Dual Enzyme-Induced Au-Ag Alloy Nanorods as Colorful Chromogenic Substrates for Sensitive Detection of Staphylococcus aureus .

Herein, we report a colorful colorimetric method for semiquantitative visual identification of Staphylococcus aureus ( S. aureus ) based on dual enzyme-induced gold-silver (Au-Ag) alloy nanorods (NRs). Alkaline phosphatase-oligonucleotide-functionalized magnetic beads (MBs-DNA-ALP) were designed as probes to monitor the concentration of S. aureus . When S. aureus was present, a naturally secreted nuclease, micrococcal nuclease, cut the AT-rich DNA sequences of MBs-DNA-ALP into fragments, resulting in the release of alkaline phosphatase (ALP). After magnetic separation, ALP induced the generation of a silver nanoshell coating on gold nanorods. The obtained Au-Ag alloy NRs caused a significant shift of the localized surface plasmon resonance peak, resulting in detection solutions of rainbow-like colors. Through naked eye observation, approximately 25 CFU/mL S. aureus could be easily detected. Additionally, quantification studies using samples spiked with S. aureus exhibited satisfactory recovery rates. The good performance of the colorful colorimetric method highlighted the effectiveness and applicability of the determination of S. aureus contamination in low-resource circumstances.