An ultra-sensitive label-free immunosensor toward alpha-fetoprotein detection based on three–dimensional ordered IrOx inverse opals

Abstract

Three-dimensional ordered macroporous iridium oxides (3DOM IrOx 0≤x≤2), were synthesized through a simple self–assembly template method and developed as an electrode material for lable–free immunosensor of cancer biomarker alpha-fetoprotein (AFP). The 3DOM IrOx was well modified on flexible fluorine-doped tin oxide (FTO) electrode and such FTO electrodes based 3DOM IrOx immnuosensor enhanced the adsorption of electrolytes, the diffusion of reactants, and also could act as a rapid electron transfer channel benefited both from the advantage of 3DOM architecture and the nature of IrOx itself. These combined characteristics greatly increased the sensitivity, shortened the response time, reduced the interference, promoted the stability and moreover, demonstrated good accuracy to detect AFP in human serum. The optimum structure and sensing properties of immnuosensor were obtained based on 3DOM IrOx annealed at 500°C. It allows detecting AFP over a wide concentration range from 1 to 250ng/mL with a detection limit of 0.3ng/mL, and a higher slope of the calibration equation. The manufactured immunosensor was also used to determine AFP in human serum with satisfactory results. This kind of 3DOM IrOx modified and FTO-based immunosensor has great application potential for the AFP electrochemical detection.