Abstract
Staphylococcus aureus (S. aureus) is one of the most common bacteria induced food poisoning and microbial infection of bloodstream in hospitals. Rapid detection is the key point for treatment, but the conventional methods in the sample pretreatment and measurement steps is rather cumbersome, entail a lot of manpower and even lack of sensitivity. Therefore, it should be desirable to develop a simple, rapid and sensitive method for the determination of S. aureus. Because of the protein A which may tightly bind to IgG just like antibody-antigen interaction is abundant on the cell envelope of S. aureus, therefore, in the present study, IgG-Barcode DNA-AuNPs probes were applied in the sandwich ELISA to determine protein A in foods and biological samples, and finally readout with ET-AAS. Under the optimized condition, we found the detection limit (DL) could reach to 0.1 ng/mL. Comparing with conventional ELISA (DL is 5 ng/mL), the sensitivity was 50 folds enhanced. In addition, DNA machine were also employed in the experiment to enhance the sensitivity. After the standard ELISA protocol, the barcode DNA on AuNPs were released for amplification, and approximately 250 folds of barcode DNA were amplified. The barcode DNA sequentially connected the magnetic microparticles (MMP) and 20 nm gold nanoparticles (AuNPs) together. After removing unbound AuNPs, the remained AuNPs were collected and determined by UV spectrometer. Comparing with conventional ELISA (DL is 5 ng/mL), the sensitivity was 50 folds enhanced. To demonstrate the feasibility, this method was also employed to determine several kinds of foods and biologic samples, and the satisfied recoveries showed the capability for real sample detection.