Label-free detection of Acinetobacter baumannii through the induced fluorescence quenching of thiolated AuAg nanoclusters

The development of time-saving analytical methods for detection of Acinetobacter baumannii is of paramount importance. In this work, we have developed a two-step strategy to prepare highly photoluminescent AuAg nanoclusters (NCs) by using Ag as linkers to connect the Au tthiol motifs forming Au /Ag tthiol motifs on the tailored thiolated Au NCs, resulting in a significant photoluminescence enhancement. The strong photoluminescence of the as-synthesized AuAg bimetallic NCs can be rapidly and selectively quenched by A. baumannii due to its induced agglomeration of AuAg bimetallic NCs, which allows this fluorescent material to act as a label free A. baumannii sensor in aqueous solution. A linear relationship was demonstrated between the fluorescence intensity of the thiolated AuAg bimetallic NCs and the concentration of A. baumannii, in the range of 1 x 104 5 x 107 colony forming unit (CFU) /mL with a limit of detection of 2.3 x 103 CFU/mL. The A. baumannii content in sputum was also analyzed. As far as we know, this is the first report of a fluorescent sensor for the detection of A. baumannii. This approach represents a rapidly alternative method for the analysis of sputum A. baumannii in clinical diagnosis.