Pt nanoparticle label-mediated deposition of Pt catalyst for ultrasensitive electrochemical immunosensors.

Herein we describe a novel signal amplification strategy for the development of ultrasensitive electrochemical immunosensors. The amplification strategy is based on platinum catalyzing a hydrogen evolution reaction. To demonstrate its practicality, the electrochemical signal enhancement strategy has been applied for the development of a novel prostate-specific antigen (PSA) immunosensor. The immunosensing protocol utilized a gold electrode with PSA capture antibodies bound to its surface via covalent bonding. After PSA was bound to the electrode surface, a secondary platinum nanoparticle-labeled detection antibody was used to complete the sandwich immunosensor. The resulting electrode was then dipped in a platinum developer solution containing 1 mM of PtCl4(2-), 0.1M of formate (reductant) and 0.5% Tween 80 (pH 6.5) to generate bare platinum catalysts in close proximity to the Au electrode surface through a seed-mediated nucleation and growth mechanism. The signal readout was obtained electrochemically via a Pt-catalyzed hydrogen evolution reaction in an acidic aqueous medium containing 10 mM of HCl and 1 M of KCl. A detection limit of 1 fg/ml was achieved.