Dielectrophoretic Characterization and Separation of Microbials on a Microfluidic Device Based on Their Inherent Electrophysiology

Infectious diseases are among the leading causes of mortality across the world, after cardiovascular disease. Global health is constantly under threat due to unpredictable outbreaks of pathogenic infections. Although antibiotics are commonly used to deactivate the microorganisms, the development of resistant and persistent strains has challenged public health and highlights the need for novel diagnostic platforms that are not based on microbial culture.

Conventional analytical methods such as, polymerase chain reaction (PCR) based DNA amplification and enzyme linked immunoassay (ELISA) are labor intensive, not non-destructive and time consuming due to their need for chemical modifications. There is hence, the need for alternate point-of-care diagnostic methods that can directly analyze intact microbial cells, in a rapid and label-free manner; for the downstream development of rapid detection methods.

Microfluidic lab-on-a-chip devices provide many unique features towards point-of-care diagnostics, such as, high sensitivity and fast detection kinetics due to their large surface to volume ratios, high accuracy due to their ability for highly parallel analysis, and they require only small quantities of reagents. Characterization and separation of biological particles based on their inherent electrophysiology, to indicate characteristic phenotypes, is an emerging strategy. To address this need, we herein study microfluidic device platforms for dielectrophoretic (DEP) separation and characterization of intact microbials, by benchmarking their efficacy versus the conventional state-of-the-art in microbiological analysis.

The World Health Organization (WHO) has reported 1.7 billion cases of diarrhoeal diseases and 1.5 million fatalities every year globally. Herein, we demonstrate the application of quantitative dielectrophoretic tracking over a wide frequency range (10 kHz–10 MHz) to separate and characterize the persistent oocyst subpopulations of Cryptosporidium parvum, a water-borne pathogen capable of causing enteric infections*1*. We also show that DEP technique can independently monitor and separate particular C.difficile strains, one of the most serious causes of antibiotic-associated diarrhea, based on their characteristic S-layers, which cause alterations in their electrophysiology*2*. We also demonstrate these capabilities of DEP towards characterizing of the electrophysiological alterations on toxigenic C.difficile (TCD) strains due to the antimicrobial and anti-adhesive effects of the thermolabile extracellular factors secreted by non-toxigenic C.difficile, as a probiotic, during co-culture*9*. We envision this non-destructive, label-free, and sensitive DEP method can be used for diagnostics and biomedical research application.