Biosensors based on DNA-functionalized CdTe quantum dots for the enhanced electrochemical detection of human-IgG

Electrochemical detection of human-IgG via biosensors is vital in clinical diagnostics, owing to their simple equipment, facile operation, high selectivity, economical, short diagnostic time, fast response, and easy miniaturization, but the need to improve sensitivity for protein detection is still a barrier limiting its wider practical applications. A hypersensitized electrochemical biosensor based on steric effects for IgG detection was developed in this work. The results indicate that IgG-modified sig-DNA attached to CdTe quantum dots (CdTe-sig-DNA) limited the ability of CdTe-sig-DNA or CdTe-sig-DNA-IgG conjugate to hybridize through the captured DNA strand (cap-DNA) immobilized on a chitosan/nitrogen-doped carbon nanocomposite (CS/N-C) modified glassy carbon electrode surface (GCE). The concentration of IgG based on CdTe concentration was detected by differential pulse anode stripping voltammetry (DPASV) on the electrode surface. The efficiency for hybridizing CdTe-sig-DNA with cap-DNA was found to be logarithmically inverse to the concentration of IgG attached. A highly sensitive and selective detection of IgG from 5 pM to 50 μM with a relatively low detection limit of 1.7 pM was achieved. Therefore, the steric hindrance effect of IgG limited the quantity of DNA that could be functionalized on CdTe QDs, significantly improving the signal, and providing a practical strategy for the clinical analysis of IgG.