ARTICLE pubs.acs.org/ac Automated Dielectrophoretic Characterization of

We report the positive dielectrophoretic (pDEP) characterization of wild-type and ethambutol-treated Mycobacterium smegmatis populations via automated pDEP cell trapping experiments. The automated technique was validated by measurements of carboxylate-modified polystyrene microspheres and Escherichia coli. The characterization ofM. smegmatis identifies a key frequency regime where the membrane-specific action of ethambutol leads to a change in the cellular dielectrophoretic response. This work represents the first such characterization ofMycobacteria and highlights the potential for DEP measurements to measure changes in mycobacterial membrane properties associated with chemical treatments or genetic mutation. Dielectrophoresis (DEP) is the transport of polarizableparticles in response to a nonuniform electric field, exclusive of electrophoresis.1 DEP forces depend on the magnitude and nonuniformity of an externally applied electric field, as well as the complex permittivity of a particle and its surrounding media.2 The complex permittivities of the particle and surrounding media are a function of the frequency of the polarizing electric field, electrical conductivity, and permittiv-ity. Material permittivity values constitute an instantaneous approximation of the medium response and are, thus, generall