|WU, XIAOMENG - University Of Georgia|
|HUANG, YAO-WEN - University Of Georgia|
|TRIPP, RALPH - University Of Georgia|
|ZHAO, YIPING - University Of Georgia|
Submitted to: Talanta
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/23/2015
Publication Date: 3/14/2015
Publication URL: http://dx.doi.org/10.1016/j.talanta.2015.02.045
Citation: Wu, X., Huang, Y., Park, B., Tripp, R., Zhao, Y. 2015. Differentiation and classification of bacteria using vancomycin functionalized silver nanorods array based surface-enhanced raman spectroscopy an chemometric analysis. Talanta. 139:96-103.
Interpretive Summary: The surface-enhanced Raman scattering (SERS) has been considered a powerful platform for the rapid and sensitive detection of bacteria. SERS could bring bacterial samples into the appropriate metallic nanostructures, thus significantly increasing the Raman vibrational signals of the bacteria. These vibrational modes represent a unique “fingerprint” spectrum consisting of Raman peaks that can be used to identify the particular bacteria being probed. For SERS based bacterial detection, the important tasks are to detect bacteria with high sensitivity from complex food matrices, and to distinguish bacterial species with their intrinsic SERS spectra. Although the origin of SERS signals from bacteria is still not clearly understood, it primarily originates from the external structure of the bacterial cells. Since the SERS spectra can be viewed as multivariate data, chemometric data analyses are used to differentiate bacteria using their spectral signatures. In order to design better differentiating strategy and validate the ability of chemometric methods to differentiate large bacterial samples, three conventional multivariate analysis methods were used to differentiate and classify the SERS spectra of bacterial species with various strains and serotypes. The results obtained from this research provide insights for the future application of SERS as a bacterial diagnostic platform for food safety.
Technical Abstract: The intrinsic surface-enhanced Raman scattering (SERS) was used for differentiating and classifying bacterial species with chemometric data analysis. Such differentiation has often been conducted with an insufficient sample population and strong interference from the food matrices. To address these problems, 27 different bacteria isolates from 12 species were analyzed using SERS with recently developed vancomycin coated silver nanorod (VAN AgNR) substrates. The VAN AgNR substrates demonstrated highly reproducible SERS spectra of the bacteria with little to no interference from the environment or bacterial by-products as compared to the pristine substrates. By taking advantage of the structural composition of the cellular wall that varies from species to species, the differentiation of bacterial species was demonstrated by multivariate analysis methods such as principle component analysis (PCA), hierarchical cluster analysis (HCA), and partial least square discriminant analysis (PLS-DA). A second chemometric analysis step within the species cluster is able to differentiate serotypes and strains. The spectral features used for serotype differentiation arises from the surface proteins, while Raman peaks from genetic materials dominate the differentiation of strains. In addition, due to the intrinsic structural differences in the cell walls, the SERS spectra were able to distinguish Gram-positive from Gram-negative bacteria with high sensitivity (98%) and specificity (100%).