Detection of total count of Staphylococcus aureus using anti-toxin antibody labelled gold magnetite nanocomposites: a novel tool for capture, detection and bacterial separation

In this contribution, we demonstrate a rapid, sensitive, specific and efficient method for detection of Staphylococcus aureus (S. aureus) as the model analyte at ultra-low concentrations using antibody labelled multifunctional gold-magnetite nanocomposites. A simple and efficient approach was adopted to construct diverse multifunctional gold magnetite nanostructures using 2,2'-(ethylenedioxy)-bis-(ethylamine) (EDBE) as a linker. The gold magnetite nanostructures were fabricated by iterative deposition of gold nanoparticles on the previously decorated gold-seed stabilized magnetite nanoparticles. These nanocomposites were further bioconjugated with an anti-a-toxin antibody with the aim to generate biorecognition probes that can specifically allow ultrasensitive detection as well as removal of S. aureus at ultra-low concentrations. The fluorescence and optical images of bacterial cells after interaction with our bioprobes showed that the pathogenic bacteria could be first immunomagnetically captured, detected and removed from S. aureus cell suspension in 30 min within the range of 10(2)-10(7) CFU mL(-1) of bacterial concentration. The detection limit achieved of S. aureus was 10(2) CFU mL(-1). The specificity of the detection of S. aureus was also verified using Escherichia coli as the model analyte using confocal microscopy. The combined functionalities of such antibody-targeted nanoprobes can be considered as a new tool box for the targeted, specific and sensitive detection of specific organisms (S. aureus) within 30 min.