Detection of escherichia coli using magnetic nanoparticles and surface-enhanced raman spectroscopy

• Main Author: Chai, Mun Kit
• Other Authors: Duan Hongwei
• Format: Final Year Project
• Language: English
• Published: 2017
• Subjects: DRNTU::Engineering::Bioengineering
• Online Access: http://hdl.handle.net/10356/71233
• Institution: Nanyang Technological University

This project aims to study the combination of Escherichia coli (E. coli) detection techniques including affinity magnetic separation and Surface Enhanced Raman Scattering (SERS). Thereafter, analysis and discussion were done to establish the relationship between the Raman intensity (a.u.) and E. coli concentration (CFU/ml). Various key procedures were executed including the synthesis of iron oxide (Fe3O4) in the nanoscale via co-precipitation technique, followed by the miniemulsion polymerization with polystyrene (PS), coating of monolayer polydopamine (PDA) and lastly, the attachment of E. coli specific antibodies onto the magnetic nanochains surface. Along with the Raman dye, gold nanorods were used as the Raman probes with the surface modifications of a mixture of Polyvinylpyrrolidone (PVP) and Sodium Dodecylsulfate (SDS) as an intermediate step before capping the nanorods with PEG and E. coli antibodies. The magnetic separation was served as a method to aggregate the magnetic nanochains, thereby significantly improving the SERS signal. E. coli was isolated and detected with the aid of E. coli antibodies and SERS respectively. Furthermore, the unique Raman spectra did not only indicate the presence of E. coli, but also relate the concentration of E. coli within the tested samples through the Raman intensity. As such, the combination of magnetic separation and SERS were proven to be useful in isolating and detecting E. coli. Hence, the detection of other bacteria types is viable via the use of respective affinity probes.