Sensitive photoelectrochemical immunoassay of Staphylococcus aureus based on one-pot electrodeposited ZnS/CdS heterojunction nanoparticles.

We report here a facile synthesis of ZnS/CdS heterojunction nanoparticles on an indium-tin oxide (ITO) electrode and their application in the ultrasensitive photoelectrochemical detection of Staphylococcus aureus (S. aureus). The ZnS/CdS/ITO electrode was prepared using one-pot electrodeposition in an acidic solution containing ZnCl2, CdCl2 and Na2S2O3. The optimal ZnS/CdS heterojunction nanoparticles with a Zn/Cd atomic ratio of 1 : 1 showed a high photoelectrochemical response to l-cysteine. l-Cysteine-encapsulated liposome (cysteine@liposome) immunonanocapsules were prepared and used as the labels for photoelectrochemical detection of S. aureus. By coupling cysteine@liposome immunonanocapsule labeling with immunomagnetic separation/enrichment and photoelectrochemical analysis using the ZnS/CdS/ITO electrode, sensitive photoelectrochemical detection of S. aureus was achieved. Under optimal conditions, the linear range for photoelectrochemical detection of S. aureus was from 1 to 4000 CFU mL-1. The proposed method was successfully used for photoelectrochemical detection of S. aureus in milk and juice samples.