A simple method for bacterial concentration, detection and identification using SERS magnetic nanoparticles

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Elizabeth Vargis


Prompt identification of bacteria is needed in a variety of situations such as the detection of biological threats and bioterrorism, proper diagnosis and treatment in life threatening cases of bacterial infection, and monitoring for bacterial contaminants in water supplies. Laser spectroscopy methods, such as surface-enhanced Raman spectroscopy (SERS), have been used for the rapid detection and identification of bacteria for several decades. These methods significantly decrease the analysis time for bacterial identification from days to minutes. However, a simple and robust method to aggregate the bacteria for analysis has yet to be commonly applied. A recent method has been developed to concentrate, detect, and identify bacteria by means of gold-coated magnetic nanoparticles (Au-MNPs). The gold coating allows for signal enhancement, which results from the interaction between laser light and the gold surface. In this environment, a bacteria sample can emit a signal four orders of magnitude greater than a bacteria excited by laser light alone. The magnetic nanoparticles (MNP) also improve the SERS signal by drawing the bacteria closer together. Under these circumstances, as few as four to six bacteria can be detected in the area of analysis. Spectra from SERS with Au-MNPs, Raman with MNPs, and Raman without MNPs were collected and compared for three types of mycobacteria. The results indicate that using SERS Au-MNPs causes a significant improvement in distinguishing between species of bacteria, and shows potential for applications in which a simple, rapid, and robust bacterial detection method is vital.

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