A Proposed Method to Isolate, Concentrate, and Identify Bacteria By Dielectrophoresis and Raman Spectroscopy

Typical bacterial identification methods can take several days to complete. This lengthy analysis time is unacceptable for emergency situations and for life threatening illnesses. In order to reduce analysis time, many researchers have used a variety of methods for bacterial identification such as polymerase chain reaction, Raman spectroscopy, fluorescent in situ hybridization, and micro-array testing. Although these methods have successfully decreased bacterial analysis time from days to a matter of hours, they require a pure sample or a way to label bacteria with fluorescent tags, antibiotics, or primers. Pure samples cannot be obtained directly from patients and appropriate fluorescently marked antibodies increase costs and may result in wasted materials due to the broad range of bacteria strains that cause infections and disease. As such, a label-free identification method is appealing to cut costs and increase simplicity and efficiency. One label-free method is dielectrophoresis (DEP), which is the phenomenon by which motion in a particle occurs as it passes through a non-uniform electric field. The motion is a result of the applied frequency of the electric field and the particles’ intrinsic properties. This study proposes to use DEP as a means to isolate and concentrate bacteria for subsequent identification through Raman spectroscopy and statistical classification methods. If successful, the method could be used to identify bacteria from a mixed sample in a matter of minutes.