Continuous dielectrophoretic bacterial separation and concentration from physiological media of high conductivity

TLDR

Biological sample processing requires purifying and concentrating analytes from complex matrices, a major obstacle for microfluidic diagnostics. This study presents a microfluidic device that continuously separates and concentrates pathogenic bacteria from physiological media such as cerebrospinal fluid and whole blood. The device integrates target‑specific dielectrophoresis, medium exchange, and concentration based on electrokinetic theory and electric‑field simulation, enabling operation in high‑conductivity physiological media. The device achieves up to 104‑fold concentration, 97 % separation efficiency for beads, 94 % and 87 % for E.

Abstract

Biological sample processing involves purifying target analytes from various sample matrices and concentrating them to a small volume from a large volume of crude sample. This complex process is the major obstacle for developing a microfluidic diagnostic platform. In this study, we present a microfluidic device that can continuously separate and concentrate pathogenic bacterial cells from complex sample matrices such as cerebrospinal fluid and whole blood. Having overcome critical limitations of dielectrophoretic (DEP) operation in physiological media of high conductivity, we utilized target specific DEP techniques to incorporate cell separation, medium exchange, and target concentration into an integrated platform. The proposed microfluidic device can uptake mL volumes of crude biological sample and selectively concentrate target cells into a submicrolitre volume, providing ∼104 fold of concentration. We designed the device based on the electrokinetic theory and electric field simulation, and tested the device performance with different sample types. The separation efficiency of the device was as high as 97.0% for a bead mixture in TAE buffer and 94.3% and 87.2% for E. coli in human cerebrospinal fluid and blood, respectively. A capture efficiency of 100% was achieved in the concentration chamber. With a relatively simple configuration, the proposed device provides a robust method of continuous sample processing, which can be readily integrated into a fully automated microfluidic diagnostic platform for pathogen detection and quantification.