Highly sensitive detection of proteins using voltammetric assay in the presence of silver nanostructures

A novel voltammetric protein assay has been demonstrated using bovine serum albumin in the presence of silver nanostructures (AgNs) formed electrochemically on gold substrates modified by self-assembled monolayer of thioctic acid. It is shown that the prepared AgNs exhibit voltammetric response characteristic of Ag and shows near Nernstian response at physiological pH. The advantages of the electrochemical assay compared to conventional protein analysis are the wide linear concentration range (10−4–10−11 g/mL) and trace level detection limits (50 pg/mL). The result of this electrochemical analysis agreed well with an independent spectrophotometric method using Bradford reagent, but the detection limit is far superior using the electrochemical method. Further, the modified electrode exhibits high sensitivity and long term stability. We invoke a new concept of surface enhanced activity of Ag+ ions at the electrochemical interface by the negatively charged bovine serum molecules.