|Sundaram, Jaya -|
|Kwon, Yongkuk -|
Submitted to: ACS Book Series: Advances in Applied Nanotechnology for Agriculture
Publication Type: Book / Chapter
Publication Acceptance Date: June 20, 2013
Publication Date: July 21, 2013
Citation: Sundaram, J., Park, B., Kwon, Y. 2013. Nanocolloid substrate for surface enhanced Raman scattering sensor for biological applications. ACS Book Series 1143: Advances in Applied Nanotechnology for Agriculture. 2:21-41. DOI: 10.102/bk-2013-1143.ch002. Interpretive Summary: During past several years, Salmonella outbreak was linked to peanut butter contamination that caused 329 illnesses, and Salmonella tainted eggs caused 1,200 illnesses. Also, poultry and poultry products are the major sources of Salmonella contamination. Since Salmonella can grow and survive even in adverse environmental conditions, control of Salmonella in food industry is a major concern for food safety. Food safety also depends on ability to detect and identify foodborne pathogens that cause severe outbreaks. However, conventional microbiological methods are time-consuming and labor-intensive. Since food is a complex matrix, it is not easy to directly detect the presence of bacterial pathogens in food matrices. Thus, development of rapid methods for foodborne pathogen detection continues being high priority for food industry. Furthermore, rapid pathogen detection is beneficial for quality control during large scale food processing and production operations. Raman spectroscopy was studied for pathogen detection based on their optical characteristics, because Raman spectroscopy provides spectral information furnished by molecular vibrations of bacteria. Molecular bonds directly affect the vibrational spectra and give specific fingerprints that can be used to characterize foodborne pathogens.
Technical Abstract: Biopolymer encapsulated with silver nanoparticle (BeSN) substrate was prepared by chemical reduction method with silver nitrate, trisodium citrate in addition to polyvinyl alcohol. Optical properties of BeSN were analyzed with UV/Vis spectroscopy and hyperspectral microscope imaging. UV/Visible spectra showed plasmon resonance absorption at 460 nm and uniform plasmon resonance peaks at spectra from hyperspectral microscope imaging. Surface enhanced Raman scattering (SERS) signals of trans-1,2-bis(4-pyridyl)ethylene (BPE) and Rhodamine 6G were measured to validate substrate repeatability. SERS with BeSN substrate was able to detect and differentiate two serotypes (Typhimurium and Enteritidis) of Salmonella spp. Also, other foodborne pathogens such as E. coli, Listeria innocua, Staphylococcus aureus and Salmonella Infantis can be identified with SERS. Based on the SERS spectral data obtained between 400 and 1800cm-1 from 15 different spots from each sample on the substrate with three replicates, Principal component analysis (PCA) demonstrated 98% variation between the serotypes (PC1 92% and PC2 6%) to differentiate Salmonella serotypes. SERS spectral comparison of different serotypes indicated that similar cell wall and cell membrane structures were observed by spectral regions between 520 and 1050 cm-1. Major differences between serotypes were identified between 1200 and 1700 cm-1 which can explain biochemical characteristics of DNA and RNA components of the cells.