An ultrasensitive biosensor for superoxide anion based on hollow porous PtAg nanospheres.

The accurate detection of the superoxide anion (O2•-) has vital academic and medical diagnostic significance due to its important dual roles in biological functioning. In this work, hollow porous PtAg nanospheres (PtAg HPNSs) were fabricated by a facile hydrothermal method followed by a dealloying procedure. The as-made PtAg nanospheres possessed hollow interiors and porous shells composed of interconnected ligaments and pores with the typical size around 4 nm. Benefitting from the unique hollow nanoporous architecture and the specific alloying effect, the PtAg HPNSs showed high electrocatalytic activity towards superoxide anions. The constructed biosensor based on PtAg HPNSs presented a fast and ultrasensitive response in a wide range of 0.8-1080 nM with much higher sensitivity of 4.5 × 10-2 μA cm-2 nM-1 and low detection limit of 0.2 nM (S/N = 3). Moreover, the novel biosensors can achieve electrochemical detection for O2•- released from living cells, exhibiting outstanding real time detection capability in cell environment. The facile controllable fabrication and unique sensing performance for PtAg HPNSs offers potential practical applications in developing highly sensitive and stable biosensor towards superoxide anion.