A mathematical model of dielectrophoretic data to connect measurements with cell properties

Abstract

Dielectrophoresis (DEP) brings about the high-resolution separations of cells and other bioparticles arising from very subtle differences in their properties. However, an unanticipated limitation has arisen: difficulty in assignment of specific biological features which vary between two cell populations. This hampers the ability to interpret the significance of the variations. To realize the opportunities made possible by dielectrophoresis, the data and the diversity of structures found in cells and bioparticles must be linked. While the crossover frequency in DEP has been studied in-depth and exploited in applications using AC fields, less attention has been given when a DC field is present. Here, a new mathematical model of dielectrophoretic data is introduced which connects the physical properties of cells to specific elements of the data from potential-or time-varied DEP experiments. The slope of the data in either analysis is related to the electrokinetic mobility, while the potential at which capture initiates in potential-based analysis is related to both the electrokinetic and dielectrophoretic mobilities. These mobilities can be assigned to cellular properties for which values appear in the literature. Representative examples of high and low values of properties such as conductivity, zeta potential, and surface charge density for bacteria including Streptococcus mutans, Rhodococcus erythropolis, Pasteurella multocida, Escherichia coli, and Staphylococcus aureus are considered. While the many properties of a cell collapse into one or two features of data, for a well-vetted system the model can indicate the extent of dissimilarity. The influence of individual properties on the features of dielectrophoretic data is summarized, allowing for further interpretation of data.

Differential Biophysical Behaviors of Closely Related Strains of Salmonella

“…Error bars reflect standard error of the mean (SEM). The slope and intercept of the linear fits were used to determine the rate of particle accumulation and onset voltage for capture (Hilton and Hayes, 2019). In this way, initial capture voltages were determined to be 1889 ± 228 V for sv.…”

“…When fully developed and vetted, this approach of serotyping will require less expense and expertise compared to producing antisera in agglutination test utilizing O and H antiserum and will not require expert genomic information interpretation skills in whole genome sequencing for identifying Salmonella (Ng and Kirkness, 2010;Ashton et al, 2016). The relationship between biophysical behaviors, zeta potential, and the mobilities has been described (Hilton and Hayes, 2019). Zeta potential has a linear relationship with EK mobility and results in the difference in the onset voltage and the concentration slope.…”

“…These values allow some insights into the molecular and structural origins of the differentiation (Hilton and Hayes, 2019). This provides strong evidence that the simple measurement of the native and unlabeled cells may provide another valuable tool in the determination of serovars and basic science studies of Salmonella.…”

“…Higher order electrophysical effects are described by DEP mobility (µ DEP ). It can be expressed as (Jones, 1995;Nili and Green, 2014;Hilton and Hayes, 2019):…”

“…where ε m is the permittivity of the medium, ζ p is the EK (zeta) potential of the particle, and ζ m is the EK (zeta) potential of the medium/wall system. The value of µ EK was determined for both strains by particle tracking velocimetry (Crowther et al, 2019;Hilton and Hayes, 2019) at various applied voltages based on: where v EK is the velocity of the particle in an open channel. The capture of the particles can be observed when the flux of particles ( j ) is zero in the channel with the condition:…”