A new electrochemical aptasensor based on gold/nitrogen-doped carbon nano-onions for the detection of Staphylococcus aureus

Bacterial diseases are serious problems in the world today. The Staphylococcus aureus (S. aureus) bacterium is one of the most invasive and resistant bacteria that infects humans, making it a common cause of hospital infections. Herein, a very sensitive aptasensor for S. aureus was constructed using nitrogen-doped carbon nano-onions, gold nanoparticles (AuNPs) and thiol-terminated, aptamer-modified, screen-printed carbon electrodes. The physicochemical characteristics of the nanoparticles and the analytical parameters of the aptasensor were determined by several methods: energy dispersive X-ray spectroscopy, scanning and transmission electron microscopy, cyclic voltammetry and electrochemical impedance spectroscopy. The aptamer was self-assembled on the electrode surface through the covalent modification of thiol groups with AuNPs. The analytical parameters of this sensor were improved by immobilizing a carbon layer on the electrode surface. The developed aptasensor can measure S. aureus quickly with a limit of detection of 3 CFU/mL in the linear range of 10–108 CFU/mL. The aptasensor for S. aureus has good repeatability, reproducibility, and long-term stability and can measure S. aureus bacteria in human serum samples.