Quantification of bacterial cells based on autofluorescence on a microfluidic platform

Ning Bao, Purdue University
Balarnurugan Jagadeesan, Purdue University
Arun K. Bhunia, Department of Food Science, Purdue University
Yuan Yao, Purdue University
Chang Lu, Birck Nanotechnology Center, Purdue University

Date of this Version

February 2008


Journal of Chromatography A, 1181 (2008) 153–158

This document has been peer-reviewed.



Bacterial counts provide important information during the processes such as pathogen detection and hygiene inspection and these processes are critical for public health and food/pharmaceutical production. In this study, we demonstrate the quantification of the number of bacterial cells based on the autofluorescence from the cell lysate on a microfluidic chip. We tested three model pathogenic bacteria (Listeria monocytogenes F4244, Salmonella Enteritidis PT1 and Escherichia coli O157:H7 EDL 933). In the experiment, a plug of similar to 150 pL containing lysate from 240 to 4100 cells was injected into a microfluidic channel with downstream laser-induced fluorescence detection under electrophoresis conditions. We found that the autofluorescence intensity increased with the number of cells almost linearly for all three bacteria. The autofluorescence remained a single peak when the cell lysate contained a mixture of different bacterial species. We also demonstrate a simple microfluidic device that integrates entrapment and electrical lysis of bacterial cells with fluorescence detection. Such a device can carry out the quantification of bacterial cells based on lysate autofluorescence without off-chip procedures. This study offers a simple and fast solution to on-chip quantification of bacterial cells without labeling. We believe that the method can be extended to other bacterial species.