title: Label-free mapping of single bacterial cells using surface-enhanced Raman spectroscopy.
abstract: Here we presented a simple, rapid and label-free surface-enhanced Raman spectroscopy (SERS) based mapping method for the detection and discrimination of Salmonella enterica and Escherichia coli on silver dendrites. The sample preparation was first optimized to maximize sensitivity. The mapping method was then used to scan through the bacterial cells adsorbed on the surface of silver dendrites. The intrinsic and distinct SERS signals of bacterial cells were used as the basis for label-free detection and discrimination. The results show the developed method is able to detect single bacterial cells adsorbed on the silver dendrites with a limit of detection as low as 10(4) CFU mL(-1), which is two orders of magnitude lower than the traditional SERS method under the same experimental condition. The time needed for collecting a 225 points map was approximately 24 minutes. Moreover, the developed SERS mapping method can realize simultaneous detection and identification of Salmonella enterica subsp. enterica BAA1045 and Escherichia coli BL21 from a mixture sample using principle component analysis. Our results demonstrate the great potential of the label-free SERS mapping method to detect, identify and quantify bacteria and bacterial mixtures simultaneously.
authors.affiliation: Department of Food Science, University of Massachusetts, Amherst, MA 01003, USA. lilihe@foodsci.umass.edu and College of Food Science and Engineering, Northwest A&F University, Yangling 712100, Shaanxi, P. R. China.
authors.forename: Panxue
authors.initials: P
authors.lastname: Wang
authors.affiliation: Department of Food Science, University of Massachusetts, Amherst, MA 01003, USA. lilihe@foodsci.umass.edu.
authors.forename: Shintaro
authors.initials: S
authors.lastname: Pang
authors.affiliation: Department of Food Science, University of Massachusetts, Amherst, MA 01003, USA. lilihe@foodsci.umass.edu.
authors.forename: Juhong
authors.initials: J
authors.lastname: Chen
authors.affiliation: Department of Food Science, University of Massachusetts, Amherst, MA 01003, USA. lilihe@foodsci.umass.edu.
authors.forename: Lynne
authors.initials: L
authors.lastname: McLandsborough
authors.affiliation: Department of Food Science, University of Massachusetts, Amherst, MA 01003, USA. lilihe@foodsci.umass.edu.
authors.forename: Sam R
authors.initials: SR
authors.lastname: Nugen
authors.affiliation: College of Food Science and Engineering, Northwest A&F University, Yangling 712100, Shaanxi, P. R. China.
authors.forename: Mingtao
authors.initials: M
authors.lastname: Fan
authors.affiliation: Department of Food Science, University of Massachusetts, Amherst, MA 01003, USA. lilihe@foodsci.umass.edu.
authors.forename: Lili
authors.initials: L
authors.lastname: He
mesh_terms: D004926:Escherichia coli / Q000166:cytology*; D019779:Salmonella enterica / Q000166:cytology*; D059010:Single-Cell Analysis / Q000379:methods*; D013059:Spectrum Analysis, Raman / Q000379:methods*; D013997:Time Factors