UV-induced peroxidase-like activity of gold nanoclusters for differentiating pathogenic bacteria and detection of enterotoxin with colorimetric readout

In this study, gold nanoclusters (AuNCs) in the presence of chitosan were prepared assisted by UV irradiation, which exhibit peroxidase-like property tested with H 2 O 2 /3,3,5,5-tetramethylbenzidine (TMB). The chitosan-AuNCs composite membrane also behaves peroxidase-like property and was characterized by TEM, AFM and SEM, which reveal the formed membrane was homogeneous and the AuNCs are predominantly spherical and well-dispersed without agglomeration in the membrane. A colorimetric assay was established by integrating immunoreactions occurred on the enzyme mimicking AuNC-chitosan composite membrane with varying colored GNPs serving as output signal. Three kinds of bacteria were chosen to serve as model bacteria to evaluate the selectivity of this sensor and Staphylococcus aureus ( S. aureus ), can be easily differentiated from Escherichia coli ( E. coli ) and Bacillus subtilis ( B. subtilis ). Such a colorimetric sensing is an extendable strategy due to the recognition element of probe may be replaceable on the catalytic AuNC-chitosan composite membrane. Staphylococcal enterotoxin B (SE-B) as low as 1.0 × 10 −12 g/mL may be sensitively detected by naked-eye readout. As a practical application, the developed colorimetric strategy was used for rapid onsite screening strategy for S. aureus and detecting SE-B in food samples. This colorimetric strategy provides promising platform for rapid onsite screening pathogenic bacteria and detection of enterotoxin in food safety and environmental monitoring.