A sensitive gold nanoparticle-based colorimetric aptasensor for Staphylococcus aureus

In this study, a gold nanoparticle-based colorimetric aptasensor for Staphylococcus aureus ( S. aureus ) using tyramine signal amplification (TSA) technology has been developed. First, the biotinylated aptamer specific for S. aureus was immobilized on the surface of the wells of the microtiter plate via biotin–avidin binding. Then, the target bacteria ( S. aureus ), biotinylated-aptamer–streptavidin-HRP conjugates, biotinylated tyramine, hydrogen peroxide and avidin–catalase were successively introduced into the wells of the microtiter plate. After that, the existing catalase consumed the hydrogen peroxide. Finally, the freshly prepared gold (III) chloride trihydrate was added, the color of the reaction production would be changed and the absorbance at 550   nm could be measured with a plate reader. Under optimized conditions, there was a linear relationship between the absorbance at 550   nm and the concentration of S. aureus over the range from 10 to 10 6   cfu   mL −1 (with an R ² of 0.9947). The limit of the developed method was determined to be 9   cfu   mL −1 .