title: Quantification of bacterial cells based on autofluorescence on a microfluidic platform.
abstract: 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 approximately 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.
authors.affiliation: Department of Agricultural and Biological Engineering, Purdue University, West Lafayette, IN 47907, USA.
authors.forename: Ning
authors.initials: N
authors.lastname: Bao
authors.forename: Balamurugan
authors.initials: B
authors.lastname: Jagadeesan
authors.forename: Arun K
authors.initials: AK
authors.lastname: Bhunia
authors.forename: Yuan
authors.initials: Y
authors.lastname: Yao
authors.forename: Chang
authors.initials: C
authors.lastname: Lu
mesh_terms: D001419:Bacteria / Q000302:isolation & purification*; D001431:Bacteriological Techniques; D015169:Colony Count, Microbial / Q000379:methods*; D004586:Electrophoresis; D019453:Escherichia coli O157 / Q000302:isolation & purification; D005453:Fluorescence; D008089:Listeria monocytogenes / Q000302:isolation & purification; D046210:Microfluidic Analytical Techniques; D012477:Salmonella enteritidis / Q000302:isolation & purification