Porous Gold Nanocages: High Atom Utilization for Thiolated Aptamer Immobilization to Well Balance the Simplicity, Sensitivity, and Cost of Disposable Aptasensors

Gold nanostructures such as nanospheres, nanorods, or nanowires have been extensively used for electrode surface modification because they not only can increase the overall electroactive surface but can also provide anchoring sites for thiolated aptamers through facile Au-S covalent bonds. However, all of those gold nanostructures used are solid and only the outer surface is attractive. In the aim to reduce the usage of precious gold, in this paper, porous gold nanocages (AuNCs) with both inner and outer walls for effective aptamer immobilization have been electrostatically adhered on a screen-printed carbon electrode (SPCE), to develop a highly sensitive aptasensor in a truly label-free manner. Specifically, the thiolated aptamers specific for aflatoxin B1 (AFB1) were chosen as the model aptamer and covalently bound to the inner and outer surface of AuNCs using Au-S chemistry. Exposing the sensing interface to targets could initiate the formation of the aptamer/target complex, resulting in an increased interfacial electron transfer resistance on the SPCE. Under optimal conditions, this aptasensor could detect AFB1 in a wide range of 0.1 pg mL(-1) to 100 ng mL(-1) with a high linear fit and has an ultralow detection limit of 0.03 pg mL(-1) (S/N = 3). The developed aptasensor has remarkable merits such as simpler operation, more cost-effective, more sensitive, and less reagent consumption. We therefore provided a universal strategy to well balance the simplicity, sensitivity, and cost of disposable aptasensors for a large population of targets having specific aptamer strands.