Label-free aptasensor targeting Staphylococcus aureus surface Protein A

The rapid detection of Staphylococcus aureus (S. aureus) is of major importance for the biomedical world in the context where the antimicrobial resistance (AMR), the "silent pandemic", is considered a global public health threat to humanity. There are various approaches to detect S. aureus either as a whole bacterium or via different biomarkers that indicate the presence of this microorganism. Herein, a label-free aptasensor was designed for the detection of a cellular bacterial wall component, protein A (PrA), as a biomarker for the bacteria presence. A rapid procedure, under 5 min, that involves the deposition of the aptamer at the surface of a gold-based screen-printed electrode was applied followed by a blocking step to prevent non-specific adsorption of the target. After the incubation with PrA, the electrochemical detection was achieved, the aptasensor exhibiting good sensitivity across a wide linear range from 25 nM to 1000 nM, with a limit of detection (LOD) of 8.33 nM in standard solutions of the target. S. aureus was detected in commercial human serum and culture samples displaying a good correlation of the signal and the number of bacteria colonies, in the latter case.