be of great significance in PEC bioanalysis in the future.
