Three-dimensional macroporous gold superior to conventional gold disk electrode in the construction of electrochemical immunobiosensor for Staphylococcus aureus detection
Herein, three-dimensional macroporous gold (3DMG) electrode is demonstrated to be a better choice than conventional gold disk electrode in the construction of an electrochemical immunobiosensor for Staphylococcus aureus (S. aureus) detection. The 3DMG electrode was prepared on a gold disk electrode by one-step electrodeposition using hydrogen bubbles as dynamic templates. The 3DMG electrode has a high electrochemically active surface area with pore sizes ranging from 20 to 50 μm, and these unique features are conducive to the immobilization of primary antibodies and the capture of S. aureus. Secondary antibody (Ab2) and alkaline phosphatase (ALP) were immobilized on mesoporous silica nanospheres (MSNs), and the resulting ALP-MSNs-Ab2 composites were utilized as signal tags to construct a sandwich-type electrochemical immunobiosensor. S. aureus was measured based on the alkaline phosphatase-catalyzed silver deposition and differential pulse voltammetric detection. The linear range is from 5 to 109 CFU mL-1, and the detection limit is 2 CFU mL-1 for S. aureus detection. Due to the signal amplification of 3DMG electrode, the sensitivity of the immunobiosensor constructing on the 3DMG electrode is 9 times that of an immunobiosensor constructing on a gold disc electrode. The proposed biosensor was successfully applied for detecting S. aureus in milk samples.