Preparation and characterization of porous gold and its application as a platform for immobilization of acetylcholine esterase

We report a method for the fabrication of a free-standing porous gold material with a high surface area and well-defined, tunable pore morphology. Porous gold is formed via a simple procedure that involves acidic treatment of a commercially available complex white gold alloy. We used SEM and AFM techniques to characterize the surface morphology, size, and shape of the mesopores as well as the surface roughness of the prepared porous gold samples. Formation of self-assembled monolayers of a flavin sulfide on the gold surface was used to estimate the total surface area of the porous gold material. The monolayers were found to be electrochemically active by cyclic and square wave voltammetry. It was found that 24 h HNO₃ treatment gave a 12 400× surface enlargement and resulted in a surface area of 14.2 m²/g, whereas 72 h HNO₃ treatment resulted in a 6900× surface enlargement and a surface area of 8.2 m²/g. In addition, the enzyme acetylcholine esterase was immobilized on the different porous gold surfaces to demonstrate biocompatibility of the porous gold material. Kinetic parameters and the amount of the immobilized acetylcholine esterase were determined.