Synthesis of coral-like gold nanocrystals with the glutamic acid–cysteine–glycine–glutamic acid–cysteine–glycine hexapeptide for the electrochemical detection of α-amanitin in urine

Abstract

Gold nanomaterials have been used widely for the construction of electrochemical sensors because of their high conductivity, chemical stability and catalytic activity, but the synthesis of gold nanocrystals with an ideal three-dimensional structure and catalytic activity still faces great challenges. The study reports the synthesis of coral-like gold nanocrystals (C–Au NCs) with the glutamic acid–cysteine–glycine–glutamic acid–cysteine–glycine (ECGECG) hexapeptide. First, trisoctahedral gold was prepared via the reduction of chloroauric acid with ascorbic acid in the presence of CTAC, KBr and KI. Then, it underwent an asymmetric structural evolution that was induced using the ECGECG hexapeptide. The resulting C–Au NCs show a three-dimensional structure comprised of ultrasmall gold nanocrystals that are connected to form an integrated whole. This unique structure realizes ultrafast electron/ion transfer, a large surface area and a greater exposure of high-index facets. Furthermore, the C–Au NCs were used for the construction of an aptasensor for the electrochemical detection of α-amanitin. The aptasensor binds strongly with α-amanitin due to their good affinity and causes a sensitive electrochemical response. The differential pulse voltammetric peak current decreased linearly with an increase in the α-amanitin concentration in the range of 4 × 10⁻¹⁴ to 1.0 × 10⁻⁹ M, with a detection limit of 1.2 × 10⁻¹⁴ M (S/N = 3). This analytical method provides the advantages of sensitivity, specificity and repeatability, and was successfully applied in the electrochemical detection of α-amanitin in urine.