With the global rise of antimicrobial resistance, rapid screening and identification of low concentrations of microorganisms in less than 1 h becomes an urgent technological need for evidence-based antibiotic therapy. Although many commercially available techniques are labeled for rapid microbial detection, they often require 24–48 h of cell enrichment to reach detectable levels. Here, it is shown that the widely used reducing agent tris(2-carboxyethyl)phosphine (TCEP) can also act as a powerful oxidant on gold nanoplates and subsequently lead to a strong catalysis of luminol chemiluminescence. The catalytic reaction results in up to 100-fold signal enhancement and unprecedented stable luminescence for up to 10 min. However, when TCEP is exposed to microorganisms, it is oxidized by the microbial surface proteins and loses its catalytic properties, leading to a decrease in chemiluminescence. The competitive interaction of TCEP with Au nanoplates and microorganisms is used to introduce a homogenous rapid detection method that allows microbial screening in less than 10 min with a limit of detection down to 100 cfu mL−1. Furthermore, the concept of microbial macromolecular shielding using antibody-conjugated polymers is introduced. The combination of TCEP redox activity and macromolecular shielding enables specific microbial identification within 1 h, without preconcentration, cell enrichment, or heavy equipment other than a hand-held luminometer. The technique is demonstrated by specific detection of methicillin-resistant Staphylococcus aureus in environmental and urine samples containing a mixture of microorganisms.
Bibliographical noteFunding Information:
The authors thank Dr. Hinh Ly for providing access to the flow injection chemiluminometer and Dr. Srinand Sreevatsan for providing MRSA bacteria. The authors are grateful for the financial support of the National Science Foundation (Award No. 1605191), the University of Minnesota MnDRIVE Global Food Venture, the USDA National Institute of Food and Agriculture, Hatch project 1006789, General Mills, Schwan Food Company Graduate Fellowship, and the Midwest Dairy Association. Parts of this work were carried out in the Characterization Facility, University of Minnesota, which receives partial support from NSF through the MRSEC program. A.A. and M.-P.N.B. proposed the concept. A.A. designed the experiments and directed the research. M.-P.N.B. performed most of the experiments, analyzed the data, and contributed to experiment design and scientific discussions. J.B. helped with sample preparation, bacterial counting with a flow cytometer, and contributed to result discussions. A.A. wrote the manuscript with input from M.-P.N.B. and J.B.
- gold nanoplates
- macromolecular shielding
- microbial detection